treatments-xml/data/03/DC/91/03DC9141FF89F95C520D57A5EC7AF82D.xml

<document id="A2544EDD309316E9ADFA0B32DC050C2D" ID-CLB-Dataset="21509" ID-DOI="10.1002/ar.20983" ID-GBIF-Dataset="1f954e21-5266-43a5-a509-0911df30ac03" ID-Zenodo-Dep="3942771" IM.metadata_requiresApprovalFor="plazi" IM.tables_requiresApprovalFor="existingObjects,plazi" IM.taxonomicNames_requiresApprovalFor="plazi" checkinTime="1592830850760" checkinUser="jeremy" docAuthor="Lawrence M. Witmer &amp; Ryan C. Ridgely" docDate="2009" docId="03DC9141FF89F95C520D57A5EC7AF82D" docLanguage="en" docName="WitmerRidgely2009.pdf.imf" docOrigin="The Anatomical Record 292" docStyle="DocumentStyle{}" docTitle="Tyrannosaurus rex Osborn 1905" docType="treatment" docVersion="12" lastPageNumber="1293" masterDocId="FFE5E939FF88F9475155526EEF07FF8B" masterDocTitle="New Insights Into the Brain, Braincase, and Ear Region of Tyrannosaurs (Dinosauria, Theropoda), with Implications for Sensory Organization and Behavior" masterLastPageNumber="1296" masterPageNumber="1266" pageNumber="1267" updateTime="1698842811325" updateUser="ExternalLinkService">
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<mods:title id="4497A5C6597E54E4BF7AA58A0157B10B">New Insights Into the Brain, Braincase, and Ear Region of Tyrannosaurs (Dinosauria, Theropoda), with Implications for Sensory Organization and Behavior</mods:title>
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<mods:namePart id="28B79C3C2E69921355C280A82621600F">Lawrence M. Witmer</mods:namePart>
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<mods:namePart id="AE807878CE3A9C4A2FF8259C5621CBBE">Ryan C. Ridgely</mods:namePart>
<mods:affiliation id="3FB7CCB1C9EDA094B5752E565325A5E0">Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Athens, Ohio</mods:affiliation>
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<treatment id="03DC9141FF89F95C520D57A5EC7AF82D" ID-DOI="http://doi.org/10.5281/zenodo.4425593" ID-GBIF-Taxon="165074811" ID-Zenodo-Dep="4425593" LSID="urn:lsid:plazi:treatment:03DC9141FF89F95C520D57A5EC7AF82D" httpUri="http://treatment.plazi.org/id/03DC9141FF89F95C520D57A5EC7AF82D" lastPageId="27" lastPageNumber="1293" pageId="1" pageNumber="1267">
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<paragraph id="8BCA2057FF89F946520D57A5EA4EFA70" blockId="1.[832,1473,1442,1958]" pageId="1" pageNumber="1267">
Institutional abbreviations are listed in 
<tableCitation id="C6F715ECFF89F946547B57A5EA84FA6B" box="[1326,1411,1483,1505]" captionStart="TABLE 1" captionStartId="2.[595,679,228,249]" captionTargetBox="[160,1472,271,763]" captionTargetPageId="2" captionText="TABLE 1. Institutional abbreviations" httpUri="http://table.plazi.org/id/DF0A70DFFF8AF9455306528AEB0AFF72" pageId="1" pageNumber="1267" tableUuid="DF0A70DFFF8AF9455306528AEB0AFF72">Table 1</tableCitation>
, and anatomical abbreviations are listed in 
<tableCitation id="C6F715ECFF89F94655A55788EA42FA70" box="[1264,1349,1510,1532]" captionStart="TABLE 2" captionStartId="3.[602,686,152,173]" captionTargetBox="[160,1472,195,2007]" captionTargetPageId="3" captionText="TABLE 2. Anatomical abbreviations" httpUri="http://table.plazi.org/id/DF0A70DFFF8BF944530F52F6EB01FF26" pageId="1" pageNumber="1267" tableUuid="DF0A70DFFF8BF944530F52F6EB01FF26">Table 2</tableCitation>
.
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The reconstructions of soft-tissue structures, sensory capabilities, and behaviors presented here are grounded in comparative approaches that draw extensively on observations made in the extant realm, in particular the extant outgroups of tyrannosaurs (birds and crocodilians; 
<bibRefCitation id="EFE45DA6FF89F946522354E8EB09F910" author="Witmer LM" box="[886,1038,1669,1692]" firstAuthor="Witmer" journalOrPublisher="J Morphol" pageId="1" pageNumber="1267" pagination="269 - 327" part="225" refId="ref24054" refString="Witmer LM. 1995. Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae. J Morphol 225: 269 - 327." title="Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae" type="journal article" year="1995">Witmer, 1995</bibRefCitation>
b). As a result, first hand knowledge of not only the bony braincase but also the relevant softtissue systems (e.g., brain, cranial nerves, vasculature, cephalic air sacs, jaw and cervical muscles) provides critical information on how these systems interact with the bone to produce interpretable osteological correlates. This tyrannosaur study is part of a much larger, phylogenetically controlled project in our laboratory looking at the evolution of all of these systems in archosaurs as a whole. We drew on this broader perspective when making identifications of structures and assigning names.
</paragraph>
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<paragraph id="8BCA2057FF8AF9455306528AEB0AFF72" blockId="2.[595,1037,228,249]" box="[595,1037,228,249]" pageId="2" pageNumber="1268">TABLE 1. Institutional abbreviations</paragraph>
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<paragraph id="8BCA2057FF8AF94551F55361EA32FD70" pageId="2" pageNumber="1268">
<table id="F975D2F7FF8A06B851F55361EAC7FD70" box="[160,1472,271,763]" gridcols="3" gridrows="20" pageId="2" pageNumber="1268">
<tr id="35452215FF8A06B851F55361EAC7FEAF" box="[160,1472,271,292]" gridrow="0" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55361EE2FFEAF" box="[160,296,271,292]" gridcol="0" gridrow="0" pageId="2" pageNumber="1268">Abbreviation</th>
<th id="76944B69FF8A06B850C05361EB18FEAF" box="[405,1055,271,292]" gridcol="1" gridrow="0" pageId="2" pageNumber="1268">Institution</th>
<th id="76944B69FF8A06B855D95361EAC7FEAF" box="[1164,1472,271,292]" gridcol="2" gridrow="0" pageId="2" pageNumber="1268">Location</th>
</tr>
<tr id="35452215FF8A06B851F55358EAC7FEC0" box="[160,1472,310,331]" gridrow="1" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55358EE2FFEC0" box="[160,296,310,331]" gridcol="0" gridrow="1" pageId="2" pageNumber="1268">AMNH</th>
<td id="76944B69FF8A06B850C05358EB18FEC0" box="[405,1055,310,331]" gridcol="1" gridrow="1" pageId="2" pageNumber="1268">American Museum of Natural History</td>
<td id="76944B69FF8A06B855D95358EAC7FEC0" box="[1164,1472,310,331]" gridcol="2" gridrow="1" pageId="2" pageNumber="1268">New York City, New York</td>
</tr>
<tr id="35452215FF8A06B851F55320EAC7FEE8" box="[160,1472,334,355]" gridrow="2" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55320EE2FFEE8" box="[160,296,334,355]" gridcol="0" gridrow="2" pageId="2" pageNumber="1268">BHI</th>
<td id="76944B69FF8A06B850C05320EB18FEE8" box="[405,1055,334,355]" gridcol="1" gridrow="2" pageId="2" pageNumber="1268">Black Hills Institute</td>
<td id="76944B69FF8A06B855D95320EAC7FEE8" box="[1164,1472,334,355]" gridcol="2" gridrow="2" pageId="2" pageNumber="1268">Hill City, South Dakota</td>
</tr>
<tr id="35452215FF8A06B851F55308EAC7FEF0" box="[160,1472,358,379]" gridrow="3" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55308EE2FFEF0" box="[160,296,358,379]" gridcol="0" gridrow="3" pageId="2" pageNumber="1268">BMNH</th>
<td id="76944B69FF8A06B850C05308EB18FEF0" box="[405,1055,358,379]" gridcol="1" gridrow="3" pageId="2" pageNumber="1268">Natural History Museum</td>
<td id="76944B69FF8A06B855D95308EAC7FEF0" box="[1164,1472,358,379]" gridcol="2" gridrow="3" pageId="2" pageNumber="1268">London, United Kingdom</td>
</tr>
<tr id="35452215FF8A06B851F55310EAC7FE18" box="[160,1472,382,403]" gridrow="4" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55310EE2FFE18" box="[160,296,382,403]" gridcol="0" gridrow="4" pageId="2" pageNumber="1268">BMR</th>
<td id="76944B69FF8A06B850C05310EB18FE18" box="[405,1055,382,403]" gridcol="1" gridrow="4" pageId="2" pageNumber="1268">Burpee Museum of Natural History</td>
<td id="76944B69FF8A06B855D95310EAC7FE18" box="[1164,1472,382,403]" gridcol="2" gridrow="4" pageId="2" pageNumber="1268">Rockford, Illinois</td>
</tr>
<tr id="35452215FF8A06B851F553F8EAC7FE20" box="[160,1472,406,427]" gridrow="5" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F553F8EE2FFE20" box="[160,296,406,427]" gridcol="0" gridrow="5" pageId="2" pageNumber="1268">CM</th>
<td id="76944B69FF8A06B850C053F8EB18FE20" box="[405,1055,406,427]" gridcol="1" gridrow="5" pageId="2" pageNumber="1268">Carnegie Museum of Natural History</td>
<td id="76944B69FF8A06B855D953F8EAC7FE20" box="[1164,1472,406,427]" gridcol="2" gridrow="5" pageId="2" pageNumber="1268">Pittsburgh, Pennsylvania</td>
</tr>
<tr id="35452215FF8A06B851F553C0EAC7FE48" box="[160,1472,430,451]" gridrow="6" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F553C0EE2FFE48" box="[160,296,430,451]" gridcol="0" gridrow="6" pageId="2" pageNumber="1268">CMN</th>
<td id="76944B69FF8A06B850C053C0EB18FE48" box="[405,1055,430,451]" gridcol="1" gridrow="6" pageId="2" pageNumber="1268">Canadian Museum of Nature</td>
<td id="76944B69FF8A06B855D953C0EAC7FE48" box="[1164,1472,430,451]" gridcol="2" gridrow="6" pageId="2" pageNumber="1268">Ottawa, Ontario, Canada</td>
</tr>
<tr id="35452215FF8A06B851F553A8EAC7FE50" box="[160,1472,454,475]" gridrow="7" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F553A8EE2FFE50" box="[160,296,454,475]" gridcol="0" gridrow="7" pageId="2" pageNumber="1268">CMNH</th>
<td id="76944B69FF8A06B850C053A8EB18FE50" box="[405,1055,454,475]" gridcol="1" gridrow="7" pageId="2" pageNumber="1268">Cleveland Museum of Natural History</td>
<td id="76944B69FF8A06B855D953A8EAC7FE50" box="[1164,1472,454,475]" gridcol="2" gridrow="7" pageId="2" pageNumber="1268">Cleveland, Ohio</td>
</tr>
<tr id="35452215FF8A06B851F553B0EAC7FE78" box="[160,1472,478,499]" gridrow="8" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F553B0EE2FFE78" box="[160,296,478,499]" gridcol="0" gridrow="8" pageId="2" pageNumber="1268">FMNH</th>
<td id="76944B69FF8A06B850C053B0EB18FE78" box="[405,1055,478,499]" gridcol="1" gridrow="8" pageId="2" pageNumber="1268">Field Museum of Natural History</td>
<td id="76944B69FF8A06B855D953B0EAC7FE78" box="[1164,1472,478,499]" gridcol="2" gridrow="8" pageId="2" pageNumber="1268">Chicago, Illinois</td>
</tr>
<tr id="35452215FF8A06B851F55398EAC7FD80" box="[160,1472,502,523]" gridrow="9" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55398EE2FFD80" box="[160,296,502,523]" gridcol="0" gridrow="9" pageId="2" pageNumber="1268">IGM</th>
<td id="76944B69FF8A06B850C05398EB18FD80" box="[405,1055,502,523]" gridcol="1" gridrow="9" pageId="2" pageNumber="1268">Institute of Geology, Mongolian Academy of Sciences</td>
<td id="76944B69FF8A06B855D95398EAC7FD80" box="[1164,1472,502,523]" gridcol="2" gridrow="9" pageId="2" pageNumber="1268">Ulan Bataar, Mongolia</td>
</tr>
<tr id="35452215FF8A06B851F55060EAC7FDA8" box="[160,1472,526,547]" gridrow="10" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55060EE2FFDA8" box="[160,296,526,547]" gridcol="0" gridrow="10" pageId="2" pageNumber="1268">MOR</th>
<td id="76944B69FF8A06B850C05060EB18FDA8" box="[405,1055,526,547]" gridcol="1" gridrow="10" pageId="2" pageNumber="1268">Museum of the Rockies, Montana State University</td>
<td id="76944B69FF8A06B855D95060EAC7FDA8" box="[1164,1472,526,547]" gridcol="2" gridrow="10" pageId="2" pageNumber="1268">Bozeman, Montana</td>
</tr>
<tr id="35452215FF8A06B851F55048EAC7FDB0" box="[160,1472,550,571]" gridrow="11" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55048EE2FFDB0" box="[160,296,550,571]" gridcol="0" gridrow="11" pageId="2" pageNumber="1268">MWC</th>
<td id="76944B69FF8A06B850C05048EB18FDB0" box="[405,1055,550,571]" gridcol="1" gridrow="11" pageId="2" pageNumber="1268">Museum of Western Colorado</td>
<td id="76944B69FF8A06B855D95048EAC7FDB0" box="[1164,1472,550,571]" gridcol="2" gridrow="11" pageId="2" pageNumber="1268">Grand Junction, Colorado</td>
</tr>
<tr id="35452215FF8A06B851F55050EAC7FDD8" box="[160,1472,574,595]" gridrow="12" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55050EE2FFDD8" box="[160,296,574,595]" gridcol="0" gridrow="12" pageId="2" pageNumber="1268">MCZ</th>
<td id="76944B69FF8A06B850C05050EB18FDD8" box="[405,1055,574,595]" gridcol="1" gridrow="12" pageId="2" pageNumber="1268">Museum of Comparative Zoology, Harvard University</td>
<td id="76944B69FF8A06B855D95050EAC7FDD8" box="[1164,1472,574,595]" gridcol="2" gridrow="12" pageId="2" pageNumber="1268">Cambridge, Massachusetts</td>
</tr>
<tr id="35452215FF8A06B851F55038EAC7FDE0" box="[160,1472,598,619]" gridrow="13" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55038EE2FFDE0" box="[160,296,598,619]" gridcol="0" gridrow="13" pageId="2" pageNumber="1268">OMNH</th>
<td id="76944B69FF8A06B850C05038EB18FDE0" box="[405,1055,598,619]" gridcol="1" gridrow="13" pageId="2" pageNumber="1268">Oklahoma Museum of Natural History, Oklahoma University</td>
<td id="76944B69FF8A06B855D95038EAC7FDE0" box="[1164,1472,598,619]" gridcol="2" gridrow="13" pageId="2" pageNumber="1268">Norman, Oklahoma</td>
</tr>
<tr id="35452215FF8A06B851F55000EAC7FD08" box="[160,1472,622,643]" gridrow="14" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55000EE2FFD08" box="[160,296,622,643]" gridcol="0" gridrow="14" pageId="2" pageNumber="1268">PIN</th>
<td id="76944B69FF8A06B850C05000EB18FD08" box="[405,1055,622,643]" gridcol="1" gridrow="14" pageId="2" pageNumber="1268">Paleontological Institute, Russian Academy of Sciences</td>
<td id="76944B69FF8A06B855D95000EAC7FD08" box="[1164,1472,622,643]" gridcol="2" gridrow="14" pageId="2" pageNumber="1268">Moscow, Russia</td>
</tr>
<tr id="35452215FF8A06B851F550E8EAC7FD10" box="[160,1472,646,667]" gridrow="15" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F550E8EE2FFD10" box="[160,296,646,667]" gridcol="0" gridrow="15" pageId="2" pageNumber="1268">ROM</th>
<td id="76944B69FF8A06B850C050E8EB18FD10" box="[405,1055,646,667]" gridcol="1" gridrow="15" pageId="2" pageNumber="1268">Royal Ontario Museum</td>
<td id="76944B69FF8A06B855D950E8EAC7FD10" box="[1164,1472,646,667]" gridcol="2" gridrow="15" pageId="2" pageNumber="1268">Toronto, Ontario, Canada</td>
</tr>
<tr id="35452215FF8A06B851F550F0EAC7FD38" box="[160,1472,670,691]" gridrow="16" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F550F0EE2FFD38" box="[160,296,670,691]" gridcol="0" gridrow="16" pageId="2" pageNumber="1268">SDSM</th>
<td id="76944B69FF8A06B850C050F0EB18FD38" box="[405,1055,670,691]" gridcol="1" gridrow="16" pageId="2" pageNumber="1268">South Dakota School of Mines and Technology</td>
<td id="76944B69FF8A06B855D950F0EAC7FD38" box="[1164,1472,670,691]" gridcol="2" gridrow="16" pageId="2" pageNumber="1268">Rapid City, South Dakota</td>
</tr>
<tr id="35452215FF8A06B851F550D8EAC7FD40" box="[160,1472,694,715]" gridrow="17" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F550D8EE2FFD40" box="[160,296,694,715]" gridcol="0" gridrow="17" pageId="2" pageNumber="1268">TMP</th>
<td id="76944B69FF8A06B850C050D8EB18FD40" box="[405,1055,694,715]" gridcol="1" gridrow="17" pageId="2" pageNumber="1268">Royal Tyrrell Museum of Palaeontology</td>
<td id="76944B69FF8A06B855D950D8EAC7FD40" box="[1164,1472,694,715]" gridcol="2" gridrow="17" pageId="2" pageNumber="1268">Drumheller, Alberta, Canada</td>
</tr>
<tr id="35452215FF8A06B851F550A0EAC7FD68" box="[160,1472,718,739]" gridrow="18" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F550A0EE2FFD68" box="[160,296,718,739]" gridcol="0" gridrow="18" pageId="2" pageNumber="1268">UMNH</th>
<td id="76944B69FF8A06B850C050A0EB18FD68" box="[405,1055,718,739]" gridcol="1" gridrow="18" pageId="2" pageNumber="1268">University of Utah Museum of Natural History</td>
<td id="76944B69FF8A06B855D950A0EAC7FD68" box="[1164,1472,718,739]" gridcol="2" gridrow="18" pageId="2" pageNumber="1268">Salt Lake City, Utah</td>
</tr>
<tr id="35452215FF8A06B851F55088EAC7FD70" box="[160,1472,742,763]" gridrow="19" pageId="2" pageNumber="1268">
<th id="76944B69FF8A06B851F55088EE2FFD70" box="[160,296,742,763]" gridcol="0" gridrow="19" pageId="2" pageNumber="1268">ZPAL</th>
<td id="76944B69FF8A06B850C05088EB18FD70" box="[405,1055,742,763]" gridcol="1" gridrow="19" pageId="2" pageNumber="1268">Institute of Paleobiology of the Polish Academy of Sciences</td>
<td id="76944B69FF8A06B855D95088EAC7FD70" box="[1164,1472,742,763]" gridcol="2" gridrow="19" pageId="2" pageNumber="1268">Warsaw, Poland</td>
</tr>
</table>
</paragraph>
<subSubSection id="C36F73DCFF8AF94551ED5125EBA1FC3B" pageId="2" pageNumber="1268" type="nomenclature">
<paragraph id="8BCA2057FF8AF94551ED5125EBA1FC3B" blockId="2.[160,800,843,1959]" lastBlockId="2.[832,1472,843,1958]" pageId="2" pageNumber="1268">
Although a number of specimens were subjected to CT scanning (see below), the total sample includes specimens studied more traditionally via observation, and this latter category was critical for establishing basic anatomy and assessing variability. Specification of a museum catalog number throughout this article indicates that the original material was studied, whereas observations from casts or the literature are indicated as such. The primary specimens of 
<taxonomicName id="4C755BD4FF8AF94550B6564FEDBDFBBD" authorityName="Osborn" authorityYear="1905" box="[483,698,1057,1078]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8AF94550B6564FEDBDFBBD" box="[483,698,1057,1078]" italics="true" pageId="2" pageNumber="1268">Tyrannosaurus rex</emphasis>
</taxonomicName>
used in this study were as follows: (1) 
<materialsCitation id="3B1D2A0AFF8AF94550AF5655EDA8FBDA" ID-GBIF-Occurrence="2813094324" box="[506,687,1083,1105]" collectionCode="AMNH" pageId="2" pageNumber="1268" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
(virtually complete and undistorted braincase), (2) 
<materialsCitation id="3B1D2A0AFF8AF94553C85638EFD2FB0D" ID-GBIF-Occurrence="2813094376" collectionCode="AMNH" pageId="2" pageNumber="1268" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
(sagittally sectioned braincase), and (3) 
<materialsCitation id="3B1D2A0AFF8AF9455387561FEFF1FB2B" ID-GBIF-Occurrence="2813094368" collectionCode="FMNH" pageId="2" pageNumber="1268" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
(complete skull). Other 
<taxonomicName id="4C755BD4FF8AF945535E56E2ED4DFB2A" authorityName="Osborn" authorityYear="1905" box="[523,586,1164,1185]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8AF945535E56E2ED4DFB2A" box="[523,586,1164,1185]" italics="true" pageId="2" pageNumber="1268">T. rex</emphasis>
</taxonomicName>
specimens studied include 
<materialsCitation id="3B1D2A0AFF8AF94551A856C8EEB8FB30" ID-GBIF-Occurrence="2813094354" box="[253,447,1189,1211]" collectionCode="AMNH" pageId="2" pageNumber="1268" specimenCode="AMNH FR 5027">AMNH FR 5027</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF945509A56C8ED4FFB30" ID-GBIF-Occurrence="2813094302" box="[463,584,1189,1211]" collectionCode="CM" pageId="2" pageNumber="1268" specimenCode="CM 79057">CM 79057</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF945530D56C8EDE7FB37" ID-GBIF-Occurrence="2813094422" box="[600,736,1190,1212]" collectionCode="TMP" pageId="2" pageNumber="1268" specimenCode="TMP 81.6.1">TMP 81.6.1</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF94553A456C8EFDFFB5E" ID-GBIF-Occurrence="2813094304" collectionCode="BHI" pageId="2" pageNumber="1268" specimenCode="BHI 3033">BHI 3033</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF94551BC56AEEE84FB5E" ID-GBIF-Occurrence="2813094346" box="[233,387,1216,1237]" collectionCode="SDSM" pageId="2" pageNumber="1268" specimenCode="SDSM 12047">SDSM 12047</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF94550C056AEED00FB5E" ID-GBIF-Occurrence="2813094390" box="[405,519,1216,1237]" collectionCode="MOR" pageId="2" pageNumber="1268" specimenCode="MOR 008">MOR 008</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF945534C56AEED8CFB5D" ID-GBIF-Occurrence="2813094326" box="[537,651,1216,1238]" collectionCode="MOR" pageId="2" pageNumber="1268" specimenCode="MOR 555">MOR 555</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF94553C856AEEC1BFB5D" ID-GBIF-Occurrence="2813094356" box="[669,796,1216,1238]" collectionCode="MOR" pageId="2" pageNumber="1268" specimenCode="MOR 1125">MOR 1125</materialsCitation>
, and 
<materialsCitation id="3B1D2A0AFF8AF945518256B5EE4DFB7A" ID-GBIF-Occurrence="2813094337" box="[215,330,1243,1265]" collectionCode="MOR" pageId="2" pageNumber="1268" specimenCode="MOR 557">MOR 557</materialsCitation>
. It should be noted that there is some debate about the alpha taxonomy of these specimens (
<bibRefCitation id="EFE45DA6FF8AF94551FD577EEEE9FAAE" author="Carr TD &amp; Williamson T." box="[168,494,1296,1318]" firstAuthor="Carr" journalOrPublisher="Zool J Linn Soc" pageId="2" pageNumber="1268" pagination="479 - 523" part="142" refId="ref20370" refString="Carr TD, Williamson T. 2004. Diversity of late Maastrichtian Tyrannosauridae (Dinosauria, Theropoda) from western North America. Zool J Linn Soc 142: 479 - 523." title="Diversity of late Maastrichtian Tyrannosauridae (Dinosauria, Theropoda) from western North America" type="journal article" year="2004">Carr and Williamson, 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8AF9455355577FED9BFAAD" author="Larson PL" box="[512,668,1296,1318]" editor="Larson P &amp; Carpenter K" firstAuthor="Larson" journalOrPublisher="Bloomington: Indiana University Press" pageId="2" pageNumber="1268" pagination="102 - 128" refId="ref22036" refString="Larson PL. 2008. Variation and sexual dimorphism in Tyrannosaurus rex. In: Larson P, Carpenter K, editors. Tyrannosaurus rex, the tyrant king. Bloomington: Indiana University Press. p 102 - 128." title="Variation and sexual dimorphism in Tyrannosaurus rex" type="book chapter" volumeTitle="Tyrannosaurus rex, the tyrant king" year="2008">Larson, 2008</bibRefCitation>
), but until any new species are formally named, we regard them all as pertaining to 
<taxonomicName id="4C755BD4FF8AF945500A5728EE99FAD0" authorityName="Osborn" authorityYear="1905" box="[351,414,1350,1371]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8AF945500A5728EE99FAD0" box="[351,414,1350,1371]" italics="true" pageId="2" pageNumber="1268">T. rex</emphasis>
</taxonomicName>
. The primary specimen of 
<taxonomicName id="4C755BD4FF8AF94553835728EE49FAFE" authorityName="Lambe" authorityYear="1914" baseAuthorityName="Lambe" baseAuthorityYear="1914" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="species" species="libratus">
<emphasis id="B901FC45FF8AF94553835728EE49FAFE" italics="true" pageId="2" pageNumber="1268">Gorgosaurus libratus</emphasis>
</taxonomicName>
was ROM 1247 (nearly complete, somewhat laterally compressed braincase). Other specimens of 
<taxonomicName id="4C755BD4FF8AF945519957F8EE51FA20" authorityName="Lambe" authorityYear="1914" box="[204,342,1430,1451]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="species" species="libratus">
<emphasis id="B901FC45FF8AF945519957F8EE51FA20" box="[204,342,1430,1451]" italics="true" pageId="2" pageNumber="1268">G. libratus</emphasis>
</taxonomicName>
studied include ROM 1422, TMP 91.36.500, TMP 94.12.602, AMNH FR 5336, and AMNH FR 5664. Specimens of 
<taxonomicName id="4C755BD4FF8AF94550EC57A5ED62FA6B" authorityName=", Maleev" authorityYear="1965" box="[441,613,1483,1504]" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8AF94550EC57A5ED62FA6B" box="[441,613,1483,1504]" italics="true" pageId="2" pageNumber="1268">Daspletosaurus</emphasis>
</taxonomicName>
studied include CMN 8506, FMNH PR308, TMP 94.143.1, TMP 2001.36.1, and MOR 590. The Cleveland skull (
<materialsCitation id="3B1D2A0AFF8AF9455385546EEFD1F9BA" ID-GBIF-Occurrence="2813094377" collectionCode="CMNH" pageId="2" pageNumber="1268" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
) was studied in detail (see Witmer and Ridgely, in press). Despite lacking the braincase, original and cast material of 
<materialsCitation id="3B1D2A0AFF8AF9455064543FEEE1F9EE" ID-GBIF-Occurrence="2813094305" box="[305,486,1616,1638]" collectionCode="BMR" pageId="2" pageNumber="1268" specimenCode="BMR P2002.4.1">BMR P2002.4.1</materialsCitation>
were also examined. The braincase of 
<taxonomicName id="4C755BD4FF8AF945507B5405EEBDF90B" authorityName=", Osborn" authorityYear="1912" box="[302,442,1643,1664]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8AF945507B5405EEBDF90B" box="[302,442,1643,1664]" italics="true" pageId="2" pageNumber="1268">Tarbosaurus</emphasis>
</taxonomicName>
was studied via a cast of a sagittally sectioned specimen (PIN 553-3/1; 
<bibRefCitation id="EFE45DA6FF8AF94553D754E8EC1BF917" author="Maleev EA" box="[642,796,1670,1692]" firstAuthor="Maleev" journalOrPublisher="Paleontol Zh" pageId="2" pageNumber="1268" pagination="141 - 143" part="1965" refId="ref22270" refString="Maleev EA. 1965. [The carnosaur dinosaur brain]. Paleontol Zh 1965: 141 - 143 (in Russian)." title="The carnosaur dinosaur brain" type="journal article" year="1965">Maleev, 1965</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF8AF94551F554CEEFDFF93E" author="Maleev EA" box="[160,216,1696,1717]" firstAuthor="Maleev" journalOrPublisher="Trudy Sov-Mong Exped Nauk" pageId="2" pageNumber="1268" pagination="132 - 191" part="1" refId="ref22294" refString="Maleev EA. 1974. [Gigantic carnosaurs of the family Tyrannosauridae]. Trudy Sov-Mong Exped Nauk 1: 132 - 191 (in Russian)." title="Gigantic carnosaurs of the family Tyrannosauridae" type="journal article" year="1974">1974</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8AF94551B054CEED19F93D" author="Saveliev SV &amp; Alifanov VR" box="[229,542,1696,1718]" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="2" pageNumber="1268" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov, 2007</bibRefCitation>
) and CT data of ZPAL MgD-I/4 provided by J. H. Hurum; these data are currently under study by the authors in collaboration with D. L. Dufeau and J. H. Hurum. Also, a newly discovered skull of a very young 
<taxonomicName id="4C755BD4FF8AF94550C15565ED27F8AB" authorityName=", Osborn" authorityYear="1912" box="[404,544,1803,1824]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8AF94550C15565ED27F8AB" box="[404,544,1803,1824]" italics="true" pageId="2" pageNumber="1268">Tarbosaurus</emphasis>
</taxonomicName>
collected by the Hayashibara Museum and Mongolian Paleontological Center was studied by the authors in connection with a project led by T. Tsuihiji (
<bibRefCitation id="EFE45DA6FF8AF94550265535ED51F8FA" author="Tsuihiji T &amp; Watabe M &amp; Witmer LM &amp; Tsubamoto T &amp; Tsogtbaatar K. &amp; J Vert Paleontol" box="[371,598,1883,1905]" etAl="et al." firstAuthor="Tsuihiji" pageId="2" pageNumber="1268" pagination="160 A" part="27 (Suppl 3)" refId="ref23870" refString="Tsuihiji T, Watabe M, Witmer LM, Tsubamoto T, Tsogtbaatar K. 2007. A juvenile skeleton of Tarbosaurus with a nearly complete skull and its implications for ontogenetic change in tyrannosaurids. J Vert Paleontol 27 (Suppl 3): 160 A." title="A juvenile skeleton of Tarbosaurus with a nearly complete skull and its implications for ontogenetic change in tyrannosaurids" type="journal article" year="2007">Tsuihiji et al., 2007</bibRefCitation>
). The grouping of these taxa more or less corresponds to traditional definitions of 
<taxonomicName id="4C755BD4FF8AF945505255FEEEC2F82D" authorityName="Osborn" authorityYear="1905" box="[263,453,1936,1958]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="2" pageNumber="1268" phylum="Chordata" rank="family">Tyrannosauridae</taxonomicName>
(e.g., 
<bibRefCitation id="EFE45DA6FF8AF945534355FEED98F82C" author="Holtz TR" box="[534,671,1936,1959]" editor="Weishampel DB &amp; Dodson P &amp; Osmolska H" firstAuthor="Holtz" journalOrPublisher="Berkeley: University of California Press" pageId="2" pageNumber="1268" pagination="111 - 136" refId="ref21413" refString="Holtz TR. 2004. Tyrannosauroidea. In: Weishampel DB, Dodson P, Osmolska H, editors. The Dinosauria. 2 nd ed. Berkeley: University of California Press. p 111 - 136." title="Tyrannosauroidea" type="book chapter" volumeTitle="The Dinosauria. 2 nd" year="2004">Holtz, 2004</bibRefCitation>
), but revisions currently being undertaken by a number of researchers may change the definitions. Consequently, we use the term ‘‘tyrannosaur’’ in a relatively general sense to include the above taxa.
</paragraph>
</subSubSection>
<subSubSection id="C36F73DCFF8AF950520D51D8EA08F9BA" lastPageId="23" lastPageNumber="1289" pageId="2" pageNumber="1268" type="description">
<paragraph id="8BCA2057FF8AF943520D51D8ED9DFD00" blockId="2.[832,1472,843,1958]" lastBlockId="4.[160,800,230,1692]" lastPageId="4" lastPageNumber="1270" pageId="2" pageNumber="1268">
<materialsCitation id="3B1D2A0AFF8AF945520D51D8EB15FC40" ID-GBIF-Occurrence="2813094421" box="[856,1042,949,971]" collectionCode="AMNH" pageId="2" pageNumber="1268" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF8AF945554A51D8EBDDFC40" ID-GBIF-Occurrence="2813094396" box="[1055,1242,949,971]" collectionCode="AMNH" pageId="2" pageNumber="1268" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
, ROM 1247, 
<materialsCitation id="3B1D2A0AFF8AF945542451D8EC7FFC6D" ID-GBIF-Occurrence="2813094371" collectionCode="CMNH" pageId="2" pageNumber="1268" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, and some elements of 
<materialsCitation id="3B1D2A0AFF8AF94555DD51BEEBFBFC6D" ID-GBIF-Occurrence="2813094430" box="[1160,1276,976,998]" collectionCode="CM" pageId="2" pageNumber="1268" specimenCode="CM 79057">CM 79057</materialsCitation>
were scanned at O’Bleness Memorial Hospital (OBMH) in Athens, Ohio, using a General Electric (GE) LightSpeed Ultra Multislice CT scanner equipped with the Extended Hounsfield option, which improves resolvability of detail from dense objects such as fossils by extending the dynamic range of images as much 16-fold. Specimens were scanned helically at a slice thickness of 625 µm, 120 kV, and usually 200–300 mA. Additional scans of some specimens were done with somewhat different parameters (e.g., 1.25 mm slice thickness, 140 kV), and an additional scan of larger specimens was done with a narrower field of view (e.g., the central region encompassing the brain cavity and labyrinth) so that a bow-tie filter could be used to decrease beam-hardening artifacts. The raw scan data were reconstructed using a bone algorithm. Data were output from the scanner in DICOM format and then imported into Amira 3.1.1 or 4.1.2 (Mercury-TGS, Chelmsford, MA) for viewing, analysis, and visualization. Datasets deriving from different scans of the same specimen were subsequently registered in Amira, and thus the benefits of the different scan parameters could be combined in a single analysis. In contrast to the above, we used the ‘‘industrial’’ CT dataset for 
<materialsCitation id="3B1D2A0AFF8AF94554275458EC91F9EE" ID-GBIF-Occurrence="2813094408" collectionCode="FMNH" pageId="2" pageNumber="1268" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
published by 
<bibRefCitation id="EFE45DA6FF8AF9455560543EEBD2F9ED" author="Brochu CA" box="[1077,1237,1616,1638]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="2" pageNumber="1268" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu (2003)</bibRefCitation>
, and that paper may be consulted for scan details. It should be noted, however, that the CT metrics (e.g., voxel size) used by 
<bibRefCitation id="EFE45DA6FF8AF94554C554E8ECB7F93E" author="Brochu CA" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="2" pageNumber="1268" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF8AF94552E854CEECF4F93D" author="Brochu CA" box="[957,1011,1696,1718]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="2" pageNumber="1268" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">2003</bibRefCitation>
) to produce the cranial endocast were in error, and thus the proportions of his illustrated digital renderings are somewhat foreshortened along the 
<emphasis id="B901FC45FF8AF94554C754B8EA9AF960" box="[1426,1437,1750,1771]" italics="true" pageId="2" pageNumber="1268">z</emphasis>
or long axis; likewise, the dataset from which he worked was mirrored such that left and right are reversed. Prior to our scanning of 
<materialsCitation id="3B1D2A0AFF8AF945554E5548EBADF8B7" ID-GBIF-Occurrence="2813094407" box="[1051,1194,1830,1852]" collectionCode="CMNH" pageId="2" pageNumber="1268" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
noted above, the Cleveland skull had been scanned at the Boeing Rocketdyne CT Lab in California at a slice thickness of 1 mm with slices in the horizontal plane (voxel sizes were 0.4042 mm X 0.4042 mm X 1.0 mm); the results presented here derive from a composite dataset generated by registering and combining five separate CT datasets (four OBMH datasets plus the Boeing dataset). All CT data, regardless of source, were analyzed on 32- and 64-bit PC workstations with 4 GB of RAM and nVidia Quadro FX 3000 or 4500 video cards and running Microsoft Windows XP Professional, Windows XP Professional X64, or Linux 2.6.18 (Debian 4.0 distribution). In all cases, structures of interest (e.g., endocast, sinuses) were highlighted and digitally extracted using Amira’s segmentation tools for quantification and visualization. Both surfaces and volumes were generated and were used to illustrate this article. To facilitate discussion, we will refer to the digital casts of structures as if they were the structures themselves (e.g., ‘‘rostral middle cerebral vein’’ versus ‘‘digital cast of rostral middle cerebral vein’’).
</paragraph>
<caption id="DF0A70DFFF8BF944530F52F6EB01FF26" ID-Table-UUID="DF0A70DFFF8BF944530F52F6EB01FF26" box="[602,1030,152,173]" httpUri="http://table.plazi.org/id/DF0A70DFFF8BF944530F52F6EB01FF26" pageId="3" pageNumber="1269" startId="3.[602,686,152,173]" subCaptionStartIDs="3.[867,1030,152,173]" subCaptionStarts="abbr" targetBox="[160,1472,195,2007]" targetIsTable="true" targetPageId="3">
<paragraph id="8BCA2057FF8BF944530F52F6EB01FF26" blockId="3.[602,1030,152,173]" box="[602,1030,152,173]" pageId="3" pageNumber="1269">TABLE 2. Anatomical abbreviations</paragraph>
</caption>
<paragraph id="8BCA2057FF8BF94451F552ADEA85F85C" pageId="3" pageNumber="1269">
<table id="F975D2F7FF8B06B851F552ADEAC7F85C" box="[160,1472,195,2007]" gridcols="2" gridrows="75" pageId="3" pageNumber="1269">
<tr id="35452215FF8B06B851F552ADEAC7FF53" box="[160,1472,195,216]" gridrow="0" pageId="3" pageNumber="1269">
<th id="76944B69FF8B06B851F552ADEE2FFF53" box="[160,296,195,216]" gridcol="0" gridrow="0" pageId="3" pageNumber="1269">Abbreviation</th>
<th id="76944B69FF8B06B8535652ADEAC7FF53" box="[515,1472,195,216]" gridcol="1" gridrow="0" pageId="3" pageNumber="1269">Meaning of abbreviation</th>
</tr>
<tr id="35452215FF8B06B851F55287EAC7FF75" box="[160,1472,233,254]" gridrow="1" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55287EE2FFF75" box="[160,296,233,254]" gridcol="0" gridrow="1" pageId="3" pageNumber="1269">ad</td>
<td id="76944B69FF8B06B853565287EAC7FF75" box="[515,1472,233,254]" gridcol="1" gridrow="1" pageId="3" pageNumber="1269">ascending diverticulum of rostral tympanic recess</td>
</tr>
<tr id="35452215FF8B06B851F5536CEAC7FE9C" box="[160,1472,258,279]" gridrow="2" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5536CEE2FFE9C" box="[160,296,258,279]" gridcol="0" gridrow="2" pageId="3" pageNumber="1269">aoc</td>
<td id="76944B69FF8B06B85356536CEAC7FE9C" box="[515,1472,258,279]" gridcol="1" gridrow="2" pageId="3" pageNumber="1269">antotic crest</td>
</tr>
<tr id="35452215FF8B06B851F55374EAC7FEA4" box="[160,1472,282,303]" gridrow="3" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55374EE2FFEA4" box="[160,296,282,303]" gridcol="0" gridrow="3" pageId="3" pageNumber="1269">aw</td>
<td id="76944B69FF8B06B853565374EAC7FEA4" box="[515,1472,282,303]" gridcol="1" gridrow="3" pageId="3" pageNumber="1269">main airway through the nasal cavity</td>
</tr>
<tr id="35452215FF8B06B851F5535FEAC7FECD" box="[160,1472,305,326]" gridrow="4" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5535FEE2FFECD" box="[160,296,305,326]" gridcol="0" gridrow="4" pageId="3" pageNumber="1269">bsr</td>
<td id="76944B69FF8B06B85356535FEAC7FECD" box="[515,1472,305,326]" gridcol="1" gridrow="4" pageId="3" pageNumber="1269">basisphenoid recess (es)</td>
</tr>
<tr id="35452215FF8B06B851F55327EAC7FED5" box="[160,1472,329,350]" gridrow="5" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55327EE2FFED5" box="[160,296,329,350]" gridcol="0" gridrow="5" pageId="3" pageNumber="1269">bt</td>
<td id="76944B69FF8B06B853565327EAC7FED5" box="[515,1472,329,350]" gridcol="1" gridrow="5" pageId="3" pageNumber="1269">basal tubera</td>
</tr>
<tr id="35452215FF8B06B851F5530CEAC7FEFC" box="[160,1472,354,375]" gridrow="6" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5530CEE2FFEFC" box="[160,296,354,375]" gridcol="0" gridrow="6" pageId="3" pageNumber="1269">car</td>
<td id="76944B69FF8B06B85356530CEAC7FEFC" box="[515,1472,354,375]" gridcol="1" gridrow="6" pageId="3" pageNumber="1269">cerebral carotid artery canal</td>
</tr>
<tr id="35452215FF8B06B851F55314EAC7FE04" box="[160,1472,378,399]" gridrow="7" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55314EE2FFE04" box="[160,296,378,399]" gridcol="0" gridrow="7" pageId="3" pageNumber="1269">c</td>
<td id="76944B69FF8B06B853565314EAC7FE04" box="[515,1472,378,399]" gridcol="1" gridrow="7" pageId="3" pageNumber="1269">cochlear duct (= lagena)</td>
</tr>
<tr id="35452215FF8B06B851F553FFEAC7FE2D" box="[160,1472,401,422]" gridrow="8" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F553FFEE2FFE2D" box="[160,296,401,422]" gridcol="0" gridrow="8" pageId="3" pageNumber="1269">cc</td>
<td id="76944B69FF8B06B8535653FFEAC7FE2D" box="[515,1472,401,422]" gridcol="1" gridrow="8" pageId="3" pageNumber="1269">columellar canal</td>
</tr>
<tr id="35452215FF8B06B851F553C7EAC7FE35" box="[160,1472,425,446]" gridrow="9" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F553C7EE2FFE35" box="[160,296,425,446]" gridcol="0" gridrow="9" pageId="3" pageNumber="1269">cer</td>
<td id="76944B69FF8B06B8535653C7EAC7FE35" box="[515,1472,425,446]" gridcol="1" gridrow="9" pageId="3" pageNumber="1269">cerebral hemisphere</td>
</tr>
<tr id="35452215FF8B06B851F553ACEAC7FE5C" box="[160,1472,450,471]" gridrow="10" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F553ACEE2FFE5C" box="[160,296,450,471]" gridcol="0" gridrow="10" pageId="3" pageNumber="1269">col</td>
<td id="76944B69FF8B06B8535653ACEAC7FE5C" box="[515,1472,450,471]" gridcol="1" gridrow="10" pageId="3" pageNumber="1269">columella (= stapes)</td>
</tr>
<tr id="35452215FF8B06B851F553B4EAC7FE64" box="[160,1472,474,495]" gridrow="11" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F553B4EE2FFE64" box="[160,296,474,495]" gridcol="0" gridrow="11" pageId="3" pageNumber="1269">crc</td>
<td id="76944B69FF8B06B8535653B4EAC7FE64" box="[515,1472,474,495]" gridcol="1" gridrow="11" pageId="3" pageNumber="1269">crus communis</td>
</tr>
<tr id="35452215FF8B06B851F5539FEAC7FD8D" box="[160,1472,497,518]" gridrow="12" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5539FEE2FFD8D" box="[160,296,497,518]" gridcol="0" gridrow="12" pageId="3" pageNumber="1269">csc</td>
<td id="76944B69FF8B06B85356539FEAC7FD8D" box="[515,1472,497,518]" gridcol="1" gridrow="12" pageId="3" pageNumber="1269">caudal (posterior vertical) semicircular canal</td>
</tr>
<tr id="35452215FF8B06B851F55067EAC7FD95" box="[160,1472,521,542]" gridrow="13" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55067EE2FFD95" box="[160,296,521,542]" gridcol="0" gridrow="13" pageId="3" pageNumber="1269">csca</td>
<td id="76944B69FF8B06B853565067EAC7FD95" box="[515,1472,521,542]" gridcol="1" gridrow="13" pageId="3" pageNumber="1269">ampulla of caudal semicircular canal</td>
</tr>
<tr id="35452215FF8B06B851F5504CEAC7FDBC" box="[160,1472,546,567]" gridrow="14" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5504CEE2FFDBC" box="[160,296,546,567]" gridcol="0" gridrow="14" pageId="3" pageNumber="1269">ct</td>
<td id="76944B69FF8B06B85356504CEAC7FDBC" box="[515,1472,546,567]" gridcol="1" gridrow="14" pageId="3" pageNumber="1269">crista tuberalis, running between paroccipital process and basal tuber</td>
</tr>
<tr id="35452215FF8B06B851F55054EAC7FDC4" box="[160,1472,570,591]" gridrow="15" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55054EE2FFDC4" box="[160,296,570,591]" gridcol="0" gridrow="15" pageId="3" pageNumber="1269">ctc</td>
<td id="76944B69FF8B06B853565054EAC7FDC4" box="[515,1472,570,591]" gridcol="1" gridrow="15" pageId="3" pageNumber="1269">condylotuberal crest, running between occipital condylar neck and basal tuber</td>
</tr>
<tr id="35452215FF8B06B851F5503FEAC7FDED" box="[160,1472,593,614]" gridrow="16" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5503FEE2FFDED" box="[160,296,593,614]" gridcol="0" gridrow="16" pageId="3" pageNumber="1269">ctr</td>
<td id="76944B69FF8B06B85356503FEAC7FDED" box="[515,1472,593,614]" gridcol="1" gridrow="16" pageId="3" pageNumber="1269">caudal tympanic recess</td>
</tr>
<tr id="35452215FF8B06B851F55007EAC7FDF5" box="[160,1472,617,638]" gridrow="17" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55007EE2FFDF5" box="[160,296,617,638]" gridcol="0" gridrow="17" pageId="3" pageNumber="1269">ctra</td>
<td id="76944B69FF8B06B853565007EAC7FDF5" box="[515,1472,617,638]" gridcol="1" gridrow="17" pageId="3" pageNumber="1269">bony aperture of caudal tympanic recess</td>
</tr>
<tr id="35452215FF8B06B851F550ECEAC7FD1C" box="[160,1472,642,663]" gridrow="18" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F550ECEE2FFD1C" box="[160,296,642,663]" gridcol="0" gridrow="18" pageId="3" pageNumber="1269">cvcm</td>
<td id="76944B69FF8B06B8535650ECEAC7FD1C" box="[515,1472,642,663]" gridcol="1" gridrow="18" pageId="3" pageNumber="1269">caudal middle cerebral vein</td>
</tr>
<tr id="35452215FF8B06B851F550F4EAC7FD24" box="[160,1472,666,687]" gridrow="19" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F550F4EE2FFD24" box="[160,296,666,687]" gridcol="0" gridrow="19" pageId="3" pageNumber="1269">dp</td>
<td id="76944B69FF8B06B8535650F4EAC7FD24" box="[515,1472,666,687]" gridcol="1" gridrow="19" pageId="3" pageNumber="1269">dural peak</td>
</tr>
<tr id="35452215FF8B06B851F550DFEAC7FD4D" box="[160,1472,689,710]" gridrow="20" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F550DFEE2FFD4D" box="[160,296,689,710]" gridcol="0" gridrow="20" pageId="3" pageNumber="1269">dv</td>
<td id="76944B69FF8B06B8535650DFEAC7FD4D" box="[515,1472,689,710]" gridcol="1" gridrow="20" pageId="3" pageNumber="1269">diploic vein draining bone tissue</td>
</tr>
<tr id="35452215FF8B06B851F550A7EAC7FD55" box="[160,1472,713,734]" gridrow="21" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F550A7EE2FFD55" box="[160,296,713,734]" gridcol="0" gridrow="21" pageId="3" pageNumber="1269">ed</td>
<td id="76944B69FF8B06B8535650A7EAC7FD55" box="[515,1472,713,734]" gridcol="1" gridrow="21" pageId="3" pageNumber="1269">endolymphatic duct canal</td>
</tr>
<tr id="35452215FF8B06B851F5508CEAC7FD7C" box="[160,1472,738,759]" gridrow="22" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5508CEE2FFD7C" box="[160,296,738,759]" gridcol="0" gridrow="22" pageId="3" pageNumber="1269">epif</td>
<td id="76944B69FF8B06B85356508CEAC7FD7C" box="[515,1472,738,759]" gridcol="1" gridrow="22" pageId="3" pageNumber="1269">articular facet for epipterygoid bone</td>
</tr>
<tr id="35452215FF8B06B851F55094EAC7FC84" box="[160,1472,762,783]" gridrow="23" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55094EE2FFC84" box="[160,296,762,783]" gridcol="0" gridrow="23" pageId="3" pageNumber="1269">fc</td>
<td id="76944B69FF8B06B853565094EAC7FC84" box="[515,1472,762,783]" gridcol="1" gridrow="23" pageId="3" pageNumber="1269">fenestra cochleae (= round window)</td>
</tr>
<tr id="35452215FF8B06B851F5517FEAC7FCAD" box="[160,1472,785,806]" gridrow="24" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5517FEE2FFCAD" box="[160,296,785,806]" gridcol="0" gridrow="24" pageId="3" pageNumber="1269">fl</td>
<td id="76944B69FF8B06B85356517FEAC7FCAD" box="[515,1472,785,806]" gridcol="1" gridrow="24" pageId="3" pageNumber="1269">flocculus (= cerebellar auricle)</td>
</tr>
<tr id="35452215FF8B06B851F55147EAC7FCB5" box="[160,1472,809,830]" gridrow="25" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55147EE2FFCB5" box="[160,296,809,830]" gridcol="0" gridrow="25" pageId="3" pageNumber="1269">fm</td>
<td id="76944B69FF8B06B853565147EAC7FCB5" box="[515,1472,809,830]" gridcol="1" gridrow="25" pageId="3" pageNumber="1269">foramen magnum</td>
</tr>
<tr id="35452215FF8B06B851F5512CEAC7FCDC" box="[160,1472,834,855]" gridrow="26" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5512CEE2FFCDC" box="[160,296,834,855]" gridcol="0" gridrow="26" pageId="3" pageNumber="1269">fv</td>
<td id="76944B69FF8B06B85356512CEAC7FCDC" box="[515,1472,834,855]" gridcol="1" gridrow="26" pageId="3" pageNumber="1269">fenestra vestibuli (= oval window)</td>
</tr>
<tr id="35452215FF8B06B851F55134EAC7FCE4" box="[160,1472,858,879]" gridrow="27" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55134EE2FFCE4" box="[160,296,858,879]" gridcol="0" gridrow="27" pageId="3" pageNumber="1269">gps</td>
<td id="76944B69FF8B06B853565134EAC7FCE4" box="[515,1472,858,879]" gridcol="1" gridrow="27" pageId="3" pageNumber="1269">glossopharyngeal sulcus</td>
</tr>
<tr id="35452215FF8B06B851F5511FEAC7FC0D" box="[160,1472,881,902]" gridrow="28" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5511FEE2FFC0D" box="[160,296,881,902]" gridcol="0" gridrow="28" pageId="3" pageNumber="1269">ibtl</td>
<td id="76944B69FF8B06B85356511FEAC7FC0D" box="[515,1472,881,902]" gridcol="1" gridrow="28" pageId="3" pageNumber="1269">interbasipterygoidal lamina, running between basipterygoid processes</td>
</tr>
<tr id="35452215FF8B06B851F551E4EAC7FC14" box="[160,1472,906,927]" gridrow="29" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F551E4EE2FFC14" box="[160,296,906,927]" gridcol="0" gridrow="29" pageId="3" pageNumber="1269">itl</td>
<td id="76944B69FF8B06B8535651E4EAC7FC14" box="[515,1472,906,927]" gridcol="1" gridrow="29" pageId="3" pageNumber="1269">intertuberal lamina, running between basal tubera</td>
</tr>
<tr id="35452215FF8B06B851F551CCEAC7FC3C" box="[160,1472,930,951]" gridrow="30" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F551CCEE2FFC3C" box="[160,296,930,951]" gridcol="0" gridrow="30" pageId="3" pageNumber="1269">lab</td>
<td id="76944B69FF8B06B8535651CCEAC7FC3C" box="[515,1472,930,951]" gridcol="1" gridrow="30" pageId="3" pageNumber="1269">endosseous labyrinth</td>
</tr>
<tr id="35452215FF8B06B851F551D4EAC7FC44" box="[160,1472,954,975]" gridrow="31" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F551D4EE2FFC44" box="[160,296,954,975]" gridcol="0" gridrow="31" pageId="3" pageNumber="1269">lsc</td>
<td id="76944B69FF8B06B8535651D4EAC7FC44" box="[515,1472,954,975]" gridcol="1" gridrow="31" pageId="3" pageNumber="1269">lateral (horizontal) semicircular canal</td>
</tr>
<tr id="35452215FF8B06B851F551BFEAC7FC6D" box="[160,1472,977,998]" gridrow="32" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F551BFEE2FFC6D" box="[160,296,977,998]" gridcol="0" gridrow="32" pageId="3" pageNumber="1269">lsca</td>
<td id="76944B69FF8B06B8535651BFEAC7FC6D" box="[515,1472,977,998]" gridcol="1" gridrow="32" pageId="3" pageNumber="1269">ampulla of lateral semicircular canal</td>
</tr>
<tr id="35452215FF8B06B851F55184EAC7FC74" box="[160,1472,1002,1023]" gridrow="33" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55184EE2FFC74" box="[160,296,1002,1023]" gridcol="0" gridrow="33" pageId="3" pageNumber="1269">lscr</td>
<td id="76944B69FF8B06B853565184EAC7FC74" box="[515,1472,1002,1023]" gridcol="1" gridrow="33" pageId="3" pageNumber="1269">lateral subcondylar recess</td>
</tr>
<tr id="35452215FF8B06B851F5566CEAC7FB9C" box="[160,1472,1026,1047]" gridrow="34" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5566CEE2FFB9C" box="[160,296,1026,1047]" gridcol="0" gridrow="34" pageId="3" pageNumber="1269">mes</td>
<td id="76944B69FF8B06B85356566CEAC7FB9C" box="[515,1472,1026,1047]" gridcol="1" gridrow="34" pageId="3" pageNumber="1269">mesethmoid ossification</td>
</tr>
<tr id="35452215FF8B06B851F55674EAC7FBA4" box="[160,1472,1050,1071]" gridrow="35" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55674EE2FFBA4" box="[160,296,1050,1071]" gridcol="0" gridrow="35" pageId="3" pageNumber="1269">mscr</td>
<td id="76944B69FF8B06B853565674EAC7FBA4" box="[515,1472,1050,1071]" gridcol="1" gridrow="35" pageId="3" pageNumber="1269">medial subcondylar recess</td>
</tr>
<tr id="35452215FF8B06B851F5565FEAC7FBCD" box="[160,1472,1073,1094]" gridrow="36" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5565FEE2FFBCD" box="[160,296,1073,1094]" gridcol="0" gridrow="36" pageId="3" pageNumber="1269">ob</td>
<td id="76944B69FF8B06B85356565FEAC7FBCD" box="[515,1472,1073,1094]" gridcol="1" gridrow="36" pageId="3" pageNumber="1269">olfactory bulb</td>
</tr>
<tr id="35452215FF8B06B851F55624EAC7FBD4" box="[160,1472,1098,1119]" gridrow="37" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55624EE2FFBD4" box="[160,296,1098,1119]" gridcol="0" gridrow="37" pageId="3" pageNumber="1269">oevc</td>
