299 lines
50 KiB
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299 lines
50 KiB
XML
<document id="99DCD6EA7A87BCEDC6AB6D5B320CE3F9" ID-DOI="10.1016/j.cretres.2015.12.016" ID-GBIF-Dataset="01816227-cd8c-4f5f-904f-e78a7c90c64c" ID-Zenodo-Dep="3890523" IM.treatments_approvedBy="admin" approvalRequired="2" approvalRequired_for_document="1" approvalRequired_for_taxonomicNames="1" checkinTime="1591188450091" checkinUser="jeremy" docAuthor="Joshua D. Schmerge & Bruce M. Rothschild" docDate="2016" docId="03DC7E37F05EFFA0FC87FA3CFBCCFD20" docLanguage="en" docName="SchmergeRothschild2016.pdf.imf" docOrigin="Cretaceous Research 61" docStyle="DocumentStyle{}" docTitle="Tyrannosaurus rex Osborn 1905" docType="treatment" docVersion="6" lastPageNumber="32" masterDocId="FFE5064FF05BFFA6FFD8FFD2FFFDFFF8" masterDocTitle="Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988" masterLastPageNumber="33" masterPageNumber="26" pageNumber="31" updateTime="1697418797726" updateUser="admin">
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<mods:titleInfo id="38846201AE42BC9D487501C81C3670CD">
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<mods:title id="9610E00A33FDF9F0A13F52CC5B8EBB38">Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988</mods:title>
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<mods:name id="8EAC6544647FF4135DF5320FDB46E36F" type="personal">
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<mods:role id="7CC258C3063147BD2697B651756E0669">
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<mods:roleTerm id="B8A16210474CFE749F5E54E64207EAD2">Author</mods:roleTerm>
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<mods:namePart id="8911FB1B904CF9AF86A0D5D70C0EDB0E">Joshua D. Schmerge</mods:namePart>
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<mods:affiliation id="2451B5FF6E198299DFB598B99CAC72DC">Biodiversity Institute, University of Kansas, 1345 Jayhawk Blvd., Lawrence, KS, 66045, USA</mods:affiliation>
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<mods:nameIdentifier id="C768C4E37208EB8847761A9B423FCCD6" type="email">schmerge@ku.edu</mods:nameIdentifier>
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<mods:name id="E1271871CF0A0078BA40979B3636102B" type="personal">
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<mods:roleTerm id="E41FCA34E196175DA3721BA6507B2CE0">Author</mods:roleTerm>
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<mods:namePart id="0FD82BFAE91F7149C1DF69FBAEAC56DB">Bruce M. Rothschild</mods:namePart>
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<mods:affiliation id="B50A48596F83FDDD4243F4C05BB33F73">Department of Vertebrate Paleontology, Carnegie Museum, 4400 Forbes Ave., Pittsburgh, PA, 44272, USA</mods:affiliation>
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</mods:name>
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<mods:typeOfResource id="34A067E383232226E20398E49D30EB56">text</mods:typeOfResource>
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<mods:title id="96425A2D12243C95B491C6D8A05A74A2">Cretaceous Research</mods:title>
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</mods:titleInfo>
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<mods:part id="A5DA1D5BC7ED1ABDCFBFB089FF6F731A">
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<mods:date id="50B39E89BB221AC9112B47CAD47FAF52">2016</mods:date>
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<mods:number id="38599C3F3E5130DAB381E2F06B34D3C3">2015-12-27</mods:number>
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</mods:detail>
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<mods:detail id="575980418117A6B0CA0C778B580E42B3" type="volume">
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<mods:number id="BA6F0BC042E5950DC15F72133D91A0C1">61</mods:number>
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</mods:detail>
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<mods:start id="9FF40C944D09D1C934C0FC812FAD74A2">26</mods:start>
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<mods:end id="D56D4F4B33790D75377993B61C588200">33</mods:end>
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<mods:classification id="67564A237F26F5EFBC54A286913DC62B">journal article</mods:classification>
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<mods:identifier id="9B6F3FD290CBDC83FD5FF913D616C222" type="DOI">10.1016/j.cretres.2015.12.016</mods:identifier>
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<mods:identifier id="F63408BD448B23005166AC47F50CC1A8" type="Zenodo-Dep">3890523</mods:identifier>
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<treatment id="03DC7E37F05EFFA0FC87FA3CFBCCFD20" ID-DOI="http://doi.org/10.5281/zenodo.4715050" ID-GBIF-Taxon="168816241" ID-Zenodo-Dep="4715050" LSID="urn:lsid:plazi:treatment:03DC7E37F05EFFA0FC87FA3CFBCCFD20" httpUri="http://treatment.plazi.org/id/03DC7E37F05EFFA0FC87FA3CFBCCFD20" lastPageId="6" lastPageNumber="32" pageId="5" pageNumber="31">
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<subSubSection id="C36F9CAAF05EFFA3FC87FA3CFBFAF838" pageId="5" pageNumber="31" type="description">
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<paragraph id="8BCACF21F05EFFA3FC87FA3CFBFAF838" blockId="5.[831,1501,1211,1984]" pageId="5" pageNumber="31">
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A frequent point of contention in the literature for using skeletal characters to differentiate
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<taxonomicName id="4C75B4A2F05EFFA3FB96F9DBFB2AF9E5" authorityName="Bakker et al." authorityYear="1988" box="[1102,1239,1545,1565]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="5" pageNumber="31" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05EFFA3FB96F9DBFB2AF9E5" box="[1102,1239,1545,1565]" italics="true" pageId="5" pageNumber="31">Nanotyrannus</emphasis>
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</taxonomicName>
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and
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<taxonomicName id="4C75B4A2F05EFFA3FAD4F9DBFA66F9E5" authorityName="Osborn" authorityYear="1905" box="[1292,1435,1545,1565]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="5" pageNumber="31" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05EFFA3FAD4F9DBFA66F9E5" box="[1292,1435,1545