<td id="76944B69FF8B06B853565624EAC7FBD4" box="[515,1472,1098,1119]" gridcol="1" gridrow="37" pageId="3" pageNumber="1269">orbital emissary vein canal</td>
</tr>
<tr id="35452215FF8B06B851F5560CEAC7FBFC" box="[160,1472,1122,1143]" gridrow="38" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5560CEE2FFBFC" box="[160,296,1122,1143]" gridcol="0" gridrow="38" pageId="3" pageNumber="1269">olf</td>
<td id="76944B69FF8B06B85356560CEAC7FBFC" box="[515,1472,1122,1143]" gridcol="1" gridrow="38" pageId="3" pageNumber="1269">olfactory region of nasal cavity</td>
</tr>
<tr id="35452215FF8B06B851F55614EAC7FB04" box="[160,1472,1146,1167]" gridrow="39" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55614EE2FFB04" box="[160,296,1146,1167]" gridcol="0" gridrow="39" pageId="3" pageNumber="1269">ons</td>
<td id="76944B69FF8B06B853565614EAC7FB04" box="[515,1472,1146,1167]" gridcol="1" gridrow="39" pageId="3" pageNumber="1269">sulcus (or sulci) for olfactory nerve branches and associated vessels</td>
</tr>
<tr id="35452215FF8B06B851F556FFEAC7FB2D" box="[160,1472,1169,1190]" gridrow="40" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F556FFEE2FFB2D" box="[160,296,1169,1190]" gridcol="0" gridrow="40" pageId="3" pageNumber="1269">opt</td>
<td id="76944B69FF8B06B8535656FFEAC7FB2D" box="[515,1472,1169,1190]" gridcol="1" gridrow="40" pageId="3" pageNumber="1269">optic lobe (= tectum)</td>
</tr>
<tr id="35452215FF8B06B851F556C4EAC7FB34" box="[160,1472,1194,1215]" gridrow="41" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F556C4EE2FFB34" box="[160,296,1194,1215]" gridcol="0" gridrow="41" pageId="3" pageNumber="1269">ot</td>
<td id="76944B69FF8B06B8535656C4EAC7FB34" box="[515,1472,1194,1215]" gridcol="1" gridrow="41" pageId="3" pageNumber="1269">olfactory turbinates</td>
</tr>
<tr id="35452215FF8B06B851F556ACEAC7FB5C" box="[160,1472,1218,1239]" gridrow="42" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F556ACEE2FFB5C" box="[160,296,1218,1239]" gridcol="0" gridrow="42" pageId="3" pageNumber="1269">otc</td>
<td id="76944B69FF8B06B8535656ACEAC7FB5C" box="[515,1472,1218,1239]" gridcol="1" gridrow="42" pageId="3" pageNumber="1269">olfactory tract cavity</td>
</tr>
<tr id="35452215FF8B06B851F556B4EAC7FB64" box="[160,1472,1242,1263]" gridrow="43" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F556B4EE2FFB64" box="[160,296,1242,1263]" gridcol="0" gridrow="43" pageId="3" pageNumber="1269">ovc</td>
<td id="76944B69FF8B06B8535656B4EAC7FB64" box="[515,1472,1242,1263]" gridcol="1" gridrow="43" pageId="3" pageNumber="1269">orbital venous canal, running from olfactory region of nasal cavity into the orbit</td>
</tr>
<tr id="35452215FF8B06B851F5569FEAC7FA8D" box="[160,1472,1265,1286]" gridrow="44" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5569FEE2FFA8D" box="[160,296,1265,1286]" gridcol="0" gridrow="44" pageId="3" pageNumber="1269">pfo</td>
<td id="76944B69FF8B06B85356569FEAC7FA8D" box="[515,1472,1265,1286]" gridcol="1" gridrow="44" pageId="3" pageNumber="1269">pituitary (= hypophyseal) fossa</td>
</tr>
<tr id="35452215FF8B06B851F55764EAC7FA94" box="[160,1472,1290,1311]" gridrow="45" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55764EE2FFA94" box="[160,296,1290,1311]" gridcol="0" gridrow="45" pageId="3" pageNumber="1269">pin</td>
<td id="76944B69FF8B06B853565764EAC7FA94" box="[515,1472,1290,1311]" gridcol="1" gridrow="45" pageId="3" pageNumber="1269">pineal peak</td>
</tr>
<tr id="35452215FF8B06B851F5574CEAC7FABC" box="[160,1472,1314,1335]" gridrow="46" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5574CEE2FFABC" box="[160,296,1314,1335]" gridcol="0" gridrow="46" pageId="3" pageNumber="1269">prp</td>
<td id="76944B69FF8B06B85356574CEAC7FABC" box="[515,1472,1314,1335]" gridcol="1" gridrow="46" pageId="3" pageNumber="1269">preotic pendant</td>
</tr>
<tr id="35452215FF8B06B851F55754EAC7FAC4" box="[160,1472,1338,1359]" gridrow="47" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55754EE2FFAC4" box="[160,296,1338,1359]" gridcol="0" gridrow="47" pageId="3" pageNumber="1269">prpn</td>
<td id="76944B69FF8B06B853565754EAC7FAC4" box="[515,1472,1338,1359]" gridcol="1" gridrow="47" pageId="3" pageNumber="1269">prootic pneumatic fossa</td>
</tr>
<tr id="35452215FF8B06B851F5573FEAC7FAED" box="[160,1472,1361,1382]" gridrow="48" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5573FEE2FFAED" box="[160,296,1361,1382]" gridcol="0" gridrow="48" pageId="3" pageNumber="1269">rhs</td>
<td id="76944B69FF8B06B85356573FEAC7FAED" box="[515,1472,1361,1382]" gridcol="1" gridrow="48" pageId="3" pageNumber="1269">retrohypophyseal pneumatic sinus</td>
</tr>
<tr id="35452215FF8B06B851F55704EAC7FAF4" box="[160,1472,1386,1407]" gridrow="49" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55704EE2FFAF4" box="[160,296,1386,1407]" gridcol="0" gridrow="49" pageId="3" pageNumber="1269">rsc</td>
<td id="76944B69FF8B06B853565704EAC7FAF4" box="[515,1472,1386,1407]" gridcol="1" gridrow="49" pageId="3" pageNumber="1269">rostral (anterior vertical) semicircular canal</td>
</tr>
<tr id="35452215FF8B06B851F557ECEAC7FA1C" box="[160,1472,1410,1431]" gridrow="50" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F557ECEE2FFA1C" box="[160,296,1410,1431]" gridcol="0" gridrow="50" pageId="3" pageNumber="1269">rsca</td>
<td id="76944B69FF8B06B8535657ECEAC7FA1C" box="[515,1472,1410,1431]" gridcol="1" gridrow="50" pageId="3" pageNumber="1269">ampulla of rostral semicircular canal</td>
</tr>
<tr id="35452215FF8B06B851F557F4EAC7FA24" box="[160,1472,1434,1455]" gridrow="51" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F557F4EE2FFA24" box="[160,296,1434,1455]" gridcol="0" gridrow="51" pageId="3" pageNumber="1269">rtr</td>
<td id="76944B69FF8B06B8535657F4EAC7FA24" box="[515,1472,1434,1455]" gridcol="1" gridrow="51" pageId="3" pageNumber="1269">rostral tympanic recess</td>
</tr>
<tr id="35452215FF8B06B851F557DFEAC7FA4D" box="[160,1472,1457,1478]" gridrow="52" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F557DFEE2FFA4D" box="[160,296,1457,1478]" gridcol="0" gridrow="52" pageId="3" pageNumber="1269">rvcm</td>
<td id="76944B69FF8B06B8535657DFEAC7FA4D" box="[515,1472,1457,1478]" gridcol="1" gridrow="52" pageId="3" pageNumber="1269">rostral middle cerebral vein</td>
</tr>
<tr id="35452215FF8B06B851F557A4EAC7FA54" box="[160,1472,1482,1503]" gridrow="53" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F557A4EE2FFA54" box="[160,296,1482,1503]" gridcol="0" gridrow="53" pageId="3" pageNumber="1269">sin</td>
<td id="76944B69FF8B06B8535657A4EAC7FA54" box="[515,1472,1482,1503]" gridcol="1" gridrow="53" pageId="3" pageNumber="1269">blind dural venous sinus of hindbrain</td>
</tr>
<tr id="35452215FF8B06B851F5578CEAC7FA7C" box="[160,1472,1506,1527]" gridrow="54" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5578CEE2FFA7C" box="[160,296,1506,1527]" gridcol="0" gridrow="54" pageId="3" pageNumber="1269">socs</td>
<td id="76944B69FF8B06B85356578CEAC7FA7C" box="[515,1472,1506,1527]" gridcol="1" gridrow="54" pageId="3" pageNumber="1269">supraoccipital pneumatic sinuses</td>
</tr>
<tr id="35452215FF8B06B851F55794EAC7F984" box="[160,1472,1530,1551]" gridrow="55" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55794EE2FF984" box="[160,296,1530,1551]" gridcol="0" gridrow="55" pageId="3" pageNumber="1269">ssr</td>
<td id="76944B69FF8B06B853565794EAC7F984" box="[515,1472,1530,1551]" gridcol="1" gridrow="55" pageId="3" pageNumber="1269">subsellar recess</td>
</tr>
<tr id="35452215FF8B06B851F5547FEAC7F9AD" box="[160,1472,1553,1574]" gridrow="56" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5547FEE2FF9AD" box="[160,296,1553,1574]" gridcol="0" gridrow="56" pageId="3" pageNumber="1269">ts</td>
<td id="76944B69FF8B06B85356547FEAC7F9AD" box="[515,1472,1553,1574]" gridcol="1" gridrow="56" pageId="3" pageNumber="1269">transverse sinus</td>
</tr>
<tr id="35452215FF8B06B851F55444EAC7F9B4" box="[160,1472,1578,1599]" gridrow="57" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55444EE2FF9B4" box="[160,296,1578,1599]" gridcol="0" gridrow="57" pageId="3" pageNumber="1269">vcd</td>
<td id="76944B69FF8B06B853565444EAC7F9B4" box="[515,1472,1578,1599]" gridcol="1" gridrow="57" pageId="3" pageNumber="1269">dorsal head vein</td>
</tr>
<tr id="35452215FF8B06B851F5542CEAC7F9DC" box="[160,1472,1602,1623]" gridrow="58" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5542CEE2FF9DC" box="[160,296,1602,1623]" gridcol="0" gridrow="58" pageId="3" pageNumber="1269">ve</td>
<td id="76944B69FF8B06B85356542CEAC7F9DC" box="[515,1472,1602,1623]" gridcol="1" gridrow="58" pageId="3" pageNumber="1269">vestibule of inner ear</td>
</tr>
<tr id="35452215FF8B06B851F55434EAC7F9E4" box="[160,1472,1626,1647]" gridrow="59" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55434EE2FF9E4" box="[160,296,1626,1647]" gridcol="0" gridrow="59" pageId="3" pageNumber="1269">vg</td>
<td id="76944B69FF8B06B853565434EAC7F9E4" box="[515,1472,1626,1647]" gridcol="1" gridrow="59" pageId="3" pageNumber="1269">fine vascular grooves on endocranial surface</td>
</tr>
<tr id="35452215FF8B06B851F5541FEAC7F90D" box="[160,1472,1649,1670]" gridrow="60" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5541FEE2FF90D" box="[160,296,1649,1670]" gridcol="0" gridrow="60" pageId="3" pageNumber="1269">II</td>
<td id="76944B69FF8B06B85356541FEAC7F90D" box="[515,1472,1649,1670]" gridcol="1" gridrow="60" pageId="3" pageNumber="1269">optic nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F554E4EAC7F914" box="[160,1472,1674,1695]" gridrow="61" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F554E4EE2FF914" box="[160,296,1674,1695]" gridcol="0" gridrow="61" pageId="3" pageNumber="1269">III</td>
<td id="76944B69FF8B06B8535654E4EAC7F914" box="[515,1472,1674,1695]" gridcol="1" gridrow="61" pageId="3" pageNumber="1269">oculomotor nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F554CCEAC7F93C" box="[160,1472,1698,1719]" gridrow="62" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F554CCEE2FF93C" box="[160,296,1698,1719]" gridcol="0" gridrow="62" pageId="3" pageNumber="1269">IV</td>
<td id="76944B69FF8B06B8535654CCEAC7F93C" box="[515,1472,1698,1719]" gridcol="1" gridrow="62" pageId="3" pageNumber="1269">trochlear nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F554D4EAC7F95A" box="[160,1472,1722,1745]" gridrow="63" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F554D4EE2FF95A" box="[160,296,1722,1745]" gridcol="0" gridrow="63" pageId="3" pageNumber="1269">V1</td>
<td id="76944B69FF8B06B8535654D4EAC7F95A" box="[515,1472,1722,1745]" gridcol="1" gridrow="63" pageId="3" pageNumber="1269">ophthalmic nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F554BFEAC7F962" box="[160,1472,1745,1769]" gridrow="64" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F554BFEE2FF962" box="[160,296,1745,1769]" gridcol="0" gridrow="64" pageId="3" pageNumber="1269">V2–3</td>
<td id="76944B69FF8B06B8535654BFEAC7F962" box="[515,1472,1745,1769]" gridcol="1" gridrow="64" pageId="3" pageNumber="1269">maxillomandibular nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F55487EAC7F88A" box="[160,1472,1769,1793]" gridrow="65" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55487EE2FF88A" box="[160,296,1769,1793]" gridcol="0" gridrow="65" pageId="3" pageNumber="1269">V2–3/VII</td>
<td id="76944B69FF8B06B853565487EAC7F88A" box="[515,1472,1769,1793]" gridcol="1" gridrow="65" pageId="3" pageNumber="1269">common external opening in braincase for maxillomandibular and facial nerve canals</td>
</tr>
<tr id="35452215FF8B06B851F5556CEAC7F89C" box="[160,1472,1794,1815]" gridrow="66" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5556CEE2FF89C" box="[160,296,1794,1815]" gridcol="0" gridrow="66" pageId="3" pageNumber="1269">VI</td>
<td id="76944B69FF8B06B85356556CEAC7F89C" box="[515,1472,1794,1815]" gridcol="1" gridrow="66" pageId="3" pageNumber="1269">abducens nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F55574EAC7F8A4" box="[160,1472,1818,1839]" gridrow="67" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55574EE2FF8A4" box="[160,296,1818,1839]" gridcol="0" gridrow="67" pageId="3" pageNumber="1269">VII</td>
<td id="76944B69FF8B06B853565574EAC7F8A4" box="[515,1472,1818,1839]" gridcol="1" gridrow="67" pageId="3" pageNumber="1269">facial nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F5555FEAC7F8C2" box="[160,1472,1841,1865]" gridrow="68" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5555FEE2FF8C2" box="[160,296,1841,1865]" gridcol="0" gridrow="68" pageId="3" pageNumber="1269">VIIpal</td>
<td id="76944B69FF8B06B85356555FEAC7F8C2" box="[515,1472,1841,1865]" gridcol="1" gridrow="68" pageId="3" pageNumber="1269">canal for palatine branch of facial nerve</td>
</tr>
<tr id="35452215FF8B06B851F55527EAC7F8D5" box="[160,1472,1865,1886]" gridrow="69" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55527EE2FF8D5" box="[160,296,1865,1886]" gridcol="0" gridrow="69" pageId="3" pageNumber="1269">VIII</td>
<td id="76944B69FF8B06B853565527EAC7F8D5" box="[515,1472,1865,1886]" gridcol="1" gridrow="69" pageId="3" pageNumber="1269">vestibulocochlear nerve canals</td>
</tr>
<tr id="35452215FF8B06B851F5550CEAC7F8FC" box="[160,1472,1890,1911]" gridrow="70" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F5550CEE2FF8FC" box="[160,296,1890,1911]" gridcol="0" gridrow="70" pageId="3" pageNumber="1269">IX</td>
<td id="76944B69FF8B06B85356550CEAC7F8FC" box="[515,1472,1890,1911]" gridcol="1" gridrow="70" pageId="3" pageNumber="1269">glossopharyngeal nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F55514EAC7F804" box="[160,1472,1914,1935]" gridrow="71" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F55514EE2FF804" box="[160,296,1914,1935]" gridcol="0" gridrow="71" pageId="3" pageNumber="1269">IX–XI</td>
<td id="76944B69FF8B06B853565514EAC7F804" box="[515,1472,1914,1935]" gridcol="1" gridrow="71" pageId="3" pageNumber="1269">shared canal for glossopharyngeal, vagus, and accessory nerves and accompanying vessels</td>
</tr>
<tr id="35452215FF8B06B851F555FFEAC7F82D" box="[160,1472,1937,1958]" gridrow="72" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F555FFEE2FF82D" box="[160,296,1937,1958]" gridcol="0" gridrow="72" pageId="3" pageNumber="1269">X</td>
<td id="76944B69FF8B06B8535655FFEAC7F82D" box="[515,1472,1937,1958]" gridcol="1" gridrow="72" pageId="3" pageNumber="1269">vagus nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F555C7EAC7F835" box="[160,1472,1961,1982]" gridrow="73" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F555C7EE2FF835" box="[160,296,1961,1982]" gridcol="0" gridrow="73" pageId="3" pageNumber="1269">XII</td>
<td id="76944B69FF8B06B8535655C7EAC7F835" box="[515,1472,1961,1982]" gridcol="1" gridrow="73" pageId="3" pageNumber="1269">hypoglossal nerve canal</td>
</tr>
<tr id="35452215FF8B06B851F555ACEAC7F85C" box="[160,1472,1986,2007]" gridrow="74" pageId="3" pageNumber="1269">
<td id="76944B69FF8B06B851F555ACEE2FF85C" box="[160,296,1986,2007]" gridcol="0" gridrow="74" pageId="3" pageNumber="1269">?</td>
<td id="76944B69FF8B06B8535655ACEAC7F85C" box="[515,1472,1986,2007]" gridcol="1" gridrow="74" pageId="3" pageNumber="1269">
canal found in some 
<taxonomicName id="4C755BD4FF8BF944538A55ACEC1DF85C" authorityName="Osborn" authorityYear="1905" box="[735,794,1986,2007]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="3" pageNumber="1269" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8BF944538A55ACEC1DF85C" box="[735,794,1986,2007]" italics="true" pageId="3" pageNumber="1269">T. rex</emphasis>
</taxonomicName>
, may be an accessory hypoglossal canal or a venous canal
</td>
</tr>
</table>
</paragraph>
<paragraph id="8BCA2057FF8CF94351ED50FEEE72FA20" blockId="4.[160,800,230,1692]" pageId="4" pageNumber="1270">
The research presented here is part of our larger project on the evolution of the brain cavity and ear regions in archosaurs, and thus we have data comparable to those presented here for a range of outgroup taxa. From this larger sample, we selected a few for comparison and illustration. Outgroup coelurosaur taxa include 
<emphasis id="B901FC45FF8CF94353EE5178EE28FCCE" italics="true" pageId="4" pageNumber="1270">Struthiomimus altus</emphasis>
(TMP 90.26.1, AMNH FR 5355), 
<emphasis id="B901FC45FF8CF94353E8515FEE6BFCEB" italics="true" pageId="4" pageNumber="1270">
<taxonomicName id="4C755BD4FF8CF94353E8515FEFD4FCEB" authorityName="Ostrom" authorityYear="1969" class="Reptilia" family="Dromaeosauridae" genus="Deinonychus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Deinonychus</taxonomicName>
antirrhopus
</emphasis>
(MOR 747, frontal, parietal, and laterosphenoids; OMNH 50268, occiput and prootic; ventral endocast restored based on 
<emphasis id="B901FC45FF8CF943534C51EFEDDDFC1D" box="[537,730,897,918]" italics="true" pageId="4" pageNumber="1270">
<taxonomicName id="4C755BD4FF8CF943534C51EFED70FC1D" box="[537,631,897,918]" class="Reptilia" family="Dromaeosauridae" genus="Tsaagan" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Tsaagan</taxonomicName>
mangas
</emphasis>
, IGM 100/1015), 
<emphasis id="B901FC45FF8CF943504851F5EEE1FC3B" box="[285,486,923,944]" italics="true" pageId="4" pageNumber="1270">
<taxonomicName id="4C755BD4FF8CF943504851F5EE7FFC3B" authorityName="Leidy" authorityYear="1856" box="[285,376,923,944]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Troodon</taxonomicName>
formosus
</emphasis>
(TMP 86.36.457, braincase lacking skull roof; TMP 79.8.1, skull roof), and 
<emphasis id="B901FC45FF8CF943539F51D8EE8AFC6E" italics="true" pageId="4" pageNumber="1270">Archaeopteryx lithographica</emphasis>
(BMNH 37001). Noncoelurosaurian outgroups include 
<emphasis id="B901FC45FF8CF94350265185ED41FB8B" box="[371,582,1003,1024]" italics="true" pageId="4" pageNumber="1270">
<taxonomicName id="4C755BD4FF8CF94350265185EEECFB8B" authorityName="Marsh" authorityYear="1877" box="[371,491,1003,1024]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Allosaurus</taxonomicName>
fragilis
</emphasis>
(UMNH VP 18050 [formerly UUVP 3304]) and 
<emphasis id="B901FC45FF8CF94350A45668EFC8FBBD" italics="true" pageId="4" pageNumber="1270">
<taxonomicName id="4C755BD4FF8CF94350A45668EDA6FB90" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[497,673,1030,1051]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Majungasaurus</taxonomicName>
crenatissimus
</emphasis>
(FMNH PR2100; see also 
<bibRefCitation id="EFE45DA6FF8CF943534E564EEFDFFBDB" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="4" pageNumber="1270" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF94351B35655ED18FBDA" author="Witmer LM &amp; Ridgely RC" box="[230,543,1083,1105]" firstAuthor="Witmer" journalOrPublisher="Anat Rec" pageId="4" pageNumber="1270" pagination="1362 - 1388" part="291" refId="ref24295" refString="Witmer LM, Ridgely RC. 2008 b. The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture. Anat Rec 291: 1362 - 1388." title="The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture" type="journal article" year="2008" yearSuffix="b">Witmer and Ridgely, 2008b</bibRefCitation>
). All of the above represent 
<emphasis id="B901FC45FF8CF94351A45638EE4DFBE0" box="[241,330,1110,1131]" italics="true" pageId="4" pageNumber="1270">de novo</emphasis>
endocasts based on new scanning, with the exception of 
<emphasis id="B901FC45FF8CF943500E561EEEFFFB0E" box="[347,504,1136,1157]" italics="true" pageId="4" pageNumber="1270">Archaeopteryx</emphasis>
from which we generated an endocast 
<emphasis id="B901FC45FF8CF943506756E5EE8EFB2B" box="[306,393,1163,1184]" italics="true" pageId="4" pageNumber="1270">de novo</emphasis>
from the scan data used by 
<bibRefCitation id="EFE45DA6FF8CF943538956E5EEC2FB37" author="Dominguez Alonso P &amp; Milner AC &amp; Ketcham RA &amp; Cookson MJ &amp; Rowe TB" etAl="et al." firstAuthor="Dominguez Alonso" journalOrPublisher="Nature" pageId="4" pageNumber="1270" pagination="666 - 669" part="430" refId="ref20788" refString="Dominguez Alonso P, Milner AC, Ketcham RA, Cookson MJ, Rowe TB. 2004. The avian nature of the brain and inner ear of Archaeopteryx. Nature 430: 666 - 669." title="The avian nature of the brain and inner ear of Archaeopteryx" type="journal article" year="2004">Domínguez Alonso et al. (2004)</bibRefCitation>
. The 
<taxonomicName id="4C755BD4FF8CF943535756C8ED7DFB30" authorityName="Marsh" authorityYear="1877" box="[514,634,1190,1211]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8CF943535756C8ED7DFB30" box="[514,634,1190,1211]" italics="true" pageId="4" pageNumber="1270">Allosaurus</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF8CF94353E156C8EFECFB5D" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8CF94353E156C8EFECFB5D" italics="true" pageId="4" pageNumber="1270">Majungasaurus</emphasis>
</taxonomicName>
braincases were scanned at OBMH using parameters similar to those listed above. 
<emphasis id="B901FC45FF8CF943532256B5EC27FB7B" box="[631,800,1243,1264]" italics="true" pageId="4" pageNumber="1270">Struthiomimus</emphasis>
was scanned at the high-resolution X-ray CT Facility at the University of Texas at Austin at a slice thickness of 312 µm. The 
<emphasis id="B901FC45FF8CF943506F5745ED30FACA" box="[314,567,1323,1345]" italics="true" pageId="4" pageNumber="1270">
<taxonomicName id="4C755BD4FF8CF943506F5745EECCFACB" authorityName="Ostrom" authorityYear="1969" box="[314,459,1323,1344]" class="Reptilia" family="Dromaeosauridae" genus="Deinonychus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Deinonychus</taxonomicName>
, 
<taxonomicName id="4C755BD4FF8CF943508C5742ED30FACA" box="[473,567,1324,1345]" class="Reptilia" family="Dromaeosauridae" genus="Tsaagan" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">Tsaagan</taxonomicName>
</emphasis>
, and 
<taxonomicName id="4C755BD4FF8CF94353295745EDD0FACB" authorityName="Leidy" authorityYear="1856" box="[636,727,1323,1344]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8CF94353295745EDD0FACB" box="[636,727,1323,1344]" italics="true" pageId="4" pageNumber="1270">Troodon</emphasis>
</taxonomicName>
specimens were scanned at the Ohio University MicroCT Scanning Facility (OUµCT) on a GE eXplore Locus MicroCT Scanner at slice thicknesses of 92 and 45 µm, 80 kV, and 500 µA.
</paragraph>
<paragraph id="8BCA2057FF8CF94351ED57DEEE2EF917" blockId="4.[160,800,230,1692]" pageId="4" pageNumber="1270">
An endocast was generated photographically from the sagittally sectioned braincase (
<materialsCitation id="3B1D2A0AFF8CF94350A957A5EDBFFA6A" ID-GBIF-Occurrence="2813094342" box="[508,696,1483,1505]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
; 
<figureCitation id="134E3CD2FF8CF943539057A5EC1EFA6B" box="[709,793,1483,1505]" captionStart="Fig" captionStartId="17.[354,384,1661,1680]" captionTargetBox="[175,1458,229,1630]" captionTargetId="figure@17.[175,1458,229,1630]" captionTargetPageId="17" captionText="Fig. 7. Endocranial region of Tyrannosaurus rex (actual fossil specimen of AMNH FR 5029, sagittally sec- tioned) in left medial view to show the fine vascular grooves on the endocranial surface.A, Labeled view show- ing the whole endocranial cavity. B, Close-up view with reversed stereopairs such that the endocranial cavity looks ‘‘filled,’’ making the view more comparable to the digital endocasts illustrated elsewhere in this article." figureDoi="http://doi.org/10.5281/zenodo.3942793" httpUri="https://zenodo.org/record/3942793/files/figure.png" pageId="4" pageNumber="1270">Fig. 7B</figureCitation>
) by taking standard stereophotographs and swapping the images left for right. Swapping the images changes the perspective from being a cavity (a negative) to being a volume (a positive). Although perhaps an unorthodox way of viewing the fossil specimen, it provides better comparability to the digital endocasts otherwise presented here.
</paragraph>
<paragraph id="8BCA2057FF8CF94350CA548CED26F971" blockId="4.[160,800,1762,1958]" box="[415,545,1762,1786]" pageId="4" pageNumber="1270">
<heading id="D082973BFF8CF94350CA548CED26F971" allCaps="true" bold="true" box="[415,545,1762,1786]" centered="true" fontSize="10" level="1" pageId="4" pageNumber="1270" reason="0">
<emphasis id="B901FC45FF8CF94350CA548CED26F971" bold="true" box="[415,545,1762,1786]" pageId="4" pageNumber="1270">RESULTS</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF8CF94351ED5565EB76FE9D" blockId="4.[160,800,1762,1958]" lastBlockId="4.[832,1472,230,278]" pageId="4" pageNumber="1270">The following presentation of results begins with the cranial endocast, followed by the endosseous labyrinth, and pneumatic sinuses. Along the way, some details of the bony braincase will be clarified. The intent of these sections is not to present exhaustive written descriptions, but rather to focus on comparisons and issues of interest, allowing our illustrations to carry the burden of presenting the morphology.</paragraph>
<paragraph id="8BCA2057FF8CF9435215532FEB20FED2" blockId="4.[832,1473,321,1958]" box="[832,1063,321,345]" pageId="4" pageNumber="1270">
<heading id="D082973BFF8CF9435215532FEB20FED2" bold="true" box="[832,1063,321,345]" fontSize="10" level="3" pageId="4" pageNumber="1270" reason="0">
<emphasis id="B901FC45FF8CF9435215532FEB20FED2" bold="true" box="[832,1063,321,345]" pageId="4" pageNumber="1270">Cranial Endocast</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF8CF943520D5305ECC1FC47" blockId="4.[832,1473,321,1958]" pageId="4" pageNumber="1270">
As noted above, there are published 
<taxonomicName id="4C755BD4FF8CF94354525302EA4EFE0A" authorityName="Osborn" authorityYear="1905" box="[1287,1353,364,385]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8CF94354525302EA4EFE0A" box="[1287,1353,364,385]" italics="true" pageId="4" pageNumber="1270">T. rex</emphasis>
</taxonomicName>
endocasts for 
<materialsCitation id="3B1D2A0AFF8CF943523E53E8EB2FFE10" ID-GBIF-Occurrence="2813094310" box="[875,1064,389,411]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
(
<bibRefCitation id="EFE45DA6FF8CF943556953E8EBD0FE10" author="Osborn HF" box="[1084,1239,390,412]" firstAuthor="Osborn" journalOrPublisher="Mem Am Mus Nat Hist" pageId="4" pageNumber="1270" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn, 1912</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF94355B253E8EA84FE17" author="Hopson JA" box="[1255,1411,390,412]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="4" pageNumber="1270" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
) and 
<materialsCitation id="3B1D2A0AFF8CF943521553CFECEAFE3E" ID-GBIF-Occurrence="2813094301" box="[832,1005,416,438]" collectionCode="FMNH" pageId="4" pageNumber="1270" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
(
<bibRefCitation id="EFE45DA6FF8CF94352AB53CEEB91FE3E" author="Brochu CA" box="[1022,1174,416,438]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="4" pageNumber="1270" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu, 2000</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF8CF94355F653CEEBDBFE3D" author="Brochu CA" box="[1187,1244,416,438]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="4" pageNumber="1270" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">2003</bibRefCitation>
). We generated new endocasts for both of these to provide an independent assessment, and 
<bibRefCitation id="EFE45DA6FF8CF943555853B8EBC6FE67" author="Brochu CA" box="[1037,1217,470,492]" firstAuthor="Brochu's" journalOrPublisher="J Vert Paleontol" pageId="4" pageNumber="1270" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu’s (2000)</bibRefCitation>
and 
<bibRefCitation id="EFE45DA6FF8CF943545C53B8EAC7FE67" author="Hopson JA" box="[1289,1472,470,492]" editor="Gans C" firstAuthor="Hopson's" journalOrPublisher="New York: Academic Press" pageId="4" pageNumber="1270" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson’s (1979)</bibRefCitation>
identifications are largely in accord with ours. For 
<materialsCitation id="3B1D2A0AFF8CF94352155065ECF5FDAB" ID-GBIF-Occurrence="2813094373" box="[832,1010,523,544]" collectionCode="FMNH" pageId="4" pageNumber="1270" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
, we used the same data as Brochu (see above for caveats regarding Brochu’s illustrations). For 
<materialsCitation id="3B1D2A0AFF8CF9435215502EEB16FDDD" ID-GBIF-Occurrence="2813094414" box="[832,1041,576,598]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
, however, although 
<bibRefCitation id="EFE45DA6FF8CF9435443502EEAC7FDDD" author="Osborn HF" box="[1302,1472,576,598]" firstAuthor="Osborn" journalOrPublisher="Mem Am Mus Nat Hist" pageId="4" pageNumber="1270" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn (1912)</bibRefCitation>
extracted a physical endocast from one side, we CT scanned both halves of 
<materialsCitation id="3B1D2A0AFF8CF94355075018EA09FD00" ID-GBIF-Occurrence="2813094362" box="[1106,1294,629,651]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
and assembled the first complete endocast of this specimen. We also generated an endocast for 
<materialsCitation id="3B1D2A0AFF8CF943552450C5EBEFFD4A" ID-GBIF-Occurrence="2813094330" box="[1137,1256,683,705]" collectionCode="CM" pageId="4" pageNumber="1270" specimenCode="CM 79057">CM 79057</materialsCitation>
, but the scan data are not sufficient to reveal much more than that it was generally similar to other 
<taxonomicName id="4C755BD4FF8CF9435538508FEBAAFD7D" authorityName="Osborn" authorityYear="1905" box="[1133,1197,737,758]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8CF9435538508FEBAAFD7D" box="[1133,1197,737,758]" italics="true" pageId="4" pageNumber="1270">T. rex</emphasis>
</taxonomicName>
endocasts. The best CT data come from 
<materialsCitation id="3B1D2A0AFF8CF94355515095EBC2FC9A" ID-GBIF-Occurrence="2813094314" box="[1028,1221,763,785]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, which is better preserved than 
<materialsCitation id="3B1D2A0AFF8CF943528E5178EBA7FCA0" ID-GBIF-Occurrence="2813094401" box="[987,1184,789,811]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
and was scanned at a higher resolution than 
<materialsCitation id="3B1D2A0AFF8CF9435518515FEA07FCCE" ID-GBIF-Occurrence="2813094340" box="[1101,1280,816,838]" collectionCode="FMNH" pageId="4" pageNumber="1270" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
. As a result, we present 
<materialsCitation id="3B1D2A0AFF8CF94352F75125EB63FCEA" ID-GBIF-Occurrence="2813094399" box="[930,1124,843,865]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
in more detail as our main example (
<figureCitation id="134E3CD2FF8CF94352E15108EB01FCF0" box="[948,1030,870,892]" captionStart="Fig" captionStartId="5.[354,384,1890,1909]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="4" pageNumber="1270">Figs. 1</figureCitation>
, 
<figureCitation id="134E3CD2FF8CF943554E5108EB2DFCF7" box="[1051,1066,870,892]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="4" pageNumber="1270">2</figureCitation>
). All endocasts are oriented with the lateral semicircular canal horizontal, corresponding to the typical tetrapod ‘‘alert’’ head posture (see Discussion).
</paragraph>
<paragraph id="8BCA2057FF8CF943520D51BEEA97F93D" blockId="4.[832,1473,321,1958]" pageId="4" pageNumber="1270">
All of the endocasts of 
<taxonomicName id="4C755BD4FF8CF943553551BFEB98FC6D" authorityName="Osborn" authorityYear="1905" box="[1120,1183,977,998]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8CF943553551BFEB98FC6D" box="[1120,1183,977,998]" italics="true" pageId="4" pageNumber="1270">T. rex</emphasis>
</taxonomicName>
are very similar and are generally long and narrow (
<figureCitation id="134E3CD2FF8CF94355DB5185EBD5FB8A" box="[1166,1234,1003,1025]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="4" pageNumber="1270">Fig. 3</figureCitation>
A–I). As is typically the case in more basal theropods, the forebrain and hindbrain are more or less horizontal, with the midbrain angled between them. But whereas the midbrain angulation in outgroups is stronger (about 45- to 60-degree angle, 
<figureCitation id="134E3CD2FF8CF94352C7561EECDCFB0E" box="[914,987,1136,1158]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="4" pageNumber="1270">Fig. 4</figureCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF94352BB561FEB88FB0E" author="Hopson JA" box="[1006,1167,1136,1158]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="4" pageNumber="1270" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF94355F4561FEA40FB0E" author="Larsson HCE" box="[1185,1351,1136,1158]" editor="Tanke DH &amp; Carpenter K" firstAuthor="Larsson" journalOrPublisher="Bloomington: Indiana University Press" pageId="4" pageNumber="1270" pagination="19 - 33" refId="ref22116" refString="Larsson HCE. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. In: Tanke DH, Carpenter K, editors. Mesozoic vertebrate life. Bloomington: Indiana University Press. p 19 - 33." title="Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution" type="book chapter" volumeTitle="Mesozoic vertebrate life" year="2001">Larsson, 2001</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF943540F561FECF0FB2A" author="Franzosa JW &amp; Rowe TB" firstAuthor="Franzosa" journalOrPublisher="J Vert Paleontol" pageId="4" pageNumber="1270" pagination="859 - 864" part="25" refId="ref21046" refString="Franzosa JW, Rowe TB. 2005. Cranial endocast of the Cretaceous Theropod Dinosaur Acrocanthosaurus atokensis. J Vert Paleontol 25: 859 - 864." title="Cranial endocast of the Cretaceous Theropod Dinosaur Acrocanthosaurus atokensis" type="journal article" year="2005">Franzosa and Rowe, 2005</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF943555156E5EA39FB2A" author="Sampson SD &amp; Witmer LM" box="[1028,1342,1163,1185]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="4" pageNumber="1270" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
), the 
<taxonomicName id="4C755BD4FF8CF94354D456E2EAB8FB2A" authorityName="Osborn" authorityYear="1905" box="[1409,1471,1164,1185]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8CF94354D456E2EAB8FB2A" box="[1409,1471,1164,1185]" italics="true" pageId="4" pageNumber="1270">T. rex</emphasis>
</taxonomicName>
endocasts are more drawn out and the angulation is shallower. The other tyrannosaur endocasts presented here, 
<taxonomicName id="4C755BD4FF8CF94352D256B5EB12FB7B" authorityName="Cope" authorityYear="1866" box="[903,1045,1243,1264]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8CF94352D256B5EB12FB7B" box="[903,1045,1243,1264]" italics="true" pageId="4" pageNumber="1270">Gorgosaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF8CF943557E56B5EB76FB7A" box="[1067,1137,1243,1265]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="4" pageNumber="1270">Fig. 3</figureCitation>
J–L) and 
<materialsCitation id="3B1D2A0AFF8CF94355BE56B5EA79FB7A" ID-GBIF-Occurrence="2813094411" box="[1259,1406,1243,1265]" collectionCode="CMNH" pageId="4" pageNumber="1270" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
(
<figureCitation id="134E3CD2FF8CF94354C056B5EC4CFA87" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="4" pageNumber="1270">Fig. 3</figureCitation>
M–O), likewise show a shallow midbrain angulation. Precise measurement of these angles is problematic because many details of brain structure are not recorded in the cranial endocast, which ultimately is a cast of the dural envelope. Despite being coelurosaurs, adult tyrannosaurs reflect the primitive noncoelurosaurian sauropsid condition, in which the relatively small brain is suspended within the larger endocranial cavity by dural venous sinuses, cerebrospinal fluid, and other tissues (
<bibRefCitation id="EFE45DA6FF8CF94352125788ECEBFA70" author="Hopson JA" box="[839,1004,1510,1531]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="4" pageNumber="1270" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF94355575788EBBFFA77" author="Hurlburt GR" bookContentInfo="250" box="[1026,1208,1510,1532]" firstAuthor="Hurlburt" journalOrPublisher="University of Toronto, Toronto, ON, Canada" pageId="4" pageNumber="1270" refId="ref21759" refString="Hurlburt GR. 1996. Relative brain size in recent and fossil amniotes: determination and interpretation. PhD Dissertation, University of Toronto, Toronto, ON, Canada. p 250." title="Relative brain size in recent and fossil amniotes: determination and interpretation" type="book" year="1996">Hurlburt, 1996</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF943559B5788EA6BFA70" author="Rogers SW" box="[1230,1388,1509,1531]" firstAuthor="Rogers" journalOrPublisher="Am J Med Gen" pageId="4" pageNumber="1270" pagination="349 - 356" part="134 A" refId="ref22919" refString="Rogers SW. 2005. Reconstructing the behaviors of extinct species: an excursion into comparative paleoneurology. Am J Med Gen 134 A: 349 - 356." title="Reconstructing the behaviors of extinct species: an excursion into comparative paleoneurology" type="journal article" year="2005">Rogers, 2005</bibRefCitation>
). Most other coelurosaurs resemble mammals, birds, and pterosaurs in having relatively large brains that mostly fill the cavity such that an endocast is a better representation of gross brain structure (
<bibRefCitation id="EFE45DA6FF8CF94355E2543EEA50F9EE" author="Jerison HJ" bookContentInfo="482" box="[1207,1367,1616,1638]" firstAuthor="Jerison" journalOrPublisher="New York: Academic Press" pageId="4" pageNumber="1270" refId="ref21918" refString="Jerison HJ. 1973. Evolution of the brain and intelligence. New York: Academic Press. p 482." title="Evolution of the brain and intelligence" type="book" year="1973">Jerison, 1973</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF9435438543EECC1F90B" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="4" pageNumber="1270" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF8CF94352805405EB80F90A" author="Franzosa JW" bookContentInfo="357" box="[981,1159,1643,1665]" firstAuthor="Franzosa" journalOrPublisher="University of Texas, Austin, Texas" pageId="4" pageNumber="1270" refId="ref21017" refString="Franzosa JW. 2004. Evolution of the brain in Theropoda (Dinosauria). PhD Dissertation, University of Texas, Austin, Texas. p 357." title="Evolution of the brain in Theropoda (Dinosauria)" type="book" year="2004">Franzosa, 2004</bibRefCitation>
). The endocast of the new, very young 
<taxonomicName id="4C755BD4FF8CF943529A54E8EB5CF910" authorityName=", Osborn" authorityYear="1912" box="[975,1115,1670,1691]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="4" pageNumber="1270" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8CF943529A54E8EB5CF910" box="[975,1115,1670,1691]" italics="true" pageId="4" pageNumber="1270">Tarbosaurus</emphasis>
</taxonomicName>
suggests that young tyrannosaurs resembled other coelurosaurs in this attribute.
</paragraph>
<paragraph id="8BCA2057FF8CF941520D54D5ECF5FEC7" blockId="4.[832,1473,321,1958]" lastBlockId="6.[832,1472,230,332]" lastPageId="6" lastPageNumber="1272" pageId="4" pageNumber="1270">
The endocasts of tyrannosaurs are dominated by large dural venous sinuses that covered much of the brain structure, especially dorsally. As in modern archosaurs (
<bibRefCitation id="EFE45DA6FF8CF94352125565ECFFF8AA" author="Sedlmayr JC" bookContentInfo="398" box="[839,1016,1803,1825]" firstAuthor="Sedlmayr" journalOrPublisher="Ohio University, Athens, Ohio" pageId="4" pageNumber="1270" refId="ref23203" refString="Sedlmayr JC. 2002. Anatomy, evolution, and functional significance of cephalic vasculature in Archosauria. Ph. D. Dissertation, Ohio University, Athens, Ohio. p 398." title="Anatomy, evolution, and functional significance of cephalic vasculature in Archosauria" type="book" year="2002">Sedlmayr, 2002</bibRefCitation>
), the dorsal longitudinal (sagittal) sinus is well developed and expanded caudally into a large occipital sinus overlying much of the hindbrain. A prominent feature of 
<materialsCitation id="3B1D2A0AFF8CF94355545535EBB9F8FA" ID-GBIF-Occurrence="2813094325" box="[1025,1214,1883,1905]" collectionCode="AMNH" pageId="4" pageNumber="1270" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
is a very tall median dural peak (
<figureCitation id="134E3CD2FF8CF94352985518EB23F807" box="[973,1060,1910,1932]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="4" pageNumber="1270">Fig. 3D</figureCitation>
); CT scans confirm that the peak is indeed blind. Although this peak has been a familiar feature since 
<bibRefCitation id="EFE45DA6FF8DF94250175288EEF4FF77" author="Osborn HF" box="[322,499,230,252]" firstAuthor="Osborn's" journalOrPublisher="Mem Am Mus Nat Hist" pageId="5" pageNumber="1271" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn’s (1912)</bibRefCitation>
paper, none of the other tyrannosaur specimens has such a tall dural prolongation, in most cases being simply the apex of the dorsal longitudinal sinus (
<figureCitation id="134E3CD2FF8DF942502B5358EEC6FEC7" box="[382,449,310,332]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="5" pageNumber="1271">Fig. 3</figureCitation>
). 
<bibRefCitation id="EFE45DA6FF8DF942508C5358EC27FEC7" author="Saveliev SV &amp; Alifanov VR" box="[473,800,310,332]" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="5" pageNumber="1271" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov (2007)</bibRefCitation>
suggested that the same peak in 
<taxonomicName id="4C755BD4FF8DF942534B533EEDADFEEE" authorityName=", Osborn" authorityYear="1912" box="[542,682,336,357]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="5" pageNumber="1271" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF8DF942534B533EEDADFEEE" box="[542,682,336,357]" italics="true" pageId="5" pageNumber="1271">Tarbosaurus</emphasis>
</taxonomicName>
was occupied by the cerebellum, but the available evidence suggests that cerebellum was located more ventrally. Alternatively, 
<bibRefCitation id="EFE45DA6FF8DF942506A53CEED79FE3D" author="Sampson SD &amp; Witmer LM" box="[319,638,416,438]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="5" pageNumber="1271" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer (2007)</bibRefCitation>
argued that a similar dural peak in noncoelurosaurian theropods corresponds well to the position (i.e., just caudal to the cerebrum) of a pineal apparatus (
<figureCitation id="134E3CD2FF8DF94255DA5288EBFBFF77" box="[1167,1276,230,252]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="5" pageNumber="1271">Fig. 4A,B</figureCitation>
), but the peak in tyrannosaurs and indeed other coelurosaurs (
<figureCitation id="134E3CD2FF8DF9425413536EEA8FFE9D" box="[1350,1416,256,278]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="5" pageNumber="1271">Fig. 4</figureCitation>
C–E) is too caudally situated to be pineal in origin. Moreover, the presence of both rostral (pineal) and caudal dural peaks in 
<emphasis id="B901FC45FF8DF94252ED533EEB66FEEE" box="[952,1121,336,357]" italics="true" pageId="5" pageNumber="1271">Struthiomimus</emphasis>
(
<figureCitation id="134E3CD2FF8DF942552C533EEBD2FEED" box="[1145,1237,336,358]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="5" pageNumber="1271">Fig. 4D</figureCitation>
) suggests that the peak in tyrannosaurs is not homologous with the pineal peak of more basal theropods. It is not presently possible to suggest a precise function for the tyrannosaur dural peak other than as housing a dural venous sinus. Likewise, why the peak is so tall in 
<materialsCitation id="3B1D2A0AFF8DF942558E53B8EA98FE60" ID-GBIF-Occurrence="2813094406" box="[1243,1439,469,491]" collectionCode="AMNH" pageId="5" pageNumber="1271" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
is obscure. The dural peak is very close to the transverse sinus system (
<figureCitation id="134E3CD2FF8EF9415012536EEE8DFE9D" box="[327,394,256,278]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="6" pageNumber="1272">Fig. 3</figureCitation>
) and so is likely to be a hypertrophied confluence of sinuses (=torcular Herophili). Indeed, some sauropods also exhibit a dural expansion associated with the confluence of sinuses (
<bibRefCitation id="EFE45DA6FF8EF94154745288EC7FFE9D" author="Witmer LM &amp; Ridgely RC" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="6" pageNumber="1272" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
), and even some ceratopsians have a median dural peak associated with the confluence (
<bibRefCitation id="EFE45DA6FF8EF941547E5375ECE1FEC7" author="Witmer LM &amp; Ridgely RC" editor="Currie PJ" firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="6" pageNumber="1272" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008" yearSuffix="a">Witmer and Ridgely, 2008a</bibRefCitation>
).
</paragraph>
<caption id="DF0A70DFFF8DF9425037550CEC13F82E" ID-DOI="http://doi.org/10.5281/zenodo.3942773" ID-Zenodo-Dep="3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="5" pageNumber="1271" startId="5.[354,384,1890,1909]" targetBox="[176,1456,556,1858]" targetPageId="5">
<paragraph id="8BCA2057FF8DF9425037550CEC13F82E" blockId="5.[336,1296,1890,1957]" pageId="5" pageNumber="1271">
Fig. 1. Cranial endocast of 
<taxonomicName id="4C755BD4FF8DF9425339550CEC16F8FE" authorityName="Osborn" authorityYear="1905" box="[620,785,1890,1909]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="5" pageNumber="1271" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8DF9425339550CEC16F8FE" box="[620,785,1890,1909]" italics="true" pageId="5" pageNumber="1271">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF8DF942524B550CECB5F8FE" ID-GBIF-Occurrence="2813094412" box="[798,946,1890,1909]" collectionCode="AMNH" pageId="5" pageNumber="1271" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in 
<emphasis id="B901FC45FF8DF94255235515EB83F806" bold="true" box="[1142,1156,1915,1933]" pageId="5" pageNumber="1271">A</emphasis>
, left lateral; 
<emphasis id="B901FC45FF8DF94255A95515EA0DF806" bold="true" box="[1276,1290,1915,1933]" pageId="5" pageNumber="1271">B</emphasis>
, ventral; 
<emphasis id="B901FC45FF8DF94250CD55FDEEA0F82E" bold="true" box="[408,423,1939,1957]" pageId="5" pageNumber="1271">C</emphasis>
, dorsal; 
<emphasis id="B901FC45FF8DF94250A255FDED01F82E" bold="true" box="[503,518,1939,1957]" pageId="5" pageNumber="1271">D</emphasis>
, rostral; and 
<emphasis id="B901FC45FF8DF942532A55FDED8BF82E" bold="true" box="[639,652,1939,1957]" pageId="5" pageNumber="1271">E</emphasis>
, caudal views.
</paragraph>
</caption>
<caption id="DF0A70DFFF8EF94150375517ED06F82F" ID-DOI="http://doi.org/10.5281/zenodo.3942775" ID-Zenodo-Dep="3942775" httpUri="https://zenodo.org/record/3942775/files/figure.png" pageId="6" pageNumber="1272" startId="6.[354,384,1913,1932]" targetBox="[272,1360,372,1882]" targetPageId="6">
<paragraph id="8BCA2057FF8EF94150375517ED06F82F" blockId="6.[336,1298,1913,1956]" pageId="6" pageNumber="1272">
Fig. 1. Stereopairs in 
<emphasis id="B901FC45FF8EF94153655514ED3EF807" bold="true" box="[560,569,1914,1932]" pageId="6" pageNumber="1272">F</emphasis>
, right lateral; 
<emphasis id="B901FC45FF8EF94153ED5514EDC0F807" bold="true" box="[696,711,1914,1932]" pageId="6" pageNumber="1272">G</emphasis>
, left lateral; 
<emphasis id="B901FC45FF8EF941526C5514EC4FF807" bold="true" box="[825,840,1914,1932]" pageId="6" pageNumber="1272">H</emphasis>
, dorsal; 
<emphasis id="B901FC45FF8EF94152CC5514EC98F807" bold="true" box="[921,927,1914,1932]" pageId="6" pageNumber="1272">I</emphasis>
, ventral; 
<emphasis id="B901FC45FF8EF94152A15514ECF8F807" bold="true" box="[1012,1023,1914,1932]" pageId="6" pageNumber="1272">J</emphasis>
, caudal; and 
<emphasis id="B901FC45FF8EF94155285514EB8CF807" bold="true" box="[1149,1163,1914,1932]" pageId="6" pageNumber="1272">K</emphasis>
, rostral views. Scale bars = 4 cm.
</paragraph>
</caption>
<caption id="DF0A70DFFF8FF9405037549DEB7EF895" ID-DOI="http://doi.org/10.5281/zenodo.3942777" ID-Zenodo-Dep="3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="7" pageNumber="1273" startId="7.[354,384,1779,1798]" targetBox="[336,1296,272,1747]" targetPageId="7">
<paragraph id="8BCA2057FF8FF9405037549DEB7EF895" blockId="7.[336,1296,1779,1822]" pageId="7" pageNumber="1273">
Fig. 2. Stereopairs of articulated braincase of 
<taxonomicName id="4C755BD4FF8FF9405245549DECB4F88D" authorityName="Osborn" authorityYear="1905" box="[784,947,1779,1798]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="7" pageNumber="1273" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF8FF9405245549DECB4F88D" box="[784,947,1779,1798]" italics="true" pageId="7" pageNumber="1273">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF8FF94052EA549DEB57F88D" ID-GBIF-Occurrence="2813094308" box="[959,1104,1779,1798]" collectionCode="AMNH" pageId="7" pageNumber="1273" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
) derived from reconstructed CT scans and shown in the following views: 
<emphasis id="B901FC45FF8FF94052675562EC47F895" bold="true" box="[818,832,1804,1822]" pageId="7" pageNumber="1273">A</emphasis>
, right lateral; 
<emphasis id="B901FC45FF8FF94052E85562ECCCF895" bold="true" box="[957,971,1804,1822]" pageId="7" pageNumber="1273">B</emphasis>
, dorsal; 
<emphasis id="B901FC45FF8FF940554E5562EB2DF895" bold="true" box="[1051,1066,1804,1822]" pageId="7" pageNumber="1273">C</emphasis>
, caudal.
</paragraph>
</caption>
<caption id="DF0A70DFFF80F94F503754B3EBDBF8AB" ID-DOI="http://doi.org/10.5281/zenodo.3942779" ID-Zenodo-Dep="3942779" httpUri="https://zenodo.org/record/3942779/files/figure.png" pageId="8" pageNumber="1274" startId="8.[354,384,1757,1776]" targetBox="[336,1296,229,1726]" targetPageId="8">
<paragraph id="8BCA2057FF80F94F503754B3EBDBF8AB" blockId="8.[336,1298,1757,1824]" pageId="8" pageNumber="1274">
Fig. 2. 
<emphasis id="B901FC45FF80F94F50F954B0EEC7F97B" bold="true" box="[428,448,1758,1776]" pageId="8" pageNumber="1274">D,</emphasis>
left lateral; 
<emphasis id="B901FC45FF80F94F537654B0ED37F97B" bold="true" box="[547,560,1758,1776]" pageId="8" pageNumber="1274">E</emphasis>
, ventral; 
<emphasis id="B901FC45FF80F94F53D554B0ED8EF97B" bold="true" box="[640,649,1758,1776]" pageId="8" pageNumber="1274">F</emphasis>
, rostral. Bone is rendered semitransparent,revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. For detailed labeling of the cranial endo- cast, bony braincase, and endosseous labyrinth, see Figs. 1, 5, and 8, respectively. Scale bars = 10 cm.
</paragraph>
</caption>
<paragraph id="8BCA2057FF80F94D51ED552EEABFFD7D" blockId="8.[160,800,1856,1958]" lastBlockId="10.[832,1472,230,1958]" lastPageId="10" lastPageNumber="1276" pageId="8" pageNumber="1274">
The transverse dural sinus is well marked on all of the tyrannosaur endocasts, being a raised ridge curving between veins diverging from the endocast rostrally and caudally. Unfortunately, both of these veins have been referred to as the middle cerebral vein, and we will not revise that terminology here, but rather differentiate the veins as rostral or caudal. The rostral middle cerebral vein takes a long course through the laterosphenoid to open very near or within the epipterygoid facet (
<figureCitation id="134E3CD2FF82F94D539A552EEC14F8DD" box="[719,787,1856,1878]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="10" pageNumber="1276">Fig. 5</figureCitation>
). Its external foramen is distinct from the maxillomandibular and ophthalmic (trigeminal) foramina, which is the derived saurischian condition (
<bibRefCitation id="EFE45DA6FF82F94D535F55FEEDADF82E" author="Rauhut OWM" box="[522,682,1936,1958]" firstAuthor="Rauhut" journalOrPublisher="Spec Pap Palaeontol" pageId="10" pageNumber="1276" pagination="1 - 213" part="69" refId="ref22734" refString="Rauhut OWM. 2003. The interrelationships and evolution of basal theropod dinosaurs. Spec Pap Palaeontol 69: 1 - 213." title="The interrelationships and evolution of basal theropod dinosaurs" type="journal article" year="2003">Rauhut, 2003</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF82F94D53EE55FEEB0AFF77" author="Sampson SD &amp; Witmer LM" box="[699,1037,230,1957]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="10" pageNumber="1276" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
). It should be noted that 
<bibRefCitation id="EFE45DA6FF82F94D54655288ECF7FE9D" author="Saveliev SV &amp; Alifanov VR" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="10" pageNumber="1276" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov (2007)</bibRefCitation>
misidentified the canal for the rostral middle cerebral vein in 
<taxonomicName id="4C755BD4FF82F94D55315375EBF7FEBB" authorityName=", Osborn" authorityYear="1912" box="[1124,1264,283,304]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF82F94D55315375EBF7FEBB" box="[1124,1264,283,304]" italics="true" pageId="10" pageNumber="1276">Tarbosaurus</emphasis>
</taxonomicName>
as being for the trochlear nerve. The caudal middle cerebral vein (=caudal petrosal sinus, external occipital vein) passes between bones to emerge on the occiput between the supraoccipital, otoccipital, and parietal (
<figureCitation id="134E3CD2FF82F94D544653E8EA5EFE17" box="[1299,1369,390,412]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="10" pageNumber="1276">Fig. 2</figureCitation>
). Linked with the transverse sinus and caudal middle cerebral vein is the dorsal head vein (
<figureCitation id="134E3CD2FF82F94D55E653D5EBFEFE5A" box="[1203,1273,443,465]" captionStart="Fig" captionStartId="6.[354,384,1913,1932]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942775" httpUri="https://zenodo.org/record/3942775/files/figure.png" pageId="10" pageNumber="1276">Fig. 1</figureCitation>
), which extends laterally to emerge at a foramen within the adductor chamber between laterosphenoid, parietal, and prootic (
<figureCitation id="134E3CD2FF82F94D521D5065EC8CFDAA" box="[840,907,523,545]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="10" pageNumber="1276">Fig. 5</figureCitation>
). In some of the tyrannosaur specimens, the bony lateral head vein canal is discontinuous as it passes through or just borders the pneumatic chamber within the prootic (
<figureCitation id="134E3CD2FF82F94D52855035EB11FDFA" box="[976,1046,603,625]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="10" pageNumber="1276">Fig. 2</figureCitation>
). The external foramina of both the dorsal head vein and caudal middle cerebral vein each lead to grooves that ultimately unite at the posttemporal foramen, suggesting that the same intra- and extracranial anastomotic loops identified in 
<taxonomicName id="4C755BD4FF82F94D544550A8EB83FD7D" authority="(Sampson and Witmer, 2007)" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF82F94D544550A8EAC7FD50" box="[1296,1472,710,731]" italics="true" pageId="10" pageNumber="1276">Majungasaurus</emphasis>
(
<bibRefCitation id="EFE45DA6FF82F94D5212508EEB7AFD7D" author="Sampson SD &amp; Witmer LM" box="[839,1149,736,758]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="10" pageNumber="1276" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
)
</taxonomicName>
are found in tyrannosaurs.
</paragraph>
<caption id="DF0A70DFFF81F94E51E75487EA22F8A7" ID-DOI="http://doi.org/10.5281/zenodo.3942781" ID-Zenodo-Dep="3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="9" pageNumber="1275" startId="9.[178,208,1769,1788]" targetBox="[246,1387,229,1733]" targetPageId="9">
<paragraph id="8BCA2057FF81F94E51E75487EA22F8A7" blockId="9.[160,801,1769,1860]" lastBlockId="9.[832,1472,1769,1836]" pageId="9" pageNumber="1275">
Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). 
<emphasis id="B901FC45FF81F94E53165574ED6DF8A7" bold="true" box="[579,618,1818,1836]" pageId="9" pageNumber="1275">A–C</emphasis>
, 
<taxonomicName id="4C755BD4FF81F94E532F5577EC27F8A7" authorityName="Osborn" authorityYear="1905" box="[634,800,1817,1836]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="9" pageNumber="1275" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF81F94E532F5577EC27F8A7" box="[634,800,1817,1836]" italics="true" pageId="9" pageNumber="1275">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF81F94E51F1555FEE38F8CF" ID-GBIF-Occurrence="2813094425" box="[164,319,1841,1860]" collectionCode="AMNH" pageId="9" pageNumber="1275" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
); 
<emphasis id="B901FC45FF81F94E5004555CEE74F8CF" bold="true" box="[337,371,1842,1860]" pageId="9" pageNumber="1275">D–F</emphasis>
, 
<taxonomicName id="4C755BD4FF81F94E50D7555FEEB0F8CF" authorityName="Osborn" authorityYear="1905" box="[386,439,1841,1860]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="9" pageNumber="1275" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF81F94E50D7555FEEB0F8CF" box="[386,439,1841,1860]" italics="true" pageId="9" pageNumber="1275">T. rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF81F94E5093555FED66F8CF" ID-GBIF-Occurrence="2813094311" box="[454,609,1841,1860]" collectionCode="AMNH" pageId="9" pageNumber="1275" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
); 
<emphasis id="B901FC45FF81F94E5327555CED96F8CF" bold="true" box="[626,657,1842,1860]" pageId="9" pageNumber="1275">G–I</emphasis>
, 
<taxonomicName id="4C755BD4FF81F94E53F7555FEDD1F8CF" authorityName="Osborn" authorityYear="1905" box="[674,726,1841,1860]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="9" pageNumber="1275" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF81F94E53F7555FEDD1F8CF" box="[674,726,1841,1860]" italics="true" pageId="9" pageNumber="1275">T. rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF81F94E53B3555FEC8CF977" ID-GBIF-Occurrence="2813094374" box="[742,907,1769,1860]" collectionCode="FMNH" pageId="9" pageNumber="1275" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
); 
<emphasis id="B901FC45FF81F94E52CC5487ECBDF970" bold="true" box="[921,954,1769,1787]" pageId="9" pageNumber="1275">J–L</emphasis>
, 
<taxonomicName id="4C755BD4FF81F94E52935487EB87F977" authorityName="Lambe" authorityYear="1914" baseAuthorityName="Lambe" baseAuthorityYear="1914" box="[966,1152,1769,1788]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="9" pageNumber="1275" phylum="Chordata" rank="species" species="libratus">
<emphasis id="B901FC45FF81F94E52935487EB87F977" box="[966,1152,1769,1788]" italics="true" pageId="9" pageNumber="1275">Gorgosaurus libratus</emphasis>
</taxonomicName>
(ROM 1247); 
<emphasis id="B901FC45FF81F94E54555487EA2BF970" bold="true" box="[1280,1324,1769,1787]" pageId="9" pageNumber="1275">M–O</emphasis>
, Cleveland skull (
<materialsCitation id="3B1D2A0AFF81F94E5210556FECBAF89F" ID-GBIF-Occurrence="2813094361" box="[837,957,1793,1812]" collectionCode="CMNH" pageId="9" pageNumber="1275" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm.
</paragraph>
</caption>
<paragraph id="8BCA2057FF82F94D520D5095EC92FB5D" blockId="10.[832,1472,230,1958]" pageId="10" pageNumber="1276">
Within the forebrain regions of the tyrannosaur endocasts, there are a variable series of venous canals that exit the endocast dorsally and laterally (
<figureCitation id="134E3CD2FF82F94D5414515EEAB4FCCD" box="[1345,1459,816,838]" captionStart-0="Fig" captionStart-1="Fig" captionStart-2="Fig" captionStartId-0="5.[354,384,1890,1909]" captionStartId-1="7.[354,384,1779,1798]" captionStartId-2="9.[178,208,1769,1788]" captionTargetBox-0="[176,1456,556,1858]" captionTargetBox-1="[336,1296,272,1747]" captionTargetBox-2="[246,1387,229,1733]" captionTargetId-0="figure@5.[176,1458,556,1859]" captionTargetId-1="figure@7.[336,1296,272,1747]" captionTargetId-2="figure@9.[246,1388,229,1733]" captionTargetPageId-0="5" captionTargetPageId-1="7" captionTargetPageId-2="9" captionText-0="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." captionText-1="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." captionText-2="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi-0="http://doi.org/10.5281/zenodo.3942773" figureDoi-1="http://doi.org/10.5281/zenodo.3942777" figureDoi-2="http://doi.org/10.5281/zenodo.3942781" httpUri-0="https://zenodo.org/record/3942773/files/figure.png" httpUri-1="https://zenodo.org/record/3942777/files/figure.png" httpUri-2="https://zenodo.org/record/3942781/files/figure.png" pageId="10" pageNumber="1276">Figs. 1–3</figureCitation>
). Many of the dorsal canals end blindly and may be regarded as diploic veins draining the bone, whereas the lateral canals open into the orbit and may be regarded as emissary veins. Some of these emissary canals open into a prominent vascular groove that runs within the roof of the orbit between the frontal and the unit comprised of the laterosphenoid, orbitosphenoid, and sphenethmoid (
<figureCitation id="134E3CD2FF82F94D52955668EB0DFB90" box="[960,1034,1029,1052]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="10" pageNumber="1276">Fig. 5</figureCitation>
). These emissary vein canals would have provided a route of venous anastomosis between the orbit and endocranial cavity. A similar arrangement of emissary canals opening into a frontosphenoidal groove in the orbital roof has been found in 
<taxonomicName id="4C755BD4FF82F94D5478561FEBC1FB2A" authority="(Sampson and Witmer, 2007)" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF82F94D5478561FEC63FB2A" italics="true" pageId="10" pageNumber="1276">Majungasaurus</emphasis>
(
<bibRefCitation id="EFE45DA6FF82F94D522C56E5EBB8FB2A" author="Sampson SD &amp; Witmer LM" box="[889,1215,1163,1185]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="10" pageNumber="1276" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
)
</taxonomicName>
and other dinosaurs (including ornithischians), and may be a conserved system.
</paragraph>
<paragraph id="8BCA2057FF82F94D520D56B5EA30F82D" blockId="10.[832,1472,230,1958]" pageId="10" pageNumber="1276">
Although the brain did not fill the endocranial cavity in adults, some portions are fairly faithfully recorded in the endocast. The cerebrum is most clearly distinguished and, as in most theropods, its lateral contours and breadth are readily apparent (
<figureCitation id="134E3CD2FF82F94D55F35728EBEEFAD7" box="[1190,1257,1350,1372]" captionStart="Fig" captionStartId="6.[354,384,1913,1932]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942775" httpUri="https://zenodo.org/record/3942775/files/figure.png" pageId="10" pageNumber="1276">Fig. 1</figureCitation>
). However, unlike most theropods, the dorsal cerebral contour is apparent (because of the absence of the pineal peak of more basal theropods), as is the ventral contour (because of wellossified sphenoid elements). As noted for 
<taxonomicName id="4C755BD4FF82F94D544C57DFEA5FFA4D" authorityName="Osborn" authorityYear="1905" box="[1305,1368,1457,1478]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF82F94D544C57DFEA5FFA4D" box="[1305,1368,1457,1478]" italics="true" pageId="10" pageNumber="1276">T. rex</emphasis>
</taxonomicName>
by 
<bibRefCitation id="EFE45DA6FF82F94D54D057DFECF0FA6A" author="Larsson HCE &amp; Sereno PC &amp; Wilson JA" etAl="et al." firstAuthor="Larsson" journalOrPublisher="J Vert Paleontol" pageId="10" pageNumber="1276" pagination="615 - 618" part="30" refId="ref22164" refString="Larsson HCE, Sereno PC, Wilson JA. 2000. Forebrain enlargement among nonavian Theropod Dinosaurs. J Vert Paleontol 30: 615 - 618." title="Forebrain enlargement among nonavian Theropod Dinosaurs" type="journal article" year="2000">Larsson et al. (2000)</bibRefCitation>
and Hurlburt et al. (in press), the cerebrum is enlarged in all of our 
<taxonomicName id="4C755BD4FF82F94D55F75788EBE6FA70" authorityName="Osborn" authorityYear="1905" box="[1186,1249,1510,1531]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF82F94D55F75788EBE6FA70" box="[1186,1249,1510,1531]" italics="true" pageId="10" pageNumber="1276">T. rex</emphasis>
</taxonomicName>
endocasts, and the same is true of the Cleveland skull (
<figureCitation id="134E3CD2FF82F94D5588546EEA1BF99D" box="[1245,1308,1536,1558]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="10" pageNumber="1276">Fig. 3</figureCitation>
M–O), 
<taxonomicName id="4C755BD4FF82F94D5439546EECA7F9BA" authorityName=", Maleev" authorityYear="1965" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF82F94D5439546EECA7F9BA" italics="true" pageId="10" pageNumber="1276">Daspletosaurus</emphasis>
</taxonomicName>
, and 
<taxonomicName id="4C755BD4FF82F94D52BA5475EB7AF9BB" authorityName="Cope" authorityYear="1866" box="[1007,1149,1563,1584]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF82F94D52BA5475EB7AF9BB" box="[1007,1149,1563,1584]" italics="true" pageId="10" pageNumber="1276">Gorgosaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF82F94D55C05475EBDCF9BA" box="[1173,1243,1563,1585]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="10" pageNumber="1276">Fig. 3</figureCitation>
J–L). The olfactory tracts, particularly in 
<taxonomicName id="4C755BD4FF82F94D551E5458EB88F9C0" authorityName="Osborn" authorityYear="1905" box="[1099,1167,1590,1611]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF82F94D551E5458EB88F9C0" box="[1099,1167,1590,1611]" italics="true" pageId="10" pageNumber="1276">T. rex</emphasis>
</taxonomicName>
, are relatively short and thick in comparison to most other theropods and clearly are much broader than was necessary to house the paired olfactory tracts and encephalic vessels. The transverse breadth could be an allometric consequence of large body size, but the similarly sized 
<taxonomicName id="4C755BD4FF82F94D544754D5EB48F967" authority="(Larsson, 2001)" baseAuthorityName="Larsson" baseAuthorityYear="2001" class="Reptilia" family="Carcharodontosauridae" genus="Carcharodontosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF82F94D544754D5EC8CF960" italics="true" pageId="10" pageNumber="1276">Carcharodontosaurus</emphasis>
(
<bibRefCitation id="EFE45DA6FF82F94D52F654B8EB4EF967" author="Larsson HCE" box="[931,1097,1750,1772]" editor="Tanke DH &amp; Carpenter K" firstAuthor="Larsson" journalOrPublisher="Bloomington: Indiana University Press" pageId="10" pageNumber="1276" pagination="19 - 33" refId="ref22116" refString="Larsson HCE. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. In: Tanke DH, Carpenter K, editors. Mesozoic vertebrate life. Bloomington: Indiana University Press. p 19 - 33." title="Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution" type="book chapter" volumeTitle="Mesozoic vertebrate life" year="2001">Larsson, 2001</bibRefCitation>
)
</taxonomicName>
has the plesiomorphic longer, narrower olfactory tract. Moreover, the tracts are relatively short and broad in the smaller sized tyrannosaur represented by the Cleveland skull. Instead, the olfactory tracts being short and broad in 
<taxonomicName id="4C755BD4FF82F94D55A3552FEA30F8DD" authorityName="Osborn" authorityYear="1905" box="[1270,1335,1857,1878]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="10" pageNumber="1276" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF82F94D55A3552FEA30F8DD" box="[1270,1335,1857,1878]" italics="true" pageId="10" pageNumber="1276">T. rex</emphasis>
</taxonomicName>
may relate more to overall braincase shape, which likewise is apomorphically broad and relatively shortened fore-aft, which is also somewhat true of 
<materialsCitation id="3B1D2A0AFF82F94D55F655FFEA35F82D" ID-GBIF-Occurrence="2813094357" box="[1187,1330,1936,1958]" collectionCode="CMNH" pageId="10" pageNumber="1276" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
.
</paragraph>
<caption id="DF0A70DFFF82F94D50FC548BED2EF973" ID-DOI="http://doi.org/10.5281/zenodo.3942783" ID-Zenodo-Dep="3942783" box="[425,553,1765,1784]" httpUri="https://zenodo.org/record/3942783/files/figure.png" pageId="10" pageNumber="1276" startId="10.[425,455,1765,1784]" targetBox="[195,765,229,1733]" targetPageId="10">
<paragraph id="8BCA2057FF82F94D50FC548BED2EF973" blockId="10.[425,553,1765,1784]" box="[425,553,1765,1784]" pageId="10" pageNumber="1276">Fig. 3. (cont.)</paragraph>
</caption>
<caption id="DF0A70DFFF83F94C51E75487EB5AF8D7" ID-DOI="http://doi.org/10.5281/zenodo.3942785" ID-Zenodo-Dep="3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="11" pageNumber="1277" startId="11.[178,208,1769,1788]" targetBox="[258,1374,229,1733]" targetPageId="11">
<paragraph id="8BCA2057FF83F94C51E75487EB5AF8D7" blockId="11.[160,800,1769,1884]" lastBlockId="11.[832,1474,1769,1884]" pageId="11" pageNumber="1277">
Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. 
<emphasis id="B901FC45FF83F94C50B9556FEEFDF898" bold="true" box="[492,506,1793,1811]" pageId="11" pageNumber="1277">A</emphasis>
, 
<emphasis id="B901FC45FF83F94C5345556FEC27F89F" box="[528,800,1793,1812]" italics="true" pageId="11" pageNumber="1277">
<taxonomicName id="4C755BD4FF83F94C5345556FED91F89F" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[528,662,1793,1812]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="11" pageNumber="1277" phylum="Chordata" rank="genus">Majungasaurus</taxonomicName>
crenatissimus
</emphasis>
(FMNH PR2100; modified from 
<bibRefCitation id="EFE45DA6FF83F94C50905577EDCDF8A7" author="Sampson SD &amp; Witmer LM" box="[453,714,1817,1836]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="11" pageNumber="1277" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
); 
<emphasis id="B901FC45FF83F94C538F5574EDEFF8A7" bold="true" box="[730,744,1818,1836]" pageId="11" pageNumber="1277">B</emphasis>
, 
<taxonomicName id="4C755BD4FF83F94C53A25577EE18F8CF" authorityName="Marsh" authorityYear="1877" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="11" pageNumber="1277" phylum="Chordata" rank="species" species="fragilis">
<emphasis id="B901FC45FF83F94C53A25577EE18F8CF" italics="true" pageId="11" pageNumber="1277">Allosaurus fragilis</emphasis>
</taxonomicName>
(UMNH VP 18050); 
<emphasis id="B901FC45FF83F94C50BC555CEEFFF8CF" bold="true" box="[489,504,1842,1860]" pageId="11" pageNumber="1277">C</emphasis>
, 
<taxonomicName id="4C755BD4FF83F94C535C555FEDB7F8CF" authorityName="Osborn" authorityYear="1905" box="[521,688,1841,1860]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="11" pageNumber="1277" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF83F94C535C555FEDB7F8CF" box="[521,688,1841,1860]" italics="true" pageId="11" pageNumber="1277">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF83F94C5395555FEFD7F8D7" ID-GBIF-Occurrence="2813094415" collectionCode="AMNH" pageId="11" pageNumber="1277" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
); 
<emphasis id="B901FC45FF83F94C518A5527EFE9F8D0" bold="true" box="[223,238,1865,1883]" pageId="11" pageNumber="1277">D</emphasis>
, 
<emphasis id="B901FC45FF83F94C51AF5527EEAAF8D7" box="[250,429,1865,1884]" italics="true" pageId="11" pageNumber="1277">Struthiomimus altus</emphasis>
(TMP 90.26.1); 
<emphasis id="B901FC45FF83F94C53155527ED4AF8D0" bold="true" box="[576,589,1865,1883]" pageId="11" pageNumber="1277">E</emphasis>
, 
<taxonomicName id="4C755BD4FF83F94C530F5527EDCAF8D7" authorityName="Ostrom" authorityYear="1969" box="[602,717,1865,1884]" class="Reptilia" family="Dromaeosauridae" genus="Deinonychus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="11" pageNumber="1277" phylum="Chordata" rank="genus">Deinonychus</taxonomicName>
antirrho- 
<emphasis id="B901FC45FF83F94C52155487EC67F977" box="[832,864,1769,1788]" italics="true" pageId="11" pageNumber="1277">pus</emphasis>
(composite of MOR 747 and OMNH 50268); and 
<emphasis id="B901FC45FF83F94C547C5487EA35F970" bold="true" box="[1321,1330,1769,1787]" pageId="11" pageNumber="1277">F</emphasis>
, 
<emphasis id="B901FC45FF83F94C546B5487ECB4F89F" italics="true" pageId="11" pageNumber="1277">Archaeopteryx lithographica</emphasis>
(BMNH 37001). 
<emphasis id="B901FC45FF83F94C5504556FEB7AF898" bold="true" box="[1105,1149,1793,1811]" pageId="11" pageNumber="1277">C, D</emphasis>
, and 
<emphasis id="B901FC45FF83F94C55E2556FEBD8F898" bold="true" box="[1207,1247,1793,1811]" pageId="11" pageNumber="1277">E+F</emphasis>
are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm.
</paragraph>
</caption>
<caption id="DF0A70DFFF84F94B51E75487EA51F8CF" ID-DOI="http://doi.org/10.5281/zenodo.3942787" ID-Zenodo-Dep="3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="12" pageNumber="1278" startId="12.[178,208,1769,1788]" targetBox="[277,1355,229,1733]" targetPageId="12">
<paragraph id="8BCA2057FF84F94B51E75487EA51F8CF" blockId="12.[160,800,1769,1860]" lastBlockId="12.[832,1472,1769,1860]" pageId="12" pageNumber="1278">
Fig. 5. Stereopairs of a braincase of 
<taxonomicName id="4C755BD4FF84F94B53475487EDB1F977" authorityName="Osborn" authorityYear="1905" box="[530,694,1769,1788]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="12" pageNumber="1278" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF84F94B53475487EDB1F977" box="[530,694,1769,1788]" italics="true" pageId="12" pageNumber="1278">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF84F94B53965487EFCAF89F" ID-GBIF-Occurrence="2813094410" collectionCode="AMNH" pageId="12" pageNumber="1278" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. 
<emphasis id="B901FC45FF84F94B52F3555CECB3F8CF" bold="true" box="[934,948,1842,1860]" pageId="12" pageNumber="1278">A</emphasis>
, left lateral view; 
<emphasis id="B901FC45FF84F94B5506555CEB66F8CF" bold="true" box="[1107,1121,1842,1860]" pageId="12" pageNumber="1278">B</emphasis>
, left lateral view, close-up.
</paragraph>
</caption>
<caption id="DF0A70DFFF85F94A5037548AEC65F884" ID-DOI="http://doi.org/10.5281/zenodo.3942789" ID-Zenodo-Dep="3942789" httpUri="https://zenodo.org/record/3942789/files/figure.png" pageId="13" pageNumber="1279" startId="13.[354,384,1764,1783]" targetBox="[284,1348,229,1733]" targetPageId="13">
<paragraph id="8BCA2057FF85F94A5037548AEC65F884" blockId="13.[336,1298,1764,1807]" pageId="13" pageNumber="1279">
Fig. 5. 
<emphasis id="B901FC45FF85F94A50E5548BEEB8F97C" bold="true" box="[432,447,1765,1783]" pageId="13" pageNumber="1279">C</emphasis>
, right rostroventrolateral view; and 
<emphasis id="B901FC45FF85F94A5240548BEC23F97C" bold="true" box="[789,804,1765,1783]" pageId="13" pageNumber="1279">D</emphasis>
, left caudoventrolateral view. Arrows point rostrally. Scale bars = 10 cm, except in 
<emphasis id="B901FC45FF85F94A53395493ED7DF884" bold="true" box="[620,634,1789,1807]" pageId="13" pageNumber="1279">B</emphasis>
where scale bar = 5 cm.
</paragraph>
</caption>
<paragraph id="8BCA2057FF85F94951ED552EEDC4F95A" blockId="13.[160,800,1856,1958]" lastBlockId="14.[160,800,1536,1958]" lastPageId="14" lastPageNumber="1280" pageId="13" pageNumber="1279">
The olfactory bulbs of 
<taxonomicName id="4C755BD4FF85F94A509C552FED0AF8DD" authorityName="Osborn" authorityYear="1905" box="[457,525,1857,1878]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="13" pageNumber="1279" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF85F94A509C552FED0AF8DD" box="[457,525,1857,1878]" italics="true" pageId="13" pageNumber="1279">T. rex</emphasis>
</taxonomicName>
have received a lot of attention since 
<bibRefCitation id="EFE45DA6FF85F94A50055535EEFAF8FA" author="Brochu CA" box="[336,509,1883,1905]" firstAuthor="Brochu's" journalOrPublisher="J Vert Paleontol" pageId="13" pageNumber="1279" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu’s (2000)</bibRefCitation>
paper on 
<materialsCitation id="3B1D2A0AFF85F94A53265535EC27F8FB" ID-GBIF-Occurrence="2813094418" box="[627,800,1883,1904]" collectionCode="FMNH" pageId="13" pageNumber="1279" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
in which he reconstructed bulbs so enormous (
<figureCitation id="134E3CD2FF85F94A53965518EC1EF800" box="[707,793,1909,1932]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="13" pageNumber="1279">Fig. 6A</figureCitation>
) that they seemingly were larger than the rest of the brain itself. This dramatic finding, implying that 
<taxonomicName id="4C755BD4FF85F94A542A552FEAB8F8DD" authorityName="Osborn" authorityYear="1905" box="[1407,1471,1857,1878]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="13" pageNumber="1279" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF85F94A542A552FEAB8F8DD" box="[1407,1471,1857,1878]" italics="true" pageId="13" pageNumber="1279">T. rex</emphasis>
</taxonomicName>
had remarkable olfactory capabilities, played into the existing debate on whether 
<taxonomicName id="4C755BD4FF85F94A552C5518EBB1F800" authorityName="Osborn" authorityYear="1905" box="[1145,1206,1910,1931]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="13" pageNumber="1279" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF85F94A552C5518EBB1F800" box="[1145,1206,1910,1931]" italics="true" pageId="13" pageNumber="1279">T. rex</emphasis>
</taxonomicName>
was primarily a predator or scavenger (
<bibRefCitation id="EFE45DA6FF85F94A554955FEEA51F82E" author="Horner JR &amp; Lessem D." bookContentInfo="239" box="[1052,1366,1936,1958]" firstAuthor="Horner" journalOrPublisher="New York: Simon and Schuster" pageId="13" pageNumber="1279" refId="ref21695" refString="Horner JR, Lessem D. 1993. The complete T. rex: how stunning new discoveries are changing our understanding of the world's most famous dinosaur. New York: Simon and Schuster. p 239." title="The complete T. rex: how stunning new discoveries are changing our understanding of the world's most famous dinosaur" type="book" year="1993">Horner and Lessem, 1993</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF85F949543E55FFEFDFF99D" author="Horner JR" editor="Rosenberg GD &amp; Wolberg DL" firstAuthor="Horner" journalOrPublisher="Paleontological Society, Special Publication" lastPageId="14" lastPageNumber="1280" pageId="13" pageNumber="1279" pagination="157 - 164" part="7" refId="ref21614" refString="Horner JR. 1994. Steak knives, beady eyes, and tiny little arms (a portrait of T. rex as a scavenger). In: Rosenberg GD, Wolberg DL, editors. Knoxville, TN: Dino fest. Paleontological Society, Special Publication 7. p 157 - 164." title="Steak knives, beady eyes, and tiny little arms (a portrait of T. rex as a scavenger)" type="book chapter" volumeTitle="Knoxville, TN: Dino fest" year="1994">Horner, 1994</bibRefCitation>
), and quickly found its way into both dinosaur texts (
<bibRefCitation id="EFE45DA6FF86F94951B25475ED65F9BA" author="Fastovsky DE &amp; Weishampel DB" bookContentInfo="500" box="[231,610,1563,1585]" firstAuthor="Fastovsky" journalOrPublisher="New York: Cambridge University Press" pageId="14" pageNumber="1280" refId="ref20991" refString="Fastovsky DE, Weishampel DB. 2005. The evolution and extinction of the dinosaurs. New York: Cambridge University Press. p 500." title="The evolution and extinction of the dinosaurs" type="book" year="2005">Fastovsky and Weishampel, 2005</bibRefCitation>
) and neuroanatomy texts (
<bibRefCitation id="EFE45DA6FF86F9495074545BEEC9F9C0" author="Striedter GF" bookContentInfo="436" box="[289,462,1589,1611]" firstAuthor="Striedter" journalOrPublisher="Sunderland: Sinauer" pageId="14" pageNumber="1280" refId="ref23798" refString="Striedter GF. 2005. Principles of brain evolution. Sunderland: Sinauer. p 436." title="Principles of brain evolution" type="book" year="2005">Striedter, 2005</bibRefCitation>
). Unfortunately, almost all of what 
<bibRefCitation id="EFE45DA6FF86F94951B8543EEE90F9ED" author="Brochu CA" box="[237,407,1616,1638]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="14" pageNumber="1280" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000)</bibRefCitation>
regarded as olfactory bulb is actually the caudal portion of the olfactory region of the nasal cavity, that is, the site of the sensory epithelium (i.e., mucous membrane) onto which odorant molecules would have diffused (
<figureCitation id="134E3CD2FF86F94950C554D5EEE3F95A" box="[400,484,1723,1745]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="14" pageNumber="1280">Fig. 6C</figureCitation>
, small arrow head).
</paragraph>
<caption id="DF0A70DFFF86F94951E756F5EEEBFA45" ID-DOI="http://doi.org/10.5281/zenodo.3942791" ID-Zenodo-Dep="3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="14" pageNumber="1280" startId="14.[178,208,1179,1198]" targetBox="[168,792,229,1147]" targetPageId="14">
<paragraph id="8BCA2057FF86F94951E756F5EEEBFA45" blockId="14.[160,801,1179,1486]" pageId="14" pageNumber="1280">
Fig. 6. Olfactory structures in 
<emphasis id="B901FC45FF86F949509F56F5ED6BFB25" box="[458,620,1179,1198]" italics="true" pageId="14" pageNumber="1280">
<taxonomicName id="4C755BD4FF86F949509F56F5ED4DFB25" authorityName="Osborn" authorityYear="1905" box="[458,586,1179,1198]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="genus">Tyrannosaurus</taxonomicName>
rex
</emphasis>
. 
<emphasis id="B901FC45FF86F949532C56F5ED80FB26" bold="true" box="[633,647,1179,1197]" pageId="14" pageNumber="1280">A</emphasis>
, 
<materialsCitation id="3B1D2A0AFF86F94953C656F5EC1AFB25" ID-GBIF-Occurrence="2813094309" box="[659,797,1179,1198]" collectionCode="FMNH" pageId="14" pageNumber="1280" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
; 
<emphasis id="B901FC45FF86F94951F556DDEFA9FB4E" bold="true" box="[160,174,1203,1221]" pageId="14" pageNumber="1280">B</emphasis>
, 
<materialsCitation id="3B1D2A0AFF86F94951EE56DDEE4AFB4D" ID-GBIF-Occurrence="2813094366" box="[187,333,1203,1222]" collectionCode="AMNH" pageId="14" pageNumber="1280" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what 
<bibRefCitation id="EFE45DA6FF86F94950B3568DED60FB7D" author="Brochu CA" box="[486,615,1251,1270]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="14" pageNumber="1280" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF86F9495321568DEDA6FB7D" author="Brochu CA" box="[628,673,1251,1270]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="14" pageNumber="1280" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">2003</bibRefCitation>
) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. 
<emphasis id="B901FC45FF86F9495087577DEEE6FAAE" bold="true" box="[466,481,1299,1317]" pageId="14" pageNumber="1280">C</emphasis>
, sagittal section of a 
<taxonomicName id="4C755BD4FF86F94953E1577DEDEFFAAD" authorityName="Osborn" authorityYear="1905" box="[692,744,1299,1318]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF86F94953E1577DEDEFFAAD" box="[692,744,1299,1318]" italics="true" pageId="14" pageNumber="1280">T. rex</emphasis>
</taxonomicName>
skull, showing the cranial endocast in place (generated by registering 
<materialsCitation id="3B1D2A0AFF86F94951F5572DEE3EFADD" ID-GBIF-Occurrence="2813094389" box="[160,313,1347,1366]" collectionCode="AMNH" pageId="14" pageNumber="1280" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
to a one-third scale restored sculpture of 
<materialsCitation id="3B1D2A0AFF86F94953B3572DEFECFAE5" ID-GBIF-Occurrence="2813094351" collectionCode="FMNH" pageId="14" pageNumber="1280" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for 
<emphasis id="B901FC45FF86F949502057D5EE9DFA46" bold="true" box="[373,410,1467,1486]" pageId="14" pageNumber="1280">A–B</emphasis>
= 5 cm.
</paragraph>
</caption>
<paragraph id="8BCA2057FF86F94951ED54B8ECECFB97" blockId="14.[160,800,1536,1958]" lastBlockId="14.[832,1473,230,1957]" pageId="14" pageNumber="1280">
The true olfactory bulbs are very well demarcated (
<bibRefCitation id="EFE45DA6FF86F94951F2549EEE8EF88D" author="Witmer LM &amp; Ridgely RC" box="[167,393,1776,1798]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="14" pageNumber="1280" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
). They are roofed for the most part by the frontal and otherwise lodged within the mesethmoid and sphenethmoid (
<figureCitation id="134E3CD2FF86F94950935548ED0BF8B0" box="[454,524,1829,1852]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="14" pageNumber="1280">Fig. 5</figureCitation>
). The rostrodorsal limit of the bulb is marked by the juncture of the frontal with the ethmoid ring, forming a clear rostral ridge in the endocast (
<figureCitation id="134E3CD2FF86F94950475518EE87F807" box="[274,384,1910,1932]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="14" pageNumber="1280">Fig. 6A,B</figureCitation>
). There are clear grooves within the walls of the ethmoid ring, both laterally on the sphe- nethmoid and on its median septum (mesethmoid; 
<figureCitation id="134E3CD2FF86F94954C05288EC7EFE9D" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="14" pageNumber="1280">Fig. 5A,C</figureCitation>
), that conducted olfactory nerve bundles, as well as blood vessels, as noted for tyrannosaurs by 
<bibRefCitation id="EFE45DA6FF86F94954065375EC82FEC7" author="Ali F &amp; Zelenitsky DK &amp; Therrien F &amp; Weishampel DB" etAl="et al." firstAuthor="Ali" journalOrPublisher="J Vert Paleontol" pageId="14" pageNumber="1280" pagination="123 - 133" part="28" refId="ref19964" refString="Ali F, Zelenitsky DK, Therrien F, Weishampel DB. 2008. Homology of the '' ethmoid complex' ' of tyrannosaurids and its implications for the reconstruction of the olfactory apparatus of non-avian theropods. J Vert Paleontol 28: 123 - 133." title="Homology of the '' ethmoid complex' ' of tyrannosaurids and its implications for the reconstruction of the olfactory apparatus of non-avian theropods" type="journal article" year="2008">Ali et al. (2008)</bibRefCitation>
and for lambeosaurs by 
<bibRefCitation id="EFE45DA6FF86F94955CE5358EA37FEC7" author="Evans DC" box="[1179,1328,310,332]" firstAuthor="Evans" journalOrPublisher="Paleobiology" pageId="14" pageNumber="1280" pagination="109 - 125" part="32" refId="ref20968" refString="Evans DC. 2006. Nasal cavity homologies and cranial crest function in Lambeosaurine Dinosaurs. Paleobiology 32: 109 - 125." title="Nasal cavity homologies and cranial crest function in Lambeosaurine Dinosaurs" type="journal article" year="2006">Evans (2006)</bibRefCitation>
. These olfactory nerve bundles joined with the bulb and are thus outside of it. It is likely that the olfactory bulb itself protruded somewhat into the sphenethmoid ring. Although quantitative assessments are beyond the scope of this article, the corrected size of the olfactory bulbs remains moderately large and are relatively larger than in coelurosaurian outgroups and large bodied basal theropods (
<bibRefCitation id="EFE45DA6FF86F94952905065EB6AFDAB" author="Larsson HCE" box="[965,1133,523,544]" editor="Tanke DH &amp; Carpenter K" firstAuthor="Larsson" journalOrPublisher="Bloomington: Indiana University Press" pageId="14" pageNumber="1280" pagination="19 - 33" refId="ref22116" refString="Larsson HCE. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. In: Tanke DH, Carpenter K, editors. Mesozoic vertebrate life. Bloomington: Indiana University Press. p 19 - 33." title="Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution" type="book chapter" volumeTitle="Mesozoic vertebrate life" year="2001">Larsson, 2001</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF86F94955D45065EABBFDAA" author="Franzosa JW &amp; Rowe TB" box="[1153,1468,523,545]" firstAuthor="Franzosa" journalOrPublisher="J Vert Paleontol" pageId="14" pageNumber="1280" pagination="859 - 864" part="25" refId="ref21046" refString="Franzosa JW, Rowe TB. 2005. Cranial endocast of the Cretaceous Theropod Dinosaur Acrocanthosaurus atokensis. J Vert Paleontol 25: 859 - 864." title="Cranial endocast of the Cretaceous Theropod Dinosaur Acrocanthosaurus atokensis" type="journal article" year="2005">Franzosa and Rowe, 2005</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF86F94952155048EB23FDB0" author="Witmer LM &amp; Ridgely RC" box="[832,1060,550,572]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="14" pageNumber="1280" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF86F94955665048EA3EFDB7" author="Zelenitsky DK &amp; Therrien F &amp; Kobayashi Y." box="[1075,1337,550,572]" etAl="et al." firstAuthor="Zelenitsky" journalOrPublisher="Proc R Soc B" pageId="14" pageNumber="1280" pagination="667 - 673" part="276" refId="ref24481" refString="Zelenitsky DK, Therrien F, Kobayashi Y. 2009. Olfactory acuity in theropods: palaeobiological and evolutionary implications. Proc R Soc B 276: 667 - 673; doi: 10.1098 / rspb. 2008.1075." title="Olfactory acuity in theropods: palaeobiological and evolutionary implications" type="journal article" year="2009">Zelenitsky et al., 2009</bibRefCitation>
). The olfactory bubs of 
<materialsCitation id="3B1D2A0AFF86F949529A502EEB5BFDDD" ID-GBIF-Occurrence="2813094388" box="[975,1116,576,598]" collectionCode="CMNH" pageId="14" pageNumber="1280" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
are relatively even larger than in 
<taxonomicName id="4C755BD4FF86F94952375032ECA3FDFA" authorityName="Osborn" authorityYear="1905" box="[866,932,604,625]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF86F94952375032ECA3FDFA" box="[866,932,604,625]" italics="true" pageId="14" pageNumber="1280">T. rex</emphasis>
</taxonomicName>
, and here the presence of preserved olfactory turbinates (Witmer and Ridgely, in press) provides very clear demarcation between neural and nasal domains. The olfactory bulb region of the PIN 553-3/1 specimen of 
<taxonomicName id="4C755BD4FF86F949521550A8ECCBFD50" authorityName=", Osborn" authorityYear="1912" box="[832,972,710,731]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF86F949521550A8ECCBFD50" box="[832,972,710,731]" italics="true" pageId="14" pageNumber="1280">Tarbosaurus</emphasis>
</taxonomicName>
is very similar to that of other tyrannosaurs, but 
<bibRefCitation id="EFE45DA6FF86F9495293508EEA12FD7E" author="Saveliev SV &amp; Alifanov VR" box="[966,1301,736,758]" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="14" pageNumber="1280" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov (2007</bibRefCitation>
, p 283) interpreted it housing not only the definitive olfactory bulb ventrally but also a ‘‘vomeronasal bulb’’ dorsally. We regard such a division as unwarranted in that the supposed line of separation represents a suture (between frontal and sphenethmoid), not a ridge separating neural domains. Moreover, extant archosaurs lack vomeronasal organs (
<bibRefCitation id="EFE45DA6FF86F94952CF51F5EB34FC3A" author="Witmer LM" box="[922,1075,923,945]" firstAuthor="Witmer" journalOrPublisher="J Morphol" pageId="14" pageNumber="1280" pagination="269 - 327" part="225" refId="ref24054" refString="Witmer LM. 1995. Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae. J Morphol 225: 269 - 327." title="Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae" type="journal article" year="1995">Witmer, 1995</bibRefCitation>
a), and there is no reason to believe that extinct archosaurs had them either (
<bibRefCitation id="EFE45DA6FF86F949547751D8EAB3FC47" author="Senter P." box="[1314,1460,950,972]" firstAuthor="Senter" journalOrPublisher="Paleobiology" pageId="14" pageNumber="1280" pagination="544 - 550" part="28" refId="ref23237" refString="Senter P. 2002. Lack of a pheromonal sense in phytosaurs and other archosaurs, and its implications for reproductive communication. Paleobiology 28: 544 - 550." title="Lack of a pheromonal sense in phytosaurs and other archosaurs, and its implications for reproductive communication" type="journal article" year="2002">Senter, 2002</bibRefCitation>
), including tyrannosaurs. Thus, we regard the entire rostralmost extent of the forebrain to pertain to the olfactory bulbs.
</paragraph>
<paragraph id="8BCA2057FF86F949520D564EEBBEF8B0" blockId="14.[832,1473,230,1957]" pageId="14" pageNumber="1280">
Whether or not the optic lobes (midbrain tectum) are visible in tyrannosaur endocasts is controversial. 
<bibRefCitation id="EFE45DA6FF86F949543A5655EC82FBE7" author="Osborn HF" firstAuthor="Osborn" journalOrPublisher="Mem Am Mus Nat Hist" pageId="14" pageNumber="1280" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn (1912)</bibRefCitation>
identified an optic lobe in 
<taxonomicName id="4C755BD4FF86F94955B75638EA20FBE0" authorityName="Osborn" authorityYear="1905" box="[1250,1319,1110,1131]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF86F94955B75638EA20FBE0" box="[1250,1319,1110,1131]" italics="true" pageId="14" pageNumber="1280">T. rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF86F949546B5638EC7FFB0D" ID-GBIF-Occurrence="2813094405" collectionCode="AMNH" pageId="14" pageNumber="1280" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
), and 
<bibRefCitation id="EFE45DA6FF86F9495295561EEB67FB0D" author="Maleev EA" box="[960,1120,1136,1158]" firstAuthor="Maleev" journalOrPublisher="Paleontol Zh" pageId="14" pageNumber="1280" pagination="141 - 143" part="1965" refId="ref22270" refString="Maleev EA. 1965. [The carnosaur dinosaur brain]. Paleontol Zh 1965: 141 - 143 (in Russian)." title="The carnosaur dinosaur brain" type="journal article" year="1965">Maleev (1965)</bibRefCitation>
did the same for 
<taxonomicName id="4C755BD4FF86F9495478561EEABEFB0E" authorityName=", Osborn" authorityYear="1912" box="[1325,1465,1136,1157]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF86F9495478561EEABEFB0E" box="[1325,1465,1136,1157]" italics="true" pageId="14" pageNumber="1280">Tarbosaurus</emphasis>
</taxonomicName>
, but 
<bibRefCitation id="EFE45DA6FF86F949523A56E5EB09FB2A" author="Brochu CA" box="[879,1038,1163,1185]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="14" pageNumber="1280" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000)</bibRefCitation>
did not identify it in 
<materialsCitation id="3B1D2A0AFF86F949545E56E5EABAFB2B" ID-GBIF-Occurrence="2813094419" box="[1291,1469,1163,1184]" collectionCode="FMNH" pageId="14" pageNumber="1280" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
. We can confirm their observations in that distinct swellings are visible in 
<materialsCitation id="3B1D2A0AFF86F949557056AEEBE6FB5D" ID-GBIF-Occurrence="2813094427" box="[1061,1249,1216,1238]" collectionCode="AMNH" pageId="14" pageNumber="1280" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
(
<figureCitation id="134E3CD2FF86F94955A156AEEA4DFB5D" box="[1268,1354,1216,1238]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="14" pageNumber="1280">Fig. 3D</figureCitation>
) and PIN 553-3/1 and absent in 
<materialsCitation id="3B1D2A0AFF86F949551156B5EBF5FB7B" ID-GBIF-Occurrence="2813094431" box="[1092,1266,1243,1264]" collectionCode="FMNH" pageId="14" pageNumber="1280" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
(
<figureCitation id="134E3CD2FF86F949545056B5EA4FFB7A" box="[1285,1352,1243,1265]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="14" pageNumber="1280">Fig. 3</figureCitation>
). To these we can add that clear swellings for optic lobes are absent in 
<materialsCitation id="3B1D2A0AFF86F9495237577EEB18FAAD" ID-GBIF-Occurrence="2813094379" box="[866,1055,1296,1318]" collectionCode="AMNH" pageId="14" pageNumber="1280" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
(
<taxonomicName id="4C755BD4FF86F9495566577FEB73FAAD" authorityName="Osborn" authorityYear="1905" box="[1075,1140,1297,1318]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF86F9495566577FEB73FAAD" box="[1075,1140,1297,1318]" italics="true" pageId="14" pageNumber="1280">T. rex</emphasis>
</taxonomicName>
) and ROM 1247 (
<taxonomicName id="4C755BD4FF86F949541B577EEC63FACB" authorityName="Cope" authorityYear="1866" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF86F949541B577EEC63FACB" italics="true" pageId="14" pageNumber="1280">Gorgosaurus</emphasis>
</taxonomicName>
), but may be present in 
<materialsCitation id="3B1D2A0AFF86F94955D85745EA1BFACA" ID-GBIF-Occurrence="2813094378" box="[1165,1308,1323,1345]" collectionCode="CMNH" pageId="14" pageNumber="1280" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
(
<figureCitation id="134E3CD2FF86F949547A5745EA74FACA" box="[1327,1395,1323,1345]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="14" pageNumber="1280">Fig. 3</figureCitation>
). 
<bibRefCitation id="EFE45DA6FF86F94954D85745ECC5FAD0" author="Maleev EA" firstAuthor="Maleev's" journalOrPublisher="Paleontol Zh" pageId="14" pageNumber="1280" pagination="141 - 143" part="1965" refId="ref22270" refString="Maleev EA. 1965. [The carnosaur dinosaur brain]. Paleontol Zh 1965: 141 - 143 (in Russian)." title="The carnosaur dinosaur brain" type="journal article" year="1965">Maleev’s (1965)</bibRefCitation>
identification of an optic lobe in 
<taxonomicName id="4C755BD4FF86F9495461572BEAC7FAD1" authorityName=", Osborn" authorityYear="1912" box="[1332,1472,1349,1370]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="14" pageNumber="1280" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF86F9495461572BEAC7FAD1" box="[1332,1472,1349,1370]" italics="true" pageId="14" pageNumber="1280">Tarbosaurus</emphasis>
</taxonomicName>
(PIN 553-3/1) was not affirmed by 
<bibRefCitation id="EFE45DA6FF86F949559F570EEC8FFA1A" author="Saveliev SV &amp; Alifanov VR" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="14" pageNumber="1280" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov (2007)</bibRefCitation>
, who assumed a much more dorsal position for the optic lobe. The interpretation of optic lobes in 
<materialsCitation id="3B1D2A0AFF86F949521557DEEB04FA4D" ID-GBIF-Occurrence="2813094370" box="[832,1027,1456,1478]" collectionCode="AMNH" pageId="14" pageNumber="1280" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
was accepted by 
<bibRefCitation id="EFE45DA6FF86F94955B657DEEA8FFA4D" author="Jerison HJ" bookContentInfo="482" box="[1251,1416,1456,1478]" firstAuthor="Jerison" journalOrPublisher="New York: Academic Press" pageId="14" pageNumber="1280" refId="ref21918" refString="Jerison HJ. 1973. Evolution of the brain and intelligence. New York: Academic Press. p 482." title="Evolution of the brain and intelligence" type="book" year="1973">Jerison (1973)</bibRefCitation>
and 
<bibRefCitation id="EFE45DA6FF86F949521557A5ECF4FA6A" author="Wharton DS" bookContentInfo="334" box="[832,1011,1483,1505]" firstAuthor="Wharton" journalOrPublisher="University of Bristol, Bristol, UK" pageId="14" pageNumber="1280" refId="ref23998" refString="Wharton DS. 2002. The evolution of the avian brain. Ph. D. Dissertation, University of Bristol, Bristol, UK. p 334." title="The evolution of the avian brain" type="book" year="2002">Wharton (2002)</bibRefCitation>
, but 
<bibRefCitation id="EFE45DA6FF86F949557A57A5EBCCFA6B" author="Hopson JA" box="[1071,1227,1483,1504]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="14" pageNumber="1280" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson (1979</bibRefCitation>
, p 96) suggested that the swelling ‘‘more likely represents the posterolateral part of the cerebrum.’’ The significance here is that laterally positioned and visible optic lobes would be a derived trait reflecting a more avian organization of the brain, with enlarged cerebrum and cerebellum pushing the lobes ventrolaterally, rather than the primitive reptilian condition of having modest-sized brain parts arranged rostrocaudally in a row. Our data on coelurosaurs other than tyrannosaurs clearly show a trend for greater visibility and more lateral positions of the optic lobes on the phylogenetic line to birds (
<figureCitation id="134E3CD2FF86F9495457549EEA41F88D" box="[1282,1350,1776,1798]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="14" pageNumber="1280">Fig. 4</figureCitation>
), and both 
<bibRefCitation id="EFE45DA6FF86F94952155564ECF1F8AB" author="Wharton DS" bookContentInfo="334" box="[832,1014,1802,1824]" firstAuthor="Wharton" journalOrPublisher="University of Bristol, Bristol, UK" pageId="14" pageNumber="1280" refId="ref23998" refString="Wharton DS. 2002. The evolution of the avian brain. Ph. D. Dissertation, University of Bristol, Bristol, UK. p 334." title="The evolution of the avian brain" type="book" year="2002">Wharton (2002)</bibRefCitation>
and 
<bibRefCitation id="EFE45DA6FF86F94955685565EBF0F8AB" author="Franzosa JW" bookContentInfo="357" box="[1085,1271,1802,1824]" firstAuthor="Franzosa" journalOrPublisher="University of Texas, Austin, Texas" pageId="14" pageNumber="1280" refId="ref21017" refString="Franzosa JW. 2004. Evolution of the brain in Theropoda (Dinosauria). PhD Dissertation, University of Texas, Austin, Texas. p 357." title="Evolution of the brain in Theropoda (Dinosauria)" type="book" year="2004">Franzosa (2004)</bibRefCitation>
found the same trend with their smaller samples.
</paragraph>
<paragraph id="8BCA2057FF86F948520D552EEEB3FC3A" blockId="14.[832,1473,230,1957]" lastBlockId="15.[160,800,230,1959]" lastPageId="15" lastPageNumber="1281" pageId="14" pageNumber="1280">
Indeed, the available endocast data on tyrannosaur optic lobes are equivocal, and we caution against making too much of subtle bulges. Phylogenetics can play a key role here in that character optimization can guide morphological interpretation. According to 
<bibRefCitation id="EFE45DA6FF87F94853C75288EFEFFE9D" author="Norell MA &amp; Clark JM &amp; Makovicky PJ" editor="Gauthier JA &amp; Gall LF" etAl="et al." firstAuthor="Norell" journalOrPublisher="New Haven: Yale Peabody Museum" pageId="15" pageNumber="1281" pagination="49 - 67" refId="ref22502" refString="Norell MA, Clark JM, Makovicky PJ. 2001. Phylogenetic relationships among Coelurosaurian Theropods. In: Gauthier JA, Gall LF, editors. New perspectives on the origin and early evolution of birds. New Haven: Yale Peabody Museum. p 49 - 67." title="Phylogenetic relationships among Coelurosaurian Theropods" type="book chapter" volumeTitle="New perspectives on the origin and early evolution of birds" year="2001">Norell et al. (2001)</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF87F94851AF536EEEA3FE9D" author="Rauhut OWM" box="[250,420,256,278]" firstAuthor="Rauhut" journalOrPublisher="Spec Pap Palaeontol" pageId="15" pageNumber="1281" pagination="1 - 213" part="69" refId="ref22734" refString="Rauhut OWM. 2003. The interrelationships and evolution of basal theropod dinosaurs. Spec Pap Palaeontol 69: 1 - 213." title="The interrelationships and evolution of basal theropod dinosaurs" type="journal article" year="2003">Rauhut (2003)</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF87F94850E3536EED40FE9D" author="Holtz TR" box="[438,583,256,278]" editor="Weishampel DB &amp; Dodson P &amp; Osmolska H" firstAuthor="Holtz" journalOrPublisher="Berkeley: University of California Press" pageId="15" pageNumber="1281" pagination="111 - 136" refId="ref21413" refString="Holtz TR. 2004. Tyrannosauroidea. In: Weishampel DB, Dodson P, Osmolska H, editors. The Dinosauria. 2 nd ed. Berkeley: University of California Press. p 111 - 136." title="Tyrannosauroidea" type="book chapter" volumeTitle="The Dinosauria. 2 nd" year="2004">Holtz (2004)</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF87F948530F536FEC1BFE9D" author="Xu X &amp; Clark JM &amp; Forster CA &amp; Norell MA &amp; Erickson GM &amp; Eberth DA &amp; Jia C &amp; Zhao Q." box="[602,796,256,278]" etAl="et al." firstAuthor="Xu" journalOrPublisher="Nature" pageId="15" pageNumber="1281" pagination="715 - 718" part="439" refId="ref24437" refString="Xu X, Clark JM, Forster CA, Norell MA, Erickson GM, Eberth DA, Jia C, Zhao Q. 2006. A basal tyrannosauroid dinosaur from the Late Jurassic of China. Nature 439: 715 - 718." title="A basal tyrannosauroid dinosaur from the Late Jurassic of China" type="journal article" year="2006">Xu et al. (2006)</bibRefCitation>
, and 
<bibRefCitation id="EFE45DA6FF87F94851815375EE7FFEBA" author="Benson RBJ" box="[212,376,283,305]" firstAuthor="Benson" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="732 - 750" part="28" refId="ref20116" refString="Benson RBJ. 2008. New information on Stokesosaurus, a tyrannosauroid (Dinosauria: Theropoda) from North America and the United Kingdom. J Vert Paleontol 28: 732 - 750." title="New information on Stokesosaurus, a tyrannosauroid (Dinosauria: Theropoda) from North America and the United Kingdom" type="journal article" year="2008">Benson (2008)</bibRefCitation>
, Tyrannosauroidea is the most basal coelurosaur clade for which reliable endocast data are available, and thus absence of visible, laterally positioned optic lobes (as in 
<materialsCitation id="3B1D2A0AFF87F94850BE5305EDBCFE0A" ID-GBIF-Occurrence="2813094367" box="[491,699,363,385]" collectionCode="AMNH" pageId="15" pageNumber="1281" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, FMNH PR3081, and ROM 1247) might be expected. However, some tyrannosaur specimens might have laterally positioned optic lobes (e.g., 
<materialsCitation id="3B1D2A0AFF87F94850ED53D5ED7EFE5A" ID-GBIF-Occurrence="2813094318" box="[440,633,443,465]" collectionCode="AMNH" pageId="15" pageNumber="1281" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF87F94853DC53D5EC1BFE5A" ID-GBIF-Occurrence="2813094331" box="[649,796,443,465]" collectionCode="CMNH" pageId="15" pageNumber="1281" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, and PIN 553-3/1). This equivocal situation may well legitimately reflect natural variation as adults or even ontogeny in that both 
<materialsCitation id="3B1D2A0AFF87F94850F45065ED29FDAA" ID-GBIF-Occurrence="2813094409" box="[417,558,523,545]" collectionCode="CMNH" pageId="15" pageNumber="1281" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
and PIN 553-3/1 are small and presumably subadult individuals. In this context, it is significant that the newly discovered very young 
<taxonomicName id="4C755BD4FF87F94851A55035EE7BFDFB" authorityName=", Osborn" authorityYear="1912" box="[240,380,603,624]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94851A55035EE7BFDFB" box="[240,380,603,624]" italics="true" pageId="15" pageNumber="1281">Tarbosaurus</emphasis>
</taxonomicName>
also seems to display more visible, ventrolaterally positioned optic lobes. Moreover, this equivocal situation could reflect a transitional state. For example, the optic lobes of ornithomimids (another fairly basal coelurosaurian clade) are not as clearly visible as are those of some taxa closer to the crown (
<figureCitation id="134E3CD2FF87F94853C2508EEDDBFD7E" box="[663,732,736,758]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">Fig. 4</figureCitation>
; 
<bibRefCitation id="EFE45DA6FF87F94853BF508FEE09FC9B" author="Hopson JA" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="15" pageNumber="1281" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF87F948504E5095EEC2FC9B" author="Wharton DS" bookContentInfo="334" box="[283,453,763,785]" firstAuthor="Wharton" journalOrPublisher="University of Bristol, Bristol, UK" pageId="15" pageNumber="1281" refId="ref23998" refString="Wharton DS. 2002. The evolution of the avian brain. Ph. D. Dissertation, University of Bristol, Bristol, UK. p 334." title="The evolution of the avian brain" type="book" year="2002">Wharton, 2002</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF87F94850875095ED86FC9B" author="Franzosa JW" bookContentInfo="357" box="[466,641,763,784]" firstAuthor="Franzosa" journalOrPublisher="University of Texas, Austin, Texas" pageId="15" pageNumber="1281" refId="ref21017" refString="Franzosa JW. 2004. Evolution of the brain in Theropoda (Dinosauria). PhD Dissertation, University of Texas, Austin, Texas. p 357." title="Evolution of the brain in Theropoda (Dinosauria)" type="book" year="2004">Franzosa, 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF87F94853DB5095EE47FCA0" author="Maxwell EE &amp; Larsson HCE" editor="Braman DR &amp; Therrien F &amp; Koppelhus EB &amp; Taylor W" firstAuthor="Maxwell" journalOrPublisher="Drumheller: Royal Tyrrell Museum of Palaeontology" pageId="15" pageNumber="1281" pagination="59" refId="ref22343" refString="Maxwell EE, Larsson HCE. 2005. Endocast of Ornithomimus. In: Braman DR, Therrien F, Koppelhus EB, Taylor W, editors. Dinosaur park symposium: short papers, abstracts, and program. Drumheller: Royal Tyrrell Museum of Palaeontology. p 59." title="Endocast of Ornithomimus" type="book chapter" volumeTitle="Dinosaur park symposium: short papers, abstracts, and program" year="2005">Maxwell and Larsson, 2005</bibRefCitation>
). It is conceivable that a transitional or incipient condition likewise may be present in tyrannosaurs such that a brain with the beginnings of a birdlike organization may be concealed within the large dural envelope of adults, perhaps for allometric reasons relating to their large body sizes.
</paragraph>
<paragraph id="8BCA2057FF87F94851ED51D8EC1FFA27" blockId="15.[160,800,230,1959]" pageId="15" pageNumber="1281">
Controversies regarding optic lobe bulges notwithstanding, some clues about relative positions of brain parts, based on consistent relationships among extant sauropsids, are provided by other features on the endocast (
<bibRefCitation id="EFE45DA6FF87F9485189564EED01FBBE" author="Ridgely RC &amp; Witmer LM" box="[220,518,1056,1078]" firstAuthor="Ridgely" journalOrPublisher="J Morphol" pageId="15" pageNumber="1281" pagination="1124" part="268" refId="ref22781" refString="Ridgely RC, Witmer LM. 2007. Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs. J Morphol 268: 1124." title="Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs" type="journal article" year="2007">Ridgely and Witmer, 2007</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF87F9485346564EED4BFBBD" author="Ridgely RC &amp; Witmer LM" box="[531,588,1056,1078]" firstAuthor="Ridgely" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="131 A" part="28 (Suppl 3)" refId="ref22818" refString="Ridgely RC, Witmer LM. 2008. Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs. J Vert Paleontol 28 (Suppl 3): 131 A." title="Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs" type="journal article" year="2008">2008</bibRefCitation>
). For example, the transverse sinus and the rostral middle cerebral vein roughly mark the boundary between the optic lobe in front and cerebellum behind (
<figureCitation id="134E3CD2FF87F9485341561EED5AFB0D" box="[532,605,1136,1158]" captionStart="Fig" captionStartId="6.[354,384,1913,1932]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942775" httpUri="https://zenodo.org/record/3942775/files/figure.png" pageId="15" pageNumber="1281">Fig. 1</figureCitation>
). The trochlear nerve canal always passes behind and then ventral to the optic lobe in extant taxa. In tyrannosaurs, the course of the trochlear canal is consistent with the putative optic lobe swellings hypothesized above, although the dural envelope is ‘‘sloppy’’ enough that the canal is not decisive in differentiating the optic lobe from the cerebellum. Another marker for cerebellar position is the position of the endosseous labyrinths, which sandwich the cerebellum between them. Again, other than gross position, little about the cerebellum can be discerned, with one exception, its floccular lobe (cerebellar auricle).
</paragraph>
<paragraph id="8BCA2057FF87F94851ED57DEEBCCFBBD" blockId="15.[160,800,230,1959]" lastBlockId="15.[832,1473,230,1958]" pageId="15" pageNumber="1281">
The flocculus is relatively small in all of the adult 
<taxonomicName id="4C755BD4FF87F94851F557A2EFE7FA6A" authorityName="Osborn" authorityYear="1905" box="[160,224,1484,1505]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F94851F557A2EFE7FA6A" box="[160,224,1484,1505]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
specimens examined here, but is relatively larger in 
<materialsCitation id="3B1D2A0AFF87F94851955788EE4AFA70" ID-GBIF-Occurrence="2813094312" box="[192,333,1509,1531]" collectionCode="CMNH" pageId="15" pageNumber="1281" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
and the subadult 
<taxonomicName id="4C755BD4FF87F94853775788EDB7FA70" authorityName="Cope" authorityYear="1866" box="[546,688,1510,1531]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94853775788EDB7FA70" box="[546,688,1510,1531]" italics="true" pageId="15" pageNumber="1281">Gorgosaurus</emphasis>
</taxonomicName>
specimen (ROM 1247; 
<figureCitation id="134E3CD2FF87F948507A546EEE7CF99E" box="[303,379,1536,1558]" captionStart="Fig" captionStartId="5.[354,384,1890,1909]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="15" pageNumber="1281">Figs. 1</figureCitation>
, 
<figureCitation id="134E3CD2FF87F94850DF546EEE9FF99D" box="[394,408,1536,1558]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="15" pageNumber="1281">3</figureCitation>
). The flocculus is generally among the easiest features to see in CT, and so we regard these results as real. 
<bibRefCitation id="EFE45DA6FF87F94850005458ED9BF9C7" author="Saveliev SV &amp; Alifanov VR" box="[341,668,1590,1612]" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="15" pageNumber="1281" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov (2007)</bibRefCitation>
referred to the flocculus in 
<taxonomicName id="4C755BD4FF87F948500C543EEEE2F9EE" authorityName=", Osborn" authorityYear="1912" box="[345,485,1616,1637]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948500C543EEEE2F9EE" box="[345,485,1616,1637]" italics="true" pageId="15" pageNumber="1281">Tarbosaurus</emphasis>
</taxonomicName>
(PIN 553-3/1) as the being the trunk of the vestibulocochlear nerve (CN VIII), but the nerve foramina are clearly identifiable more ventrally. In the adult 
<taxonomicName id="4C755BD4FF87F948502E54CFEEBDF93D" authorityName="Osborn" authorityYear="1905" box="[379,442,1697,1718]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F948502E54CFEEBDF93D" box="[379,442,1697,1718]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
specimens, the flocculus generally has the tabular shape (i.e., flat in section) observed in noncoelurosaurian theropods (e.g., 
<taxonomicName id="4C755BD4FF87F948532354B8EC1EF960" authorityName="Reig" authorityYear="1963" box="[630,793,1750,1771]" class="Reptilia" family="Herrerasauridae" genus="Herrerasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948532354B8EC1EF960" box="[630,793,1750,1771]" italics="true" pageId="15" pageNumber="1281">Herrerasaurus</emphasis>
</taxonomicName>
, MCZ 7063; 
<emphasis id="B901FC45FF87F9485073549FEEBDF88D" box="[294,442,1777,1798]" italics="true" pageId="15" pageNumber="1281">Ceratosaurus</emphasis>
, MWC 1.1; 
<taxonomicName id="4C755BD4FF87F9485310549EEDBAF88E" authorityName="Marsh" authorityYear="1877" box="[581,701,1776,1797]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F9485310549EEDBAF88E" box="[581,701,1776,1797]" italics="true" pageId="15" pageNumber="1281">Allosaurus</emphasis>
</taxonomicName>
, UMNH VP 18050; 
<taxonomicName id="4C755BD4FF87F94850795565EEF3F8AB" box="[300,500,1803,1824]" class="Reptilia" family="Carcharodontosauridae" genus="Acrocanthosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94850795565EEF3F8AB" box="[300,500,1803,1824]" italics="true" pageId="15" pageNumber="1281">Acrocanthosaurus</emphasis>
</taxonomicName>
, OMNH 10146; 
<figureCitation id="134E3CD2FF87F948539D5565EC14F8AA" box="[712,787,1803,1825]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">Fig. 4</figureCitation>
), whereas the flocculus in coelurosaurs tends to be relatively larger, rounder at its base, and often has a distal swelling (e.g., 
<taxonomicName id="4C755BD4FF87F94850125535EEA5F8FB" authorityName="Leidy" authorityYear="1856" box="[327,418,1883,1904]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94850125535EEA5F8FB" box="[327,418,1883,1904]" italics="true" pageId="15" pageNumber="1281">Troodon</emphasis>
</taxonomicName>
, TMP 86.36.457; 
<emphasis id="B901FC45FF87F94853255535EC1EF8FB" box="[624,793,1883,1904]" italics="true" pageId="15" pageNumber="1281">Struthiomimus</emphasis>
, TMP 90.26.1, AMNH FR 5355; 
<taxonomicName id="4C755BD4FF87F94853455518EDB8F800" authorityName="Matthew &amp; Brown" authorityYear="1922" box="[528,703,1910,1931]" class="Reptilia" family="Dromaeosauridae" genus="Dromaeosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94853455518EDB8F800" box="[528,703,1910,1931]" italics="true" pageId="15" pageNumber="1281">Dromaeosaurus</emphasis>
</taxonomicName>
, AMNH FR 5356; 
<taxonomicName id="4C755BD4FF87F948504055FEEEADF82E" authorityName="Gilmore" authorityYear="1924" box="[277,426,1936,1957]" class="Reptilia" family="Caenagnathidae" genus="Chirostenotes" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948504055FEEEADF82E" box="[277,426,1936,1957]" italics="true" pageId="15" pageNumber="1281">Chirostenotes</emphasis>
</taxonomicName>
, ROM 43250; 
<figureCitation id="134E3CD2FF87F948530D55FEED98F82C" box="[600,671,1936,1959]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">Fig. 4</figureCitation>
). A significant difference between 
<taxonomicName id="4C755BD4FF87F94855375288EBA2FF70" authorityName="Osborn" authorityYear="1905" box="[1122,1189,230,251]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F94855375288EBA2FF70" box="[1122,1189,230,251]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
and other theropods is that the floccular cast is relatively so small that it barely crosses the plane of the rostral semicircular canal, which is in stark contrast to theropods generally in which the flocculus extends far beyond the rostral semicircular canal to be largely surrounded by the three semicircular canals (
<figureCitation id="134E3CD2FF87F94852C253E8ECDBFE17" box="[919,988,390,412]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">Fig. 4</figureCitation>
). 
<taxonomicName id="4C755BD4FF87F94852A453E8EB78FE10" authorityName="Cope" authorityYear="1866" box="[1009,1151,390,411]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94852A453E8EB78FE10" box="[1009,1151,390,411]" italics="true" pageId="15" pageNumber="1281">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247) is closer to the typical condition, as is the very young 
<taxonomicName id="4C755BD4FF87F948547853CEEABEFE3E" authorityName=", Osborn" authorityYear="1912" box="[1325,1465,416,437]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948547853CEEABEFE3E" box="[1325,1465,416,437]" italics="true" pageId="15" pageNumber="1281">Tarbosaurus</emphasis>
</taxonomicName>
. 
<materialsCitation id="3B1D2A0AFF87F948521553D5ECD5FE5A" ID-GBIF-Occurrence="2813094307" box="[832,978,443,465]" collectionCode="CMNH" pageId="15" pageNumber="1281" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, however, is more like adult 
<taxonomicName id="4C755BD4FF87F948547053D2EA61FE5A" authorityName="Osborn" authorityYear="1905" box="[1317,1382,444,465]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F948547053D2EA61FE5A" box="[1317,1382,444,465]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
in that the flocculus barely breaks the plane of the rostral semicircular canal. The adult 
<taxonomicName id="4C755BD4FF87F948552D539FEBBAFD8D" authorityName="Osborn" authorityYear="1905" box="[1144,1213,497,518]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F948552D539FEBBAFD8D" box="[1144,1213,497,518]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
condition may relate simply to its larger size (the condition in 
<materialsCitation id="3B1D2A0AFF87F94854655065EAC7FDAA" ID-GBIF-Occurrence="2813094394" box="[1328,1472,523,545]" collectionCode="CMNH" pageId="15" pageNumber="1281" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
notwithstanding; see below), but also may reflect a real difference in brain structure. The cerebellum (of which the flocculus is an appendage) was apparently located more rostrodorsally in 
<taxonomicName id="4C755BD4FF87F948551E5018EB8AFD00" authorityName="Osborn" authorityYear="1905" box="[1099,1165,630,651]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F948551E5018EB8AFD00" box="[1099,1165,630,651]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
(as indicated by the position of the transverse sinus), whereas the labyrinth was constrained to remain nearer the base of the brainstem adjacent to its innervation from the eighth cranial nerve. Thus, the flocculus in 
<taxonomicName id="4C755BD4FF87F9485535508FEBA0FD7D" authorityName="Osborn" authorityYear="1905" box="[1120,1191,737,758]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F9485535508FEBA0FD7D" box="[1120,1191,737,758]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
may simply not have reached the labyrinth. However, not only are there potential differences in brain structure (cerebellar position), but also the flocculus on the endocast is truly apomorphically small-and not only relative to body mass but also absolutely in that the floccular dimensions of all three adult 
<taxonomicName id="4C755BD4FF87F948529951EFEB0AFC1D" authorityName="Osborn" authorityYear="1905" box="[972,1037,897,918]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F948529951EFEB0AFC1D" box="[972,1037,897,918]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
specimens are smaller than those in smaller-bodied theropods, such as 
<taxonomicName id="4C755BD4FF87F948559051F5EA8AFC3B" box="[1221,1421,923,944]" class="Reptilia" family="Carcharodontosauridae" genus="Acrocanthosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948559051F5EA8AFC3B" box="[1221,1421,923,944]" italics="true" pageId="15" pageNumber="1281">Acrocanthosaurus</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF87F948521551D8ECBFFC40" authorityName="Marsh" authorityYear="1877" box="[832,952,950,971]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948521551D8ECBFFC40" box="[832,952,950,971]" italics="true" pageId="15" pageNumber="1281">Allosaurus</emphasis>
</taxonomicName>
. In 
<figureCitation id="134E3CD2FF87F94852BA51D8EB32FC40" box="[1007,1077,950,972]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">Fig. 4</figureCitation>
, 
<taxonomicName id="4C755BD4FF87F948551351D8EBB9FC40" authorityName="Marsh" authorityYear="1877" box="[1094,1214,950,971]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F948551351D8EBB9FC40" box="[1094,1214,950,971]" italics="true" pageId="15" pageNumber="1281">Allosaurus</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF87F94855AA51D8EA46FC40" authorityName="Osborn" authorityYear="1905" box="[1279,1345,950,971]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F94855AA51D8EA46FC40" box="[1279,1345,950,971]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
are reproduced at the same scale, and the flocculus is clearly larger in the former; note also that, based on transverse sinus position, the cerebellum of 
<taxonomicName id="4C755BD4FF87F94855895668EA53FB90" authorityName="Marsh" authorityYear="1877" box="[1244,1364,1030,1051]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F94855895668EA53FB90" box="[1244,1364,1030,1051]" italics="true" pageId="15" pageNumber="1281">Allosaurus</emphasis>
</taxonomicName>
has the more typical caudoventral position.
</paragraph>
<paragraph id="8BCA2057FF87F948520D5655EA93F9ED" blockId="15.[832,1473,230,1958]" pageId="15" pageNumber="1281">
The cranial nerve trunks are clearly identifiable on the endocasts, and they generally conform to a pattern that is highly conserved among dinosaurs (
<bibRefCitation id="EFE45DA6FF87F9485430561FEC7EFB2A" author="Hopson JA" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="15" pageNumber="1281" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
). Thus, we will not describe all the trunks in detail (see 
<figureCitation id="134E3CD2FF87F948522156C8ECDAFB37" box="[884,989,1190,1212]" captionStart-0="Fig" captionStart-1="Fig" captionStart-2="Fig" captionStart-3="Fig" captionStartId-0="5.[354,384,1890,1909]" captionStartId-1="7.[354,384,1779,1798]" captionStartId-2="9.[178,208,1769,1788]" captionStartId-3="11.[178,208,1769,1788]" captionTargetBox-0="[176,1456,556,1858]" captionTargetBox-1="[336,1296,272,1747]" captionTargetBox-2="[246,1387,229,1733]" captionTargetBox-3="[258,1374,229,1733]" captionTargetId-0="figure@5.[176,1458,556,1859]" captionTargetId-1="figure@7.[336,1296,272,1747]" captionTargetId-2="figure@9.[246,1388,229,1733]" captionTargetId-3="figure@11.[258,1375,229,1733]" captionTargetPageId-0="5" captionTargetPageId-1="7" captionTargetPageId-2="9" captionTargetPageId-3="11" captionText-0="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." captionText-1="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." captionText-2="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." captionText-3="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi-0="http://doi.org/10.5281/zenodo.3942773" figureDoi-1="http://doi.org/10.5281/zenodo.3942777" figureDoi-2="http://doi.org/10.5281/zenodo.3942781" figureDoi-3="http://doi.org/10.5281/zenodo.3942785" httpUri-0="https://zenodo.org/record/3942773/files/figure.png" httpUri-1="https://zenodo.org/record/3942777/files/figure.png" httpUri-2="https://zenodo.org/record/3942781/files/figure.png" httpUri-3="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">Figs. 1–4</figureCitation>
). The cranial nerves were probably accompanied by veins (as in extant archosaurs; 
<bibRefCitation id="EFE45DA6FF87F948540456AEEC7FFB7A" author="Sedlmayr JC" bookContentInfo="398" firstAuthor="Sedlmayr" journalOrPublisher="Ohio University, Athens, Ohio" pageId="15" pageNumber="1281" refId="ref23203" refString="Sedlmayr JC. 2002. Anatomy, evolution, and functional significance of cephalic vasculature in Archosauria. Ph. D. Dissertation, Ohio University, Athens, Ohio. p 398." title="Anatomy, evolution, and functional significance of cephalic vasculature in Archosauria" type="book" year="2002">Sedlmayr, 2002</bibRefCitation>
), and the size of the canals may not be fully indicative of the enclosed nerve. For example, the oculomotor canal is quite large in all of the 
<taxonomicName id="4C755BD4FF87F9485593577FEA00FAAD" authorityName="Osborn" authorityYear="1905" box="[1222,1287,1297,1318]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF87F9485593577FEA00FAAD" box="[1222,1287,1297,1318]" italics="true" pageId="15" pageNumber="1281">T. rex</emphasis>
</taxonomicName>
endocasts, suggesting that substantial orbital veins accompanied cranial nerve III. It should be noted that 
<bibRefCitation id="EFE45DA6FF87F948547B5728EB06FAFD" author="Saveliev SV &amp; Alifanov VR" firstAuthor="Saveliev" journalOrPublisher="Paleontol J" pageId="15" pageNumber="1281" pagination="47 - 55" part="41" refId="ref23134" refString="Saveliev SV, Alifanov VR. 2007. A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae). Paleontol J 41: 47 - 55." title="A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)" type="journal article" year="2007">Saveliev and Alifanov’s (2007)</bibRefCitation>
criticisms of 
<bibRefCitation id="EFE45DA6FF87F94855FA570EEA64FAFD" author="Brochu CA" box="[1199,1379,1376,1398]" firstAuthor="Brochu's" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu’s (2000)</bibRefCitation>
cranial nerve identifications are almost entirely in error, and our findings largely support those of 
<bibRefCitation id="EFE45DA6FF87F948544157F8EABAFA27" author="Brochu CA" box="[1300,1469,1430,1452]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000)</bibRefCitation>
. Tyrannosaurs differ from other theropods in a number of features. One feature found in all of the tyrannosaurs in our study but, thus far, nowhere else is the lateral union of the facial (CN VII) and maxillomandibular (CN V 
<subScript id="17F12212FF87F94854CF5464EABFF993" attach="left" box="[1434,1464,1546,1560]" fontSize="6" pageId="15" pageNumber="1281">2–3</subScript>
) canals (
<figureCitation id="134E3CD2FF87F94852C95475ECE9F9BB" box="[924,1006,1563,1585]" captionStart="Fig" captionStartId="5.[354,384,1890,1909]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="15" pageNumber="1281">Figs. 1</figureCitation>
, 
<figureCitation id="134E3CD2FF87F94855565475EB17F9BA" box="[1027,1040,1563,1585]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="15" pageNumber="1281">3</figureCitation>
) such that they open in a common bony aperture on the external surface of the braincase (
<figureCitation id="134E3CD2FF87F948521D543EEC8FF9ED" box="[840,904,1616,1638]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="15" pageNumber="1281">Fig. 5</figureCitation>
) rather than separately as in other theropods.
</paragraph>
<paragraph id="8BCA2057FF87F957520D5405EFE3FD2D" blockId="15.[832,1473,230,1958]" lastBlockId="16.[160,801,229,1959]" lastPageId="16" lastPageNumber="1282" pageId="15" pageNumber="1281">
As other workers have noted (e.g., 
<bibRefCitation id="EFE45DA6FF87F94855B75405EABBF90B" author="Bakker RT &amp; Williams M &amp; Currie PJ" box="[1250,1468,1643,1665]" etAl="et al." firstAuthor="Bakker" journalOrPublisher="Hunteria" pageId="15" pageNumber="1281" pagination="1 - 30" part="1" refId="ref20052" refString="Bakker RT, Williams M, Currie PJ. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30." title="Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana" type="journal article" year="1988">Bakker et al., 1988</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF87F948521554E8ECD0F910" author="Brochu CA" box="[832,983,1670,1692]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu, 2000</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF87F94852B154E8EB85F917" author="Currie PJ" box="[996,1154,1670,1692]" firstAuthor="Currie" journalOrPublisher="Acta Palaeontol Pol" pageId="15" pageNumber="1281" pagination="191 - 226" part="48" refId="ref20688" refString="Currie PJ. 2003 b. Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontol Pol 48: 191 - 226." title="Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada" type="journal article" year="2003" yearSuffix="b">Currie, 2003b</bibRefCitation>
), tyrannosaurs have a separate bony foramen for the ophthalmic branch of the trigeminal nerve (CN V 
<subScript id="17F12212FF87F948550254AAEB66F959" attach="right" box="[1111,1121,1732,1746]" fontSize="6" pageId="15" pageNumber="1281">1</subScript>
; 
<figureCitation id="134E3CD2FF87F948552154D5EBBEF95A" box="[1140,1209,1723,1745]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="15" pageNumber="1281">Fig. 5</figureCitation>
), and a separate ophthalmic foramen is common among tetanurans although not universal (e.g., 
<taxonomicName id="4C755BD4FF87F9485571549EEB9BF88E" authorityName="Marsh" authorityYear="1877" box="[1060,1180,1776,1797]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="15" pageNumber="1281" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF87F9485571549EEB9BF88E" box="[1060,1180,1776,1797]" italics="true" pageId="15" pageNumber="1281">Allosaurus</emphasis>
</taxonomicName>
has a separate foramen, but not most carcharodontosaurids [
<bibRefCitation id="EFE45DA6FF87F94855835565EA70F8AB" author="Larsson HCE" box="[1238,1399,1803,1824]" editor="Tanke DH &amp; Carpenter K" firstAuthor="Larsson" journalOrPublisher="Bloomington: Indiana University Press" pageId="15" pageNumber="1281" pagination="19 - 33" refId="ref22116" refString="Larsson HCE. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. In: Tanke DH, Carpenter K, editors. Mesozoic vertebrate life. Bloomington: Indiana University Press. p 19 - 33." title="Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution" type="book chapter" volumeTitle="Mesozoic vertebrate life" year="2001">Larsson, 2001</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF87F94854D65565EB0FF8B0" author="Coria RA &amp; Currie PJ" firstAuthor="Coria" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="802 - 811" part="22" refId="ref20533" refString="Coria RA, Currie PJ. 2002. The braincase of Giganotosaurus carolinii (Dinosauria: Theropoda) from the Upper Cretaceous of Argentina. J Vert Paleontol 22: 802 - 811." title="The braincase of Giganotosaurus carolinii (Dinosauria: Theropoda) from the Upper Cretaceous of Argentina" type="journal article" year="2002">Coria and Currie, 2002</bibRefCitation>
; but see 
<bibRefCitation id="EFE45DA6FF87F94855205548EAA9F8B7" author="Brusatte SL &amp; Sereno PC" box="[1141,1454,1829,1852]" firstAuthor="Brusatte" journalOrPublisher="J Vert Paleontol" pageId="15" pageNumber="1281" pagination="902 - 916" part="27" refId="ref20236" refString="Brusatte SL, Sereno PC. 2007. A new species of Carcharodontosaurus (Dinosauria: Theropoda) from the Cenomanian of Niger and a revision of the genus. J Vert Paleontol 27: 902 - 916." title="A new species of Carcharodontosaurus (Dinosauria: Theropoda) from the Cenomanian of Niger and a revision of the genus" type="journal article" year="2007">Brusatte and Sereno, 2007</bibRefCitation>
]). However, tyrannosaurids are different in that the ophthalmic and maxillomandibular canals branch separately off of the endocast (
<figureCitation id="134E3CD2FF87F94855665518EB83F800" box="[1075,1156,1910,1932]" captionStart="Fig" captionStartId="5.[354,384,1890,1909]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="15" pageNumber="1281">Figs. 1</figureCitation>
, 
<figureCitation id="134E3CD2FF87F94855CD5518EBA0F800" box="[1176,1191,1910,1931]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="15" pageNumber="1281">3</figureCitation>
, 
<figureCitation id="134E3CD2FF87F94855EF5518EBDEF807" box="[1210,1241,1910,1932]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="15" pageNumber="1281">4C</figureCitation>
) rather than being united by a short trunk before diverging, as in 
<taxonomicName id="4C755BD4FF98F95751F55288EE1FFF70" authorityName="Marsh" authorityYear="1877" box="[160,280,230,251]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95751F55288EE1FFF70" box="[160,280,230,251]" italics="true" pageId="16" pageNumber="1282">Allosaurus</emphasis>
</taxonomicName>
(UMNH VP 18050, UMNH VP 18055; 
<figureCitation id="134E3CD2FF98F95753A05288EFC6FE9D" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="16" pageNumber="1282">Fig. 4B</figureCitation>
), 
<emphasis id="B901FC45FF98F9575188536EEE81FE9E" box="[221,390,256,277]" italics="true" pageId="16" pageNumber="1282">Struthiomimus</emphasis>
(TMP 90.26.1; 
<figureCitation id="134E3CD2FF98F957531E536EEDADFE9D" box="[587,682,256,278]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="16" pageNumber="1282">Fig. 4D</figureCitation>
), 
<taxonomicName id="4C755BD4FF98F9575390536EEC27FE9E" authorityName="Leidy" authorityYear="1856" box="[709,800,256,277]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F9575390536EEC27FE9E" box="[709,800,256,277]" italics="true" pageId="16" pageNumber="1282">Troodon</emphasis>
</taxonomicName>
(TMP 86.36.457; 
<figureCitation id="134E3CD2FF98F957503D5375EEB8FEBA" box="[360,447,283,305]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="16" pageNumber="1282">Fig. 4E</figureCitation>
), and 
<taxonomicName id="4C755BD4FF98F957535B5372EDBAFEBA" authorityName="Matthew &amp; Brown" authorityYear="1922" box="[526,701,284,305]" class="Reptilia" family="Dromaeosauridae" genus="Dromaeosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957535B5372EDBAFEBA" box="[526,701,284,305]" italics="true" pageId="16" pageNumber="1282">Dromaeosaurus</emphasis>
</taxonomicName>
(AMNH FR 5356), among others. 
<taxonomicName id="4C755BD4FF98F957509D5358ED51FEC0" authorityName="Cope" authorityYear="1866" box="[456,598,310,331]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957509D5358ED51FEC0" box="[456,598,310,331]" italics="true" pageId="16" pageNumber="1282">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247; 
<figureCitation id="134E3CD2FF98F95753A05358EFAAFEED" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="16" pageNumber="1282">Fig. 3</figureCitation>
) takes this even further by having the two canals widely separated. As noted by 
<bibRefCitation id="EFE45DA6FF98F95753565305EDE9FE0A" author="Witmer LM &amp; Ridgely RC" box="[515,750,363,385]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="16" pageNumber="1282" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al. (2008)</bibRefCitation>
, the fact that the ophthalmic and maxillomandibular canals of tyrannosaurs and many other tetanurans arise separately from the endocast indicates that the trigeminal ganglion (the collection of nerve cell bodies proximal to the trigeminal branches) must have been located internally within the endocranial cavity. Having an intracranial position of the trigeminal ganglion is a derived feature found in extant birds, whereas the ganglion of extant crocodilians and many extinct clades such as sauropods had an extracranial position (
<bibRefCitation id="EFE45DA6FF98F957532E501BEFDEFD2D" author="Witmer LM &amp; Ridgely RC" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="16" pageNumber="1282" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
).
</paragraph>
<paragraph id="8BCA2057FF98F95751ED50C5ED20F9BA" blockId="16.[160,801,229,1959]" pageId="16" pageNumber="1282">
Another difference pertains to the region of the pituitary fossa. For 
<taxonomicName id="4C755BD4FF98F957500850A8ED0AFD50" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[349,525,710,731]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957500850A8ED0AFD50" box="[349,525,710,731]" italics="true" pageId="16" pageNumber="1282">Majungasaurus</emphasis>
</taxonomicName>
, 
<bibRefCitation id="EFE45DA6FF98F957537750A8EFE2FD7D" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="16" pageNumber="1282" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer (2007)</bibRefCitation>
described a cavernous-sinus-like morphology in which, as in extant archosaurs (
<bibRefCitation id="EFE45DA6FF98F957537E5095EDE7FC9A" author="Sedlmayr JC" bookContentInfo="398" box="[555,736,763,785]" firstAuthor="Sedlmayr" journalOrPublisher="Ohio University, Athens, Ohio" pageId="16" pageNumber="1282" refId="ref23203" refString="Sedlmayr JC. 2002. Anatomy, evolution, and functional significance of cephalic vasculature in Archosauria. Ph. D. Dissertation, Ohio University, Athens, Ohio. p 398." title="Anatomy, evolution, and functional significance of cephalic vasculature in Archosauria" type="book" year="2002">Sedlmayr, 2002</bibRefCitation>
) and mammals, the abducens and oculomotor canals (again, containing veins as well as nerves) join with the cerebral carotid canal in the pituitary fossa or infundibular region (where the pituitary fossa joins the main cranial cavity). A cavernous sinus involving the abducens and/ or oculomotor canals characterizes many archosaurs and basal theropods (e.g., 
<taxonomicName id="4C755BD4FF98F95750BD51D8ED89FC40" authorityName="Reig" authorityYear="1963" box="[488,654,950,971]" class="Reptilia" family="Herrerasauridae" genus="Herrerasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95750BD51D8ED89FC40" box="[488,654,950,971]" italics="true" pageId="16" pageNumber="1282">Herrerasaurus</emphasis>
</taxonomicName>
MCZ 7063; 
<taxonomicName id="4C755BD4FF98F95751F551BEEE1CFC6E" authorityName="Marsh" authorityYear="1877" box="[160,283,976,997]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95751F551BEEE1CFC6E" box="[160,283,976,997]" italics="true" pageId="16" pageNumber="1282">Allosaurus</emphasis>
</taxonomicName>
, UMNH VP 18055; 
<taxonomicName id="4C755BD4FF98F957531851BEEC1EFC6E" box="[589,793,976,997]" class="Reptilia" family="Carcharodontosauridae" genus="Acrocanthosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957531851BEEC1EFC6E" box="[589,793,976,997]" italics="true" pageId="16" pageNumber="1282">Acrocanthosaurus</emphasis>
</taxonomicName>
, OMNH 10146; 
<taxonomicName id="4C755BD4FF98F957500D5185ED49FB8B" baseAuthorityName="Larsson" baseAuthorityYear="2001" box="[344,590,1003,1024]" class="Reptilia" family="Carcharodontosauridae" genus="Carcharodontosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957500D5185ED49FB8B" box="[344,590,1003,1024]" italics="true" pageId="16" pageNumber="1282">Carcharodontosaurus</emphasis>
</taxonomicName>
[
<bibRefCitation id="EFE45DA6FF98F95753375185EC09FB8A" author="Larsson HCE" box="[610,782,1002,1025]" editor="Tanke DH &amp; Carpenter K" firstAuthor="Larsson" journalOrPublisher="Bloomington: Indiana University Press" pageId="16" pageNumber="1282" pagination="19 - 33" refId="ref22116" refString="Larsson HCE. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. In: Tanke DH, Carpenter K, editors. Mesozoic vertebrate life. Bloomington: Indiana University Press. p 19 - 33." title="Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution" type="book chapter" volumeTitle="Mesozoic vertebrate life" year="2001">Larsson, 2001</bibRefCitation>
]). Most coelurosaurs (e.g., 
<taxonomicName id="4C755BD4FF98F95750EA5668ED1EFB90" authorityName="Leidy" authorityYear="1856" box="[447,537,1030,1051]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95750EA5668ED1EFB90" box="[447,537,1030,1051]" italics="true" pageId="16" pageNumber="1282">Troodon</emphasis>
</taxonomicName>
, TMP 86.36.457; 
<taxonomicName id="4C755BD4FF98F95753BB5668EE2FFBBD" authorityName="Matthew &amp; Brown" authorityYear="1922" class="Reptilia" family="Dromaeosauridae" genus="Dromaeosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95753BB5668EE2FFBBD" italics="true" pageId="16" pageNumber="1282">Dromaeosaurus</emphasis>
</taxonomicName>
, AMNH FR 5356), however, show a derived condition in which the abducens and oculomotor canals tend to open into the endocranial cavity separate from the pituitary/infundibular region such that there is, strictly speaking, no cavernous sinus. All three 
<taxonomicName id="4C755BD4FF98F957538856E2EC1AFB2A" authorityName="Osborn" authorityYear="1905" box="[733,797,1164,1185]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF98F957538856E2EC1AFB2A" box="[733,797,1164,1185]" italics="true" pageId="16" pageNumber="1282">T. rex</emphasis>
</taxonomicName>
endocasts clearly display the derived coelurosaurian condition (
<figureCitation id="134E3CD2FF98F957504956AEEE8CFB5D" box="[284,395,1216,1238]" captionStart-0="Fig" captionStart-1="Fig" captionStart-2="Fig" captionStart-3="Fig" captionStart-4="Fig" captionStartId-0="5.[354,384,1890,1909]" captionStartId-1="7.[354,384,1779,1798]" captionStartId-2="9.[178,208,1769,1788]" captionStartId-3="11.[178,208,1769,1788]" captionStartId-4="12.[178,208,1769,1788]" captionTargetBox-0="[176,1456,556,1858]" captionTargetBox-1="[336,1296,272,1747]" captionTargetBox-2="[246,1387,229,1733]" captionTargetBox-3="[258,1374,229,1733]" captionTargetBox-4="[277,1355,229,1733]" captionTargetId-0="figure@5.[176,1458,556,1859]" captionTargetId-1="figure@7.[336,1296,272,1747]" captionTargetId-2="figure@9.[246,1388,229,1733]" captionTargetId-3="figure@11.[258,1375,229,1733]" captionTargetId-4="figure@12.[277,1357,229,1733]" captionTargetPageId-0="5" captionTargetPageId-1="7" captionTargetPageId-2="9" captionTargetPageId-3="11" captionTargetPageId-4="12" captionText-0="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." captionText-1="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." captionText-2="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." captionText-3="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." captionText-4="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi-0="http://doi.org/10.5281/zenodo.3942773" figureDoi-1="http://doi.org/10.5281/zenodo.3942777" figureDoi-2="http://doi.org/10.5281/zenodo.3942781" figureDoi-3="http://doi.org/10.5281/zenodo.3942785" figureDoi-4="http://doi.org/10.5281/zenodo.3942787" httpUri-0="https://zenodo.org/record/3942773/files/figure.png" httpUri-1="https://zenodo.org/record/3942777/files/figure.png" httpUri-2="https://zenodo.org/record/3942781/files/figure.png" httpUri-3="https://zenodo.org/record/3942785/files/figure.png" httpUri-4="https://zenodo.org/record/3942787/files/figure.png" pageId="16" pageNumber="1282">Figs. 1–5</figureCitation>
). The relevant area of ROM 1247 (
<taxonomicName id="4C755BD4FF98F95751FD56B5EE3EFB7B" authorityName="Cope" authorityYear="1866" box="[168,313,1243,1264]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95751FD56B5EE3EFB7B" box="[168,313,1243,1264]" italics="true" pageId="16" pageNumber="1282">Gorgosaurus</emphasis>
</taxonomicName>
) is missing (drilled out for a mounting rod). The area is preserved in 
<materialsCitation id="3B1D2A0AFF98F95753435698EDACFA87" ID-GBIF-Occurrence="2813094438" box="[534,683,1270,1292]" collectionCode="CMNH" pageId="16" pageNumber="1282" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, however, and is very different from the three definitive 
<taxonomicName id="4C755BD4FF98F9575380577FEC1EFAAD" authorityName="Osborn" authorityYear="1905" box="[725,793,1297,1318]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF98F9575380577FEC1EFAAD" box="[725,793,1297,1318]" italics="true" pageId="16" pageNumber="1282">T. rex</emphasis>
</taxonomicName>
. The abducens canals in 
<materialsCitation id="3B1D2A0AFF98F95750EA5745ED57FACA" ID-GBIF-Occurrence="2813094327" box="[447,592,1323,1345]" collectionCode="CMNH" pageId="16" pageNumber="1282" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
almost intersects the pituitary fossa (
<figureCitation id="134E3CD2FF98F95750C45728EEDFFAD7" box="[401,472,1350,1372]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="16" pageNumber="1282">Fig. 3</figureCitation>
) rather than, as in 
<taxonomicName id="4C755BD4FF98F95753805728EC1EFAD0" authorityName="Osborn" authorityYear="1905" box="[725,793,1350,1371]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF98F95753805728EC1EFAD0" box="[725,793,1350,1371]" italics="true" pageId="16" pageNumber="1282">T. rex</emphasis>
</taxonomicName>
, strongly diverging lateral to it. It is tempting to score 
<materialsCitation id="3B1D2A0AFF98F95751F55715EE37FA1A" ID-GBIF-Occurrence="2813094321" box="[160,304,1403,1425]" collectionCode="CMNH" pageId="16" pageNumber="1282" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
with the primitive condition, but its diencephalic region is either highly apomorphic (being shifted relatively forward, again unlike 
<taxonomicName id="4C755BD4FF98F957533E57DFEDACFA4D" authorityName="Osborn" authorityYear="1905" box="[619,683,1457,1478]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF98F957533E57DFEDACFA4D" box="[619,683,1457,1478]" italics="true" pageId="16" pageNumber="1282">T. rex</emphasis>
</taxonomicName>
) or is distorted because of postmortem factors (see below). Thus, we regard the condition in the Cleveland skull as either a transformation from the derived coelurosaur condition or an artifact of preservation.
</paragraph>
<paragraph id="8BCA2057FF98F95751ED5458EBACFD07" blockId="16.[160,801,229,1959]" lastBlockId="16.[832,1472,230,1958]" pageId="16" pageNumber="1282">
The vagal (or jugular) canal, transmitting cranial nerves X and XI and probably a small posterior cerebral (jugular) vein, clearly passes caudal to the crista tuberalis (the web of otoccipital connecting the paroccipital process to the basal tuber; 
<bibRefCitation id="EFE45DA6FF98F957509554CFED72F93D" author="Kurzanov SM" box="[448,629,1696,1718]" firstAuthor="Kurzanov" journalOrPublisher="Paleontol J" pageId="16" pageNumber="1282" pagination="361 - 369" part="1976" refId="ref22003" refString="Kurzanov SM. 1976. Brain-case structure in the carnosaur Itemirus N. gen. and some aspects of the cranial anatomy of dinosaurs. Paleontol J 1976: 361 - 369." title="Brain-case structure in the carnosaur Itemirus N. gen. and some aspects of the cranial anatomy of dinosaurs" type="journal article" year="1976">Kurzanov, 1976</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF98F95753D054CEEE30F95A" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="16" pageNumber="1282" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
) to open on the occiput (
<figureCitation id="134E3CD2FF98F957530754D5ED99F95B" box="[594,670,1723,1745]" captionStart="Fig" captionStartId="5.[354,384,1890,1909]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="16" pageNumber="1282">Figs. 1</figureCitation>
, 
<figureCitation id="134E3CD2FF98F95753F854D5EDBBF95B" box="[685,700,1723,1744]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="16" pageNumber="1282">2</figureCitation>
, 
<figureCitation id="134E3CD2FF98F957539F54D5EDDEF95A" box="[714,729,1723,1745]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="16" pageNumber="1282">5</figureCitation>
). This condition was recently identified in abelisaurids (
<bibRefCitation id="EFE45DA6FF98F957538D54B8EEA4F88D" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="16" pageNumber="1282" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
), and thus is not as advanced a feature as once thought (
<bibRefCitation id="EFE45DA6FF98F95750EB5565ED7CF8AB" author="Chatterjee S." box="[446,635,1803,1825]" firstAuthor="Chatterjee" journalOrPublisher="Natl Geogr Res Expl" pageId="16" pageNumber="1282" pagination="274 - 285" part="9" refId="ref20403" refString="Chatterjee S. 1993. Shuvosaurus, a new theropod. Natl Geogr Res Expl 9: 274 - 285." title="Shuvosaurus, a new theropod" type="journal article" year="1993">Chatterjee, 1993</bibRefCitation>
; see also 
<bibRefCitation id="EFE45DA6FF98F95753BE5562EE16F8B7" author="Rauhut OWM" firstAuthor="Rauhut" journalOrPublisher="Spec Pap Palaeontol" pageId="16" pageNumber="1282" pagination="1 - 213" part="69" refId="ref22734" refString="Rauhut OWM. 2003. The interrelationships and evolution of basal theropod dinosaurs. Spec Pap Palaeontol 69: 1 - 213." title="The interrelationships and evolution of basal theropod dinosaurs" type="journal article" year="2003">Rauhut, 2003</bibRefCitation>
). In 
<taxonomicName id="4C755BD4FF98F957501F5548EEDFF8B0" authorityName="Cope" authorityYear="1866" box="[330,472,1830,1851]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957501F5548EEDFF8B0" box="[330,472,1830,1851]" italics="true" pageId="16" pageNumber="1282">Gorgosaurus</emphasis>
</taxonomicName>
and adult 
<taxonomicName id="4C755BD4FF98F95753095548ED9BF8B0" authorityName="Osborn" authorityYear="1905" box="[604,668,1830,1851]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF98F95753095548ED9BF8B0" box="[604,668,1830,1851]" italics="true" pageId="16" pageNumber="1282">T. rex</emphasis>
</taxonomicName>
specimens, the vagal canal opens caudally within the paracondylar fossa adjacent to the hypoglossal canal (
<figureCitation id="134E3CD2FF98F95753C55535EDDEF8FA" box="[656,729,1883,1905]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="16" pageNumber="1282">Fig. 3</figureCitation>
), just as in 
<taxonomicName id="4C755BD4FF98F95751A75518EE6DF800" authorityName="Marsh" authorityYear="1877" box="[242,362,1910,1931]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95751A75518EE6DF800" box="[242,362,1910,1931]" italics="true" pageId="16" pageNumber="1282">Allosaurus</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF98F95750E25518EE45F82C" authority="(Sampson and Witmer, 2007)" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95750E25518ED60F800" box="[439,615,1910,1931]" italics="true" pageId="16" pageNumber="1282">Majungasaurus</emphasis>
(
<bibRefCitation id="EFE45DA6FF98F957532A5518EE3DF82C" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="16" pageNumber="1282" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
)
</taxonomicName>
. In 
<materialsCitation id="3B1D2A0AFF98F957503B55FFEEFAF82D" ID-GBIF-Occurrence="2813094382" box="[366,509,1936,1958]" collectionCode="CMNH" pageId="16" pageNumber="1282" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, however, the vagal canal extends strongly laterally to open not next to the hypoglossal but relatively far lateral to it (
<figureCitation id="134E3CD2FF98F95755A5536EEA35FE9D" box="[1264,1330,256,278]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="16" pageNumber="1282">Fig. 3</figureCitation>
); this difference is real and cannot be attributed to postmortem deformation. The glossopharyngeal nerve did not run through the vagal canal in potentially any of the tyrannosaurs under study here, but rather passed rostral to the crista tuberalis, running through a separate canal rostral to the vagal canal and ventral to the columellar canal (
<figureCitation id="134E3CD2FF98F95752C553D5ECD3FE5A" box="[912,980,443,465]" captionStart="Fig" captionStartId="6.[354,384,1913,1932]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942775" httpUri="https://zenodo.org/record/3942775/files/figure.png" pageId="16" pageNumber="1282">Fig. 1</figureCitation>
). The lateral course of the nerve is indicated by a well-marked sulcus on the rostral surface of the crista tuberalis just ventral to the aperture of the caudal tympanic recess (CTR) (
<figureCitation id="134E3CD2FF98F95755FD5065EBEAFDAA" box="[1192,1261,523,545]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="16" pageNumber="1282">Fig. 5</figureCitation>
). 
<bibRefCitation id="EFE45DA6FF98F95754515065EAC7FDAA" author="Kurzanov SM" box="[1284,1472,523,545]" firstAuthor="Kurzanov" journalOrPublisher="Paleontol J" pageId="16" pageNumber="1282" pagination="361 - 369" part="1976" refId="ref22003" refString="Kurzanov SM. 1976. Brain-case structure in the carnosaur Itemirus N. gen. and some aspects of the cranial anatomy of dinosaurs. Paleontol J 1976: 361 - 369." title="Brain-case structure in the carnosaur Itemirus N. gen. and some aspects of the cranial anatomy of dinosaurs" type="journal article" year="1976">Kurzanov (1976)</bibRefCitation>
and 
<bibRefCitation id="EFE45DA6FF98F95752275048EBB7FDB7" author="Sampson SD &amp; Witmer LM" box="[882,1200,550,572]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="16" pageNumber="1282" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer (2007)</bibRefCitation>
reported similar glossopharyngeal grooves for 
<taxonomicName id="4C755BD4FF98F9575534502FEBB8FDDD" authorityName="Kurzanov" authorityYear="1976" box="[1121,1215,577,598]" class="Reptilia" family="Dromaeosauridae" genus="Itemirus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F9575534502FEBB8FDDD" box="[1121,1215,577,598]" italics="true" pageId="16" pageNumber="1282">Itemirus</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF98F957545F502FEABDFDDD" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[1290,1466,577,598]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F957545F502FEABDFDDD" box="[1290,1466,577,598]" italics="true" pageId="16" pageNumber="1282">Majungasaurus</emphasis>
</taxonomicName>
, respectively, and the same is found in 
<taxonomicName id="4C755BD4FF98F95754445035EA8EFDFB" authorityName="Marsh" authorityYear="1877" box="[1297,1417,603,624]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="16" pageNumber="1282" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF98F95754445035EA8EFDFB" box="[1297,1417,603,624]" italics="true" pageId="16" pageNumber="1282">Allosaurus</emphasis>
</taxonomicName>
and may be more widely distributed.
</paragraph>
<paragraph id="8BCA2057FF98F957520D50FFEBA4F90A" blockId="16.[832,1472,230,1958]" pageId="16" pageNumber="1282">
One underappreciated benefit of CT-based endocasts is that the full lengths of nerve and vascular canals can be traced all the way to their foramina on the external surface of the braincase. Identifying braincase foramina can be daunting because of the high variability of the surface of the braincase. However, based on our broader studies, the internal (endocranial) ends of these canals are highly conserved across archosaurs and are easily identified. Thus, visualizing the full lengths of the endocast canals simultaneously with the bony braincase makes identifying external braincase foramina a trivial matter (
<figureCitation id="134E3CD2FF98F95752CB51D8ECE4FC47" box="[926,995,950,972]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="16" pageNumber="1282">Fig. 5</figureCitation>
). In this light, we would note that many of the foramina are incorrectly labeled by previous workers (e.g., 
<bibRefCitation id="EFE45DA6FF98F95752E25185EB50FB8B" author="Osborn HF" box="[951,1111,1003,1025]" firstAuthor="Osborn" journalOrPublisher="Mem Am Mus Nat Hist" pageId="16" pageNumber="1282" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn, 1912</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF98F957553E5185EA0CFB8A" author="Brochu CA" box="[1131,1291,1003,1025]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="16" pageNumber="1282" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu, 2003</bibRefCitation>
). For example, many of 
<bibRefCitation id="EFE45DA6FF98F95752EC5668EB77FB97" author="Osborn HF" box="[953,1136,1030,1052]" firstAuthor="Osborn's" journalOrPublisher="Mem Am Mus Nat Hist" pageId="16" pageNumber="1282" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn’s (1912)</bibRefCitation>
identifications are painted directly on 
<materialsCitation id="3B1D2A0AFF98F957529D564FEB8EFBBD" ID-GBIF-Occurrence="2813094316" box="[968,1161,1056,1078]" collectionCode="AMNH" pageId="16" pageNumber="1282" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, a photograph of which is shown in figure 7 in 
<bibRefCitation id="EFE45DA6FF98F95755635655EBDDFBDA" author="Osborn HF" box="[1078,1242,1083,1105]" firstAuthor="Osborn" journalOrPublisher="Mem Am Mus Nat Hist" pageId="16" pageNumber="1282" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn (1912)</bibRefCitation>
. Almost all of these are incorrect: e.g., (1) ‘‘fen. ov.’’ (fenestra ovalis, = f. vestibuli) is the aperture of the CTR, (2) ‘‘VII’’ is the columellar canal, (3) ‘‘V 
<subScript id="17F12212FF98F957555D56FAEB26FB29" attach="left" box="[1032,1057,1172,1186]" fontSize="6" pageId="16" pageNumber="1282">2,3</subScript>
’’ is the prootic pneumatic recess, (4) ‘‘V 
<subScript id="17F12212FF98F957520E56C1EC62FB36" attach="left" box="[859,869,1199,1213]" fontSize="6" pageId="16" pageNumber="1282">1</subScript>
’’ is the common opening of CN V 
<subScript id="17F12212FF98F957558856C1EBFCFB36" attach="left" box="[1245,1275,1199,1213]" fontSize="6" pageId="16" pageNumber="1282">2–3</subScript>
and CN VII, and (5) ‘‘IV’’ is CN V 
<subScript id="17F12212FF98F957555756A4EB0BFB53" attach="left" box="[1026,1036,1226,1240]" fontSize="6" pageId="16" pageNumber="1282">1</subScript>
. Brochu’s braincase illustration (
<bibRefCitation id="EFE45DA6FF98F95754DA56AEECB7FB7B" author="Brochu CA" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="16" pageNumber="1282" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu, 2003</bibRefCitation>
: Fig. 30) corrects some of Osborn’s errors, but a few still remain: (1) ‘‘V 
<subScript id="17F12212FF98F95755335691EB78FA86" attach="left" box="[1126,1151,1279,1293]" fontSize="6" pageId="16" pageNumber="1282">2,3</subScript>
’’ is the common opening of CN V 
<subScript id="17F12212FF98F957522B5774EC9AFAA3" attach="left" box="[894,925,1306,1320]" fontSize="6" pageId="16" pageNumber="1282">2–3</subScript>
and CN VII, (2) ‘‘VII’’ is probably either the columellar recess or the glossopharyngeal foramen, (3) ‘‘car’’ (carotid foramen) is unknown because the carotid foramen is tucked up deep to the preotic pendant within the rostral tympanic recess (RTR), (4) ‘‘eor’’ (external otic recess) is also unknown because none of the specimens has an aperture in that position, (5) ‘‘III’’ is CN IV (trochlear canal), and (6) ‘‘IV’’ is CN III (oculomotor canal). In contrast with the external openings, 
<bibRefCitation id="EFE45DA6FF98F95754355788EC82F99D" author="Osborn HF" firstAuthor="Osborn's" journalOrPublisher="Mem Am Mus Nat Hist" pageId="16" pageNumber="1282" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn’s (1912)</bibRefCitation>
identifications painted on the endocranial surface of 
<materialsCitation id="3B1D2A0AFF98F95752095475EB15F9BA" ID-GBIF-Occurrence="2813094435" box="[860,1042,1563,1585]" collectionCode="AMNH" pageId="16" pageNumber="1282" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
are virtually all correct (
<figureCitation id="134E3CD2FF98F957547A5475EA76F9BB" box="[1327,1393,1563,1585]" captionStart="Fig" captionStartId="17.[354,384,1661,1680]" captionTargetBox="[175,1458,229,1630]" captionTargetId="figure@17.[175,1458,229,1630]" captionTargetPageId="17" captionText="Fig. 7. Endocranial region of Tyrannosaurus rex (actual fossil specimen of AMNH FR 5029, sagittally sec- tioned) in left medial view to show the fine vascular grooves on the endocranial surface.A, Labeled view show- ing the whole endocranial cavity. B, Close-up view with reversed stereopairs such that the endocranial cavity looks ‘‘filled,’’ making the view more comparable to the digital endocasts illustrated elsewhere in this article." figureDoi="http://doi.org/10.5281/zenodo.3942793" httpUri="https://zenodo.org/record/3942793/files/figure.png" pageId="16" pageNumber="1282">Fig. 7</figureCitation>
), highlighting the difficulty of correlating conservative endocranial morphology with variable external morphology without the aid of CT scanning.
</paragraph>
<paragraph id="8BCA2057FF98F955520D54E8ED0EFE5B" blockId="16.[832,1472,230,1958]" lastBlockId="18.[160,801,230,465]" lastPageId="18" lastPageNumber="1284" pageId="16" pageNumber="1282">
Despite the benefits of digital endocasts, CT scanning currently cannot adequately resolve very fine features, such as the faint bony grooves produced by meningeal blood vessels. First illustrated by 
<bibRefCitation id="EFE45DA6FF98F957558054B8EA75F967" author="Russell DA" box="[1237,1394,1750,1772]" firstAuthor="Russell" journalOrPublisher="Can J Earth Sci" pageId="16" pageNumber="1282" pagination="595 - 612" part="6" refId="ref23009" refString="Russell DA. 1969. A new specimen of Stenonychosaurus from the Oldman Formation (Cretaceous) of Alberta. Can J Earth Sci 6: 595 - 612." title="A new specimen of Stenonychosaurus from the Oldman Formation (Cretaceous) of Alberta" type="journal article" year="1969">Russell (1969</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF98F95754D654B8EABEF967" author="Russell DA" box="[1411,1465,1750,1772]" firstAuthor="Russell" journalOrPublisher="Can J Earth Sci" pageId="16" pageNumber="1282" pagination="375 - 402" part="9" refId="ref23065" refString="Russell DA. 1972. Ostrich dinosaurs from the Late Cretaceous of western Canada. Can J Earth Sci 9: 375 - 402." title="Ostrich dinosaurs from the Late Cretaceous of western Canada" type="journal article" year="1972">1972</bibRefCitation>
) for troodontids and ornithomimosaurs, the presence of such vascular grooves has been used as evidence that the brain so filled the endocranial cavity that grooves were etched in the bone (
<bibRefCitation id="EFE45DA6FF98F9575524552EEA16F8DD" author="Hopson JA" box="[1137,1297,1856,1878]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="16" pageNumber="1282" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
). The presence of fine vascular grooves has since been reported in oviraptorosaurs (
<bibRefCitation id="EFE45DA6FF98F95752AB551BEBB7F807" author="Osmolska H." box="[1022,1200,1909,1932]" firstAuthor="Osmolska" journalOrPublisher="Acta Palaeontol Pol" pageId="16" pageNumber="1282" pagination="321 - 324" part="49" refId="ref22629" refString="Osmolska H. 2004. Evidence on relation of brain to endocranial cavity in oviraptorid dinosaurs. Acta Palaeontol Pol 49: 321 - 324." title="Evidence on relation of brain to endocranial cavity in oviraptorid dinosaurs" type="journal article" year="2004">Osmólska, 2004</bibRefCitation>
) and even some ornithischians (hadrosaurs and pachycephalosaurs; 
<bibRefCitation id="EFE45DA6FF98F956542155FFEFDFF8AA" author="Evans DC" firstAuthor="Evans" journalOrPublisher="Acta Palaeontol Pol" lastPageId="17" lastPageNumber="1283" pageId="16" pageNumber="1282" pagination="617 - 622" part="50" refId="ref20944" refString="Evans DC. 2005. New evidence on brain-endocranial cavity relationships in Ornithischian Dinosaurs. Acta Palaeontol Pol 50: 617 - 622." title="New evidence on brain-endocranial cavity relationships in Ornithischian Dinosaurs" type="journal article" year="2005">Evans, 2005</bibRefCitation>
), again carrying the implication that at least parts of the brain closely fit the endocranial surface. We report here similar grooves in 
<taxonomicName id="4C755BD4FF99F95650FC552FEEE1F8DD" authorityName="Osborn" authorityYear="1905" box="[425,486,1857,1878]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="17" pageNumber="1283" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF99F95650FC552FEEE1F8DD" box="[425,486,1857,1878]" italics="true" pageId="17" pageNumber="1283">T. rex</emphasis>
</taxonomicName>
based on direct observation of the endocranial surface of 
<materialsCitation id="3B1D2A0AFF99F95650AE5535EDBEF8FA" ID-GBIF-Occurrence="2813094375" box="[507,697,1883,1905]" collectionCode="AMNH" pageId="17" pageNumber="1283" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
(
<figureCitation id="134E3CD2FF99F95653985535EC14F8FB" box="[717,787,1883,1905]" captionStart="Fig" captionStartId="17.[354,384,1661,1680]" captionTargetBox="[175,1458,229,1630]" captionTargetId="figure@17.[175,1458,229,1630]" captionTargetPageId="17" captionText="Fig. 7. Endocranial region of Tyrannosaurus rex (actual fossil specimen of AMNH FR 5029, sagittally sec- tioned) in left medial view to show the fine vascular grooves on the endocranial surface.A, Labeled view show- ing the whole endocranial cavity. B, Close-up view with reversed stereopairs such that the endocranial cavity looks ‘‘filled,’’ making the view more comparable to the digital endocasts illustrated elsewhere in this article." figureDoi="http://doi.org/10.5281/zenodo.3942793" httpUri="https://zenodo.org/record/3942793/files/figure.png" pageId="17" pageNumber="1283">Fig. 7</figureCitation>
). There are very clearly a series of multiply branching grooves on the internal surface of the laterosphenoid, perhaps extending onto the adjacent prootic and basisphenoid. Moreover, our cast of PIN 553-3/1 (
<taxonomicName id="4C755BD4FF99F95654055548EC63F8DD" authorityName=", Osborn" authorityYear="1912" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="17" pageNumber="1283" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF99F95654055548EC63F8DD" italics="true" pageId="17" pageNumber="1283">Tarbosaurus</emphasis>
</taxonomicName>
) shows similar fine grooves in the same general positions. We agree with other workers (
<bibRefCitation id="EFE45DA6FF99F95654755535EABBF8FB" author="Osborn HF" box="[1312,1468,1883,1905]" firstAuthor="Osborn" journalOrPublisher="Mem Am Mus Nat Hist" pageId="17" pageNumber="1283" pagination="1 - 30" part="1" refId="ref22607" refString="Osborn HF. 1912. Crania of Tyrannosaurus and Allosaurus. Mem Am Mus Nat Hist 1: 1 - 30." title="Crania of Tyrannosaurus and Allosaurus" type="journal article" year="1912">Osborn, 1912</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF99F95652155518ECE7F800" author="Hopson JA" box="[832,992,1910,1931]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="17" pageNumber="1283" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF99F95652A45518EB8BF807" author="Brochu CA" box="[1009,1164,1910,1932]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="17" pageNumber="1283" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu, 2003</bibRefCitation>
) that the brain generally did not fill its cavity, but these grooves suggest that, using the same argumentation as other workers, some parts of the brain were closely appressed to the bone. Although in all the other reported cases the best grooves were in cerebral regions, the clearest grooves in 
<materialsCitation id="3B1D2A0AFF9AF95553845358EFF8FEED" ID-GBIF-Occurrence="2813094345" collectionCode="AMNH" pageId="18" pageNumber="1284" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
are not in the cerebrum but rather just behind it. Another alternative is that fine vascular grooving may not always indicate a close fit between brain and endocranium, in which case caution should be exerted when interpreting such grooves.
</paragraph>
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<paragraph id="8BCA2057FF99F95650375413EBF6F953" blockId="17.[336,1296,1661,1752]" pageId="17" pageNumber="1283">
Fig. 7. Endocranial region of 
<taxonomicName id="4C755BD4FF99F95653255413EC17F91B" authorityName="Osborn" authorityYear="1905" box="[624,784,1661,1680]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="17" pageNumber="1283" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF99F95653255413EC17F91B" box="[624,784,1661,1680]" italics="true" pageId="17" pageNumber="1283">Tyrannosaurus rex</emphasis>
</taxonomicName>
(actual fossil specimen of 
<materialsCitation id="3B1D2A0AFF99F95652AB5413EB8AF91B" ID-GBIF-Occurrence="2813094322" box="[1022,1165,1661,1680]" collectionCode="AMNH" pageId="17" pageNumber="1283" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
, sagittally sec- tioned) in left medial view to show the fine vascular grooves on the endocranial surface. 
<emphasis id="B901FC45FF99F956551C54F8EB50F923" bold="true" box="[1097,1111,1686,1704]" pageId="17" pageNumber="1283">A</emphasis>
, Labeled view show- ing the whole endocranial cavity. 
<emphasis id="B901FC45FF99F956532354C0ED83F94B" bold="true" box="[630,644,1710,1728]" pageId="17" pageNumber="1283">B</emphasis>
, Close-up view with reversed stereopairs such that the endocranial cavity looks ‘‘filled,’’ making the view more comparable to the digital endocasts illustrated elsewhere in this article.
</paragraph>
</caption>
<paragraph id="8BCA2057FF9AF95551F55392EE25FD9F" blockId="18.[160,801,508,1958]" box="[160,290,508,532]" pageId="18" pageNumber="1284">
<heading id="D082973BFF9AF95551F55392EE25FD9F" bold="true" box="[160,290,508,532]" fontSize="10" level="3" pageId="18" pageNumber="1284" reason="0">
<emphasis id="B901FC45FF9AF95551F55392EE25FD9F" bold="true" box="[160,290,508,532]" pageId="18" pageNumber="1284">Inner Ear</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF9AF95551ED5048ED11FACA" blockId="18.[160,801,508,1958]" pageId="18" pageNumber="1284">
Casts of the endosseous labyrinths were digitally extracted from all of the tyrannosaurs in the sample here, as well as numerous outgroups. Complete labyrinths are available for 
<taxonomicName id="4C755BD4FF9AF95550EF5018EEFCFD00" authorityName="Osborn" authorityYear="1905" box="[442,507,630,651]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF95550EF5018EEFCFD00" box="[442,507,630,651]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF9AF95553685018EDCCFD00" authorityName="Cope" authorityYear="1866" box="[573,715,630,651]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95553685018EDCCFD00" box="[573,715,630,651]" italics="true" pageId="18" pageNumber="1284">Gorgosaurus</emphasis>
</taxonomicName>
, and a partial labyrinth for 
<materialsCitation id="3B1D2A0AFF9AF95550D950FFED1DFD2D" ID-GBIF-Occurrence="2813094372" box="[396,538,656,678]" collectionCode="CMNH" pageId="18" pageNumber="1284" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
(
<figureCitation id="134E3CD2FF9AF955537F50FFED6BFD2C" box="[554,620,657,679]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8</figureCitation>
). 
<bibRefCitation id="EFE45DA6FF9AF95553D650FFEC1BFD2D" author="Brochu CA" box="[643,796,657,679]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="18" pageNumber="1284" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF95551F550C5EFD1FD4A" author="Brochu CA" box="[160,214,683,705]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="18" pageNumber="1284" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">2003</bibRefCitation>
) illustrated some fragments of the labyrinth of 
<materialsCitation id="3B1D2A0AFF9AF95551F550A8EE57FD50" ID-GBIF-Occurrence="2813094433" box="[160,336,710,731]" collectionCode="FMNH" pageId="18" pageNumber="1284" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
; we were able to extract the semicircular canals completely (
<figureCitation id="134E3CD2FF9AF955502A508FEEC2FD7C" box="[383,453,737,759]" captionStart="Fig" captionStartId="9.[178,208,1769,1788]" captionTargetBox="[246,1387,229,1733]" captionTargetId="figure@9.[246,1388,229,1733]" captionTargetPageId="9" captionText="Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942781" httpUri="https://zenodo.org/record/3942781/files/figure.png" pageId="18" pageNumber="1284">Fig. 3</figureCitation>
), and they resemble those of the better preserved 
<taxonomicName id="4C755BD4FF9AF95550DE5092EECFFC9A" authorityName="Osborn" authorityYear="1905" box="[395,456,764,785]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF95550DE5092EECFFC9A" box="[395,456,764,785]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
specimens. All of the tyrannosaur labyrinths are generally similar to each other and resemble those of other theropods in being somewhat triangular in lateral view (
<bibRefCitation id="EFE45DA6FF9AF955509E5125ED62FCEB" author="Rogers SW" box="[459,613,843,864]" firstAuthor="Rogers" journalOrPublisher="Neuron" pageId="18" pageNumber="1284" pagination="673 - 679" part="21" refId="ref22861" refString="Rogers SW. 1998. Exploring dinosaur neuropaleobiology: viewpoint computed tomography scanning and analysis of an Allosaurus fragilis endocast. Neuron 21: 673 - 679." title="Exploring dinosaur neuropaleobiology: viewpoint computed tomography scanning and analysis of an Allosaurus fragilis endocast" type="journal article" year="1998">Rogers, 1998</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF95553225125EDA8FCEB" author="Rogers SW" box="[631,687,843,864]" firstAuthor="Rogers" journalOrPublisher="Anat Rec" pageId="18" pageNumber="1284" pagination="162 - 173" part="257" refId="ref22889" refString="Rogers SW. 1999. Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast. Anat Rec 257: 162 - 173." title="Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast" type="journal article" year="1999">1999</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9AF95553945122EFDFFCF0" author="Larsson HCE" editor="Tanke DH &amp; Carpenter K" firstAuthor="Larsson" journalOrPublisher="Bloomington: Indiana University Press" pageId="18" pageNumber="1284" pagination="19 - 33" refId="ref22116" refString="Larsson HCE. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. In: Tanke DH, Carpenter K, editors. Mesozoic vertebrate life. Bloomington: Indiana University Press. p 19 - 33." title="Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution" type="book chapter" volumeTitle="Mesozoic vertebrate life" year="2001">Larsson, 2001</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9AF95551B25108ED14FCF7" author="Franzosa JW &amp; Rowe TB" box="[231,531,870,892]" firstAuthor="Franzosa" journalOrPublisher="J Vert Paleontol" pageId="18" pageNumber="1284" pagination="859 - 864" part="25" refId="ref21046" refString="Franzosa JW, Rowe TB. 2005. Cranial endocast of the Cretaceous Theropod Dinosaur Acrocanthosaurus atokensis. J Vert Paleontol 25: 859 - 864." title="Cranial endocast of the Cretaceous Theropod Dinosaur Acrocanthosaurus atokensis" type="journal article" year="2005">Franzosa and Rowe, 2005</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9AF95553765108EFDEFC1C" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="18" pageNumber="1284" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
). The semicircular canals are generally thin, elongate, and roughly mutually orthogonal. The only canal that deviates from planarity is the caudal semicircular canal, which is somewhat rostrally bowed dorsally, but not as markedly as in most other coelurosaurs. This departure from planarity of the caudal canal results from the caudodorsal expansion of the rostral semicircular canal beyond the common crus, which has the effect of ‘‘twisting’’ the common crus such that the caudal canal joins the common crus rostrolaterally, imparting a slight rostral bowing of the caudal canal. Although this twisting of the common crus in tyrannosaurs is not as prominent as in other coelurosaurs (e.g., 
<emphasis id="B901FC45FF9AF955532256AFEC27FB5D" box="[631,800,1217,1238]" italics="true" pageId="18" pageNumber="1284">Struthiomimus</emphasis>
[
<figureCitation id="134E3CD2FF9AF95551F256B5EFF7FB7A" box="[167,240,1242,1265]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8</figureCitation>
Q–T], 
<taxonomicName id="4C755BD4FF9AF955501756B5EE9AFB7B" authorityName="Leidy" authorityYear="1856" box="[322,413,1243,1264]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF955501756B5EE9AFB7B" box="[322,413,1243,1264]" italics="true" pageId="18" pageNumber="1284">Troodon</emphasis>
</taxonomicName>
, 
<emphasis id="B901FC45FF9AF95550E156B5EDE8FB7B" box="[436,751,1243,1264]" italics="true" pageId="18" pageNumber="1284">
<taxonomicName id="4C755BD4FF9AF95550E156B5ED42FB7B" authorityName="Ostrom" authorityYear="1969" box="[436,581,1243,1264]" class="Reptilia" family="Dromaeosauridae" genus="Deinonychus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">Deinonychus</taxonomicName>
, 
<taxonomicName id="4C755BD4FF9AF955530F56B5EDE8FB7B" authorityName="Gilmore" authorityYear="1924" box="[602,751,1243,1264]" class="Reptilia" family="Caenagnathidae" genus="Chirostenotes" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">Chirostenotes</taxonomicName>
</emphasis>
), it still represents a more derived state than that observed in more basal theropods (e.g., 
<taxonomicName id="4C755BD4FF9AF9555357577FED7DFAAD" authorityName="Marsh" authorityYear="1877" box="[514,634,1297,1318]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF9555357577FED7DFAAD" box="[514,634,1297,1318]" italics="true" pageId="18" pageNumber="1284">Allosaurus</emphasis>
</taxonomicName>
, 
<taxonomicName id="4C755BD4FF9AF95553D8577FEFC3FACA" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95553D8577FEFC3FACA" italics="true" pageId="18" pageNumber="1284">Majungasaurus</emphasis>
</taxonomicName>
; 
<bibRefCitation id="EFE45DA6FF9AF95551865745ED0CFACA" author="Sampson SD &amp; Witmer LM" box="[211,523,1323,1345]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="18" pageNumber="1284" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
).
</paragraph>
<paragraph id="8BCA2057FF9AF95551ED5728EA38FE3D" blockId="18.[160,801,508,1958]" lastBlockId="18.[832,1473,230,1345]" pageId="18" pageNumber="1284">
The rostral canal of tyrannosaurs resembles that of other theropods in being the longest, but it is like that of other coelurosaurs in being expanded rostrally as well as caudodorsally (
<figureCitation id="134E3CD2FF9AF955501F57F8EE98FA27" box="[330,415,1430,1452]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8A</figureCitation>
), rather than being more strongly elliptical as in noncoelurosaurian theropods (
<figureCitation id="134E3CD2FF9AF95553E257DEEC13FA4C" box="[695,788,1456,1479]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8U</figureCitation>
). The caudal and lateral semicircular canals are very similar in size and shape, and both are relatively circular. The more circular shape of the lateral canal (
<figureCitation id="134E3CD2FF9AF9555397546EEC1FF99C" box="[706,792,1536,1559]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8B</figureCitation>
) contrasts with the shape reported by 
<bibRefCitation id="EFE45DA6FF9AF95553105472EDDEF9BB" author="Rogers SW" box="[581,729,1563,1585]" firstAuthor="Rogers" journalOrPublisher="Neuron" pageId="18" pageNumber="1284" pagination="673 - 679" part="21" refId="ref22861" refString="Rogers SW. 1998. Exploring dinosaur neuropaleobiology: viewpoint computed tomography scanning and analysis of an Allosaurus fragilis endocast. Neuron 21: 673 - 679." title="Exploring dinosaur neuropaleobiology: viewpoint computed tomography scanning and analysis of an Allosaurus fragilis endocast" type="journal article" year="1998">Rogers (1998</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF95553B15475EC1BF9BB" author="Rogers SW" box="[740,796,1563,1584]" firstAuthor="Rogers" journalOrPublisher="Anat Rec" pageId="18" pageNumber="1284" pagination="162 - 173" part="257" refId="ref22889" refString="Rogers SW. 1999. Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast. Anat Rec 257: 162 - 173." title="Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast" type="journal article" year="1999">1999</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF95551F55458EFDFF9C7" author="Rogers SW" box="[160,216,1590,1612]" firstAuthor="Rogers" journalOrPublisher="Am J Med Gen" pageId="18" pageNumber="1284" pagination="349 - 356" part="134 A" refId="ref22919" refString="Rogers SW. 2005. Reconstructing the behaviors of extinct species: an excursion into comparative paleoneurology. Am J Med Gen 134 A: 349 - 356." title="Reconstructing the behaviors of extinct species: an excursion into comparative paleoneurology" type="journal article" year="2005">2005</bibRefCitation>
, p 352) for 
<taxonomicName id="4C755BD4FF9AF955500F5458EED5F9C0" authorityName="Marsh" authorityYear="1877" box="[346,466,1590,1611]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF955500F5458EED5F9C0" box="[346,466,1590,1611]" italics="true" pageId="18" pageNumber="1284">Allosaurus</emphasis>
</taxonomicName>
, in which the lateral canal is ‘‘hooked’’ caudally such that it makes a sharp bend. Our 
<taxonomicName id="4C755BD4FF9AF95551F55405EE1FF90B" authorityName="Marsh" authorityYear="1877" box="[160,280,1643,1664]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95551F55405EE1FF90B" box="[160,280,1643,1664]" italics="true" pageId="18" pageNumber="1284">Allosaurus</emphasis>
</taxonomicName>
labyrinth shows the same ‘‘hook’’ (
<figureCitation id="134E3CD2FF9AF95553EE5405EC13F90A" box="[699,788,1643,1665]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8V</figureCitation>
), but the tyrannosaurs all more closely resemble 
<emphasis id="B901FC45FF9AF95553EE54E8EFEBF93D" italics="true" pageId="18" pageNumber="1284">Struthiomimus</emphasis>
(
<figureCitation id="134E3CD2FF9AF95551A954CEEE49F93C" box="[252,334,1696,1719]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8R</figureCitation>
) and other coelurosaurs (including birds) in that the lateral canal sweeps laterally in a broader arc. The differences in this attribute can be subtle and variable. For example, 
<materialsCitation id="3B1D2A0AFF9AF95550E1549FED73F88D" ID-GBIF-Occurrence="2813094434" box="[436,628,1776,1798]" collectionCode="AMNH" pageId="18" pageNumber="1284" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
(
<figureCitation id="134E3CD2FF9AF95553DF549EEDE6F88C" box="[650,737,1776,1799]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8B</figureCitation>
) and 
<materialsCitation id="3B1D2A0AFF9AF95551F55562EE4BF8AB" ID-GBIF-Occurrence="2813094391" box="[160,332,1803,1825]" collectionCode="FMNH" pageId="18" pageNumber="1284" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
(not figured) more closely resemble 
<emphasis id="B901FC45FF9AF95553B35565EE10F8B0" italics="true" pageId="18" pageNumber="1284">Struthiomimus</emphasis>
than does 
<materialsCitation id="3B1D2A0AFF9AF95550C05548ED4CF8B0" ID-GBIF-Occurrence="2813094429" box="[405,587,1829,1851]" collectionCode="AMNH" pageId="18" pageNumber="1284" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
(
<figureCitation id="134E3CD2FF9AF955530E5548EDAAF8B7" box="[603,685,1830,1852]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8F</figureCitation>
), which is more similar to 
<taxonomicName id="4C755BD4FF9AF955500E552FEEEEF8DD" authorityName="Cope" authorityYear="1866" box="[347,489,1857,1878]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF955500E552FEEEEF8DD" box="[347,489,1857,1878]" italics="true" pageId="18" pageNumber="1284">Gorgosaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF9AF95550AE552EED4DF8DC" box="[507,586,1856,1879]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8J</figureCitation>
) and 
<materialsCitation id="3B1D2A0AFF9AF95553C4552FEC27F8DD" ID-GBIF-Occurrence="2813094380" box="[657,800,1856,1878]" collectionCode="CMNH" pageId="18" pageNumber="1284" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
(
<figureCitation id="134E3CD2FF9AF95551FD5535EE05F8FA" box="[168,258,1883,1905]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8N</figureCitation>
). This variability may relate to true biological variation or slight diagenetic deformation, but it ultimately speaks to the subtlety of some differences in canal structure. The caudal canal extends just slightly ventral to the lateral canal such that the two are indistinct caudally (
<figureCitation id="134E3CD2FF9AF95552DD5375ECCEFEBA" box="[904,969,283,305]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8</figureCitation>
). This condition characterizes tyrannosaurs, basal theropods (
<bibRefCitation id="EFE45DA6FF9AF95555555358EA3CFEC7" author="Sampson SD &amp; Witmer LM" box="[1024,1339,310,332]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="18" pageNumber="1284" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
), and many coelurosaurs, although some advanced maniraptorans (e.g., 
<taxonomicName id="4C755BD4FF9AF95552D25305EB1BFE0B" authorityName="Gilmore" authorityYear="1924" box="[903,1052,363,384]" class="Reptilia" family="Caenagnathidae" genus="Chirostenotes" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95552D25305EB1BFE0B" box="[903,1052,363,384]" italics="true" pageId="18" pageNumber="1284">Chirostenotes</emphasis>
</taxonomicName>
but not 
<emphasis id="B901FC45FF9AF95555CE5305EA3FFE0B" box="[1179,1336,363,384]" italics="true" pageId="18" pageNumber="1284">Archaeopteryx</emphasis>
) show the beginnings of the derived avian condition of having the lateral and caudal canals distinct throughout.
</paragraph>
<paragraph id="8BCA2057FF9AF955520D53D5EA17FACB" blockId="18.[832,1473,230,1345]" pageId="18" pageNumber="1284">
The vestibule of the inner ear has the typical archosaurian condition of not extending dorsally beyond the level of the lateral canal. The endolymphatic canal enters the vestibule near the base of the common crus (
<figureCitation id="134E3CD2FF9AF955521D5048EC8AFDB7" box="[840,909,550,572]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8</figureCitation>
), which is the condition in theropods as diverse as 
<emphasis id="B901FC45FF9AF9555234502FECF2FDDD" box="[865,1013,577,598]" italics="true" pageId="18" pageNumber="1284">Ceratosaurus</emphasis>
(MWC 1.1), 
<taxonomicName id="4C755BD4FF9AF95555D2502FEA31FDDD" authorityName="Matthew &amp; Brown" authorityYear="1922" box="[1159,1334,577,598]" class="Reptilia" family="Dromaeosauridae" genus="Dromaeosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95555D2502FEA31FDDD" box="[1159,1334,577,598]" italics="true" pageId="18" pageNumber="1284">Dromaeosaurus</emphasis>
</taxonomicName>
(AMNH FR 5356), and 
<taxonomicName id="4C755BD4FF9AF955529A5035EB63FDFB" authorityName="Gilmore" authorityYear="1924" box="[975,1124,603,624]" class="Reptilia" family="Caenagnathidae" genus="Chirostenotes" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF955529A5035EB63FDFB" box="[975,1124,603,624]" italics="true" pageId="18" pageNumber="1284">Chirostenotes</emphasis>
</taxonomicName>
(ROM 43250). The cochlear duct (lagena) projects rostroventrally and slightly medially from the vestibule (
<figureCitation id="134E3CD2FF9AF955550750FEEB92FD2D" box="[1106,1173,656,678]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8</figureCitation>
). It is long and slender in 
<taxonomicName id="4C755BD4FF9AF955521550C2EC83FD4A" authorityName="Osborn" authorityYear="1905" box="[832,900,684,705]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF955521550C2EC83FD4A" box="[832,900,684,705]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
, but may be somewhat shorter in 
<taxonomicName id="4C755BD4FF9AF955546750C5EAC7FD4B" authorityName="Cope" authorityYear="1866" box="[1330,1472,683,704]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF955546750C5EAC7FD4B" box="[1330,1472,683,704]" italics="true" pageId="18" pageNumber="1284">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247 is not well enough preserved to be certain). The cochlea of 
<materialsCitation id="3B1D2A0AFF9AF95552A7508EEB86FD7D" ID-GBIF-Occurrence="2813094393" box="[1010,1153,736,758]" collectionCode="CMNH" pageId="18" pageNumber="1284" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
is relatively very long and thin, even more so than in 
<taxonomicName id="4C755BD4FF9AF95555D55092EBC7FC9A" authorityName="Osborn" authorityYear="1905" box="[1152,1216,764,785]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF95555D55092EBC7FC9A" box="[1152,1216,764,785]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
. It is very straight in all the tyrannosaurs and not medially curved as in 
<emphasis id="B901FC45FF9AF95554D35178ECB0FCCE" italics="true" pageId="18" pageNumber="1284">Struthiomimus</emphasis>
and 
<taxonomicName id="4C755BD4FF9AF95552A8515EEB5FFCCE" authorityName="Leidy" authorityYear="1856" box="[1021,1112,816,837]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95552A8515EEB5FFCCE" box="[1021,1112,816,837]" italics="true" pageId="18" pageNumber="1284">Troodon</emphasis>
</taxonomicName>
. The cochlea varies in length and orientation in theropods, and it may emerge that a long, slender, straight lagena is a tyrannosaur apomorphy. The site where the footplate of the columella contacted the vestibule is very clear and corresponds to the bony fenestra vestibuli (
<figureCitation id="134E3CD2FF9AF955550151DBEB91FC47" box="[1108,1174,949,972]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">Fig. 8</figureCitation>
). Directly caudoventral to the latter is the cast of the fenestra cochleae, marking the position of the perilymphatic duct and secondary tympanic membrane, which is clearly distinct from the vagal canal located caudal to it (
<figureCitation id="134E3CD2FF9AF95555EB564EEA0BFBBE" box="[1214,1292,1056,1078]" captionStart="Fig" captionStartId="5.[354,384,1890,1909]" captionTargetBox="[176,1456,556,1858]" captionTargetId="figure@5.[176,1458,556,1859]" captionTargetPageId="5" captionText="Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views." figureDoi="http://doi.org/10.5281/zenodo.3942773" httpUri="https://zenodo.org/record/3942773/files/figure.png" pageId="18" pageNumber="1284">Figs. 1</figureCitation>
, 
<figureCitation id="134E3CD2FF9AF955544B564EEA2AFBBE" box="[1310,1325,1056,1077]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="18" pageNumber="1284">8</figureCitation>
, 
<figureCitation id="134E3CD2FF9AF9555468564EEA59FBBD" box="[1341,1374,1056,1078]" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="18" pageNumber="1284">9B</figureCitation>
). Unlike most theropods, the fenestra vestibuli is not located on the braincase surface, but rather is recessed far medially such that the columella must pass through a tube, the columellar canal, to reach the fenestra vestibuli (
<figureCitation id="134E3CD2FF9AF95554C056E5EC66FB37" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="18" pageNumber="1284">Fig. 9B</figureCitation>
). In 
<materialsCitation id="3B1D2A0AFF9AF95552CA56C8EB58FB30" ID-GBIF-Occurrence="2813094323" box="[927,1119,1189,1211]" collectionCode="AMNH" pageId="18" pageNumber="1284" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, the columellar canal is more than 40 mm in length, sandwiched between the otoccipital and a superficial lamina of prootic (
<figureCitation id="134E3CD2FF9AF95555AD56B5EA3CFB7A" box="[1272,1339,1243,1265]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="18" pageNumber="1284">Fig. 5</figureCitation>
). In 
<materialsCitation id="3B1D2A0AFF9AF955542456B5EC72FA80" ID-GBIF-Occurrence="2813094352" collectionCode="CMNH" pageId="18" pageNumber="1284" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
(
<figureCitation id="134E3CD2FF9AF95552D85698ECEDFA87" box="[909,1002,1270,1292]" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="18" pageNumber="1284">Fig. 9A</figureCitation>
), 
<materialsCitation id="3B1D2A0AFF9AF95555535698EBBDFA80" ID-GBIF-Occurrence="2813094383" box="[1030,1210,1270,1291]" collectionCode="FMNH" pageId="18" pageNumber="1284" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
(
<taxonomicName id="4C755BD4FF9AF95555865698EA1EFA80" authorityName="Osborn" authorityYear="1905" box="[1235,1305,1270,1291]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF95555865698EA1EFA80" box="[1235,1305,1270,1291]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
), and FMNH PR308 (
<taxonomicName id="4C755BD4FF9AF95552CC577EEB42FAAE" authorityName=", Maleev" authorityYear="1965" box="[921,1093,1296,1317]" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF95552CC577EEB42FAAE" box="[921,1093,1296,1317]" italics="true" pageId="18" pageNumber="1284">Daspletosaurus</emphasis>
</taxonomicName>
), the columellae are preserved in place passing through the tubular recess.
</paragraph>
<paragraph id="8BCA2057FF9AF95552155715EA19FA18" blockId="18.[832,1310,1403,1427]" box="[832,1310,1403,1427]" pageId="18" pageNumber="1284">
<heading id="D082973BFF9AF95552155715EA19FA18" bold="true" box="[832,1310,1403,1427]" fontSize="10" level="3" pageId="18" pageNumber="1284" reason="0">
<emphasis id="B901FC45FF9AF95552155715EA19FA18" bold="true" box="[832,1310,1403,1427]" pageId="18" pageNumber="1284">Pneumatic Sinuses of the Braincase</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF9AF955520D57C8EA24F82D" blockId="18.[832,1472,1446,1958]" pageId="18" pageNumber="1284">
A complex series of air-filled (pneumatic) sinuses permeate the braincases of tyrannosaurs (
<figureCitation id="134E3CD2FF9AF955544457AEEA5EFA5D" box="[1297,1369,1472,1494]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="18" pageNumber="1284">Fig. 2</figureCitation>
), as has been discussed by 
<bibRefCitation id="EFE45DA6FF9AF955554E57B5EBB8FA7A" author="Russell DA" box="[1051,1215,1499,1521]" firstAuthor="Russell" journalOrPublisher="Natl Mus Nat Sci Pub Palaeontol" pageId="18" pageNumber="1284" pagination="1 - 34" part="1" refId="ref23039" refString="Russell DA. 1970. Tyrannosaurs from the Late Cretaceous of Western Canada. Natl Mus Nat Sci Pub Palaeontol 1: 1 - 34." title="Tyrannosaurs from the Late Cretaceous of Western Canada" type="journal article" year="1970">Russell (1970)</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF955559A57B5EABBFA7A" author="Bakker RT &amp; Williams M &amp; Currie PJ" box="[1231,1468,1499,1521]" etAl="et al." firstAuthor="Bakker" journalOrPublisher="Hunteria" pageId="18" pageNumber="1284" pagination="1 - 30" part="1" refId="ref20052" refString="Bakker RT, Williams M, Currie PJ. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30." title="Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana" type="journal article" year="1988">Bakker et al. (1988)</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF95552155798ECEAF987" author="Molnar RE" box="[832,1005,1526,1548]" firstAuthor="Molnar" journalOrPublisher="Palaeontogr Abt A" pageId="18" pageNumber="1284" pagination="137 - 176" part="217" refId="ref22394" refString="Molnar RE. 1991. The cranial morphology of Tyrannosaurus rex. Palaeontogr Abt A 217: 137 - 176." title="The cranial morphology of Tyrannosaurus rex" type="journal article" year="1991">Molnar (1991)</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF9AF95555535798EBB4F987" author="Brochu CA" box="[1030,1203,1526,1548]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="18" pageNumber="1284" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu (2003)</bibRefCitation>
, and 
<bibRefCitation id="EFE45DA6FF9AF955545C5798EABBF987" author="Currie PJ" box="[1289,1468,1526,1548]" firstAuthor="Currie" journalOrPublisher="Acta Palaeontol Pol" pageId="18" pageNumber="1284" pagination="191 - 226" part="48" refId="ref20688" refString="Currie PJ. 2003 b. Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontol Pol 48: 191 - 226." title="Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada" type="journal article" year="2003" yearSuffix="b">Currie (2003b)</bibRefCitation>
, among others. We will base the discussion here largely on our previous attempts to homologize and codify theropod pneumatic sinuses (
<bibRefCitation id="EFE45DA6FF9AF955553C5428EA0CF9D0" author="Witmer LM" box="[1129,1291,1606,1628]" editor="Currie PJ &amp; Padian K" firstAuthor="Witmer" journalOrPublisher="New York: Academic Press" pageId="18" pageNumber="1284" pagination="151 - 159" refId="ref24134" refString="Witmer LM. 1997. Craniofacial air sinus systems. In: Currie PJ, Padian K, editors. Encyclopedia of dinosaurs. New York: Academic Press. p 151 - 159." title="Craniofacial air sinus systems" type="book chapter" volumeTitle="Encyclopedia of dinosaurs" year="1997">Witmer, 1997</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9AF95554755428ECE6F9FE" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="18" pageNumber="1284" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9AF95552A3540EEA45F9FD" author="Witmer LM &amp; Ridgely RC" box="[1014,1346,1632,1654]" firstAuthor="Witmer" journalOrPublisher="Anat Rec" pageId="18" pageNumber="1284" pagination="1362 - 1388" part="291" refId="ref24295" refString="Witmer LM, Ridgely RC. 2008 b. The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture. Anat Rec 291: 1362 - 1388." title="The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture" type="journal article" year="2008" yearSuffix="b">Witmer and Ridgely, 2008b</bibRefCitation>
, in press; 
<bibRefCitation id="EFE45DA6FF9AF95552155415EB19F91A" author="Witmer LM &amp; Ridgely RC" box="[832,1054,1659,1681]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="18" pageNumber="1284" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
). 
<figureCitation id="134E3CD2FF9AF95555645415EB97F91B" box="[1073,1168,1659,1681]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="18" pageNumber="1284">Figure 2</figureCitation>
presents the basic pattern of sinuses in 
<taxonomicName id="4C755BD4FF9AF955528A54F8EB27F920" authorityName="Osborn" authorityYear="1905" box="[991,1056,1686,1707]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF955528A54F8EB27F920" box="[991,1056,1686,1707]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
based on 
<materialsCitation id="3B1D2A0AFF9AF95555C854F8EA5BF920" ID-GBIF-Occurrence="2813094363" box="[1181,1372,1685,1707]" collectionCode="AMNH" pageId="18" pageNumber="1284" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, but the other specimens (
<materialsCitation id="3B1D2A0AFF9AF955555F54DEEBCFF94D" ID-GBIF-Occurrence="2813094426" box="[1034,1224,1712,1734]" collectionCode="AMNH" pageId="18" pageNumber="1284" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
and 
<materialsCitation id="3B1D2A0AFF9AF955545D54DFEABEF94D" ID-GBIF-Occurrence="2813094436" box="[1288,1465,1712,1734]" collectionCode="FMNH" pageId="18" pageNumber="1284" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
) are very similar. The different colors in 
<figureCitation id="134E3CD2FF9AF955545154A2EA43F96A" box="[1284,1348,1740,1762]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="18" pageNumber="1284">Fig. 2</figureCitation>
reflect our assessments of the individual sinuses; given that some of the sinuses communicate broadly, some distinctions, although founded in anatomy and occasionally subtle differences in X-ray attenuation in the rock matrix, have an arbitrary component. 
<figureCitation id="134E3CD2FF9AF955550E5536EBC0F8E6" box="[1115,1223,1880,1902]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="18" pageNumber="1284">Figure 10</figureCitation>
compares the sinuses in 
<taxonomicName id="4C755BD4FF9AF9555235551BECA7F801" authorityName="Osborn" authorityYear="1905" box="[864,928,1909,1930]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9AF9555235551BECA7F801" box="[864,928,1909,1930]" italics="true" pageId="18" pageNumber="1284">T. rex</emphasis>
</taxonomicName>
with those in 
<taxonomicName id="4C755BD4FF9AF955551E551BEBDEF801" authorityName="Cope" authorityYear="1866" box="[1099,1241,1909,1930]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="18" pageNumber="1284" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9AF955551E551BEBDEF801" box="[1099,1241,1909,1930]" italics="true" pageId="18" pageNumber="1284">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247) and in 
<materialsCitation id="3B1D2A0AFF9AF955521555FEECC8F82D" ID-GBIF-Occurrence="2813094424" box="[832,975,1936,1958]" collectionCode="CMNH" pageId="18" pageNumber="1284" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, using the same color scheme.
</paragraph>
<caption id="DF0A70DFFF9BF95451E75567EA95F8EF" ID-DOI="http://doi.org/10.5281/zenodo.3942795" ID-Zenodo-Dep="3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="19" pageNumber="1285" startId="19.[178,208,1801,1820]" targetBox="[216,1416,260,1764]" targetPageId="19">
<paragraph id="8BCA2057FF9BF95451E75567EC27F8EF" blockId="19.[160,800,1801,1892]" pageId="19" pageNumber="1285">
Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. 
<emphasis id="B901FC45FF9BF95450B65554ED0DF8C7" bold="true" box="[483,522,1850,1868]" pageId="19" pageNumber="1285">A–D</emphasis>
, 
<taxonomicName id="4C755BD4FF9BF95453435557EDBFF8C7" authorityName="Osborn" authorityYear="1905" box="[534,696,1849,1868]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="19" pageNumber="1285" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9BF95453435557EDBFF8C7" box="[534,696,1849,1868]" italics="true" pageId="19" pageNumber="1285">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF9BF95453915557EFD7F8EF" ID-GBIF-Occurrence="2813094395" collectionCode="AMNH" pageId="19" pageNumber="1285" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
); 
<emphasis id="B901FC45FF9BF95451B5553FEE01F8E8" bold="true" box="[224,262,1873,1891]" pageId="19" pageNumber="1285">E–H</emphasis>
, 
<taxonomicName id="4C755BD4FF9BF9545040553FEE4FF8EF" authorityName="Osborn" authorityYear="1905" box="[277,328,1873,1892]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="19" pageNumber="1285" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9BF9545040553FEE4FF8EF" box="[277,328,1873,1892]" italics="true" pageId="19" pageNumber="1285">T. rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF9BF9545000553FEEEBF8EF" ID-GBIF-Occurrence="2813094369" box="[341,492,1873,1892]" collectionCode="AMNH" pageId="19" pageNumber="1285" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
); 
<emphasis id="B901FC45FF9BF95450A9553FED1FF8E8" bold="true" box="[508,536,1873,1891]" pageId="19" pageNumber="1285">I–L</emphasis>
, 
<taxonomicName id="4C755BD4FF9BF9545372553FEDE4F8EF" authorityName="Lambe" authorityYear="1914" baseAuthorityName="Lambe" baseAuthorityYear="1914" box="[551,739,1873,1892]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="19" pageNumber="1285" phylum="Chordata" rank="species" species="libratus">
<emphasis id="B901FC45FF9BF9545372553FEDE4F8EF" box="[551,739,1873,1892]" italics="true" pageId="19" pageNumber="1285">Gorgosaurus libratus</emphasis>
</taxonomicName>
(ROM
</paragraph>
<paragraph id="8BCA2057FF9BF95452155567EA95F8EF" blockId="19.[832,1474,1801,1892]" pageId="19" pageNumber="1285">
1247, composite of both sides); 
<emphasis id="B901FC45FF9BF95455225567EB9AF890" bold="true" box="[1143,1181,1801,1819]" pageId="19" pageNumber="1285">M–P</emphasis>
, Cleveland skull (
<materialsCitation id="3B1D2A0AFF9BF95454125567EABAF897" ID-GBIF-Occurrence="2813094358" box="[1351,1469,1801,1820]" collectionCode="CMNH" pageId="19" pageNumber="1285" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, composite of both sides, restored parts in yellow); 
<emphasis id="B901FC45FF9BF954545B554CEA35F8BF" bold="true" box="[1294,1330,1826,1844]" pageId="19" pageNumber="1285">Q–T</emphasis>
, 
<emphasis id="B901FC45FF9BF954546A554FEC6DF8C7" italics="true" pageId="19" pageNumber="1285">Struthiomimus altus</emphasis>
(AMNH FR 5355); and 
<emphasis id="B901FC45FF9BF95455175554EB6FF8C7" bold="true" box="[1090,1128,1850,1868]" pageId="19" pageNumber="1285">U–X</emphasis>
, 
<taxonomicName id="4C755BD4FF9BF95455205557EA16F8C7" authorityName="Marsh" authorityYear="1877" box="[1141,1297,1849,1868]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="19" pageNumber="1285" phylum="Chordata" rank="species" species="fragilis">
<emphasis id="B901FC45FF9BF95455205557EA16F8C7" box="[1141,1297,1849,1868]" italics="true" pageId="19" pageNumber="1285">Allosaurus fragilis</emphasis>
</taxonomicName>
(UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm).
</paragraph>
</caption>
<caption id="DF0A70DFFF9CF95351E75449ED78F941" ID-DOI="http://doi.org/10.5281/zenodo.3942797" ID-Zenodo-Dep="3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="20" pageNumber="1286" startId="20.[178,208,1575,1594]" targetBox="[168,792,229,1543]" targetPageId="20">
<paragraph id="8BCA2057FF9CF95351E75449ED78F941" blockId="20.[160,800,1575,1738]" pageId="20" pageNumber="1286">
Fig. 9. Columella and columellar region. 
<emphasis id="B901FC45FF9CF953537A5449ED3AF9B2" bold="true" box="[559,573,1575,1593]" pageId="20" pageNumber="1286">A</emphasis>
, braincase of the Cleveland skull (
<materialsCitation id="3B1D2A0AFF9CF95350575451EE71F9D9" ID-GBIF-Occurrence="2813094413" box="[258,374,1599,1618]" collectionCode="CMNH" pageId="20" pageNumber="1286" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. 
<emphasis id="B901FC45FF9CF95352595439EC1DF9E2" bold="true" box="[780,794,1623,1641]" pageId="20" pageNumber="1286">B</emphasis>
, Cranial endocast and labyrinth of 
<taxonomicName id="4C755BD4FF9CF953508C5401ED7AF909" authorityName="Osborn" authorityYear="1905" box="[473,637,1647,1666]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9CF953508C5401ED7AF909" box="[473,637,1647,1666]" italics="true" pageId="20" pageNumber="1286">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF9CF95353DC5401EC1CF909" ID-GBIF-Occurrence="2813094329" box="[649,795,1647,1666]" collectionCode="AMNH" pageId="20" pageNumber="1286" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm.
</paragraph>
</caption>
<paragraph id="8BCA2057FF9CF95351ED5569EA72FB0D" blockId="20.[160,800,1799,1958]" lastBlockId="20.[832,1472,230,1958]" pageId="20" pageNumber="1286">
Six main sinus systems can be identified in all of the tyrannosaur braincases. It is useful heuristically to group these into three ‘‘families,’’ which is an appropriate metaphor in that some sinuses within a family may well be ‘‘offspring’’ (i.e., diverticula) of others: (1) the tympanic or middle ear system, (2) the median pharyngeal system, and (3) the subcondylar system. The tympanic family derives from pneumatic diverticula of the middle ear sac. Tyrannosaurs clearly have rostral and caudal tympanic recesses, but the dorsal tympanic recess, which is present variably in other coelurosaurs (
<bibRefCitation id="EFE45DA6FF9CF95352125305ECE1FE0B" author="Witmer LM" box="[839,998,363,385]" editor="Currie PJ &amp; Padian K" firstAuthor="Witmer" journalOrPublisher="New York: Academic Press" pageId="20" pageNumber="1286" pagination="151 - 159" refId="ref24134" refString="Witmer LM. 1997. Craniofacial air sinus systems. In: Currie PJ, Padian K, editors. Encyclopedia of dinosaurs. New York: Academic Press. p 151 - 159." title="Craniofacial air sinus systems" type="book chapter" volumeTitle="Encyclopedia of dinosaurs" year="1997">Witmer, 1997</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF95352A25305EA40FE0B" author="Makovicky PJ &amp; Norell MA" box="[1015,1351,363,385]" firstAuthor="Makovicky" journalOrPublisher="Am Mus Novit" pageId="20" pageNumber="1286" pagination="1 - 16" part="3247" refId="ref22239" refString="Makovicky PJ, Norell MA. 1998. A partial ornithomimid braincase from Ukhaa Tolgod (Upper Cretaceous, Mongolia). Am Mus Novit 3247: 1 - 16." title="A partial ornithomimid braincase from Ukhaa Tolgod (Upper Cretaceous, Mongolia)" type="journal article" year="1998">Makovicky and Norell, 1998</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF953540D5305ECA3FE10" author="Norell MA &amp; Makovicky PJ &amp; Clark JM" editor="Currie PJ &amp; Koppelhus EB &amp; Shugar MA &amp; Wright JL" etAl="et al." firstAuthor="Norell" journalOrPublisher="Bloomington: Indiana University Press" pageId="20" pageNumber="1286" pagination="133 - 143" refId="ref22552" refString="Norell MA, Makovicky PJ, Clark JM. 2004. The braincase of Velociraptor. In: Currie PJ, Koppelhus EB, Shugar MA, Wright JL, editors. Feathered dragons: studies on the transition from dinosaurs to birds. Bloomington: Indiana University Press. p 133 - 143." title="The braincase of Velociraptor" type="book chapter" volumeTitle="Feathered dragons: studies on the transition from dinosaurs to birds" year="2004">Norell et al., 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF95352E453E8EB49FE17" author="Rauhut OWM" box="[945,1102,390,412]" firstAuthor="Rauhut" journalOrPublisher="Can J Earth Sci" pageId="20" pageNumber="1286" pagination="1109 - 1122" part="41" refId="ref22757" refString="Rauhut OWM. 2004. Braincase structure of the middle Jurassic theropod Piatnitzkysaurus. Can J Earth Sci 41: 1109 - 1122." title="Braincase structure of the middle Jurassic theropod Piatnitzkysaurus" type="journal article" year="2004">Rauhut, 2004</bibRefCitation>
), is apparently absent. Pneumaticity of the quadrate and articular bones also belongs to this family (
<bibRefCitation id="EFE45DA6FF9CF953529E53D5EB62FE5A" author="Witmer LM" box="[971,1125,443,465]" firstAuthor="Witmer" journalOrPublisher="Zool J Linn Soc" pageId="20" pageNumber="1286" pagination="327 - 378" part="100" refId="ref24027" refString="Witmer LM. 1990. The craniofacial air sac system of Mesozoic birds (Aves). Zool J Linn Soc 100: 327 - 378." title="The craniofacial air sac system of Mesozoic birds (Aves)" type="journal article" year="1990">Witmer, 1990</bibRefCitation>
), and, despite their being well developed in tyrannosaurs (
<bibRefCitation id="EFE45DA6FF9CF953552853B8EA13FE60" author="Molnar RE" box="[1149,1300,470,492]" firstAuthor="Molnar" journalOrPublisher="Palaeontogr Abt A" pageId="20" pageNumber="1286" pagination="137 - 176" part="217" refId="ref22394" refString="Molnar RE. 1991. The cranial morphology of Tyrannosaurus rex. Palaeontogr Abt A 217: 137 - 176." title="The cranial morphology of Tyrannosaurus rex" type="journal article" year="1991">Molnar, 1991</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF953547753B8EABBFE60" author="Witmer LM" box="[1314,1468,470,492]" editor="Currie PJ &amp; Padian K" firstAuthor="Witmer" journalOrPublisher="New York: Academic Press" pageId="20" pageNumber="1286" pagination="151 - 159" refId="ref24134" refString="Witmer LM. 1997. Craniofacial air sinus systems. In: Currie PJ, Padian K, editors. Encyclopedia of dinosaurs. New York: Academic Press. p 151 - 159." title="Craniofacial air sinus systems" type="book chapter" volumeTitle="Encyclopedia of dinosaurs" year="1997">Witmer, 1997</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF9535215539EECDEFD8E" author="Brochu CA" box="[832,985,496,518]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="20" pageNumber="1286" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu, 2003</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF95352B2539EEA18FD8D" author="Witmer LM &amp; Ridgely RC" box="[999,1311,496,518]" firstAuthor="Witmer" journalOrPublisher="Anat Rec" pageId="20" pageNumber="1286" pagination="1362 - 1388" part="291" refId="ref24295" refString="Witmer LM, Ridgely RC. 2008 b. The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture. Anat Rec 291: 1362 - 1388." title="The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture" type="journal article" year="2008" yearSuffix="b">Witmer and Ridgely, 2008b</bibRefCitation>
, in press), we ignore them here to focus on the braincase. The RTR arises in the region of the cerebral carotid foramen, invading the basisphenoid deep to the otosphenoidal crest and preotic pendant, typically extending caudally somewhat within the basicranium as well as dorsally into the laterosphenoid and/or prootic (
<figureCitation id="134E3CD2FF9CF95355A850FEEA4CFD2E" box="[1277,1355,656,678]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="20" pageNumber="1286">Figs. 2</figureCitation>
, 
<figureCitation id="134E3CD2FF9CF953540C50FEEA6FFD2D" box="[1369,1384,656,678]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="20" pageNumber="1286">5</figureCitation>
). There is contralateral communication of left and right RTRs within the basisphenoid caudoventral to the pituitary fossa (retrohypophyseal sinus; Witmer and Ridgely, in press). 
<taxonomicName id="4C755BD4FF9CF95352C75095EB27FC9B" authorityName="Cope" authorityYear="1866" box="[914,1056,763,784]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9CF95352C75095EB27FC9B" box="[914,1056,763,784]" italics="true" pageId="20" pageNumber="1286">Gorgosaurus</emphasis>
</taxonomicName>
and 
<materialsCitation id="3B1D2A0AFF9CF953550E5095EBEFFC9A" ID-GBIF-Occurrence="2813094392" box="[1115,1256,763,785]" collectionCode="CMNH" pageId="20" pageNumber="1286" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
have another RTR extension rostral to the pituitary fossa that is absent in 
<taxonomicName id="4C755BD4FF9CF9535215515FEC87FCCD" authorityName="Osborn" authorityYear="1905" box="[832,896,817,838]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9CF9535215515FEC87FCCD" box="[832,896,817,838]" italics="true" pageId="20" pageNumber="1286">T. rex</emphasis>
</taxonomicName>
(prohypophyseal sinus; 
<figureCitation id="134E3CD2FF9CF95355C3515EEBEFFCCD" box="[1174,1256,816,838]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="20" pageNumber="1286">Fig. 10</figureCitation>
). 
<taxonomicName id="4C755BD4FF9CF95355AA515FEA8AFCCD" authorityName="Cope" authorityYear="1866" box="[1279,1421,817,838]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9CF95355AA515FEA8AFCCD" box="[1279,1421,817,838]" italics="true" pageId="20" pageNumber="1286">Gorgosaurus</emphasis>
</taxonomicName>
and 
<materialsCitation id="3B1D2A0AFF9CF95352155125ECDFFCEA" ID-GBIF-Occurrence="2813094347" box="[832,984,843,865]" collectionCode="CMNH" pageId="20" pageNumber="1286" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
also share a well-developed ascending diverticulum of the RTR that extends dorsally into the laterosphenoid between the ophthalmic and maxillomandibular nerves (
<figureCitation id="134E3CD2FF9CF953555451F5EB5FFC3A" box="[1025,1112,923,945]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="20" pageNumber="1286">Fig. 10</figureCitation>
), whereas 
<taxonomicName id="4C755BD4FF9CF95355B451F2EA21FC3A" authorityName="Osborn" authorityYear="1905" box="[1249,1318,924,945]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9CF95355B451F2EA21FC3A" box="[1249,1318,924,945]" italics="true" pageId="20" pageNumber="1286">T. rex</emphasis>
</taxonomicName>
has at best (
<materialsCitation id="3B1D2A0AFF9CF953521251D8EB0CFC40" ID-GBIF-Occurrence="2813094402" box="[839,1035,949,971]" collectionCode="AMNH" pageId="20" pageNumber="1286" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
) a rudimentary ascending diverticulum, and it usually is absent (
<materialsCitation id="3B1D2A0AFF9CF95355F151BEEA64FC6D" ID-GBIF-Occurrence="2813094332" box="[1188,1379,976,998]" collectionCode="AMNH" pageId="20" pageNumber="1286" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, 
<materialsCitation id="3B1D2A0AFF9CF953542751BFEC9EFB8A" ID-GBIF-Occurrence="2813094437" collectionCode="FMNH" pageId="20" pageNumber="1286" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
); it is also absent in the 
<taxonomicName id="4C755BD4FF9CF95355965185EA68FB8B" authorityName=", Maleev" authorityYear="1965" box="[1219,1391,1003,1024]" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9CF95355965185EA68FB8B" box="[1219,1391,1003,1024]" italics="true" pageId="20" pageNumber="1286">Daspletosaurus</emphasis>
</taxonomicName>
in our sample (TMP 2001.36.1). As noted above, 
<taxonomicName id="4C755BD4FF9CF953544C5668EA5FFB90" authorityName="Osborn" authorityYear="1905" box="[1305,1368,1030,1051]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9CF953544C5668EA5FFB90" box="[1305,1368,1030,1051]" italics="true" pageId="20" pageNumber="1286">T. rex</emphasis>
</taxonomicName>
typically has a blind pneumatic fossa within the prootic just caudal to the maxillomandibular-facial foramen (
<figureCitation id="134E3CD2FF9CF95354345655EABCFBDA" box="[1377,1467,1083,1105]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="20" pageNumber="1286">Fig. 5B</figureCitation>
; 
<bibRefCitation id="EFE45DA6FF9CF95352155638ECDBFBE7" author="Brochu CA" box="[832,988,1110,1132]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="20" pageNumber="1286" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">Brochu, 2003</bibRefCitation>
). This prootic recess seems to have little direct relationship with the main part of the RTR.
</paragraph>
<paragraph id="8BCA2057FF9CF950520D56E5EEF6FE9D" blockId="20.[832,1472,230,1958]" lastBlockId="23.[160,800,230,1958]" lastPageId="23" lastPageNumber="1289" pageId="20" pageNumber="1286">
The caudal tympanic recess and its extensions comprise volumetrically the largest braincase sinus in tyrannosaurs. The CTR aperture is in the typical location just ventral to the otosphenoidal crest, bounded mostly by the otoccipital and roofed by the prootic. The aperture is very large in 
<materialsCitation id="3B1D2A0AFF9CF95352CA577EEB52FAAD" ID-GBIF-Occurrence="2813094348" box="[927,1109,1296,1318]" collectionCode="AMNH" pageId="20" pageNumber="1286" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
(
<figureCitation id="134E3CD2FF9CF9535530577EEBB4FAAE" box="[1125,1203,1296,1318]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="20" pageNumber="1286">Figs. 2</figureCitation>
, 
<figureCitation id="134E3CD2FF9CF9535595577EEBCAFAAD" box="[1216,1229,1296,1318]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="20" pageNumber="1286">5</figureCitation>
) but smaller in other specimens. The position of the columellar canal shows that the columella would traverse the CTR aperture in 
<taxonomicName id="4C755BD4FF9CF95354FE5728EC66FAFD" authorityName="Osborn" authorityYear="1905" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9CF95354FE5728EC66FAFD" italics="true" pageId="20" pageNumber="1286">T. rex</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF9CF95352CF570FEB2FFAFD" authorityName="Cope" authorityYear="1866" box="[922,1064,1377,1398]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9CF95352CF570FEB2FFAFD" box="[922,1064,1377,1398]" italics="true" pageId="20" pageNumber="1286">Gorgosaurus</emphasis>
</taxonomicName>
, and the 
<emphasis id="B901FC45FF9CF95355C6570FEBDBFAFD" box="[1171,1244,1377,1398]" italics="true" pageId="20" pageNumber="1286">in situ</emphasis>
columella of 
<materialsCitation id="3B1D2A0AFF9CF9535424570EEC72FA1A" ID-GBIF-Occurrence="2813094333" collectionCode="CMNH" pageId="20" pageNumber="1286" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
confirms this relationship (
<figureCitation id="134E3CD2FF9CF95355FD5715EBFBFA1A" box="[1192,1276,1403,1425]" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="20" pageNumber="1286">Fig. 9A</figureCitation>
). In all the tyrannosaurs studied here, the CTR expands dorsally in the paroccipital process, and then extends laterally within the process and also dorsomedially into the supraoccipital. The contralateral supraoccipital sinuses are confluent above the hindbrain, and the caudal middle cerebral veins partially separate cells of the supraoccipital sinus (
<figureCitation id="134E3CD2FF9CF953521D5458EC92F9C0" box="[840,917,1590,1612]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="20" pageNumber="1286">Figs. 2</figureCitation>
, 
<figureCitation id="134E3CD2FF9CF95352F75458ECB8F9C7" box="[930,959,1590,1612]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="20" pageNumber="1286">10</figureCitation>
). In 
<materialsCitation id="3B1D2A0AFF9CF95352A65458EBAFF9C0" ID-GBIF-Occurrence="2813094355" box="[1011,1192,1589,1611]" collectionCode="AMNH" pageId="20" pageNumber="1286" specimenCode="AMNH FR 5029">AMNH FR 5029</materialsCitation>
and 
<materialsCitation id="3B1D2A0AFF9CF95355B45458EA96F9C0" ID-GBIF-Occurrence="2813094334" box="[1249,1425,1590,1611]" collectionCode="FMNH" pageId="20" pageNumber="1286" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
, the supraoccipital and paroccipital sinuses communicate via relatively narrow pneumatic tubes, whereas they are more broadly confluent in 
<materialsCitation id="3B1D2A0AFF9CF953552954E8EA39F917" ID-GBIF-Occurrence="2813094423" box="[1148,1342,1670,1692]" collectionCode="AMNH" pageId="20" pageNumber="1286" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
. The exact patterns, sizes, and shapes of the pneumatic ‘‘bubbles’’ vary from specimen to specimen and even from side to side, which is characteristic of pneumatic systems, yet the basic patterns are consistent. All of the 
<taxonomicName id="4C755BD4FF9CF953546C549FEA7FF88D" authorityName="Osborn" authorityYear="1905" box="[1337,1400,1777,1798]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9CF953546C549FEA7FF88D" box="[1337,1400,1777,1798]" italics="true" pageId="20" pageNumber="1286">T. rex</emphasis>
</taxonomicName>
CTRs lack any significant extension ventrally into the crista tuberalis from the main CTR aperture, such that there is little to no communication between the CTR and the lateral subcondylar recess. The same is generally true of 
<taxonomicName id="4C755BD4FF9CF95352155518ECC9F800" authorityName="Cope" authorityYear="1866" box="[832,974,1910,1931]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="20" pageNumber="1286" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9CF95352155518ECC9F800" box="[832,974,1910,1931]" italics="true" pageId="20" pageNumber="1286">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247), but 
<materialsCitation id="3B1D2A0AFF9CF95355C35518EA26F800" ID-GBIF-Occurrence="2813094385" box="[1174,1313,1909,1931]" collectionCode="CMNH" pageId="20" pageNumber="1286" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
has relatively broad communication between the CTR and lateral subcondylar recess within the crista tuberalis (
<figureCitation id="134E3CD2FF9FF950539D5288EC1BFF70" box="[712,796,230,252]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="23" pageNumber="1289">Fig. 10</figureCitation>
; Witmer and Ridgely, in press).
</paragraph>
<caption id="DF0A70DFFF9DF9525037548AEA0AF8B4" ID-DOI="http://doi.org/10.5281/zenodo.3942799" ID-Zenodo-Dep="3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="21" pageNumber="1287" startId="21.[354,384,1764,1783]" targetBox="[241,1391,229,1733]" targetPageId="21">
<paragraph id="8BCA2057FF9DF9525037548AEA0AF8B4" blockId="21.[336,1298,1764,1855]" pageId="21" pageNumber="1287">
Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. 
<emphasis id="B901FC45FF9DF952528E557BECEEF8AC" bold="true" box="[987,1001,1813,1831]" pageId="21" pageNumber="1287">A</emphasis>
, 
<taxonomicName id="4C755BD4FF9DF95252AC557AEBA7F8AC" authorityName="Osborn" authorityYear="1905" box="[1017,1184,1812,1831]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="21" pageNumber="1287" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9DF95252AC557AEBA7F8AC" box="[1017,1184,1812,1831]" italics="true" pageId="21" pageNumber="1287">Tyrannosaurus rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF9DF95255E5557AEE87F8B4" ID-GBIF-Occurrence="2813094343" collectionCode="AMNH" pageId="21" pageNumber="1287" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
); 
<emphasis id="B901FC45FF9DF95250DB5543EE9BF8B4" bold="true" box="[398,412,1837,1855]" pageId="21" pageNumber="1287">B</emphasis>
, 
<taxonomicName id="4C755BD4FF9DF95250FD5542ED65F8B4" authorityName="Lambe" authorityYear="1914" baseAuthorityName="Lambe" baseAuthorityYear="1914" box="[424,610,1836,1855]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="21" pageNumber="1287" phylum="Chordata" rank="species" species="libratus">
<emphasis id="B901FC45FF9DF95250FD5542ED65F8B4" box="[424,610,1836,1855]" italics="true" pageId="21" pageNumber="1287">Gorgosaurus libratus</emphasis>
</taxonomicName>
(ROM 1247); and 
<emphasis id="B901FC45FF9DF952525C5543EC1FF8B4" bold="true" box="[777,792,1837,1855]" pageId="21" pageNumber="1287">C</emphasis>
, the Cleveland skull (
<materialsCitation id="3B1D2A0AFF9DF952528F5542EB4AF8B4" ID-GBIF-Occurrence="2813094360" box="[986,1101,1836,1855]" collectionCode="CMNH" pageId="21" pageNumber="1287" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
). Scale bars = 5 cm.
</paragraph>
</caption>
<caption id="DF0A70DFFF9EF95151E75487ECC3F8FF" ID-DOI="http://doi.org/10.5281/zenodo.3942801" ID-Zenodo-Dep="3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="22" pageNumber="1288" startId="22.[178,208,1769,1788]" targetBox="[192,1441,229,1733]" targetPageId="22">
<paragraph id="8BCA2057FF9EF95151E75487EC27F8FF" blockId="22.[160,801,1769,1908]" pageId="22" pageNumber="1288">
Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. 
<emphasis id="B901FC45FF9EF951531F556FED5FF898" bold="true" box="[586,600,1793,1811]" pageId="22" pageNumber="1288">A</emphasis>
, 
<emphasis id="B901FC45FF9EF9515331556FEFF5F8A7" italics="true" pageId="22" pageNumber="1288">
<taxonomicName id="4C755BD4FF9EF9515331556FEDEDF89F" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[612,746,1793,1812]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="genus">Majungasaurus</taxonomicName>
crenatissimus
</emphasis>
(FMNH PR2100; modified from 
<bibRefCitation id="EFE45DA6FF9EF951534C5577EC1EF8A7" author="Sampson SD &amp; Witmer LM" box="[537,793,1817,1836]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="22" pageNumber="1288" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
); 
<emphasis id="B901FC45FF9EF95151F5555CEFA9F8CF" bold="true" box="[160,174,1842,1860]" pageId="22" pageNumber="1288">B</emphasis>
, 
<taxonomicName id="4C755BD4FF9EF95151EB555FEE5AF8CF" authorityName="Marsh" authorityYear="1877" box="[190,349,1841,1860]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="species" species="fragilis">
<emphasis id="B901FC45FF9EF95151EB555FEE5AF8CF" box="[190,349,1841,1860]" italics="true" pageId="22" pageNumber="1288">Allosaurus fragilis</emphasis>
</taxonomicName>
(UMNH VP 18050, registered to MOR 693); 
<emphasis id="B901FC45FF9EF951525E555CEC1DF8CF" bold="true" box="[779,794,1842,1860]" pageId="22" pageNumber="1288">C</emphasis>
, 
<taxonomicName id="4C755BD4FF9EF95151F55527EE5AF8D7" authorityName="Lambe" authorityYear="1914" baseAuthorityName="Lambe" baseAuthorityYear="1914" box="[160,349,1865,1884]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="species" species="libratus">
<emphasis id="B901FC45FF9EF95151F55527EE5AF8D7" box="[160,349,1865,1884]" italics="true" pageId="22" pageNumber="1288">Gorgosaurus libratus</emphasis>
</taxonomicName>
(ROM 1247, registered to a cast of AMNH FR 5664); 
<emphasis id="B901FC45FF9EF95151B1550FEFF4F8F8" bold="true" box="[228,243,1889,1907]" pageId="22" pageNumber="1288">D</emphasis>
, the Cleveland skull (
<materialsCitation id="3B1D2A0AFF9EF9515099550FED43F8FF" ID-GBIF-Occurrence="2813094319" box="[460,580,1889,1908]" collectionCode="CMNH" pageId="22" pageNumber="1288" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
); 
<emphasis id="B901FC45FF9EF951530C550FED61F8F8" bold="true" box="[601,614,1889,1907]" pageId="22" pageNumber="1288">E</emphasis>
, 
<taxonomicName id="4C755BD4FF9EF951532D550FEC27F8FF" authorityName="Osborn" authorityYear="1905" box="[632,800,1889,1908]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="species" species="rex">Tyrannosaurus rex</taxonomicName>
</paragraph>
<paragraph id="8BCA2057FF9EF95152155487EC42F977" blockId="22.[832,1472,1769,1908]" box="[832,837,1769,1788]" pageId="22" pageNumber="1288">(</paragraph>
<paragraph id="8BCA2057FF9EF95152115487ECC3F8FF" blockId="22.[832,1472,1769,1908]" pageId="22" pageNumber="1288">
<materialsCitation id="3B1D2A0AFF9EF95152115487ECD9F977" ID-GBIF-Occurrence="2813094420" box="[836,990,1769,1788]" collectionCode="AMNH" pageId="22" pageNumber="1288" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, registered to a model of a 
<taxonomicName id="4C755BD4FF9EF95155A05487EA2DF977" authorityName="Osborn" authorityYear="1905" box="[1269,1322,1769,1788]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9EF95155A05487EA2DF977" box="[1269,1322,1769,1788]" italics="true" pageId="22" pageNumber="1288">T. rex</emphasis>
</taxonomicName>
skull); 
<emphasis id="B901FC45FF9EF95154275487EA7CF970" bold="true" box="[1394,1403,1769,1787]" pageId="22" pageNumber="1288">F</emphasis>
, 
<taxonomicName id="4C755BD4FF9EF95154DE5487EAC7F977" authorityName="Osborn" authorityYear="1905" box="[1419,1472,1769,1788]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9EF95154DE5487EAC7F977" box="[1419,1472,1769,1788]" italics="true" pageId="22" pageNumber="1288">T. rex</emphasis>
</taxonomicName>
(
<materialsCitation id="3B1D2A0AFF9EF9515210556FECD6F89F" ID-GBIF-Occurrence="2813094339" box="[837,977,1793,1812]" collectionCode="FMNH" pageId="22" pageNumber="1288" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
); 
<emphasis id="B901FC45FF9EF95152B7556FECF6F898" bold="true" box="[994,1009,1793,1811]" pageId="22" pageNumber="1288">G</emphasis>
, 
<emphasis id="B901FC45FF9EF95152AA556FEBB4F89F" box="[1023,1203,1793,1812]" italics="true" pageId="22" pageNumber="1288">Struthiomimus altus</emphasis>
(TMP 90.26.1); and 
<emphasis id="B901FC45FF9EF9515421556FEA84F898" bold="true" box="[1396,1411,1793,1811]" pageId="22" pageNumber="1288">H</emphasis>
, 
<emphasis id="B901FC45FF9EF95154C4556FECB8F8A7" italics="true" pageId="22" pageNumber="1288">
<taxonomicName id="4C755BD4FF9EF95154C4556FEC65F8A7" authorityName="Leidy" authorityYear="1856" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="genus">Troodon</taxonomicName>
formosus
</emphasis>
(composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of 
<emphasis id="B901FC45FF9EF9515559555FEBD5F8CF" box="[1036,1234,1841,1860]" italics="true" pageId="22" pageNumber="1288">
<taxonomicName id="4C755BD4FF9EF9515559555FEB9FF8CF" authorityName="Osborn" authorityYear="1924" box="[1036,1176,1841,1860]" class="Reptilia" family="Troodontidae" genus="Saurornithoides" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="22" pageNumber="1288" phylum="Chordata" rank="genus">Saurornithoides</taxonomicName>
junior
</emphasis>
, IGM 100/1). Scale bars pertain to 
<emphasis id="B901FC45FF9EF95152CB5527ECC2F8D0" bold="true" box="[926,965,1865,1883]" pageId="22" pageNumber="1288">A–D</emphasis>
(top bar), 
<emphasis id="B901FC45FF9EF95155735527EB4EF8D0" bold="true" box="[1062,1097,1865,1883]" pageId="22" pageNumber="1288">E–F</emphasis>
(middle bar), and 
<emphasis id="B901FC45FF9EF95155A75527EA1DF8D0" bold="true" box="[1266,1306,1865,1883]" pageId="22" pageNumber="1288">G–H</emphasis>
(lower bar). Scale bars = 10 cm.
</paragraph>
</caption>
<paragraph id="8BCA2057FF9FF95051ED5375EE8AFA87" blockId="23.[160,800,230,1958]" pageId="23" pageNumber="1289">
The median pharyngeal family probably derives from a diverticulum of the pharynx separate from the middle ear sac (
<bibRefCitation id="EFE45DA6FF9FF9505053533EEEA4FEEE" author="Witmer LM" box="[262,419,336,358]" editor="Currie PJ &amp; Padian K" firstAuthor="Witmer" journalOrPublisher="New York: Academic Press" pageId="23" pageNumber="1289" pagination="151 - 159" refId="ref24134" refString="Witmer LM. 1997. Craniofacial air sinus systems. In: Currie PJ, Padian K, editors. Encyclopedia of dinosaurs. New York: Academic Press. p 151 - 159." title="Craniofacial air sinus systems" type="book chapter" volumeTitle="Encyclopedia of dinosaurs" year="1997">Witmer, 1997</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95050E6533EEDDBFEED" author="Chure DJ &amp; Madsen JH, Jr." box="[435,732,336,358]" firstAuthor="Chure" journalOrPublisher="J Vert Paleontol" pageId="23" pageNumber="1289" pagination="115 - 125" part="18" refId="ref20424" refString="Chure DJ, Madsen JH, Jr. 1998. An unusual braincase (? Stokesosaurus clevelandi) from the Cleveland-Lloyd Dinosaur Quarry, Utah (Morrison Formation; Late Jurassic). J Vert Paleontol 18: 115 - 125." title="An unusual braincase (? Stokesosaurus clevelandi) from the Cleveland-Lloyd Dinosaur Quarry, Utah (Morrison Formation; Late Jurassic)" type="journal article" year="1998">Chure and Madsen, 1998</bibRefCitation>
), producing two typical sinuses, the subsellar and basisphenoid recesses. These recesses are separated only by a thin lamina of bone, yet in some respects they seem to pertain to different anatomical domains, with the subsellar sinus being linked more to the orbital and palatal domains, whereas the basisphenoid sinus is connected more to the cervical and middle ear domains. Despite these differences, both pneumatic sinuses are grouped together in the same ‘‘family’’ because they are both median in position and direct pneumatization from the pharynx seems most likely. The subsellar recess in tyrannosaurs is well developed, occupying the triangular fossa rostral to the interbasipterygoid lamina and ventral to the pituitary fossa (
<figureCitation id="134E3CD2FF9FF95050B550A8ED35FD50" box="[480,562,710,732]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="23" pageNumber="1289">Figs. 2</figureCitation>
, 
<figureCitation id="134E3CD2FF9FF950531650A8ED55FD57" box="[579,594,710,732]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="23" pageNumber="1289">5</figureCitation>
). In 
<materialsCitation id="3B1D2A0AFF9FF95053C550A8EC27FD57" ID-GBIF-Occurrence="2813094349" box="[656,800,710,732]" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
and especially 
<taxonomicName id="4C755BD4FF9FF9505002508FEEE2FD7D" authorityName="Cope" authorityYear="1866" box="[343,485,737,758]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF9505002508FEEE2FD7D" box="[343,485,737,758]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
, the subsellar recess has pneumatic extensions into the thin cultriform process (
<figureCitation id="134E3CD2FF9FF95051FD5178EFFCFCA7" box="[168,251,790,812]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="23" pageNumber="1289">Fig. 10</figureCitation>
). In 
<taxonomicName id="4C755BD4FF9FF95050605178EE72FCA0" authorityName="Osborn" authorityYear="1905" box="[309,373,790,811]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF95050605178EE72FCA0" box="[309,373,790,811]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
, the subsellar recess extends into at least the base of the cultriform process, and, in 
<materialsCitation id="3B1D2A0AFF9FF9505384515EEE06FCEA" ID-GBIF-Occurrence="2813094317" collectionCode="AMNH" pageId="23" pageNumber="1289" specimenCode="AMNH FR 5117">AMNH FR 5117</materialsCitation>
, there is a large pneumatic foramen (on the left side only) leading from the subsellar recess into the basipterygoid process. The pattern of basisphenoid sinuses is complex in theropods generally and more so in tyrannosaurs. In general, the basisphenoid sinuses occupy the median space bounded by the basipterygoid processes in front and basal tubera behind. Primitively, there is a single pyramidal cavity, which may split caudodorsally into two recesses separated by a median septum (
<bibRefCitation id="EFE45DA6FF9FF95050535655ED35FBDB" author="Chure DJ &amp; Madsen JH, Jr." box="[262,562,1083,1105]" firstAuthor="Chure" journalOrPublisher="J Vert Paleontol" pageId="23" pageNumber="1289" pagination="115 - 125" part="18" refId="ref20424" refString="Chure DJ, Madsen JH, Jr. 1998. An unusual braincase (? Stokesosaurus clevelandi) from the Cleveland-Lloyd Dinosaur Quarry, Utah (Morrison Formation; Late Jurassic). J Vert Paleontol 18: 115 - 125." title="An unusual braincase (? Stokesosaurus clevelandi) from the Cleveland-Lloyd Dinosaur Quarry, Utah (Morrison Formation; Late Jurassic)" type="journal article" year="1998">Chure and Madsen, 1998</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95053175655EC1BFBDB" author="Norell MA &amp; Makovicky PJ &amp; Clark JM" box="[578,796,1083,1105]" editor="Currie PJ &amp; Koppelhus EB &amp; Shugar MA &amp; Wright JL" etAl="et al." firstAuthor="Norell" journalOrPublisher="Bloomington: Indiana University Press" pageId="23" pageNumber="1289" pagination="133 - 143" refId="ref22552" refString="Norell MA, Makovicky PJ, Clark JM. 2004. The braincase of Velociraptor. In: Currie PJ, Koppelhus EB, Shugar MA, Wright JL, editors. Feathered dragons: studies on the transition from dinosaurs to birds. Bloomington: Indiana University Press. p 133 - 143." title="The braincase of Velociraptor" type="book chapter" volumeTitle="Feathered dragons: studies on the transition from dinosaurs to birds" year="2004">Norell et al., 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95051F55638EE3BFBE0" author="Rauhut OWM" box="[160,316,1110,1132]" firstAuthor="Rauhut" journalOrPublisher="Can J Earth Sci" pageId="23" pageNumber="1289" pagination="1109 - 1122" part="41" refId="ref22757" refString="Rauhut OWM. 2004. Braincase structure of the middle Jurassic theropod Piatnitzkysaurus. Can J Earth Sci 41: 1109 - 1122." title="Braincase structure of the middle Jurassic theropod Piatnitzkysaurus" type="journal article" year="2004">Rauhut, 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF950501F5638ED81FBE7" author="Sampson SD &amp; Witmer LM" box="[330,646,1110,1132]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="23" pageNumber="1289" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
). Most tyrannosaurs have this system plus, in some taxa, another pair of often large apertures located more rostrally within the interbasipterygoid lamina, ventrolaterally near the basipterygoid processes (e.g., 
<taxonomicName id="4C755BD4FF9FF95053DE56AFEC1EFB5D" authorityName="Cope" authorityYear="1866" box="[651,793,1217,1238]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF95053DE56AFEC1EFB5D" box="[651,793,1217,1238]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
, 
<taxonomicName id="4C755BD4FF9FF95051F556B5EE4BFB7B" authorityName=", Maleev" authorityYear="1965" box="[160,332,1243,1264]" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF95051F556B5EE4BFB7B" box="[160,332,1243,1264]" italics="true" pageId="23" pageNumber="1289">Daspletosaurus</emphasis>
</taxonomicName>
; 
<bibRefCitation id="EFE45DA6FF9FF950500E56B5EEF4FB7B" author="Russell DA" box="[347,499,1243,1265]" firstAuthor="Russell" journalOrPublisher="Natl Mus Nat Sci Pub Palaeontol" pageId="23" pageNumber="1289" pagination="1 - 34" part="1" refId="ref23039" refString="Russell DA. 1970. Tyrannosaurs from the Late Cretaceous of Western Canada. Natl Mus Nat Sci Pub Palaeontol 1: 1 - 34." title="Tyrannosaurs from the Late Cretaceous of Western Canada" type="journal article" year="1970">Russell, 1970</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF950535556B5EDDCFB7B" author="Bakker RT &amp; Williams M &amp; Currie PJ" box="[512,731,1243,1265]" etAl="et al." firstAuthor="Bakker" journalOrPublisher="Hunteria" pageId="23" pageNumber="1289" pagination="1 - 30" part="1" refId="ref20052" refString="Bakker RT, Williams M, Currie PJ. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30." title="Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana" type="journal article" year="1988">Bakker et al., 1988</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95053B256B5EFDFFA80" author="Carr TD" firstAuthor="Carr" journalOrPublisher="J Vert Paleontol" pageId="23" pageNumber="1289" pagination="497 - 520" part="19" refId="ref20345" refString="Carr TD. 1999. Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria). J Vert Paleontol 19: 497 - 520." title="Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria)" type="journal article" year="1999">Carr, 1999</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95051B15698EE85FA87" author="Currie PJ" box="[228,386,1270,1292]" firstAuthor="Currie" journalOrPublisher="Acta Palaeontol Pol" pageId="23" pageNumber="1289" pagination="191 - 226" part="48" refId="ref20688" refString="Currie PJ. 2003 b. Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontol Pol 48: 191 - 226." title="Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada" type="journal article" year="2003" yearSuffix="b">Currie, 2003b</bibRefCitation>
).
</paragraph>
<paragraph id="8BCA2057FF9FF95051ED577FEA0BFD8D" blockId="23.[160,800,230,1958]" lastBlockId="23.[832,1473,230,1585]" pageId="23" pageNumber="1289">
In 
<taxonomicName id="4C755BD4FF9FF950518E577FEE6EFAAD" authorityName="Cope" authorityYear="1866" box="[219,361,1297,1318]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF950518E577FEE6EFAAD" box="[219,361,1297,1318]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247), the rostral basisphenoid apertures open into large pneumatic chambers that fill the basipterygoid processes and basisphenoid, but remain separate from the subsellar recess and RTR; the caudal basisphenoid sinus system ramifies dorsally, but it cannot be determined (due to crushing) whether there is a median septum. 
<taxonomicName id="4C755BD4FF9FF95050CA57DFEEE5FA4D" authorityName="Osborn" authorityYear="1905" box="[415,482,1457,1478]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF95050CA57DFEEE5FA4D" box="[415,482,1457,1478]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
is apomorphic in that the basisphenoid sinus is highly compressed fore-aft by apposition of the interbasipterygoid and intertuberal laminae (
<bibRefCitation id="EFE45DA6FF9FF9505059546EEEF6F99D" author="Bakker RT &amp; Williams M &amp; Currie PJ" box="[268,497,1536,1558]" etAl="et al." firstAuthor="Bakker" journalOrPublisher="Hunteria" pageId="23" pageNumber="1289" pagination="1 - 30" part="1" refId="ref20052" refString="Bakker RT, Williams M, Currie PJ. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30." title="Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana" type="journal article" year="1988">Bakker et al., 1988</bibRefCitation>
). As a result of this compression, the primitive caudal basisphenoid sinus system was reduced or lost, but the rostral system was retained, as indicated by the retention of the large apertures in the interbasipterygoid lamina (
<figureCitation id="134E3CD2FF9FF95053555405ED49F90B" box="[512,590,1643,1665]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="23" pageNumber="1289">Figs. 2</figureCitation>
, 
<figureCitation id="134E3CD2FF9FF95053095405ED6CF90A" box="[604,619,1643,1665]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="23" pageNumber="1289">5</figureCitation>
, 
<figureCitation id="134E3CD2FF9FF950532D5405ED92F90A" box="[632,661,1643,1665]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="23" pageNumber="1289">10</figureCitation>
). As in 
<taxonomicName id="4C755BD4FF9FF95053BB5405EE03F910" authorityName="Cope" authorityYear="1866" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF95053BB5405EE03F910" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
, the basipterygoid processes and basisphenoid are highly pneumatized via these apertures. 
<materialsCitation id="3B1D2A0AFF9FF950538454CEEFD2F95A" ID-GBIF-Occurrence="2813094336" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
is highly divergent with regard to its basisphenoid sinuses (
<bibRefCitation id="EFE45DA6FF9FF950505154B8EEEFF960" author="Bakker RT &amp; Williams M &amp; Currie PJ" box="[260,488,1750,1772]" etAl="et al." firstAuthor="Bakker" journalOrPublisher="Hunteria" pageId="23" pageNumber="1289" pagination="1 - 30" part="1" refId="ref20052" refString="Bakker RT, Williams M, Currie PJ. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30." title="Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana" type="journal article" year="1988">Bakker et al., 1988</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95050A254B8ED73F967" author="Carr TD" box="[503,628,1750,1772]" firstAuthor="Carr" journalOrPublisher="J Vert Paleontol" pageId="23" pageNumber="1289" pagination="497 - 520" part="19" refId="ref20345" refString="Carr TD. 1999. Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria). J Vert Paleontol 19: 497 - 520." title="Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria)" type="journal article" year="1999">Carr, 1999</bibRefCitation>
). They are not compressed to the extent seen in 
<taxonomicName id="4C755BD4FF9FF9505378549FED68F88D" authorityName="Osborn" authorityYear="1905" box="[557,623,1777,1798]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF9505378549FED68F88D" box="[557,623,1777,1798]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
and seemingly present a distorted, asymmetrical pattern of apertures. As elaborated elsewhere (Witmer and Ridgely, in press), CT scanning shows that 
<materialsCitation id="3B1D2A0AFF9FF95050E3552EED45F8DD" ID-GBIF-Occurrence="2813094353" box="[438,578,1856,1878]" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
ultimately displays the primitive condition (albeit with an apomorphic transformation; 
<figureCitation id="134E3CD2FF9FF950504B5518EE75F807" box="[286,370,1910,1932]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="23" pageNumber="1289">Fig. 10</figureCitation>
). That is, the single rostral aperture in the interbasipterygoid lamina diverges dorsally into roughly paired sinuses, and likewise, the caudal aperture splits dorsally into paired sinuses. These sinuses, although perhaps now reconcilable with other basal tyrannosaurs (e.g., 
<taxonomicName id="4C755BD4FF9FF950556D5358EBC1FEC0" authorityName="Cope" authorityYear="1866" box="[1080,1222,310,331]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF950556D5358EBC1FEC0" box="[1080,1222,310,331]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
), exhibit numerous unique attributes, such as only weak pneumatization of the basipterygoid processes and unusual communications with other pneumatic sinuses. Although the braincase region indeed exhibits some postmortem deformation, we regard that deformation as not being significant enough to account for the disparity in basisphenoid sinuses exhibited by the Cleveland skull.
</paragraph>
<paragraph id="8BCA2057FF9FF950520D5065EA08F9BA" blockId="23.[832,1473,230,1585]" pageId="23" pageNumber="1289">
The final ‘‘family’’ of braincase sinuses consists of the subcondylar recesses (lateral and medial) that comprise apertures located within a fossa on the occiput and most intimately involve the basioccipital and otoccipital (
<bibRefCitation id="EFE45DA6FF9FF95052125018ECEFFD07" author="Witmer LM" box="[839,1000,630,652]" editor="Currie PJ &amp; Padian K" firstAuthor="Witmer" journalOrPublisher="New York: Academic Press" pageId="23" pageNumber="1289" pagination="151 - 159" refId="ref24134" refString="Witmer LM. 1997. Craniofacial air sinus systems. In: Currie PJ, Padian K, editors. Encyclopedia of dinosaurs. New York: Academic Press. p 151 - 159." title="Craniofacial air sinus systems" type="book chapter" volumeTitle="Encyclopedia of dinosaurs" year="1997">Witmer, 1997</bibRefCitation>
). Subcondylar recesses are found in a wide range of theropods (
<bibRefCitation id="EFE45DA6FF9FF950553A50FEEABBFD2D" author="Makovicky PJ &amp; Norell MA" box="[1135,1468,656,678]" firstAuthor="Makovicky" journalOrPublisher="Am Mus Novit" pageId="23" pageNumber="1289" pagination="1 - 16" part="3247" refId="ref22239" refString="Makovicky PJ, Norell MA. 1998. A partial ornithomimid braincase from Ukhaa Tolgod (Upper Cretaceous, Mongolia). Am Mus Novit 3247: 1 - 16." title="A partial ornithomimid braincase from Ukhaa Tolgod (Upper Cretaceous, Mongolia)" type="journal article" year="1998">Makovicky and Norell, 1998</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF950521550C5ECDCFD4B" author="Rauhut OWM" box="[832,987,683,705]" firstAuthor="Rauhut" journalOrPublisher="Can J Earth Sci" pageId="23" pageNumber="1289" pagination="1109 - 1122" part="41" refId="ref22757" refString="Rauhut OWM. 2004. Braincase structure of the middle Jurassic theropod Piatnitzkysaurus. Can J Earth Sci 41: 1109 - 1122." title="Braincase structure of the middle Jurassic theropod Piatnitzkysaurus" type="journal article" year="2004">Rauhut, 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF9FF95052B350C5EA1AFD4A" author="Sampson SD &amp; Witmer LM" box="[998,1309,683,705]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="23" pageNumber="1289" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
), although the precise source of the pneumatic diverticulum (i.e., tympanic vs. pulmonary vs. pharyngeal) is not entirely clear. For tyrannosaurs, a pulmonary or tympanic source is more likely. The subcondylar fossa of 
<taxonomicName id="4C755BD4FF9FF95055A45178EA37FCA0" authorityName="Osborn" authorityYear="1905" box="[1265,1328,790,811]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF95055A45178EA37FCA0" box="[1265,1328,790,811]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
is relatively very shallow, bounded medially and ventrally by the condylotuberal crest (running between the neck of the occipital condyle and the basal tuber; Witmer and Ridgely, in press). The condylotuberal crest is relatively low and subtle in 
<taxonomicName id="4C755BD4FF9FF950555C51F2EB40FC3A" authorityName="Osborn" authorityYear="1905" box="[1033,1095,924,945]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF950555C51F2EB40FC3A" box="[1033,1095,924,945]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF9FF950550251F5EB9FFC3A" box="[1111,1176,923,945]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="23" pageNumber="1289">Fig. 5</figureCitation>
), but it is much more pronounced and sharper in 
<taxonomicName id="4C755BD4FF9FF950550851D8EBECFC40" authorityName="Cope" authorityYear="1866" box="[1117,1259,950,971]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF950550851D8EBECFC40" box="[1117,1259,950,971]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
(ROM 1247, TMP 94.12.602), 
<taxonomicName id="4C755BD4FF9FF950528551BEEB7BFC6E" authorityName=", Maleev" authorityYear="1965" box="[976,1148,976,997]" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF950528551BEEB7BFC6E" box="[976,1148,976,997]" italics="true" pageId="23" pageNumber="1289">Daspletosaurus</emphasis>
</taxonomicName>
(CMN 8506, MOR 590, FMNH PR308), and 
<materialsCitation id="3B1D2A0AFF9FF950557C5185EBBEFB8A" ID-GBIF-Occurrence="2813094381" box="[1065,1209,1003,1025]" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
. Thus, the subcondylar fossa is much deeper in these other tyrannosaurs than in 
<taxonomicName id="4C755BD4FF9FF950520A564FEC9AFBBD" authorityName="Osborn" authorityYear="1905" box="[863,925,1057,1078]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF950520A564FEC9AFBBD" box="[863,925,1057,1078]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
. Within the subcondylar fossa, there is typically a pneumatic aperture within the basioccipital and another within the otoccipital, leading to the medial and lateral subcondylar recesses, respectively. 
<taxonomicName id="4C755BD4FF9FF9505467561FEAC7FB0D" authorityName="Cope" authorityYear="1866" box="[1330,1472,1137,1158]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF9505467561FEAC7FB0D" box="[1330,1472,1137,1158]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
and 
<materialsCitation id="3B1D2A0AFF9FF950522656E5EB06FB2A" ID-GBIF-Occurrence="2813094328" box="[883,1025,1163,1185]" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
both display the primitive condition of having the apertures located close together, near and on either side of the basioccipital-otoccipital suture, whereas in definitive 
<taxonomicName id="4C755BD4FF9FF950556F56B2EB7DFB7A" authorityName="Osborn" authorityYear="1905" box="[1082,1146,1244,1265]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF950556F56B2EB7DFB7A" box="[1082,1146,1244,1265]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
the apertures are relatively widely separated. The medial subcondylar recess in all the tyrannosaurs studied here pneumatizes the basioccipital and extends into the condylar neck. The lateral subcondylar recess occupies the otoccipital and extends into the crista tuberalis in 
<materialsCitation id="3B1D2A0AFF9FF95055D7570EEA14FAFD" ID-GBIF-Occurrence="2813094440" box="[1154,1299,1376,1398]" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
and especially 
<taxonomicName id="4C755BD4FF9FF95052155715ECC9FA1B" authorityName="Cope" authorityYear="1866" box="[832,974,1403,1424]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF95052155715ECC9FA1B" box="[832,974,1403,1424]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
, whereas it barely extends at all into the crista tuberalis in 
<taxonomicName id="4C755BD4FF9FF950554557F8EB49FA20" authorityName="Osborn" authorityYear="1905" box="[1040,1102,1430,1451]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF950554557F8EB49FA20" box="[1040,1102,1430,1451]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF9FF950550A57F8EBABFA20" box="[1119,1196,1430,1452]" captionStart="Fig" captionStartId="7.[354,384,1779,1798]" captionTargetBox="[336,1296,272,1747]" captionTargetId="figure@7.[336,1296,272,1747]" captionTargetPageId="7" captionText="Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal." figureDoi="http://doi.org/10.5281/zenodo.3942777" httpUri="https://zenodo.org/record/3942777/files/figure.png" pageId="23" pageNumber="1289">Figs. 2</figureCitation>
, 
<figureCitation id="134E3CD2FF9FF95055EC57F8EBCFFA27" box="[1209,1224,1430,1452]" captionStart="Fig" captionStartId="12.[178,208,1769,1788]" captionTargetBox="[277,1355,229,1733]" captionTargetId="figure@12.[277,1357,229,1733]" captionTargetPageId="12" captionText="Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up." figureDoi="http://doi.org/10.5281/zenodo.3942787" httpUri="https://zenodo.org/record/3942787/files/figure.png" pageId="23" pageNumber="1289">5</figureCitation>
, 
<figureCitation id="134E3CD2FF9FF950558357F8EBF4FA27" box="[1238,1267,1430,1452]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="23" pageNumber="1289">10</figureCitation>
). The communications of the subcondylar recesses with other braincase sinuses are variable, but one perhaps significant difference is that the lateral subcondylar recess communicates broadly with the CTR in 
<materialsCitation id="3B1D2A0AFF9FF950553D546FEBFFF99D" ID-GBIF-Occurrence="2813094397" box="[1128,1272,1536,1558]" collectionCode="CMNH" pageId="23" pageNumber="1289" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
but not at all in definitive 
<taxonomicName id="4C755BD4FF9FF95052E55472ECE9F9BA" authorityName="Osborn" authorityYear="1905" box="[944,1006,1564,1585]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF9FF95052E55472ECE9F9BA" box="[944,1006,1564,1585]" italics="true" pageId="23" pageNumber="1289">T. rex</emphasis>
</taxonomicName>
or 
<taxonomicName id="4C755BD4FF9FF95055405475EBA4F9BB" authorityName="Cope" authorityYear="1866" box="[1045,1187,1563,1584]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="23" pageNumber="1289" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF9FF95055405475EBA4F9BB" box="[1045,1187,1563,1584]" italics="true" pageId="23" pageNumber="1289">Gorgosaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF9FF95055E65475EA04F9BA" box="[1203,1283,1563,1585]" captionStart="Fig" captionStartId="21.[354,384,1764,1783]" captionTargetBox="[241,1391,229,1733]" captionTargetId="figure@21.[241,1391,229,1733]" captionTargetPageId="21" captionText="Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942799" httpUri="https://zenodo.org/record/3942799/files/figure.png" pageId="23" pageNumber="1289">Fig. 10</figureCitation>
).
</paragraph>
</subSubSection>
<subSubSection id="C36F73DCFF9FF95C5572541DEC7AF82D" lastPageId="27" lastPageNumber="1293" pageId="23" pageNumber="1289" type="discussion">
<paragraph id="8BCA2057FF9FF9505572541DEBDEF900" blockId="23.[832,1472,1651,1958]" box="[1063,1241,1651,1675]" pageId="23" pageNumber="1289">
<heading id="D082973BFF9FF9505572541DEBDEF900" allCaps="true" bold="true" box="[1063,1241,1651,1675]" centered="true" fontSize="10" level="1" pageId="23" pageNumber="1289" reason="0">
<emphasis id="B901FC45FF9FF9505572541DEBDEF900" bold="true" box="[1063,1241,1651,1675]" pageId="23" pageNumber="1289">DISCUSSION</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF9FF950521554FFEAA3F922" blockId="23.[832,1472,1651,1958]" box="[832,1444,1681,1705]" pageId="23" pageNumber="1289">
<heading id="D082973BFF9FF950521554FFEAA3F922" bold="true" box="[832,1444,1681,1705]" fontSize="10" level="3" pageId="23" pageNumber="1289" reason="0">
<emphasis id="B901FC45FF9FF950521554FFEAA3F922" bold="true" box="[832,1444,1681,1705]" pageId="23" pageNumber="1289">Inferences on Sensory Function and Behavior</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF9FF95F520D54D5EDD7FE9D" blockId="23.[832,1472,1651,1958]" lastBlockId="24.[160,800,230,278]" lastPageId="24" lastPageNumber="1290" pageId="23" pageNumber="1289">Much has been written on the sensory capabilities of tyrannosaurs, which is justified given that tyrannosaurs have perhaps the best fossil record of any predatory dinosaur group. However, there are severe limits on what inferences can be made, because we lack critical information on central neural connectivity as well as peripheral responses and sensitivities. Thus, it is important not to try to paint with too fine a brush. Keeping such caveats in mind, a comparative approach, coupled with application of well-understood biophysical principles, can shed light on general sensory attributes.</paragraph>
<paragraph id="8BCA2057FF90F95F51ED5320EE06FC3A" blockId="24.[160,801,334,1959]" pageId="24" pageNumber="1290">
<emphasis id="B901FC45FF90F95F51ED5320EE3CFEED" bold="true" box="[184,315,334,358]" italics="true" pageId="24" pageNumber="1290">Olfaction.</emphasis>
We would expect there to be significant differences in olfactory capabilities based on the reconstructed olfactory bulbs of 
<taxonomicName id="4C755BD4FF90F95F508A53E8ED25FE10" authorityName="Osborn" authorityYear="1905" box="[479,546,390,411]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF90F95F508A53E8ED25FE10" box="[479,546,390,411]" italics="true" pageId="24" pageNumber="1290">T. rex</emphasis>
</taxonomicName>
presented by 
<bibRefCitation id="EFE45DA6FF90F95F538553E8EFD8FE3E" author="Brochu CA" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol" pageId="24" pageNumber="1290" pagination="1 - 6" part="20" refId="ref20179" refString="Brochu CA. 2000. A digitally rendered endocast for Tyrannosaurus rex. J Vert Paleontol 20: 1 - 6." title="A digitally rendered endocast for Tyrannosaurus rex" type="journal article" year="2000">Brochu (2000</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF90F95F51A553CEEE2FFE3E" author="Brochu CA" box="[240,296,416,437]" firstAuthor="Brochu" journalOrPublisher="J Vert Paleontol Mem" pageId="24" pageNumber="1290" pagination="1 - 140" part="7" refId="ref20201" refString="Brochu CA. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. J Vert Paleontol Mem 7: 1 - 140." title="Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull" type="journal article" year="2003">2003</bibRefCitation>
; 
<figureCitation id="134E3CD2FF90F95F506D53CEEE89FE3D" box="[312,398,416,438]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="24" pageNumber="1290">Fig. 6A</figureCitation>
) and by us (
<figureCitation id="134E3CD2FF90F95F537953CEED9AFE3D" box="[556,669,416,438]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="24" pageNumber="1290">Fig. 6A,B</figureCitation>
). Had Brochu’s hypothesis been corroborated it would indeed have justified—even demanded—inferences of extraordinary olfactory capabilities (
<bibRefCitation id="EFE45DA6FF90F95F50F0539EEDE7FD8D" author="Larson PL &amp; Donnan K." bookContentInfo="404" box="[421,736,496,518]" firstAuthor="Larson" journalOrPublisher="Montpelier: Invisible Cities Press" pageId="24" pageNumber="1290" refId="ref22077" refString="Larson PL, Donnan K. 2002. Rex appeal: the amazing story of Sue, the dinosaur that changed science, the law, and my life. Montpelier: Invisible Cities Press. p 404." title="Rex appeal: the amazing story of Sue, the dinosaur that changed science, the law, and my life" type="book" year="2002">Larson and Donnan, 2002</bibRefCitation>
) and perhaps supported the notion of special adaptations for scavenging (
<bibRefCitation id="EFE45DA6FF90F95F507A5048EEDAFDB0" author="Barsbold R." box="[303,477,550,572]" firstAuthor="Barsbold" journalOrPublisher="Trans Jt Sov Mongol Paleontol Exp" pageId="24" pageNumber="1290" pagination="5 - 119" part="19" refId="ref20086" refString="Barsbold R. 1983. Carnivorous dinosaurs from the Cretaceous of Mongolia. Trans Jt Sov Mongol Paleontol Exp 19: 5 - 119. (in Russian)." title="Carnivorous dinosaurs from the Cretaceous of Mongolia" type="journal article" year="1983">Barsbold, 1983</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F50BA5048ED8EFDB0" author="Horner JR" box="[495,649,550,571]" editor="Rosenberg GD &amp; Wolberg DL" firstAuthor="Horner" journalOrPublisher="Paleontological Society, Special Publication" pageId="24" pageNumber="1290" pagination="157 - 164" part="7" refId="ref21614" refString="Horner JR. 1994. Steak knives, beady eyes, and tiny little arms (a portrait of T. rex as a scavenger). In: Rosenberg GD, Wolberg DL, editors. Knoxville, TN: Dino fest. Paleontological Society, Special Publication 7. p 157 - 164." title="Steak knives, beady eyes, and tiny little arms (a portrait of T. rex as a scavenger)" type="book chapter" volumeTitle="Knoxville, TN: Dino fest" year="1994">Horner, 1994</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F53CC5048EE23FDDD" author="Horner JR &amp; Dobb E." bookContentInfo="256" firstAuthor="Horner" journalOrPublisher="New York: Harper Collins" pageId="24" pageNumber="1290" refId="ref21670" refString="Horner JR, Dobb E. 1997. Dinosaur lives: unearthing an evolutionary saga. New York: Harper Collins. p 256." title="Dinosaur lives: unearthing an evolutionary saga" type="book" year="1997">Horner and Dobb, 1997</bibRefCitation>
). Our new findings (see also 
<bibRefCitation id="EFE45DA6FF90F95F532B502EEFDFFDFB" author="Witmer LM &amp; Ridgely RC" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="24" pageNumber="1290" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F51BC5035EEF5FDFA" author="Zelenitsky DK &amp; Therrien F &amp; Kobayashi Y." box="[233,498,603,625]" etAl="et al." firstAuthor="Zelenitsky" journalOrPublisher="Proc R Soc B" pageId="24" pageNumber="1290" pagination="667 - 673" part="276" refId="ref24481" refString="Zelenitsky DK, Therrien F, Kobayashi Y. 2009. Olfactory acuity in theropods: palaeobiological and evolutionary implications. Proc R Soc B 276: 667 - 673; doi: 10.1098 / rspb. 2008.1075." title="Olfactory acuity in theropods: palaeobiological and evolutionary implications" type="journal article" year="2009">Zelenitsky et al., 2009</bibRefCitation>
) argue for moderation in inferring tyrannosaur olfactory capabilities, but even these findings suggest that tyrannosaurs devoted an unusually large amount of neural tissue to the olfactory apparatus. 
<taxonomicName id="4C755BD4FF90F95F507650A8EE63FD50" authorityName="Osborn" authorityYear="1905" box="[291,356,710,731]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF90F95F507650A8EE63FD50" box="[291,356,710,731]" italics="true" pageId="24" pageNumber="1290">T. rex</emphasis>
</taxonomicName>
and especially 
<materialsCitation id="3B1D2A0AFF90F95F534950A8EDABFD50" ID-GBIF-Occurrence="2813094439" box="[540,684,709,731]" collectionCode="CMNH" pageId="24" pageNumber="1290" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
had relatively large olfactory lobes in comparison to other theropods (our data for 
<taxonomicName id="4C755BD4FF90F95F50215095ED05FC9B" authorityName="Cope" authorityYear="1866" box="[372,514,763,784]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF90F95F50215095ED05FC9B" box="[372,514,763,784]" italics="true" pageId="24" pageNumber="1290">Gorgosaurus</emphasis>
</taxonomicName>
are inconclusive because the sphenethmoid is not preserved in ROM 1247). Qualitative assessments of olfactory acuity will be quantitatively tested elsewhere using volumetric data, but the recent quantitative study using linear measurements presented by 
<bibRefCitation id="EFE45DA6FF90F95F506D51EEED3EFC1D" author="Zelenitsky DK &amp; Therrien F &amp; Kobayashi Y." box="[312,569,896,918]" etAl="et al." firstAuthor="Zelenitsky" journalOrPublisher="Proc R Soc B" pageId="24" pageNumber="1290" pagination="667 - 673" part="276" refId="ref24481" refString="Zelenitsky DK, Therrien F, Kobayashi Y. 2009. Olfactory acuity in theropods: palaeobiological and evolutionary implications. Proc R Soc B 276: 667 - 673; doi: 10.1098 / rspb. 2008.1075." title="Olfactory acuity in theropods: palaeobiological and evolutionary implications" type="journal article" year="2009">Zelenitsky et al. (2009)</bibRefCitation>
fully supports these findings.
</paragraph>
<paragraph id="8BCA2057FF90F95F51ED51D8EBA3FDFB" blockId="24.[160,801,334,1959]" lastBlockId="24.[832,1473,230,625]" pageId="24" pageNumber="1290">
Additional information on olfaction can be obtained by consideration of the nasal cavity. 
<bibRefCitation id="EFE45DA6FF90F95F536151BEEFF5FB8A" author="Witmer LM &amp; Ridgely RC" firstAuthor="Witmer" journalOrPublisher="Anat Rec" pageId="24" pageNumber="1290" pagination="1362 - 1388" part="291" refId="ref24295" refString="Witmer LM, Ridgely RC. 2008 b. The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture. Anat Rec 291: 1362 - 1388." title="The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture" type="journal article" year="2008" yearSuffix="b">Witmer and Ridgely (2008b)</bibRefCitation>
recently reconstructed the cephalic air spaces in 
<taxonomicName id="4C755BD4FF90F95F51F55668EFD8FB90" authorityName="Osborn" authorityYear="1905" box="[160,223,1030,1051]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF90F95F51F55668EFD8FB90" box="[160,223,1030,1051]" italics="true" pageId="24" pageNumber="1290">T. rex</emphasis>
</taxonomicName>
, revealing the basic structure and relative sizes of various parts of the nasal cavity. As shown in 
<figureCitation id="134E3CD2FF90F95F539F564EEC27FBBD" box="[714,800,1056,1078]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="24" pageNumber="1290">Fig. 6C</figureCitation>
here, the nasal cavity of 
<taxonomicName id="4C755BD4FF90F95F50E95652EEFCFBDA" authorityName="Osborn" authorityYear="1905" box="[444,507,1084,1105]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF90F95F50E95652EEFCFBDA" box="[444,507,1084,1105]" italics="true" pageId="24" pageNumber="1290">T. rex</emphasis>
</taxonomicName>
was very long, extending from the rostroventrally positioned nostril (
<bibRefCitation id="EFE45DA6FF90F95F53925638EFD1FB0D" author="Witmer LM" firstAuthor="Witmer" journalOrPublisher="Science" pageId="24" pageNumber="1290" pagination="850 - 853" part="293" refId="ref24169" refString="Witmer LM. 2001. Nostril position in dinosaurs and other vertebrates and its significance for nasal function. Science 293: 850 - 853." title="Nostril position in dinosaurs and other vertebrates and its significance for nasal function" type="journal article" year="2001">Witmer, 2001</bibRefCitation>
) to the front of the braincase medial to the orbits. The front portion of the nasal cavity is largely devoted to respiration, and the large arrow shows the respiratory airway from nostril to pharynx. The caudal portion, however, corresponds to the olfactory region in modern vertebrates (
<bibRefCitation id="EFE45DA6FF90F95F505B5698EEADFA80" author="Witmer LM" box="[270,426,1269,1292]" firstAuthor="Witmer" journalOrPublisher="J Morphol" pageId="24" pageNumber="1290" pagination="269 - 327" part="225" refId="ref24054" refString="Witmer LM. 1995. Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae. J Morphol 225: 269 - 327." title="Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae" type="journal article" year="1995">Witmer, 1995</bibRefCitation>
a) and represents the cul-de-sac found in virtually all tetrapods (
<bibRefCitation id="EFE45DA6FF90F95F5367577EEDC2FAAD" author="Negus V." bookContentInfo="402" box="[562,709,1296,1318]" firstAuthor="Negus" journalOrPublisher="London: Livingstone" pageId="24" pageNumber="1290" refId="ref22449" refString="Negus V. 1958. The comparative anatomy and physiology of the nose and paranasal sinuses. London: Livingstone. p 402." title="The comparative anatomy and physiology of the nose and paranasal sinuses" type="book" year="1958">Negus, 1958</bibRefCitation>
) where reduced airflow rates (
<figureCitation id="134E3CD2FF90F95F50F65745EEFDFACA" box="[419,506,1323,1345]" captionStart="Fig" captionStartId="14.[178,208,1179,1198]" captionTargetBox="[168,792,229,1147]" captionTargetId="figure@14.[168,794,229,1147]" captionTargetPageId="14" captionText="Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm." figureDoi="http://doi.org/10.5281/zenodo.3942791" httpUri="https://zenodo.org/record/3942791/files/figure.png" pageId="24" pageNumber="1290">Fig. 6C</figureCitation>
, small arrow) allow odorant molecules to diffuse to their receptors on the olfactory epithelium (
<bibRefCitation id="EFE45DA6FF90F95F503B570EED6BFAFE" author="Simmen D &amp; Scherrer JL &amp; Moe K &amp; Heinz B." box="[366,620,1376,1398]" etAl="et al." firstAuthor="Simmen" journalOrPublisher="Arch Otolaryngol Head Neck Surg" pageId="24" pageNumber="1290" pagination="1015 - 1021" part="125" refId="ref23346" refString="Simmen D, Scherrer JL, Moe K, Heinz B. 1999. A dynamic and direct visualization model for the study of nasal airflow. Arch Otolaryngol Head Neck Surg 125: 1015 - 1021." title="A dynamic and direct visualization model for the study of nasal airflow" type="journal article" year="1999">Simmen et al., 1999</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F53D4570EEC1BFAFD" author="Settles GS" box="[641,796,1376,1398]" firstAuthor="Settles" journalOrPublisher="J Fluids Eng" pageId="24" pageNumber="1290" pagination="189 - 218" part="127" refId="ref23314" refString="Settles GS. 2005. Sniffers: fluid-dynamic sampling for olfactory trace detection in nature and homeland security-the 2004 freeman scholar lecture. J Fluids Eng 127: 189 - 218." title="Sniffers: fluid-dynamic sampling for olfactory trace detection in nature and homeland security-the 2004 freeman scholar lecture" type="journal article" year="2005">Settles, 2005</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F51F55715EE83FA1A" author="Craven BA &amp; Neuberger T &amp; Paterson EG &amp; Webb AG &amp; Josephson EM &amp; Morrison EE &amp; Settles GS" box="[160,388,1403,1425]" etAl="et al." firstAuthor="Craven" journalOrPublisher="Anat Rec" pageId="24" pageNumber="1290" pagination="1325 - 1340" part="290" refId="ref20567" refString="Craven BA, Neuberger T, Paterson EG, Webb AG, Josephson EM, Morrison EE, Settles GS. 2007. Reconstruction and morphometric analysis of the nasal airway of the dog (Canis familiaris) and implications regarding olfactory airflow. Anat Rec 290: 1325 - 1340." title="Reconstruction and morphometric analysis of the nasal airway of the dog (Canis familiaris) and implications regarding olfactory airflow" type="journal article" year="2007">Craven et al., 2007</bibRefCitation>
). We have no way of knowing how much of this huge olfactory chamber in tyrannosaurs was actually cloaked in the sensory olfactory epithelium. In extant archosaurs, the vast majority of the equivalent epithelial region is, in fact, histologically olfactory (
<bibRefCitation id="EFE45DA6FF90F95F51F2546EEE46F99D" author="Witmer LM" box="[167,321,1536,1558]" firstAuthor="Witmer" journalOrPublisher="J Morphol" pageId="24" pageNumber="1290" pagination="269 - 327" part="225" refId="ref24054" refString="Witmer LM. 1995. Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae. J Morphol 225: 269 - 327." title="Homology of facial structures in extant archosaurs (birds and crocodilians), with special reference to paranasal pneumaticity and nasal conchae" type="journal article" year="1995">Witmer, 1995</bibRefCitation>
a), and this would be a very large territory in tyrannosaurs. Indeed, some tyrannosaur specimens preserve olfactory turbinates (e.g., 
<materialsCitation id="3B1D2A0AFF90F95F537E5458EDBCF9C0" ID-GBIF-Occurrence="2813094315" box="[555,699,1589,1611]" collectionCode="CMNH" pageId="24" pageNumber="1290" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
; 
<figureCitation id="134E3CD2FF90F95F53925458EC1CF9C0" box="[711,795,1590,1612]" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="24" pageNumber="1290">Fig. 9A</figureCitation>
; Witmer and Ridgely, in press), suggesting that increasing olfactory epithelial surface area was important. Thus, it is perhaps not unreasonable to suggest that much of the observed olfactory region was indeed sensory. The large size of the olfactory chamber in tyrannosaurs would produce a caudally decreasing gradient in airflow rates. Given that the ability of odorant molecules to adsorb to the epithelial mucosa varies in a complex manner with airflow rate (
<bibRefCitation id="EFE45DA6FF90F95F50B05548ED7AF8B7" author="Dawes JDK" box="[485,637,1830,1852]" firstAuthor="Dawes" journalOrPublisher="J Laryngol Otol" pageId="24" pageNumber="1290" pagination="583 - 593" part="66" refId="ref20745" refString="Dawes JDK. 1952. The course of the nasal airstreams. J Laryngol Otol 66: 583 - 593." title="The course of the nasal airstreams" type="journal article" year="1952">Dawes, 1952</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F53DA5548EFDFF8DE" author="Sobel N &amp; Khan RM &amp; Saltman A &amp; Sullivan EV &amp; Gabrieli JDE" etAl="et al." firstAuthor="Sobel" journalOrPublisher="Nature" pageId="24" pageNumber="1290" pagination="35" part="402" refId="ref23527" refString="Sobel N, Khan RM, Saltman A, Sullivan EV, Gabrieli JDE. 1999. The world smells different to each nostril. Nature 402: 35." title="The world smells different to each nostril" type="journal article" year="1999">Sobel et al., 1999</bibRefCitation>
; see also 
<bibRefCitation id="EFE45DA6FF90F95F5012552EED73F8DD" author="Mainland J &amp; Sobel N." box="[327,628,1856,1878]" firstAuthor="Mainland" journalOrPublisher="Chem Senses" pageId="24" pageNumber="1290" pagination="181 - 196" part="31" refId="ref22214" refString="Mainland J, Sobel N. 2006. The sniff is part of the olfactory percept. Chem Senses 31: 181 - 196." title="The sniff is part of the olfactory percept" type="journal article" year="2006">Mainland and Sobel, 2006</bibRefCitation>
), the large airflow-rate gradient in tyrannosaurs might have provided a refined mechanism for discriminating odors. Moreover, 
<bibRefCitation id="EFE45DA6FF90F95F51F555FFEE8DF82C" author="Craven BA &amp; Neuberger T &amp; Paterson EG &amp; Webb AG &amp; Josephson EM &amp; Morrison EE &amp; Settles GS" box="[160,394,1936,1959]" etAl="et al." firstAuthor="Craven" journalOrPublisher="Anat Rec" pageId="24" pageNumber="1290" pagination="1325 - 1340" part="290" refId="ref20567" refString="Craven BA, Neuberger T, Paterson EG, Webb AG, Josephson EM, Morrison EE, Settles GS. 2007. Reconstruction and morphometric analysis of the nasal airway of the dog (Canis familiaris) and implications regarding olfactory airflow. Anat Rec 290: 1325 - 1340." title="Reconstruction and morphometric analysis of the nasal airway of the dog (Canis familiaris) and implications regarding olfactory airflow" type="journal article" year="2007">Craven et al. (2007)</bibRefCitation>
showed that surface area requirements for olfaction are much greater than for the respiratory function, because odorant receptors tend to have regional specificity requiring adequate surface area to accommodate the numerous receptor types. Thus, again, the large area devoted to the olfactory region in tyrannosaurs may indicate a discriminating sense of smell, particularly given the new findings from genomics (
<bibRefCitation id="EFE45DA6FF90F95F542553E8ECB8FE3D" author="Steiger SS &amp; Fidler AE &amp; Valcu M &amp; Kempenaers B." etAl="et al." firstAuthor="Steiger" journalOrPublisher="Proc R Soc B" pageId="24" pageNumber="1290" pagination="2309 - 2317" part="275" refId="ref23738" refString="Steiger SS, Fidler AE, Valcu M, Kempenaers B. 2008. Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds? Proc R Soc B 275: 2309 - 2317." title="Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds?" type="journal article" year="2008">Steiger et al., 2008</bibRefCitation>
) and ethology (e.g., 
<bibRefCitation id="EFE45DA6FF90F95F55F253CEEA32FE3E" author="Nevitt GA" box="[1191,1333,416,438]" firstAuthor="Nevitt" journalOrPublisher="J Exp Biol" pageId="24" pageNumber="1290" pagination="1706 - 1713" part="211" refId="ref22473" refString="Nevitt GA. 2008. Sensory ecology on the high seas: the odor world of the procellariiform seabirds. J Exp Biol 211: 1706 - 1713." title="Sensory ecology on the high seas: the odor world of the procellariiform seabirds" type="journal article" year="2008">Nevitt, 2008</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F541453CEEC71FE5A" author="Roth TC, II &amp; Cox JG &amp; Lima SL" etAl="et al." firstAuthor="Roth" journalOrPublisher="Anim Behav" pageId="24" pageNumber="1290" pagination="2021 - 2027" part="76" refId="ref22948" refString="Roth TC, II, Cox JG, Lima SL. 2008. Can foraging birds assess predation risk by scent? Anim Behav 76: 2021 - 2027." title="Can foraging birds assess predation risk by scent?" type="journal article" year="2008">Roth et al., 2008</bibRefCitation>
) that extant theropods (birds) may rely much more on olfactory cues than previously thought. The importance of scaling of these phenomena is completely unknown, but such a determination will become tractable as data of the kind presented here and elsewhere (
<bibRefCitation id="EFE45DA6FF90F95F5212502EEB95FDDD" author="Witmer LM &amp; Ridgely RC" box="[839,1170,576,598]" firstAuthor="Witmer" journalOrPublisher="Anat Rec" pageId="24" pageNumber="1290" pagination="1362 - 1388" part="291" refId="ref24295" refString="Witmer LM, Ridgely RC. 2008 b. The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture. Anat Rec 291: 1362 - 1388." title="The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture" type="journal article" year="2008" yearSuffix="b">Witmer and Ridgely, 2008b</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F55F2502EEABEFDDC" author="Zelenitsky DK &amp; Therrien F &amp; Kobayashi Y." box="[1191,1465,576,599]" etAl="et al." firstAuthor="Zelenitsky" journalOrPublisher="Proc R Soc B" pageId="24" pageNumber="1290" pagination="667 - 673" part="276" refId="ref24481" refString="Zelenitsky DK, Therrien F, Kobayashi Y. 2009. Olfactory acuity in theropods: palaeobiological and evolutionary implications. Proc R Soc B 276: 667 - 673; doi: 10.1098 / rspb. 2008.1075." title="Olfactory acuity in theropods: palaeobiological and evolutionary implications" type="journal article" year="2009">Zelenitsky et al., 2009</bibRefCitation>
) become available for more taxa.
</paragraph>
<paragraph id="8BCA2057FF90F95F520D50F5EAA1F9D2" blockId="24.[832,1473,667,1625]" pageId="24" pageNumber="1290">
<emphasis id="B901FC45FF90F95F520D50F5ECCBFD38" bold="true" box="[856,972,667,691]" italics="true" pageId="24" pageNumber="1290">Hearing.</emphasis>
Information on the sense of hearing comes from two sources in the braincase, the cochlear portion of the inner ear and the pneumatic sinuses of the middle ear. As noted above, tyrannosaurs have a relatively very elongate cochlear duct, and such is not universally the case in theropods. The length of the cochlea is causally related to the length of the neuroepithelium of the basilar papilla and has been correlated with rough measures of auditory capability or at least the behavioral importance of hearing (
<bibRefCitation id="EFE45DA6FF90F95F554A51E3EBAAFC28" author="Baird IL" box="[1055,1197,909,931]" editor="Gans C &amp; Parsons TS" firstAuthor="Baird" journalOrPublisher="New York: Academic Press" pageId="24" pageNumber="1290" pagination="193 - 275" refId="ref20010" refString="Baird IL. 1970. The anatomy of the reptilian ear. In: Gans C, Parsons TS, editors. Biology of the reptilian. Vol. II. New York: Academic Press. p 193 - 275." title="The anatomy of the reptilian ear" type="book chapter" volumeTitle="Biology of the reptilian. Vol. II" year="1970">Baird, 1970</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F559451E0EA53FC28" author="Wever EG" bookContentInfo="1024" box="[1217,1364,910,931]" firstAuthor="Wever" journalOrPublisher="Princeton: Princeton University Press" pageId="24" pageNumber="1290" refId="ref23980" refString="Wever EG. 1978. The reptile ear. Princeton: Princeton University Press. p 1024." title="The reptile ear" type="book" year="1978">Wever, 1978</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F543C51E3EC7FFC36" author="Manley GA" bookContentInfo="288" firstAuthor="Manley" journalOrPublisher="New York: Springer-Verlag" pageId="24" pageNumber="1290" refId="ref22322" refString="Manley GA. 1990. Peripheral hearing mechanisms in reptiles and birds. New York: Springer-Verlag. p 288." title="Peripheral hearing mechanisms in reptiles and birds" type="book" year="1990">Manley, 1990</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F52D051C6EBA3FC35" author="Gleich O &amp; Manley GA" box="[901,1188,936,958]" editor="Dooling RJ &amp; Fay RR &amp; Popper AN" firstAuthor="Gleich" journalOrPublisher="New York: Springer" pageId="24" pageNumber="1290" pagination="70 - 138" refId="ref21156" refString="Gleich O, Manley GA. 2000. The hearing organ of birds and Crocodilia. In: Dooling RJ, Fay RR, Popper AN, editors. Comparative hearing: birds and reptiles. New York: Springer. p 70 - 138." title="The hearing organ of birds and Crocodilia" type="book chapter" volumeTitle="Comparative hearing: birds and reptiles" year="2000">Gleich and Manley, 2000</bibRefCitation>
). Thus, by this measure, hearing was particularly important to tyrannosaurs. 
<bibRefCitation id="EFE45DA6FF90F95F521551B0EB1AFC78" author="Gleich O &amp; Dooling RJ &amp; Manley GA" box="[832,1053,989,1012]" etAl="et al." firstAuthor="Gleich" journalOrPublisher="Naturwissenschaften" pageId="24" pageNumber="1290" pagination="595 - 598" part="92" refId="ref21119" refString="Gleich O, Dooling RJ, Manley GA. 2005. Audiogram, body mass, and basilar papilla length: correlations in birds and predictions for extinct archosaurs. Naturwissenschaften 92: 595 - 598." title="Audiogram, body mass, and basilar papilla length: correlations in birds and predictions for extinct archosaurs" type="journal article" year="2005">Gleich et al. (2005)</bibRefCitation>
also showed in extant taxa an allometric relationship between body mass and length of the basilar papilla, and also an inverse relationship between these two parameters and an animal’s most sensitive (‘‘best’’) frequency; that is, larger animals tend to have relatively longer basilar papillae and are more sensitive to low-frequency sounds. 
<bibRefCitation id="EFE45DA6FF90F95F55275610EA5AFB18" author="Gleich O &amp; Dooling RJ &amp; Manley GA" box="[1138,1373,1149,1172]" etAl="et al." firstAuthor="Gleich" journalOrPublisher="Naturwissenschaften" pageId="24" pageNumber="1290" pagination="595 - 598" part="92" refId="ref21119" refString="Gleich O, Dooling RJ, Manley GA. 2005. Audiogram, body mass, and basilar papilla length: correlations in birds and predictions for extinct archosaurs. Naturwissenschaften 92: 595 - 598." title="Audiogram, body mass, and basilar papilla length: correlations in birds and predictions for extinct archosaurs" type="journal article" year="2005">Gleich et al. (2005)</bibRefCitation>
had no tyrannosaurs in their sample of fossil archosaurs (only 
<taxonomicName id="4C755BD4FF90F95F521556DDECE4FB43" authorityName="Riggs" authorityYear="1903" box="[832,995,1203,1224]" class="Reptilia" family="Brachiosauridae" genus="Brachiosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF90F95F521556DDECE4FB43" box="[832,995,1203,1224]" italics="true" pageId="24" pageNumber="1290">Brachiosaurus</emphasis>
</taxonomicName>
, 
<taxonomicName id="4C755BD4FF90F95F555556DDEB7FFB43" authorityName="Marsh" authorityYear="1877" box="[1024,1144,1203,1224]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="24" pageNumber="1290" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF90F95F555556DDEB7FFB43" box="[1024,1144,1203,1224]" italics="true" pageId="24" pageNumber="1290">Allosaurus</emphasis>
</taxonomicName>
, and 
<emphasis id="B901FC45FF90F95F558D56DDEA72FB43" box="[1240,1397,1203,1224]" italics="true" pageId="24" pageNumber="1290">Archaeopteryx</emphasis>
), but applying their findings to our data would suggest that tyrannosaurs, in particular, emphasized low frequencies. These results agree with the acoustic consequences of extensive tympanic pneumaticity in tyrannosaurs in that a larger volume impacts the impedance-matching function of the middle ear by reducing stiffness at low frequencies as well as contributing to frequency-dependent amplification of sounds (
<bibRefCitation id="EFE45DA6FF90F95F55D057E6EA25FA16" author="Henson OW, Jr." box="[1157,1314,1416,1437]" editor="Keidel WD &amp; Neff WD" firstAuthor="Henson" journalOrPublisher="New York: Springer-Verlag" pageId="24" pageNumber="1290" pagination="39 - 110" refId="ref21320" refString="Henson OW, Jr. 1974. Comparative anatomy of the middle ear. In: Keidel WD, Neff WD, editors. Handbook of sensory physiology. Vol. V / 1: Auditory system: anatomy, physiology (ear). New York: Springer-Verlag. p 39 - 110." title="Comparative anatomy of the middle ear" type="book chapter" volumeTitle="Handbook of sensory physiology. Vol. V / 1: Auditory system: anatomy, physiology (ear)" year="1974">Henson, 1974</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F546557E7EABBFA16" author="Wever EG" bookContentInfo="1024" box="[1328,1468,1416,1438]" firstAuthor="Wever" journalOrPublisher="Princeton: Princeton University Press" pageId="24" pageNumber="1290" refId="ref23980" refString="Wever EG. 1978. The reptile ear. Princeton: Princeton University Press. p 1024." title="The reptile ear" type="book" year="1978">Wever, 1978</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F521557CDECD1FA33" author="Pickles JO" bookContentInfo="367" box="[832,982,1443,1465]" firstAuthor="Pickles" journalOrPublisher="New York: Academic Press" pageId="24" pageNumber="1290" refId="ref22708" refString="Pickles JO. 1988. An introduction to the physiology of hearing. 2 nd ed. New York: Academic Press. p 367." title="An introduction to the physiology of hearing. 2 nd ed" type="book" year="1988">Pickles, 1988</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F52B457CDEB7EFA33" author="Manley GA" bookContentInfo="288" box="[993,1145,1443,1465]" firstAuthor="Manley" journalOrPublisher="New York: Springer-Verlag" pageId="24" pageNumber="1290" refId="ref22322" refString="Manley GA. 1990. Peripheral hearing mechanisms in reptiles and birds. New York: Springer-Verlag. p 288." title="Peripheral hearing mechanisms in reptiles and birds" type="book" year="1990">Manley, 1990</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F55D157CDEA66FA33" author="Dooling RJ &amp; Lohr B &amp; Dent ML" box="[1156,1377,1443,1465]" editor="Dooling RJ &amp; Fay RR &amp; Popper AN" etAl="et al." firstAuthor="Dooling" journalOrPublisher="New York: Springer" pageId="24" pageNumber="1290" pagination="308 - 359" refId="ref20825" refString="Dooling RJ, Lohr B, Dent ML. 2000. Hearing in birds and reptiles. In: Dooling RJ, Fay RR, Popper AN, editors. Comparative hearing: birds and reptiles. New York: Springer. p 308 - 359." title="Hearing in birds and reptiles" type="book chapter" volumeTitle="Comparative hearing: birds and reptiles" year="2000">Dooling et al., 2000</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F543857CDEB1CFA5F" author="Witmer LM &amp; Ridgely RC" firstAuthor="Witmer" journalOrPublisher="Anat Rec" pageId="24" pageNumber="1290" pagination="1362 - 1388" part="291" refId="ref24295" refString="Witmer LM, Ridgely RC. 2008 b. The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture. Anat Rec 291: 1362 - 1388." title="The paranasal air sinuses of predatory and armored dinosaurs (Archosauria: Theropoda and Ankylosauria) and their contribution to cephalic architecture" type="journal article" year="2008" yearSuffix="b">Witmer and Ridgely, 2008b</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF90F95F557C57D0EA0BFA5F" author="Witmer LM &amp; Ridgely RC" box="[1065,1292,1470,1492]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="24" pageNumber="1290" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
). The columella and tympanum obviously also bear on hearing, and these are under comparative study by the authors, but, even absent analysis of these, all indications are that hearing in tyrannosaurs was important and lowfrequency sounds were behaviorally the most relevant.
</paragraph>
<paragraph id="8BCA2057FF90F95E520D54EDEED2FC1D" blockId="24.[832,1472,1667,1958]" lastBlockId="25.[160,801,230,1638]" lastPageId="25" lastPageNumber="1291" pageId="24" pageNumber="1290">
<emphasis id="B901FC45FF90F95F520D54EDEB06F910" bold="true" box="[856,1025,1667,1691]" italics="true" pageId="24" pageNumber="1290">Equilibrium.</emphasis>
The sense of balance is governed by the vestibular portion of the inner ear (otolith organs, semicircular canals), as well as central processing of these inputs in the brain. The otolith organs of the utricle, saccule, and lagena sense linear acceleration due to translational head movements. These structures are hidden within the bony labyrinth, and we have little direct information on these in tyrannosaurs. The tyrannosaur labyrinths, however, do preserve the bony semicircular canals that, in life, housed the membranous ducts that responded to angular acceleration due to rotational head movements (
<figureCitation id="134E3CD2FF91F95E507B5288EE68FF77" box="[302,367,230,252]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="25" pageNumber="1291">Fig. 8</figureCitation>
). The interpretation of behavior based on the structure of the semicircular canals has been controversial because of lingering uncertainties (both theoretical and experimental) about the biophysical attributes of the canals, as well as apparent conflicting information from empirical comparative studies (see 
<bibRefCitation id="EFE45DA6FF91F95E51F553E8EEA4FE17" author="Graf W &amp; Klam F." box="[160,419,390,412]" firstAuthor="Graf" journalOrPublisher="C R Palevol" pageId="25" pageNumber="1291" pagination="637 - 655" part="5" refId="ref21202" refString="Graf W, Klam F. 2006. Le systeme vestibulaire: anatomie fonctionnelle et comparee, evolution et developpement. C R Palevol 5: 637 - 655." title="Le systeme vestibulaire: anatomie fonctionnelle et comparee, evolution et developpement" type="journal article" year="2006">Graf and Klam, 2006</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E50E053E8ED4DFE17" author="Hullar TE" box="[437,586,390,412]" firstAuthor="Hullar" journalOrPublisher="Anat Rec" pageId="25" pageNumber="1291" pagination="466 - 472" part="288 A" refId="ref21734" refString="Hullar TE. 2006. Semicircular canal geometry, afferent sensitivity, and animal behavior. Anat Rec 288 A: 466 - 472." title="Semicircular canal geometry, afferent sensitivity, and animal behavior" type="journal article" year="2006">Hullar, 2006</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E530953E8EFDEFE3D" author="Sipla JS &amp; Spoor F." editor="Thewissen JGM &amp; Nummela S" firstAuthor="Sipla" journalOrPublisher="Berkeley: University of California Press" pageId="25" pageNumber="1291" pagination="227 - 232" refId="ref23419" refString="Sipla JS, Spoor F. 2008. The physics and physiology of balance. In: Thewissen JGM, Nummela S, editors. Sensory evolution on the threshold: adaptations in secondarily aquatic vertebrates. Berkeley: University of California Press. p 227 - 232." title="The physics and physiology of balance" type="book chapter" volumeTitle="Sensory evolution on the threshold: adaptations in secondarily aquatic vertebrates" year="2008">Sipla and Spoor, 2008</bibRefCitation>
). It is well beyond our scope to review these controversies here. Ultimately, the question comes down to the functional significance of apomorphic canals. For example, 
<bibRefCitation id="EFE45DA6FF91F95E5187539EEE6CFD8D" author="Clarke AH" box="[210,363,496,518]" firstAuthor="Clarke" journalOrPublisher="J Vestib Res" pageId="25" pageNumber="1291" pagination="65 - 71" part="15" refId="ref20466" refString="Clarke AH. 2005. On the vestibular labyrinth of Brachiosaurus brancai. J Vestib Res 15: 65 - 71." title="On the vestibular labyrinth of Brachiosaurus brancai" type="journal article" year="2005">Clarke (2005)</bibRefCitation>
interpreted the elongate rostral semicircular canal of 
<taxonomicName id="4C755BD4FF91F95E50375065ED02FDAB" authorityName="Riggs" authorityYear="1903" box="[354,517,523,544]" class="Reptilia" family="Brachiosauridae" genus="Brachiosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF91F95E50375065ED02FDAB" box="[354,517,523,544]" italics="true" pageId="25" pageNumber="1291">Brachiosaurus</emphasis>
</taxonomicName>
as enhancing sensitivity so as to modulate slow, stately, pitching movement of the head. This notion agrees with 
<bibRefCitation id="EFE45DA6FF91F95E5359502FEC1BFDDD" author="Jones GM &amp; Spells KE" box="[524,796,576,598]" firstAuthor="Jones" journalOrPublisher="Proc R Soc Lond B Biol Sci" pageId="25" pageNumber="1291" pagination="403 - 419" part="157" refId="ref21939" refString="Jones GM, Spells KE. 1963. A theoretical and comparative study of the functional dependence of the semicircular canal upon its physical dimensions. Proc R Soc Lond B Biol Sci 157: 403 - 419." title="A theoretical and comparative study of the functional dependence of the semicircular canal upon its physical dimensions" type="journal article" year="1963">Jones and Spells (1963</bibRefCitation>
, p 405) who found that larger animals tend to have more elongate (and hence ‘‘more responsive’’) canals, suggesting to them that ‘‘it seems plausible that larger animals::: [have] in general, more sluggish head movements.’’ On the other hand, this seems to contradict a wealth of empirical data linking expanded canal sizes in birds (
<bibRefCitation id="EFE45DA6FF91F95E51FD5095EE56FC9B" author="Tanturri V." box="[168,337,763,785]" firstAuthor="Tanturri" journalOrPublisher="Monatssch Ohrenheilk Laryngo-Rhinol" pageId="25" pageNumber="1291" pagination="1 - 27" part="67" refId="ref23815" refString="Tanturri V. 1933. Zur anatomie und physiologie des labyrinthes der Vogel. Monatssch Ohrenheilk Laryngo-Rhinol 67: 1 - 27." title="Zur anatomie und physiologie des labyrinthes der Vogel" type="journal article" year="1933">Tanturri, 1933</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E50355095ED33FC9B" author="Turkewitsch BG" box="[352,564,763,785]" firstAuthor="Turkewitsch" journalOrPublisher="Z Anat Entwicklungsgesch" pageId="25" pageNumber="1291" pagination="551 - 608" part="103" refId="ref23918" refString="Turkewitsch BG. 1934. Zur anatomie des Gehororgans der Vogel (Canales semicirulares). Z Anat Entwicklungsgesch 103: 551 - 608." title="Zur anatomie des Gehororgans der Vogel (Canales semicirulares)" type="journal article" year="1934">Turkewitsch, 1934</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E53165095EE4CFCA7" author="Hadziselimovic H &amp; Savkovic LJ" firstAuthor="Hadziselimovic" journalOrPublisher="Acta Anat" pageId="25" pageNumber="1291" pagination="306 - 315" part="57" refId="ref21232" refString="Hadziselimovic H, Savkovic LJ. 1964. Appearance of semicircular canals in birds in relation to mode of life. Acta Anat 57: 306 - 315." title="Appearance of semicircular canals in birds in relation to mode of life" type="journal article" year="1964">Hadziselimovic and Savkovic, 1964</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E500C5178ED2FFCA7" author="Money KE &amp; Londolt JP &amp; Correia MJ &amp; Laufer J." box="[345,552,790,812]" etAl="et al." firstAuthor="Money" journalOrPublisher="Brain Behav Evol" pageId="25" pageNumber="1291" pagination="212 - 227" part="10" refId="ref22415" refString="Money KE, Londolt JP, Correia MJ, Laufer J. 1974. Anatomical and physiological investigations of the vestibular system of birds. Brain Behav Evol 10: 212 - 227." title="Anatomical and physiological investigations of the vestibular system of birds" type="journal article" year="1974">Money et al. 1974</bibRefCitation>
) and primates (
<bibRefCitation id="EFE45DA6FF91F95E53B55178EE91FCCE" author="Spoor F &amp; Zonneveld F." firstAuthor="Spoor" journalOrPublisher="Yb Phys Anthropol" pageId="25" pageNumber="1291" pagination="211 - 251" part="41" refId="ref23713" refString="Spoor F, Zonneveld F. 1998. Comparative review of the human bony labyrinth. Yb Phys Anthropol 41: 211 - 251." title="Comparative review of the human bony labyrinth" type="journal article" year="1998">Spoor and Zonneveld, 1998</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E50FD515EED35FCCE" author="Spoor F." box="[424,562,816,837]" editor="Franzen JL &amp; Kohler M &amp; Moya-Sola S" firstAuthor="Spoor" journalOrPublisher="Stuttgart: Courier Forschungsinstitut Senkenberg" pageId="25" pageNumber="1291" pagination="93 - 104" refId="ref23557" refString="Spoor F. 2003. The semicircular canal system and locomotor behaviour, with special reference to hominin evolution. In: Franzen JL, Kohler M, Moya-Sola S, editors. Walking upright. Vol. 243. Stuttgart: Courier Forschungsinstitut Senkenberg. p 93 - 104." title="The semicircular canal system and locomotor behaviour, with special reference to hominin evolution" type="book chapter" volumeTitle="Walking upright. Vol. 243" year="2003">Spoor, 2003</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E5316515EEC1EFCCD" author="Spoor F &amp; Garland T, Jr &amp; Krovitz G &amp; Ryan TM &amp; Silcox MT &amp; Walker A." box="[579,793,816,838]" etAl="et al." firstAuthor="Spoor" journalOrPublisher="Proc Natl Acad Sci USA" pageId="25" pageNumber="1291" pagination="10808 - 10812" part="104" refId="ref23608" refString="Spoor F, Garland T, Jr, Krovitz G, Ryan TM, Silcox MT, Walker A. 2007. The primate semicircular canal system and locomotion. Proc Natl Acad Sci USA 104: 10808 - 10812." title="The primate semicircular canal system and locomotion" type="journal article" year="2007">Spoor et al., 2007</bibRefCitation>
) with the quick head and body movements that characterize the more highly agile and acrobatic or aerobatic species within these clades.
</paragraph>
<paragraph id="8BCA2057FF91F95E51ED51F5EEB4F9ED" blockId="25.[160,801,230,1638]" pageId="25" pageNumber="1291">
This latter interpretation seems to better match the widely held inference of high levels of agility, quickness, and activity in nonavian coelurosaurs. Viewed in this light, and keeping all caveats surrounding semicircular canal biophysics in mind, the elongate canals of tyrannosaurs would be consistent with their active and agile coelurosaurian heritage. Tyrannosaur canal dimensions cannot be attributed solely to scaling phenomena, because their canal shapes and sizes (adjusted for body mass) resemble those of 
<emphasis id="B901FC45FF91F95E508356E5ED78FB2B" box="[470,639,1163,1184]" italics="true" pageId="25" pageNumber="1291">Struthiomimus</emphasis>
(
<figureCitation id="134E3CD2FF91F95E53CD56E5EDE7FB2A" box="[664,736,1163,1185]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="25" pageNumber="1291">Fig. 8</figureCitation>
Q–T), 
<taxonomicName id="4C755BD4FF91F95E51F556C8EFFCFB30" authorityName="Leidy" authorityYear="1856" box="[160,251,1190,1211]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF91F95E51F556C8EFFCFB30" box="[160,251,1190,1211]" italics="true" pageId="25" pageNumber="1291">Troodon</emphasis>
</taxonomicName>
, 
<taxonomicName id="4C755BD4FF91F95E505F56C8EE9FFB30" authorityName="Ostrom" authorityYear="1969" box="[266,408,1190,1211]" class="Reptilia" family="Dromaeosauridae" genus="Deinonychus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF91F95E505F56C8EE9FFB30" box="[266,408,1190,1211]" italics="true" pageId="25" pageNumber="1291">Deinonychus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF91F95E50FD56C8EEFAFB37" box="[424,509,1190,1212]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="25" pageNumber="1291">Fig. 4E</figureCitation>
), 
<emphasis id="B901FC45FF91F95E534756C8EDA8FB30" box="[530,687,1190,1211]" italics="true" pageId="25" pageNumber="1291">Archaeopteryx</emphasis>
(
<figureCitation id="134E3CD2FF91F95E539556C8EC13FB37" box="[704,788,1190,1212]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="25" pageNumber="1291">Fig. 4F</figureCitation>
), and the other small-bodied coelurosaurs in our broader sample more so than canal shape in large-bodied, more basal theropods, such as 
<taxonomicName id="4C755BD4FF91F95E509C5698ED46FA80" authorityName="Marsh" authorityYear="1877" box="[457,577,1270,1291]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF91F95E509C5698ED46FA80" box="[457,577,1270,1291]" italics="true" pageId="25" pageNumber="1291">Allosaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF91F95E53005698ED90FA87" box="[597,663,1270,1292]" captionStart="Fig" captionStartId="19.[178,208,1801,1820]" captionTargetBox="[216,1416,260,1764]" captionTargetId="figure@19.[216,1418,260,1764]" captionTargetPageId="19" captionText="Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm)." figureDoi="http://doi.org/10.5281/zenodo.3942795" httpUri="https://zenodo.org/record/3942795/files/figure.png" pageId="25" pageNumber="1291">Fig. 8</figureCitation>
U–X), 
<taxonomicName id="4C755BD4FF91F95E53B35698EEDEFAAD" authority=", Ceratosaurus" authorityName="Ceratosaurus" class="Reptilia" family="Carcharodontosauridae" genus="Acrocanthosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF91F95E53B35698EE31FAAE" italics="true" pageId="25" pageNumber="1291">Acrocanthosaurus</emphasis>
, 
<emphasis id="B901FC45FF91F95E5010577FEEDEFAAD" box="[325,473,1297,1318]" italics="true" pageId="25" pageNumber="1291">Ceratosaurus</emphasis>
</taxonomicName>
, and 
<taxonomicName id="4C755BD4FF91F95E534C577FEEA2FACA" authority="(Sampson and Witmer, 2007)" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF91F95E534C577FEDCEFAAD" box="[537,713,1297,1318]" italics="true" pageId="25" pageNumber="1291">Majungasaurus</emphasis>
(
<bibRefCitation id="EFE45DA6FF91F95E538D577EEE9AFACA" author="Sampson SD &amp; Witmer LM" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="25" pageNumber="1291" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
)
</taxonomicName>
. Tyrannosaurs do resemble other theropods in general in having the rostral canal the longest of the three, which may well be associated with bipedality. A link between rostral canal elongation and bipedality was proposed by 
<bibRefCitation id="EFE45DA6FF91F95E508A57F8EDABFA20" author="Spoor F &amp; Wood B &amp; Zonneveld F." box="[479,684,1430,1452]" etAl="et al." firstAuthor="Spoor" journalOrPublisher="Nature" pageId="25" pageNumber="1291" pagination="645 - 648" part="369" refId="ref23649" refString="Spoor F, Wood B, Zonneveld F. 1994. Implications of early hominid labyrinthine morphology for evolution of human bipedal locomotion. Nature 369: 645 - 648." title="Implications of early hominid labyrinthine morphology for evolution of human bipedal locomotion" type="journal article" year="1994">Spoor et al. (1994</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF91F95E53EF57F8EDF7FA27" author="Spoor F &amp; Wood B &amp; Zonneveld F." box="[698,752,1430,1452]" firstAuthor="Spoor" journalOrPublisher="J Hum Evol" pageId="25" pageNumber="1291" pagination="183 - 187" part="30" refId="ref23680" refString="Spoor F, Wood B, Zonneveld F. 1996. Evidence for a link between human semicircular canal size and bipedal behaviour. J Hum Evol 30: 183 - 187." title="Evidence for a link between human semicircular canal size and bipedal behaviour" type="journal article" year="1996">1996</bibRefCitation>
) for hominids and by 
<bibRefCitation id="EFE45DA6FF91F95E503B57DEED47FA4D" author="Sipla JS &amp; Georgi J &amp; Forster CA" box="[366,576,1456,1478]" etAl="et al." firstAuthor="Sipla" journalOrPublisher="J Vert Paleontol" pageId="25" pageNumber="1291" pagination="113 A" part="24 (Suppl 3)" refId="ref23384" refString="Sipla JS, Georgi J, Forster CA. 2004. The semicircular canals of dinosaurs: tracking major transitions in locomotion. J Vert Paleontol 24 (Suppl 3): 113 A." title="The semicircular canals of dinosaurs: tracking major transitions in locomotion" type="journal article" year="2004">Sipla et al. (2004)</bibRefCitation>
for dinosaurs, and our large sample generally supports that association. However, further elongation of the rostral canal and, additionally, the lateral canal in tyrannosaurs and other coelurosaurs cannot be explained solely by bipedality and may relate, at least in part, to gaze stabilization mechanisms (see below).
</paragraph>
<paragraph id="8BCA2057FF91F95E51ED54F0EA7EFA77" blockId="25.[160,801,1694,1958]" lastBlockId="25.[832,1473,230,1532]" pageId="25" pageNumber="1291">
<emphasis id="B901FC45FF91F95E51ED54F0EE17F93D" bold="true" box="[184,272,1694,1718]" italics="true" pageId="25" pageNumber="1291">Vision.</emphasis>
Our data provide little information on the sense of sight, at least with regard to such parameters as acuity and sensitivity. The controversy surrounding the positions of the optic lobes—whether they are laterally displaced as in birds or medially located as in rep-tiles—probably has little bearing on assessing vision in that it generally has been thought that the lateral position of the optic lobes in birds and pterosaurs has more to do with the relative sizes of the cerebrum and cerebellum than the optic lobe itself (
<bibRefCitation id="EFE45DA6FF91F95E534355FEEDB4F82E" author="Jerison HJ" bookContentInfo="482" box="[534,691,1936,1958]" firstAuthor="Jerison" journalOrPublisher="New York: Academic Press" pageId="25" pageNumber="1291" refId="ref21918" refString="Jerison HJ. 1973. Evolution of the brain and intelligence. New York: Academic Press. p 482." title="Evolution of the brain and intelligence" type="book" year="1973">Jerison, 1973</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E539355FFEC7FFF70" author="Hopson JA" box="[710,888,230,1958]" editor="Gans C" firstAuthor="Hopson" journalOrPublisher="New York: Academic Press" pageId="25" pageNumber="1291" pagination="39 - 146" refId="ref21525" refString="Hopson JA. 1979. Paleoneurology. In: Gans C, editor. Biology of the reptilia. Vol. IX: Neurology A. New York: Academic Press. p 39 - 146." title="Paleoneurology" type="book chapter" volumeTitle="Biology of the reptilia. Vol. IX: Neurology A" year="1979">Hopson, 1979</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E52D95288EB87FF77" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" box="[908,1152,230,252]" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="25" pageNumber="1291" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
). 
<bibRefCitation id="EFE45DA6FF91F95E55CE5288EA41FF77" author="Stevens KA" box="[1179,1350,230,252]" firstAuthor="Stevens" journalOrPublisher="J Vert Paleontol" pageId="25" pageNumber="1291" pagination="321 - 330" part="26" refId="ref23778" refString="Stevens KA. 2006. Binocular vision in theropod dinosaurs. J Vert Paleontol 26: 321 - 330." title="Binocular vision in theropod dinosaurs" type="journal article" year="2006">Stevens (2006)</bibRefCitation>
discussed tyrannosaur vision in detail, and our findings again do not relate closely to many of the attributes he analyzed, with the exception of head posture, which is discussed below. Our findings on the inner ear, however, do relate to the behavioral importance of vision in that there is a tight functional relationship between the semicircular canals and eye muscles associated with the vestibulo-ocular reflex (VOR; 
<bibRefCitation id="EFE45DA6FF91F95E554453D5EA6CFE5B" author="Schwarz DWF &amp; Tomlinson RD" box="[1041,1387,443,465]" editor="Jackler TK &amp; Brackmann DE" firstAuthor="Schwarz" journalOrPublisher="Philadelphia: Mosby" pageId="25" pageNumber="1291" pagination="59 - 98" refId="ref23168" refString="Schwarz DWF, Tomlinson RD. 1994. Physiology of the vestibular system. In: Jackler TK, Brackmann DE, editors. Neurotology. Philadelphia: Mosby. p 59 - 98." title="Physiology of the vestibular system" type="book chapter" volumeTitle="Neurotology" year="1994">Schwarz and Tomlinson, 1994</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E542C53D5EB19FE60" author="Cohen B &amp; Raphan T." editor="Highstein SM &amp; Fay RR &amp; Popper AN" firstAuthor="Cohen" journalOrPublisher="New York: Springer" pageId="25" pageNumber="1291" pagination="235 - 285" refId="ref20488" refString="Cohen B, Raphan T. 2004. The physiology of the vestibuloocular reflex (VOR). In: Highstein SM, Fay RR, Popper AN, editors. The vestibular system. New York: Springer. p 235 - 285." title="The physiology of the vestibuloocular reflex (VOR)" type="book chapter" volumeTitle="The vestibular system" year="2004">Cohen and Raphan, 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E556453B8EA30FE67" author="Graf W &amp; Klam F." box="[1073,1335,470,492]" firstAuthor="Graf" journalOrPublisher="C R Palevol" pageId="25" pageNumber="1291" pagination="637 - 655" part="5" refId="ref21202" refString="Graf W, Klam F. 2006. Le systeme vestibulaire: anatomie fonctionnelle et comparee, evolution et developpement. C R Palevol 5: 637 - 655." title="Le systeme vestibulaire: anatomie fonctionnelle et comparee, evolution et developpement" type="journal article" year="2006">Graf and Klam, 2006</bibRefCitation>
). The VOR ensures that as the head turns (sensed by the semicircular canals) the eye muscles make coordinated and compensatory movements to maintain an image focused on the retina. In species for which tracking movements of the eyes are important, including aerial/arboreal specialists and visually oriented predators, the semicircular canal system tends to be well developed (
<bibRefCitation id="EFE45DA6FF91F95E541350FEECFEFD4B" author="Spoor F &amp; Zonneveld F." firstAuthor="Spoor" journalOrPublisher="Yb Phys Anthropol" pageId="25" pageNumber="1291" pagination="211 - 251" part="41" refId="ref23713" refString="Spoor F, Zonneveld F. 1998. Comparative review of the human bony labyrinth. Yb Phys Anthropol 41: 211 - 251." title="Comparative review of the human bony labyrinth" type="journal article" year="1998">Spoor and Zonneveld, 1998</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E555050C5EBE6FD4B" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" box="[1029,1249,683,705]" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="25" pageNumber="1291" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E55B850C5EAB2FD4A" author="Spoor F &amp; Garland T, Jr &amp; Krovitz G &amp; Ryan TM &amp; Silcox MT &amp; Walker A." box="[1261,1461,683,705]" etAl="et al." firstAuthor="Spoor" journalOrPublisher="Proc Natl Acad Sci USA" pageId="25" pageNumber="1291" pagination="10808 - 10812" part="104" refId="ref23608" refString="Spoor F, Garland T, Jr, Krovitz G, Ryan TM, Silcox MT, Walker A. 2007. The primate semicircular canal system and locomotion. Proc Natl Acad Sci USA 104: 10808 - 10812." title="The primate semicircular canal system and locomotion" type="journal article" year="2007">Spoor et al., 2007</bibRefCitation>
). Conversely, reduction of ocular musculature and diminished VOR in cetaceans has been linked to their reduced canal systems (
<bibRefCitation id="EFE45DA6FF91F95E52AA5095EA56FC9A" author="Spoor F &amp; Zonneveld F." box="[1023,1361,763,785]" firstAuthor="Spoor" journalOrPublisher="Yb Phys Anthropol" pageId="25" pageNumber="1291" pagination="211 - 251" part="41" refId="ref23713" refString="Spoor F, Zonneveld F. 1998. Comparative review of the human bony labyrinth. Yb Phys Anthropol 41: 211 - 251." title="Comparative review of the human bony labyrinth" type="journal article" year="1998">Spoor and Zonneveld, 1998</bibRefCitation>
). To our knowledge, there are no broad quantitative studies specifically relating VOR performance with degree of canal elongation, but the two no doubt are linked. As noted above, rostral canal and especially lateral canal elongation in tyrannosaurs and other coelurosaurs cannot be fully explained by either scaling phenomena or bipedality. Instead, we propose that these changes may be adaptations for gaze stabilization, most likely related to predatory habits. The lateral canal is particularly elongate in 
<taxonomicName id="4C755BD4FF91F95E52C95668ECDAFB90" authorityName="Osborn" authorityYear="1905" box="[924,989,1030,1051]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF91F95E52C95668ECDAFB90" box="[924,989,1030,1051]" italics="true" pageId="25" pageNumber="1291">T. rex</emphasis>
</taxonomicName>
, suggesting that mediolateral movements of the eyes and head were behaviorally important. This suggestion is consistent with 
<bibRefCitation id="EFE45DA6FF91F95E55EE5655EC8AFBE7" author="Snively E &amp; Russell AP" firstAuthor="Snively" journalOrPublisher="Anat Rec" pageId="25" pageNumber="1291" pagination="934 - 957" part="290" refId="ref23468" refString="Snively E, Russell AP. 2007 a. Functional variation of neck muscles and their relation to feeding style in Tyrannosauridae and other large theropod dinosaurs. Anat Rec 290: 934 - 957." title="Functional variation of neck muscles and their relation to feeding style in Tyrannosauridae and other large theropod dinosaurs" type="journal article" year="2007" yearSuffix="a">Snively and Russell’s (2007a</bibRefCitation>
,b) findings that tyrannosaur neck morphology emphasized quick and powerful lateroflexion. These inferences regarding the importance of rapid eye, head, and neck movements based on semicircular canal morphology might seem to be at odds with the apparently small flocculus observed in definitive adult 
<taxonomicName id="4C755BD4FF91F95E546656B2EA74FB7A" authorityName="Osborn" authorityYear="1905" box="[1331,1395,1244,1265]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="25" pageNumber="1291" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF91F95E546656B2EA74FB7A" box="[1331,1395,1244,1265]" italics="true" pageId="25" pageNumber="1291">T. rex</emphasis>
</taxonomicName>
, given that the flocculus in extant birds is associated with the vestibular system and VOR (see 
<bibRefCitation id="EFE45DA6FF91F95E55E6577EEA89FAAE" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" box="[1203,1422,1296,1318]" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="25" pageNumber="1291" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
and references therein). However, as noted above, it is very possible that the floccular endocast in fully adult tyrannosaurs is not a fair proxy for the size of the neural structure in life, in that there is good evidence that the endocranial cavity continues to grow after the cessation of brain growth. Thus, it is possible (perhaps likely) that a relatively large flocculus was present but failed to extend deeply into the otic region of the braincase.
</paragraph>
<paragraph id="8BCA2057FF91F95D520D545DEEF6FCF7" blockId="25.[832,1472,1587,1958]" lastBlockId="26.[160,801,230,1958]" lastPageId="26" lastPageNumber="1292" pageId="25" pageNumber="1291">
<emphasis id="B901FC45FF91F95E520D545DEB14F9C0" bold="true" box="[856,1043,1587,1611]" italics="true" pageId="25" pageNumber="1291">Head posture.</emphasis>
Although 
<bibRefCitation id="EFE45DA6FF91F95E55C1545BEA28F9C0" author="Hullar TE" box="[1172,1327,1589,1611]" firstAuthor="Hullar" journalOrPublisher="Anat Rec" pageId="25" pageNumber="1291" pagination="466 - 472" part="288 A" refId="ref21734" refString="Hullar TE. 2006. Semicircular canal geometry, afferent sensitivity, and animal behavior. Anat Rec 288 A: 466 - 472." title="Semicircular canal geometry, afferent sensitivity, and animal behavior" type="journal article" year="2006">Hullar (2006)</bibRefCitation>
was critical about many aspects of basing behavioral inferences on semicircular canal structure, he fully supported the evidence linking orientation of the lateral semicircular canal with head posture. Indeed, there is a strong empirical relationship extending across amniotes between the planar elevation of the lateral canal and the stereotyped ‘‘alert’’ posture adopted by an animal, such that the head is typically oriented with the lateral canal roughly horizontal or perhaps slightly elevated (
<bibRefCitation id="EFE45DA6FF91F95E545E5548EABBF8B0" author="Lebedkin S." box="[1291,1468,1830,1852]" firstAuthor="Lebedkin" journalOrPublisher="Anat Anz" pageId="25" pageNumber="1291" pagination="447 - 460" part="58" refId="ref22191" refString="Lebedkin S. 1924. Uber die Lage des Canalis semicircularis lateralis bei Saugern. Anat Anz 58: 447 - 460." title="Uber die Lage des Canalis semicircularis lateralis bei Saugern" type="journal article" year="1924">Lebedkin, 1924</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E5215552EECDAF8DE" author="de Beer GR" box="[832,989,1856,1878]" firstAuthor="de Beer" journalOrPublisher="Proc Linn Soc Lond" pageId="25" pageNumber="1291" pagination="125 - 139" part="159" refId="ref20766" refString="de Beer GR. 1947. How animals hold their heads. Proc Linn Soc Lond 159: 125 - 139." title="How animals hold their heads" type="journal article" year="1947">de Beer, 1947</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E52BC552EEB72F8DD" author="Duijm M." box="[1001,1141,1856,1878]" firstAuthor="Duijm" journalOrPublisher="Proc K Ned Akad Wet C" pageId="25" pageNumber="1291" pagination="202 - 211,260 - 271" part="54" refId="ref20872" refString="Duijm M. 1951. On the head posture of some birds and its relation to some anatomical features. Proc K Ned Akad Wet C 54: 202 - 211,260 - 271." title="On the head posture of some birds and its relation to some anatomical features" type="journal volume" year="1951">Duijm, 1951</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E55D6552EEA5CF8DE" author="Blanks RHI &amp; Curthoys IS &amp; Markham CH" box="[1155,1371,1856,1878]" etAl="et al." firstAuthor="Blanks" journalOrPublisher="Am J Physiol" pageId="25" pageNumber="1291" pagination="55 - 62" part="223" refId="ref20150" refString="Blanks RHI, Curthoys IS, Markham CH. 1972. Planar relationships of semicircular canals in the cat. Am J Physiol 223: 55 - 62." title="Planar relationships of semicircular canals in the cat" type="journal article" year="1972">Blanks et al., 1972</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E543D552EECA5F8FA" author="Vidal PP &amp; Graf W &amp; Berthoz A." etAl="et al." firstAuthor="Vidal" journalOrPublisher="Brain Behav Evol" pageId="25" pageNumber="1291" pagination="549 - 559" part="61" refId="ref23943" refString="Vidal PP, Graf W, Berthoz A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. I. Resting position. Brain Behav Evol 61: 549 - 559." title="The orientation of the cervical vertebral column in unrestrained awake animals. I. Resting position" type="journal article" year="1986">Vidal et al., 1986</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E52FB5535EB95F8FB" author="Erichsen JT &amp; Hodos W &amp; Evinger C &amp; Bessette BB &amp; Phillips SJ" box="[942,1170,1883,1905]" etAl="et al" firstAuthor="Erichsen" journalOrPublisher="Brain Behav Evol" pageId="25" pageNumber="1291" pagination="268 - 278" part="33" refId="ref20906" refString="Erichsen JT, Hodos W, Evinger C, Bessette BB, Phillips SJ. 1989. Head orientation in pigeons: postural, locomotor and visual determinants. Brain Behav Evol 33: 268 - 278." title="Head orientation in pigeons: postural, locomotor and visual determinants" type="journal article" year="1989">Erichsen et al, 1989</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E55C85535EA7FF8FB" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" box="[1181,1400,1883,1905]" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="25" pageNumber="1291" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF91F95E54D15535EABBF8FB" author="Ridgely RC &amp; Witmer LM" box="[1412,1468,1883,1904]" editor="Endo H &amp; Frey R" firstAuthor="Witmer" journalOrPublisher="J Vert Paleontol" pageId="25" pageNumber="1291" pagination="131 A" part="28 (Suppl 3)" refId="ref22818" refString="Ridgely RC, Witmer LM. 2008. Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs. J Vert Paleontol 28 (Suppl 3): 131 A." title="Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs" type="journal article" volumeTitle="Anatomical imaging: towards a new morphology" year="2008">2008</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E52155518EB43F807" author="Graf W &amp; Klam F." box="[832,1092,1910,1932]" firstAuthor="Graf" journalOrPublisher="C R Palevol" pageId="25" pageNumber="1291" pagination="637 - 655" part="5" refId="ref21202" refString="Graf W, Klam F. 2006. Le systeme vestibulaire: anatomie fonctionnelle et comparee, evolution et developpement. C R Palevol 5: 637 - 655." title="Le systeme vestibulaire: anatomie fonctionnelle et comparee, evolution et developpement" type="journal article" year="2006">Graf and Klam, 2006</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF91F95E55035518EBEBF807" author="Hullar TE" box="[1110,1260,1910,1932]" firstAuthor="Hullar" journalOrPublisher="Anat Rec" pageId="25" pageNumber="1291" pagination="466 - 472" part="288 A" refId="ref21734" refString="Hullar TE. 2006. Semicircular canal geometry, afferent sensitivity, and animal behavior. Anat Rec 288 A: 466 - 472." title="Semicircular canal geometry, afferent sensitivity, and animal behavior" type="journal article" year="2006">Hullar, 2006</bibRefCitation>
). Recently, 
<bibRefCitation id="EFE45DA6FF91F95E542C5518ECCEF82D" author="Taylor MP &amp; Wedel MJ &amp; Naish D." etAl="et al." firstAuthor="Taylor" journalOrPublisher="Acta Palaeontol Pol" pageId="25" pageNumber="1291" pagination="213 - 220" part="54" refId="ref23838" refString="Taylor MP, Wedel MJ, Naish D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontol Pol 54: 213 - 220." title="Head and neck posture in sauropod dinosaurs inferred from extant animals" type="journal article" year="2009">Taylor et al. (2009)</bibRefCitation>
questioned the relationship between lateral canal orientation and head posture (largely in the context of debates on sauropod neck postures), arguing that ‘‘although it has been claimed that HSCCs [horizontal semicircular canals, a synonym for lateral semicircular canals] are 
<emphasis id="B901FC45FF92F95D5073533EEE9EFEEE" box="[294,409,336,357]" italics="true" pageId="26" pageNumber="1292">habitually</emphasis>
held horizontally’’ (p 216, emphasis added), the behavioral data show considerable variation in canal orientation. We note that our work (
<bibRefCitation id="EFE45DA6FF92F95D539953E8EE36FE3E" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="26" pageNumber="1292" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF92F95D501053CEEE7AFE3E" author="Ridgely RC &amp; Witmer LM" box="[325,381,416,437]" editor="Endo H &amp; Frey R" firstAuthor="Witmer" journalOrPublisher="J Vert Paleontol" pageId="26" pageNumber="1292" pagination="131 A" part="28 (Suppl 3)" refId="ref22818" refString="Ridgely RC, Witmer LM. 2008. Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs. J Vert Paleontol 28 (Suppl 3): 131 A." title="Gross anatomical brain region approximation (GABRA): a new technique for assessing brain structure in dinosaurs and other fossil archosaurs" type="journal article" volumeTitle="Anatomical imaging: towards a new morphology" year="2008">2008</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF92F95D50C753CEEDE6FE3D" author="Sampson SD &amp; Witmer LM" box="[402,737,416,438]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="26" pageNumber="1292" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
) has referred to 
<emphasis id="B901FC45FF92F95D507153D5EE5FFE5B" box="[292,344,443,464]" italics="true" pageId="26" pageNumber="1292">alert</emphasis>
not 
<emphasis id="B901FC45FF92F95D50C553D5EEE8FE5B" box="[400,495,443,464]" italics="true" pageId="26" pageNumber="1292">habitual</emphasis>
postures, recognizing that animals obviously orient their heads in many different postures depending on momentary behavioral requirements. 
<bibRefCitation id="EFE45DA6FF92F95D51AF5065EE91FDAA" author="Duijm M." box="[250,406,523,545]" firstAuthor="Duijm" journalOrPublisher="Proc K Ned Akad Wet C" pageId="26" pageNumber="1292" pagination="202 - 211,260 - 271" part="54" refId="ref20872" refString="Duijm M. 1951. On the head posture of some birds and its relation to some anatomical features. Proc K Ned Akad Wet C 54: 202 - 211,260 - 271." title="On the head posture of some birds and its relation to some anatomical features" type="journal volume" year="1951">Duijm (1951)</bibRefCitation>
, for example, indeed recorded a range of postures for birds, but, as acknowledged by 
<bibRefCitation id="EFE45DA6FF92F95D51F5502EEE84FDDD" author="Taylor MP &amp; Wedel MJ &amp; Naish D." box="[160,387,576,598]" etAl="et al." firstAuthor="Taylor" journalOrPublisher="Acta Palaeontol Pol" pageId="26" pageNumber="1292" pagination="213 - 220" part="54" refId="ref23838" refString="Taylor MP, Wedel MJ, Naish D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontol Pol 54: 213 - 220." title="Head and neck posture in sauropod dinosaurs inferred from extant animals" type="journal article" year="2009">Taylor et al. (2009)</bibRefCitation>
, the mean avian alert posture was with the lateral canal basically held horizontally. Likewise, 
<bibRefCitation id="EFE45DA6FF92F95D51B4501BEEA0FD00" author="Vidal PP &amp; Graf W &amp; Berthoz A." box="[225,423,629,651]" etAl="et al." firstAuthor="Vidal" journalOrPublisher="Brain Behav Evol" pageId="26" pageNumber="1292" pagination="549 - 559" part="61" refId="ref23943" refString="Vidal PP, Graf W, Berthoz A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. I. Resting position. Brain Behav Evol 61: 549 - 559." title="The orientation of the cervical vertebral column in unrestrained awake animals. I. Resting position" type="journal article" year="1986">Vidal et al. (1986</bibRefCitation>
, p 549) noted considerable variation in lateral canal orientation during different behaviors, but ‘‘at other times, presumably when the vigilance level increased [i.e., when alert], the horizontal canals were brought into the earth horizontal plane.’’ In truth, many of the older studies need to be replicated using more modern imaging and analytical methods, but we remain comfortable using labyrinth orientation when animals are alert as a biologically meaningful and consistent comparative approach.
</paragraph>
<paragraph id="8BCA2057FF92F95D51ED51EEEE8BF9C0" blockId="26.[160,801,230,1958]" pageId="26" pageNumber="1292">
<figureCitation id="134E3CD2FF92F95D51ED51EEEE2DFC1E" box="[184,298,896,918]" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Figure 11</figureCitation>
presents a number of theropods in their alert head postures as determined by orienting the skull with the lateral canal roughly horizontal. Assuming alert postures seek to optimize the cephalic sensory systems (hence aligning the labyrinth more or less with earth-horizontal), it is reasonable to assume that these would be similar to postures maximizing the binocular field of view (
<bibRefCitation id="EFE45DA6FF92F95D501D5655ED32FBDB" author="Witmer LM &amp; Chatterjee S &amp; Franzosa JW &amp; Rowe TB" box="[328,565,1083,1105]" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Nature" pageId="26" pageNumber="1292" pagination="950 - 953" part="425" refId="ref24195" refString="Witmer LM, Chatterjee S, Franzosa JW, Rowe TB. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behavior. Nature 425: 950 - 953." title="Neuroanatomy of flying reptiles and implications for flight, posture and behavior" type="journal article" year="2003">Witmer et al., 2003</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF92F95D53125655EDECFBDA" author="Stevens KA" box="[583,747,1083,1105]" firstAuthor="Stevens" journalOrPublisher="J Vert Paleontol" pageId="26" pageNumber="1292" pagination="321 - 330" part="26" refId="ref23778" refString="Stevens KA. 2006. Binocular vision in theropod dinosaurs. J Vert Paleontol 26: 321 - 330." title="Binocular vision in theropod dinosaurs" type="journal article" year="2006">Stevens, 2006</bibRefCitation>
). As noted by 
<bibRefCitation id="EFE45DA6FF92F95D505F5638ED4BFBE7" author="Sampson SD &amp; Witmer LM" box="[266,588,1110,1132]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="26" pageNumber="1292" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer (2007)</bibRefCitation>
and 
<bibRefCitation id="EFE45DA6FF92F95D53D25638EC1BFBE0" author="Rogers SW" box="[647,796,1110,1131]" firstAuthor="Rogers" journalOrPublisher="Neuron" pageId="26" pageNumber="1292" pagination="673 - 679" part="21" refId="ref22861" refString="Rogers SW. 1998. Exploring dinosaur neuropaleobiology: viewpoint computed tomography scanning and analysis of an Allosaurus fragilis endocast. Neuron 21: 673 - 679." title="Exploring dinosaur neuropaleobiology: viewpoint computed tomography scanning and analysis of an Allosaurus fragilis endocast" type="journal article" year="1998">Rogers (1998</bibRefCitation>
, 
<bibRefCitation id="EFE45DA6FF92F95D51F5561EEFDFFB0D" author="Rogers SW" box="[160,216,1136,1158]" firstAuthor="Rogers" journalOrPublisher="Anat Rec" pageId="26" pageNumber="1292" pagination="162 - 173" part="257" refId="ref22889" refString="Rogers SW. 1999. Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast. Anat Rec 257: 162 - 173." title="Allosaurus, crocodiles, and birds: evolutionary clues from spiral computed tomography of an endocast" type="journal article" year="1999">1999</bibRefCitation>
), 
<taxonomicName id="4C755BD4FF92F95D51A4561FEEA6FB0D" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[241,417,1137,1158]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D51A4561FEEA6FB0D" box="[241,417,1137,1158]" italics="true" pageId="26" pageNumber="1292">Majungasaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF92F95D50E3561EED1DFB0D" box="[438,538,1136,1158]" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Fig. 11A</figureCitation>
) and 
<taxonomicName id="4C755BD4FF92F95D5332561EEDD8FB0E" authorityName="Marsh" authorityYear="1877" box="[615,735,1136,1157]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D5332561EEDD8FB0E" box="[615,735,1136,1157]" italics="true" pageId="26" pageNumber="1292">Allosaurus</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF92F95D53A0561EEFCAFB2A" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Fig. 11B</figureCitation>
), respectively, have an essentially horizontal head posture. The 
<taxonomicName id="4C755BD4FF92F95D506056C8EEAAFB30" authorityName="Marsh" authorityYear="1877" box="[309,429,1190,1211]" class="Reptilia" family="Allosauridae" genus="Allosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D506056C8EEAAFB30" box="[309,429,1190,1211]" italics="true" pageId="26" pageNumber="1292">Allosaurus</emphasis>
</taxonomicName>
findings agree with those of 
<bibRefCitation id="EFE45DA6FF92F95D53A156C8EE2FFB5D" author="Stevens KA" firstAuthor="Stevens" journalOrPublisher="J Vert Paleontol" pageId="26" pageNumber="1292" pagination="321 - 330" part="26" refId="ref23778" refString="Stevens KA. 2006. Binocular vision in theropod dinosaurs. J Vert Paleontol 26: 321 - 330." title="Binocular vision in theropod dinosaurs" type="journal article" year="2006">Stevens (2006)</bibRefCitation>
, and Samson and Witmer (2007) likewise suggested that in 
<taxonomicName id="4C755BD4FF92F95D502C56B2ED2EFB7A" baseAuthorityName="Sampson and Witmer" baseAuthorityYear="2007" box="[377,553,1244,1265]" class="Reptilia" family="Abelisauridae" genus="Majungasaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D502C56B2ED2EFB7A" box="[377,553,1244,1265]" italics="true" pageId="26" pageNumber="1292">Majungasaurus</emphasis>
</taxonomicName>
the posture elevates the lacrimal rugosities such that they minimize obstruction of the binocular field of view. Among the coelurosaurian outgroups of tyrannosaurs, both 
<emphasis id="B901FC45FF92F95D53225745EC27FACB" box="[631,800,1323,1344]" italics="true" pageId="26" pageNumber="1292">Struthiomimus</emphasis>
(
<figureCitation id="134E3CD2FF92F95D51FD5728EE0EFAD7" box="[168,265,1350,1372]" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Fig. 11G</figureCitation>
) and 
<taxonomicName id="4C755BD4FF92F95D50195728EEA0FAD0" authorityName="Leidy" authorityYear="1856" box="[332,423,1350,1371]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D50195728EEA0FAD0" box="[332,423,1350,1371]" italics="true" pageId="26" pageNumber="1292">Troodon</emphasis>
</taxonomicName>
(
<figureCitation id="134E3CD2FF92F95D50ED5728ED1DFAD7" box="[440,538,1350,1372]" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Fig. 11H</figureCitation>
) have a fairly strongly down-turned alert posture, similar to what 
<bibRefCitation id="EFE45DA6FF92F95D539C570EEFE2FA1A" author="Stevens KA" firstAuthor="Stevens" journalOrPublisher="J Vert Paleontol" pageId="26" pageNumber="1292" pagination="321 - 330" part="26" refId="ref23778" refString="Stevens KA. 2006. Binocular vision in theropod dinosaurs. J Vert Paleontol 26: 321 - 330." title="Binocular vision in theropod dinosaurs" type="journal article" year="2006">Stevens (2006)</bibRefCitation>
predicted for 
<taxonomicName id="4C755BD4FF92F95D50D95715EEE0FA1B" authorityName="Leidy" authorityYear="1856" box="[396,487,1403,1424]" class="Reptilia" family="Troodontidae" genus="Troodon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D50D95715EEE0FA1B" box="[396,487,1403,1424]" italics="true" pageId="26" pageNumber="1292">Troodon</emphasis>
</taxonomicName>
. Labyrinths from all three 
<taxonomicName id="4C755BD4FF92F95D51F557F8EFE2FA20" authorityName="Osborn" authorityYear="1905" box="[160,229,1430,1451]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF92F95D51F557F8EFE2FA20" box="[160,229,1430,1451]" italics="true" pageId="26" pageNumber="1292">T. rex</emphasis>
</taxonomicName>
specimens indicate similar alert postures (
<figureCitation id="134E3CD2FF92F95D53A057F8EFE1FA4D" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Fig. 11D,E</figureCitation>
), with the head somewhat depressed (5- to 10- degree angle), actually slightly more so than what 
<bibRefCitation id="EFE45DA6FF92F95D53A157A5EE24FA77" author="Stevens KA" firstAuthor="Stevens" journalOrPublisher="J Vert Paleontol" pageId="26" pageNumber="1292" pagination="321 - 330" part="26" refId="ref23778" refString="Stevens KA. 2006. Binocular vision in theropod dinosaurs. J Vert Paleontol 26: 321 - 330." title="Binocular vision in theropod dinosaurs" type="journal article" year="2006">Stevens (2006)</bibRefCitation>
found. 
<taxonomicName id="4C755BD4FF92F95D50D55788ED09FA70" authorityName="Cope" authorityYear="1866" box="[384,526,1510,1531]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D50D55788ED09FA70" box="[384,526,1510,1531]" italics="true" pageId="26" pageNumber="1292">Gorgosaurus</emphasis>
</taxonomicName>
(as measured by registering ROM 1247 to a cast of AMNH FR 5664; 
<figureCitation id="134E3CD2FF92F95D53EF546EEC1EF99D" box="[698,793,1536,1558]" captionStart="Fig" captionStartId="22.[178,208,1769,1788]" captionTargetBox="[192,1441,229,1733]" captionTargetId="figure@22.[192,1443,229,1733]" captionTargetPageId="22" captionText="Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm." figureDoi="http://doi.org/10.5281/zenodo.3942801" httpUri="https://zenodo.org/record/3942801/files/figure.png" pageId="26" pageNumber="1292">Fig. 11C</figureCitation>
) is fairly similar to 
<taxonomicName id="4C755BD4FF92F95D50D45472EEC5F9BA" authorityName="Osborn" authorityYear="1905" box="[385,450,1564,1585]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF92F95D50D45472EEC5F9BA" box="[385,450,1564,1585]" italics="true" pageId="26" pageNumber="1292">T. rex</emphasis>
</taxonomicName>
in having a somewhat downturned head posture.
</paragraph>
<paragraph id="8BCA2057FF92F95D51ED543EEB5EFC47" blockId="26.[160,801,230,1958]" lastBlockId="26.[832,1473,230,972]" pageId="26" pageNumber="1292">
The outlier is 
<materialsCitation id="3B1D2A0AFF92F95D500D543EEEEFF9ED" ID-GBIF-Occurrence="2813094338" box="[344,488,1616,1638]" collectionCode="CMNH" pageId="26" pageNumber="1292" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, which has a more strongly depressed head posture (25- to 30-degree angle) than almost any of the other theropods in our sample (although still much less down-turned than in diplodocid sauropods; 
<bibRefCitation id="EFE45DA6FF92F95D504A54D5EEF2F95B" author="Sereno PC &amp; Wilson JA &amp; Witmer LM &amp; Whitlock JA &amp; Maga A &amp; Ide O &amp; Rowe TA" box="[287,501,1723,1745]" etAl="et al." firstAuthor="Sereno" journalOrPublisher="PLoS ONE" pageId="26" pageNumber="1292" pagination="e 1230" part="2" refId="ref23267" refString="Sereno PC, Wilson JA, Witmer LM, Whitlock JA, Maga A, Ide O, Rowe TA. 2007. Structural extremes in a Cretaceous dinosaur. PLoS ONE 2: e 1230; doi: 10.1371 / journal. pone. 0001230." title="Structural extremes in a Cretaceous dinosaur" type="journal article" year="2007">Sereno et al., 2007</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF92F95D535454D5EDD8F95A" author="Witmer LM &amp; Ridgely RC" box="[513,735,1723,1745]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="26" pageNumber="1292" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
). It is fair to wonder whether postmortem distortion can account for its head posture, in that, indeed, there are some signs of very slight displacements of some of the braincase bones. If one were to assume that the head posture of the animal represented by the Cleveland skull matched that of definitive adult 
<taxonomicName id="4C755BD4FF92F95D534F5532ED5DF8FA" authorityName="Osborn" authorityYear="1905" box="[538,602,1884,1905]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF92F95D534F5532ED5DF8FA" box="[538,602,1884,1905]" italics="true" pageId="26" pageNumber="1292">T. rex</emphasis>
</taxonomicName>
, one would have to argue for postmortem deformation of 
<materialsCitation id="3B1D2A0AFF92F95D53D85518EC27F800" ID-GBIF-Occurrence="2813094364" box="[653,800,1909,1931]" collectionCode="CMNH" pageId="26" pageNumber="1292" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
producing 
<emphasis id="B901FC45FF92F95D504D55FEEE74F82E" box="[280,371,1936,1957]" italics="true" pageId="26" pageNumber="1292">selective</emphasis>
rostrodorsal rotation of the braincase relative to the rest of the skull, and we have found none of the significant displacements or disarticulations that would require. For example, the upper part of the braincase that encloses the labyrinth (the orientation of which again provides the signal for reconstructing alert postures) does not show nearly enough displacement between bones to account for the reconstructed head posture. Likewise, the preserved columellae traverse this region and are completely straight, undistorted, and in place (
<figureCitation id="134E3CD2FF92F95D54C053D5EC65FE67" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="26" pageNumber="1292">Fig. 9A</figureCitation>
), as are the epipterygoids that pass from the palate to the braincase. Moreover, the cultriform process of 
<materialsCitation id="3B1D2A0AFF92F95D5424539EEC72FDAA" ID-GBIF-Occurrence="2813094320" collectionCode="CMNH" pageId="26" pageNumber="1292" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
is not directed rostrodorsally, as would be expected if the braincase was selectively distorted and rotated; on the contrary, the cultriform process is lower and straighter than in most other tyrannosaurs (Witmer and Ridgely, in press). Significantly, 
<bibRefCitation id="EFE45DA6FF92F95D556C5018EBE3FD07" author="Stevens KA" box="[1081,1252,630,652]" firstAuthor="Stevens" journalOrPublisher="J Vert Paleontol" pageId="26" pageNumber="1292" pagination="321 - 330" part="26" refId="ref23778" refString="Stevens KA. 2006. Binocular vision in theropod dinosaurs. J Vert Paleontol 26: 321 - 330." title="Binocular vision in theropod dinosaurs" type="journal article" year="2006">Stevens (2006)</bibRefCitation>
found almost the same degree of head depression for 
<materialsCitation id="3B1D2A0AFF92F95D559950FFEA5DFD2D" ID-GBIF-Occurrence="2813094416" box="[1228,1370,656,678]" collectionCode="CMNH" pageId="26" pageNumber="1292" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
. The fact that our data are internally consistent, as well as consistent with Stevens’ (2006) very different dataset, suggests that these findings are robust and reflect real behavioral similarities (e.g., between 
<taxonomicName id="4C755BD4FF92F95D55275092EBB4FC9A" authorityName="Osborn" authorityYear="1905" box="[1138,1203,764,785]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF92F95D55275092EBB4FC9A" box="[1138,1203,764,785]" italics="true" pageId="26" pageNumber="1292">T. rex</emphasis>
</taxonomicName>
and 
<taxonomicName id="4C755BD4FF92F95D55A05095EA84FC9B" authorityName="Cope" authorityYear="1866" box="[1269,1411,763,784]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D55A05095EA84FC9B" box="[1269,1411,763,784]" italics="true" pageId="26" pageNumber="1292">Gorgosaurus</emphasis>
</taxonomicName>
) and differences (e.g., between 
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and other tyrannosaurs). It also may be pointed out that the reconstructed head postures for the tyrannosaurs presented here (including 
<materialsCitation id="3B1D2A0AFF92F95D52E25108EB44FCF7" ID-GBIF-Occurrence="2813094335" box="[951,1091,870,892]" collectionCode="CMNH" pageId="26" pageNumber="1292" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
) result in very similar and comparable orientations of the occiput and cranial base relative to the neck, and thus similar attachments and actions of the cervical musculature.
</paragraph>
<paragraph id="8BCA2057FF92F95D520D566DEAC2FB90" blockId="26.[832,1477,1027,1958]" box="[856,1477,1027,1051]" pageId="26" pageNumber="1292">
<heading id="D082973BFF92F95D520D566DEAC2FB90" bold="true" box="[856,1477,1027,1051]" fontSize="10" level="3" pageId="26" pageNumber="1292" reason="0">
<emphasis id="B901FC45FF92F95D520D566DEAC2FB90" bold="true" box="[856,1477,1027,1051]" italics="true" pageId="26" pageNumber="1292">Implications of tyrannosaur sensory systems.</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF92F95C520D564EEE09FD4A" blockId="26.[832,1477,1027,1958]" lastBlockId="27.[160,801,230,705]" lastPageId="27" lastPageNumber="1293" pageId="26" pageNumber="1292">
On the basis of the above inferences regarding the sensory biology of tyrannosaurs, we can make some assessments as to the broader behavioral implications of these findings. The overall picture that emerges is that the brain and sensory structures were consistent with an active predatory mode of life. Although the debate has often focused on whether one species, 
<taxonomicName id="4C755BD4FF92F95D547956AFEA6BFB5D" authorityName="Osborn" authorityYear="1905" box="[1324,1388,1217,1238]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF92F95D547956AFEA6BFB5D" box="[1324,1388,1217,1238]" italics="true" pageId="26" pageNumber="1292">T. rex</emphasis>
</taxonomicName>
, was a scavenger or a predator (see 
<bibRefCitation id="EFE45DA6FF92F95D55C256B5EA24FB7A" author="Holtz TR" box="[1175,1315,1242,1265]" editor="Larson P &amp; Carpenter K" firstAuthor="Holtz" journalOrPublisher="Bloomington: Indiana University Press" pageId="26" pageNumber="1292" pagination="370 - 396" refId="ref21452" refString="Holtz TR. 2008. A critical reappraisal of the obligate scavenging hypothesis for Tyrannosaurus rex and other tyrant dinosaurs. In: Larson P, Carpenter K, editors. Tyrannosaurus rex, the tyrant king. Bloomington: Indiana University Press. p 370 - 396." title="A critical reappraisal of the obligate scavenging hypothesis for Tyrannosaurus rex and other tyrant dinosaurs" type="book chapter" volumeTitle="Tyrannosaurus rex, the tyrant king" year="2008">Holtz [2008]</bibRefCitation>
for an excellent recent review), the findings presented here show that that this one species was much like the other tyrannosaurids in our sample (e.g., 
<taxonomicName id="4C755BD4FF92F95D55C15745EA25FACB" authorityName="Cope" authorityYear="1866" box="[1172,1314,1323,1344]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D55C15745EA25FACB" box="[1172,1314,1323,1344]" italics="true" pageId="26" pageNumber="1292">Gorgosaurus</emphasis>
</taxonomicName>
, 
<taxonomicName id="4C755BD4FF92F95D54645745EC63FAD0" authorityName=", Maleev" authorityYear="1965" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D54645745EC63FAD0" italics="true" pageId="26" pageNumber="1292">Daspletosaurus</emphasis>
</taxonomicName>
, 
<taxonomicName id="4C755BD4FF92F95D52205728EB06FAD0" authorityName=", Osborn" authorityYear="1912" box="[885,1025,1350,1371]" class="Reptilia" family="Tyrannosauridae" genus="Tarbosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="26" pageNumber="1292" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF92F95D52205728EB06FAD0" box="[885,1025,1350,1371]" italics="true" pageId="26" pageNumber="1292">Tarbosaurus</emphasis>
</taxonomicName>
, 
<materialsCitation id="3B1D2A0AFF92F95D55445728EBA7FAD0" ID-GBIF-Occurrence="2813094365" box="[1041,1184,1349,1371]" collectionCode="CMNH" pageId="26" pageNumber="1292" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
) with regard to its brain and sensory structures. And likewise, tyrannosaurs generally have the attributes we might expect given their phylogenetic position between more basal theropods and more advanced coelurosaurs. For example, their cerebral hemispheres are moderately expanded, and it seems likely that their optic lobes were in an intermediate posi-tion—not the ‘‘reptilian position’’ inferred for more basal theropods (
<bibRefCitation id="EFE45DA6FF92F95D52975475EA0DF9BA" author="Sampson SD &amp; Witmer LM" box="[962,1290,1563,1585]" firstAuthor="Sampson" journalOrPublisher="Soc Vert Paleontol Mem 8, J Vert Paleontol" pageId="26" pageNumber="1292" pagination="32 - 102" part="27" refId="ref23090" refString="Sampson SD, Witmer LM. 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Soc Vert Paleontol Mem 8, J Vert Paleontol 27 (Suppl 2): 32 - 102." title="Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar" type="journal article" year="2007">Sampson and Witmer, 2007</bibRefCitation>
), but not quite the fully ‘‘avian position’’ observed in more advanced coelurosaurs (
<figureCitation id="134E3CD2FF92F95D52EB543EEB01F9ED" box="[958,1030,1616,1638]" captionStart="Fig" captionStartId="11.[178,208,1769,1788]" captionTargetBox="[258,1374,229,1733]" captionTargetId="figure@11.[258,1375,229,1733]" captionTargetPageId="11" captionText="Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.3942785" httpUri="https://zenodo.org/record/3942785/files/figure.png" pageId="26" pageNumber="1292">Fig. 4</figureCitation>
). The visual systems of tyrannosaurs were those of a predator in that, based on the structure of the endosseous labyrinth, they had the capability to engage in rapid tracking movements of the eyes, head, and neck. Their cochleae were elongate, suggesting that the reception of air-borne sounds was important, and the length of the cochlea and the extensive pneumatic chambers further suggests that low-frequency sounds were emphasized. Low frequencies are transmitted with relatively little attenuation over long distances and through dense or closed habitats (
<bibRefCitation id="EFE45DA6FF92F95D55985535EA78F8FA" author="Garstang M." box="[1229,1407,1883,1905]" firstAuthor="Garstang" journalOrPublisher="J Comp Physiol A" pageId="26" pageNumber="1292" pagination="791 - 805" part="190" refId="ref21073" refString="Garstang M. 2004. Long-distance, low-frequency elephant communication. J Comp Physiol A 190: 791 - 805." title="Long-distance, low-frequency elephant communication" type="journal article" year="2004">Garstang, 2004</bibRefCitation>
), and thus enhanced low-frequency hearing could have been important for tracking prey movements, as well as for other behavioral reasons, such as breeding or territoriality. One remarkable apomorphy of tyrannosaurs is the expansion of the olfactory apparatus, both the neural processing component (the olfactory bulb; see also 
<bibRefCitation id="EFE45DA6FF93F95C53B75358EE0BFEEE" author="Ali F &amp; Zelenitsky DK &amp; Therrien F &amp; Weishampel DB" etAl="et al." firstAuthor="Ali" journalOrPublisher="J Vert Paleontol" pageId="27" pageNumber="1293" pagination="123 - 133" part="28" refId="ref19964" refString="Ali F, Zelenitsky DK, Therrien F, Weishampel DB. 2008. Homology of the '' ethmoid complex' ' of tyrannosaurids and its implications for the reconstruction of the olfactory apparatus of non-avian theropods. J Vert Paleontol 28: 123 - 133." title="Homology of the '' ethmoid complex' ' of tyrannosaurids and its implications for the reconstruction of the olfactory apparatus of non-avian theropods" type="journal article" year="2008">Ali et al., 2008</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF93F95C5075533EED30FEED" author="Zelenitsky DK &amp; Therrien F &amp; Kobayashi Y." box="[288,567,336,358]" etAl="et al." firstAuthor="Zelenitsky" journalOrPublisher="Proc R Soc B" pageId="27" pageNumber="1293" pagination="667 - 673" part="276" refId="ref24481" refString="Zelenitsky DK, Therrien F, Kobayashi Y. 2009. Olfactory acuity in theropods: palaeobiological and evolutionary implications. Proc R Soc B 276: 667 - 673; doi: 10.1098 / rspb. 2008.1075." title="Olfactory acuity in theropods: palaeobiological and evolutionary implications" type="journal article" year="2009">Zelenitsky et al., 2009</bibRefCitation>
) and the olfactory region of the nasal cavity. This enhanced sense of smell was one of the key elements in the argument for scavenging (e.g., to locate carcasses), but, of course, many behaviors often use odors (e.g., maintenance of a territory), including predation (e.g., locating and tracking prey). Indeed, the finding of enlarged olfactory bulbs in herbivorous dinosaurs (sauropods; 
<bibRefCitation id="EFE45DA6FF93F95C53605065EC1EFDAA" author="Witmer LM &amp; Ridgely RC" box="[565,793,523,545]" editor="Currie PJ" etAl="et al." firstAuthor="Witmer" journalOrPublisher="Ottawa: National Research Council of Canada Monograph Series" pageId="27" pageNumber="1293" pagination="117 - 144" refId="ref24229" refString="Witmer LM, Ridgely RC. 2008 a. Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization. In: Currie PJ, editor. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. Ottawa: National Research Council of Canada Monograph Series. p 117 - 144." title="Structure of the brain cavity and inner ear of the centrosaurine ceratopsid Pachyrhinosaurus based on CT scanning and 3 D visualization" type="book chapter" volumeTitle="A new horned dinosaur from an Upper Cretaceous bone bed in Alberta" year="2008">Witmer et al., 2008</bibRefCitation>
) reveals that prey, as well as predator and scavenger, can benefit from an enhanced sense of smell. Thus, tyrannosaurs had the sensorineural tools of a predator, but, as with virtually all extant predators today, almost certainly were willing to scavenge a carcass when available.
</paragraph>
<paragraph id="8BCA2057FF93F95C51F55085EC0EFC88" blockId="27.[160,777,747,771]" box="[160,777,747,771]" pageId="27" pageNumber="1293">
<heading id="D082973BFF93F95C51F55085EC0EFC88" bold="true" box="[160,777,747,771]" fontSize="10" level="3" pageId="27" pageNumber="1293" reason="0">
<emphasis id="B901FC45FF93F95C51F55085EC0EFC88" bold="true" box="[160,777,747,771]" pageId="27" pageNumber="1293">
The Status of the Cleveland Skull, 
<materialsCitation id="3B1D2A0AFF93F95C533B5085EC0EFC88" ID-GBIF-Occurrence="2813094417" box="[622,777,747,771]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
</emphasis>
</heading>
</paragraph>
<paragraph id="8BCA2057FF93F95C51ED5178EA4FFE9E" blockId="27.[160,801,790,1958]" lastBlockId="27.[832,1473,230,1958]" pageId="27" pageNumber="1293">
As noted at the outset, controversy has followed 
<materialsCitation id="3B1D2A0AFF93F95C51F5515EEE35FCCD" ID-GBIF-Occurrence="2813094344" box="[160,306,816,838]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
, resting in recent years on the question of whether it represents a juvenile 
<taxonomicName id="4C755BD4FF93F95C537B5122ED75FCEA" authorityName="Osborn" authorityYear="1905" box="[558,626,844,865]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C537B5122ED75FCEA" box="[558,626,844,865]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
or a separate taxon (
<taxonomicName id="4C755BD4FF93F95C51A45108ED06FCF0" baseAuthorityName="Gilmore" baseAuthorityYear="1946" box="[241,513,870,891]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="lancensis">
<emphasis id="B901FC45FF93F95C51A45108ED06FCF0" box="[241,513,870,891]" italics="true" pageId="27" pageNumber="1293">Nanotyrannus lancensis</emphasis>
</taxonomicName>
). We explored this question elsewhere (Witmer and Ridgely, in press) and found there to be no clear resolution, a position we take here as well. We identified a series of primitive characters in 
<materialsCitation id="3B1D2A0AFF93F95C51F551BEEE35FC6D" ID-GBIF-Occurrence="2813094387" box="[160,306,976,998]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
that are absent in 
<taxonomicName id="4C755BD4FF93F95C537F51BFED6AFC6D" authorityName="Osborn" authorityYear="1905" box="[554,621,977,998]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C537F51BFED6AFC6D" box="[554,621,977,998]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
but are found more basally (e.g., in 
<taxonomicName id="4C755BD4FF93F95C50F35185ED33FB8B" authorityName="Cope" authorityYear="1866" box="[422,564,1003,1024]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF93F95C50F35185ED33FB8B" box="[422,564,1003,1024]" italics="true" pageId="27" pageNumber="1293">Gorgosaurus</emphasis>
</taxonomicName>
), such as a narrow lanceolate vomer (rather than broad and diamond shaped), adjacent medial and lateral subcondylar recess foramina (rather than widely spaced), a strong condylotuberal crest (rather than subtle), a low cultriform process (rather than strongly vaulted), a relatively small subsellar recess (rather than large), a laterally positioned vagus foramen (rather medially positioned), a high number of dentary tooth positions (rather than a low number), among others (Witmer and Ridgely, in press). To this list can be added the presence of two paired sets of basisphenoid sinus apertures (rather than a single set) and having an extensive medial subcondylar recess (rather than a more moderate one). An ascending diverticulum of the RTR is found within the laterosphenoids of 
<materialsCitation id="3B1D2A0AFF93F95C50D75715ED12FA1A" ID-GBIF-Occurrence="2813094432" box="[386,533,1403,1425]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
and 
<taxonomicName id="4C755BD4FF93F95C530B5715EDEBFA1B" authorityName="Cope" authorityYear="1866" box="[606,748,1403,1424]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF93F95C530B5715EDEBFA1B" box="[606,748,1403,1424]" italics="true" pageId="27" pageNumber="1293">Gorgosaurus</emphasis>
</taxonomicName>
but none of the 
<taxonomicName id="4C755BD4FF93F95C506757F8EE73FA20" authorityName="Osborn" authorityYear="1905" box="[306,372,1430,1451]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C506757F8EE73FA20" box="[306,372,1430,1451]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
(nor the sole 
<taxonomicName id="4C755BD4FF93F95C537557F8EDCBFA20" authorityName=", Maleev" authorityYear="1965" box="[544,716,1430,1451]" class="Reptilia" family="Tyrannosauridae" genus="Daspletosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF93F95C537557F8EDCBFA20" box="[544,716,1430,1451]" italics="true" pageId="27" pageNumber="1293">Daspletosaurus</emphasis>
</taxonomicName>
in our sample), but we do not yet know if this similarity is primitive or derived. Nevertheless, a few features may be added to those listed by others (e.g., 
<bibRefCitation id="EFE45DA6FF93F95C53295788EDF0FA77" author="Carr TD" box="[636,759,1510,1532]" firstAuthor="Carr" journalOrPublisher="J Vert Paleontol" pageId="27" pageNumber="1293" pagination="497 - 520" part="19" refId="ref20345" refString="Carr TD. 1999. Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria). J Vert Paleontol 19: 497 - 520." title="Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria)" type="journal article" year="1999">Carr, 1999</bibRefCitation>
) in favor of referral of 
<materialsCitation id="3B1D2A0AFF93F95C50D5546EED08F99D" ID-GBIF-Occurrence="2813094341" box="[384,527,1536,1558]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
to 
<taxonomicName id="4C755BD4FF93F95C536C546FED7EF99D" authorityName="Osborn" authorityYear="1905" box="[569,633,1537,1558]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C536C546FED7EF99D" box="[569,633,1537,1558]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
. For example, both have a highly elongate lagena, potentially a laterally positioned optic lobe, and a highly enlarged olfactory bulb, although none of these characters is without problems. Indeed, perhaps the most remarkable attribute of the braincase of 
<materialsCitation id="3B1D2A0AFF93F95C503754E8EEF6F917" ID-GBIF-Occurrence="2813094441" box="[354,497,1670,1692]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
is simply how different it is, and not just from 
<taxonomicName id="4C755BD4FF93F95C50C554CFEEC9F93D" authorityName="Osborn" authorityYear="1905" box="[400,462,1697,1718]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C50C554CFEEC9F93D" box="[400,462,1697,1718]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
, but also from other tyrannosaurs. As just noted, the entire skull and endocast are unique among tyrannosaurs in being very strongly down-turned. Aspects of the cranial endocast are very unusual, such as the rostrally offset pituitary fossa and orbital cranial nerves. The broad communication between the CTR and lateral subcondylar recess was not found in any of the other tyrannosaurs, nor were the highly asymmetrical basisphenoid sinus apertures. The pneumatic foramen in the quadratojugal of 
<materialsCitation id="3B1D2A0AFF93F95C53C755FFEC27F82D" ID-GBIF-Occurrence="2813094303" box="[658,800,1936,1958]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
(Witmer and Ridgely, in press) has been reported in no other tyrannosaur other than 
<materialsCitation id="3B1D2A0AFF93F95C55C7536FEA43FE9E" ID-GBIF-Occurrence="2813094398" box="[1170,1348,256,278]" collectionCode="BMR" pageId="27" pageNumber="1293" specimenCode="BMR P2002.4.1">BMR P2002.4.1</materialsCitation>
.
</paragraph>
<paragraph id="8BCA2057FF93F95C520D5375ECE8FCF7" blockId="27.[832,1473,230,1958]" pageId="27" pageNumber="1293">
We have evaluated explanations for the divergent nature of the braincase of 
<materialsCitation id="3B1D2A0AFF93F95C553E5358EBFDFEC7" ID-GBIF-Occurrence="2813094306" box="[1131,1274,310,332]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
. For example, we cannot ascribe the differences to diagenetic factors such as crushing or plastic deformation. It is true that the skull has suffered postmortem damage, most markedly to the snout and laterotemporal fossa regions, and, as noted above, there are some subtle displacements between some of the bones of the braincase. As is typically the case with fossils, there are various cracks and defects. However, the braincase as a whole is basically symmetrical, as are the endocast and labyrinths. There are no large fractures or faults passing through the braincase that have disrupted relationships. Again, both of the delicate columellae are preserved in place and are undistorted (
<figureCitation id="134E3CD2FF93F95C528250FEEB35FD2D" box="[983,1074,656,678]" captionStart="Fig" captionStartId="20.[178,208,1575,1594]" captionTargetBox="[168,792,229,1543]" captionTargetId="figure@20.[168,794,229,1543]" captionTargetPageId="20" captionText="Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm." figureDoi="http://doi.org/10.5281/zenodo.3942797" httpUri="https://zenodo.org/record/3942797/files/figure.png" pageId="27" pageNumber="1293">Fig. 9A</figureCitation>
). Other than the minor displacements noted, the skull remains remarkably well articulated, including the palate and such delicate elements as the epipterygoids. Indeed, there is postmortem distortion and breakage which no doubt has had some impact on the soft-tissue reconstructions presented here, but we have been unable to find significant enough evidence for distortion to explain away our basic findings as artifacts of preservation.
</paragraph>
<paragraph id="8BCA2057FF93F95C520D51EEECD3FA6A" blockId="27.[832,1473,230,1958]" pageId="27" pageNumber="1293">
Pathology also seems an unlikely explanation, again given the overall symmetry and absence of obvious pathological signs (e.g., tumor growth). 
<bibRefCitation id="EFE45DA6FF93F95C558051D8EA7FFC47" author="Gilmore CW" box="[1237,1400,950,972]" firstAuthor="Gilmore" journalOrPublisher="Smithsonian Misc Coll" pageId="27" pageNumber="1293" pagination="1 - 19" part="106" refId="ref21094" refString="Gilmore CW. 1946. A new carnivorous dinosaur from the Lance formation of Montana. Smithsonian Misc Coll 106: 1 - 19." title="A new carnivorous dinosaur from the Lance formation of Montana" type="journal article" year="1946">Gilmore (1946</bibRefCitation>
, p 10) suggested that the asymmetric basisphenoid sinus apertures represented ‘‘an unhealthy condition of the bone,’’ but none of the other major workers on this specimen (e.g., 
<bibRefCitation id="EFE45DA6FF93F95C52D1564EEB74FBBD" author="Bakker RT &amp; Williams M &amp; Currie PJ" box="[900,1139,1056,1078]" etAl="et al." firstAuthor="Bakker" journalOrPublisher="Hunteria" pageId="27" pageNumber="1293" pagination="1 - 30" part="1" refId="ref20052" refString="Bakker RT, Williams M, Currie PJ. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30." title="Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana" type="journal article" year="1988">Bakker et al., 1988</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF93F95C55D0564FEA01FBBD" author="Carr TD" box="[1157,1286,1057,1078]" firstAuthor="Carr" journalOrPublisher="J Vert Paleontol" pageId="27" pageNumber="1293" pagination="497 - 520" part="19" refId="ref20345" refString="Carr TD. 1999. Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria). J Vert Paleontol 19: 497 - 520." title="Craniofacial ontogeny in Tyrannosaurid Dinosaurs (Dinosauria, Coelurosauria)" type="journal article" year="1999">Carr, 1999</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF93F95C544D564EEABBFBBD" author="Currie PJ" box="[1304,1468,1056,1078]" firstAuthor="Currie" journalOrPublisher="Acta Palaeontol Pol" pageId="27" pageNumber="1293" pagination="191 - 226" part="48" refId="ref20688" refString="Currie PJ. 2003 b. Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontol Pol 48: 191 - 226." title="Cranial anatomy of Tyrannosaurid Dinosaurs from the Late Cretaceous of Alberta, Canada" type="journal article" year="2003" yearSuffix="b">Currie, 2003b</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF93F95C52155655ECD2FBDA" author="Larson PL" box="[832,981,1083,1105]" editor="Larson P &amp; Carpenter K" firstAuthor="Larson" journalOrPublisher="Bloomington: Indiana University Press" pageId="27" pageNumber="1293" pagination="102 - 128" refId="ref22036" refString="Larson PL. 2008. Variation and sexual dimorphism in Tyrannosaurus rex. In: Larson P, Carpenter K, editors. Tyrannosaurus rex, the tyrant king. Bloomington: Indiana University Press. p 102 - 128." title="Variation and sexual dimorphism in Tyrannosaurus rex" type="book chapter" volumeTitle="Tyrannosaurus rex, the tyrant king" year="2008">Larson, 2008</bibRefCitation>
) invoked pathology to explain the strange basisphenoid sinuses. The last credible alternative is perhaps the most obvious: ontogeny. However, the differences are so striking that it is simply difficult for us to accept so much ontogenetic change (Witmer and Ridgely, in press), particularly in systems as fundamental and conservative as the brain cavity and inner ear. 
<materialsCitation id="3B1D2A0AFF93F95C542456B5EC72FA87" ID-GBIF-Occurrence="2813094359" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
was not a particularly young individual, and, given the widespread ontogenetic precociousness of the brain and ear (
<bibRefCitation id="EFE45DA6FF93F95C52E65745EBD4FACB" author="Jeffery N &amp; Spoor F." box="[947,1235,1323,1345]" firstAuthor="Jeffery" journalOrPublisher="J Anat" pageId="27" pageNumber="1293" pagination="71 - 92" part="204" refId="ref21892" refString="Jeffery N, Spoor F. 2004. Prenatal growth and development of the modern human labyrinth. J Anat 204: 71 - 92." title="Prenatal growth and development of the modern human labyrinth" type="journal article" year="2004">Jeffery and Spoor, 2004</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF93F95C55B35745EC7FFAD7" author="Butler AB &amp; Hodos W." bookContentInfo="715" firstAuthor="Butler" journalOrPublisher="New York: Wiley-Liss" pageId="27" pageNumber="1293" refId="ref20275" refString="Butler AB, Hodos W. 2005. Comparative vertebrate neuroanatomy: evolution and adaptation, 2 nd ed. New York: Wiley-Liss. p 715." title="Comparative vertebrate neuroanatomy: evolution and adaptation, 2 nd ed" type="book" year="2005">Butler and Hodos, 2005</bibRefCitation>
; 
<bibRefCitation id="EFE45DA6FF93F95C52D15728EB29FAD7" author="Striedter GF" bookContentInfo="436" box="[900,1070,1350,1372]" firstAuthor="Striedter" journalOrPublisher="Sunderland: Sinauer" pageId="27" pageNumber="1293" refId="ref23798" refString="Striedter GF. 2005. Principles of brain evolution. Sunderland: Sinauer. p 436." title="Principles of brain evolution" type="book" year="2005">Striedter, 2005</bibRefCitation>
), it may be unreasonable to believe that these structures transformed into something like those of definitive 
<taxonomicName id="4C755BD4FF93F95C55465712EB55FA1A" authorityName="Osborn" authorityYear="1905" box="[1043,1106,1404,1425]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C55465712EB55FA1A" box="[1043,1106,1404,1425]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
. Indeed, the endocast and labyrinth of ROM 1247 (i.e., juvenile 
<taxonomicName id="4C755BD4FF93F95C55E957F8EA4DFA20" authorityName="Cope" authorityYear="1866" box="[1212,1354,1430,1451]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="genus">
<emphasis id="B901FC45FF93F95C55E957F8EA4DFA20" box="[1212,1354,1430,1451]" italics="true" pageId="27" pageNumber="1293">Gorgosaurus</emphasis>
</taxonomicName>
) are more generally similar to adult 
<taxonomicName id="4C755BD4FF93F95C55D957DFEBD4FA4D" authorityName="Osborn" authorityYear="1905" box="[1164,1235,1457,1478]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C55D957DFEBD4FA4D" box="[1164,1235,1457,1478]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
than are those of 
<materialsCitation id="3B1D2A0AFF93F95C521557A5ECC8FA6A" ID-GBIF-Occurrence="2813094400" box="[832,975,1483,1505]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
.
</paragraph>
<paragraph id="8BCA2057FF93F95C520D5788EC7AF82D" blockId="27.[832,1473,230,1958]" pageId="27" pageNumber="1293">
It is indeed frustrating that one of the only skeletal elements that is missing from the beautifully preserved 
<materialsCitation id="3B1D2A0AFF93F95C52155475ECF0F9BB" ID-GBIF-Occurrence="2813094313" box="[832,1015,1563,1584]" collectionCode="BMR" pageId="27" pageNumber="1293" specimenCode="BMR P2002.4.1">BMR P2002.4.1</materialsCitation>
is, in fact, the braincase. Given the obvious closeness of 
<materialsCitation id="3B1D2A0AFF93F95C557D5458EBB1F9C0" ID-GBIF-Occurrence="2813094403" box="[1064,1206,1589,1611]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
and 
<materialsCitation id="3B1D2A0AFF93F95C55A55458EAA4F9C0" ID-GBIF-Occurrence="2813094350" box="[1264,1443,1590,1611]" collectionCode="BMR" pageId="27" pageNumber="1293" specimenCode="BMR P2002.4.1">BMR P2002.4.1</materialsCitation>
, it would likely have been taxonomically decisive. Our data on 
<materialsCitation id="3B1D2A0AFF93F95C52315405ECF4F90A" ID-GBIF-Occurrence="2813094404" box="[868,1011,1643,1665]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
may be taken as evidence for the validity of 
<taxonomicName id="4C755BD4FF93F95C52D354E8EB14F910" baseAuthorityName="Gilmore" baseAuthorityYear="1946" box="[902,1043,1670,1691]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="lancensis">
<emphasis id="B901FC45FF93F95C52D354E8EB14F910" box="[902,1043,1670,1691]" italics="true" pageId="27" pageNumber="1293">N. lancensis</emphasis>
</taxonomicName>
on the grounds that it is ‘‘too different’’ from 
<taxonomicName id="4C755BD4FF93F95C52E654CFECE8F93D" authorityName="Osborn" authorityYear="1905" box="[947,1007,1697,1718]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" kingdom="Animalia" order="Dinosauria" pageId="27" pageNumber="1293" phylum="Chordata" rank="species" species="rex">
<emphasis id="B901FC45FF93F95C52E654CFECE8F93D" box="[947,1007,1697,1718]" italics="true" pageId="27" pageNumber="1293">T. rex</emphasis>
</taxonomicName>
. However, we are hesitant to argue that the debate over its status is settled for the simple reason of sample size. 
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presents one specimen—one highly divergent specimen. Although we see no clear signs of distortion or pathology in the braincase, its divergent nature concerns us, and we maintain that the possibility remains that future discoveries will show 
<materialsCitation id="3B1D2A0AFF93F95C52155535ECD5F8FA" ID-GBIF-Occurrence="2813094428" box="[832,978,1883,1905]" collectionCode="CMNH" pageId="27" pageNumber="1293" specimenCode="CMNH 7541">CMNH 7541</materialsCitation>
to be aberrant. For that reason, we urge caution and continue to regard the specimen’s status as open.
</paragraph>
</subSubSection>
</treatment>
</document>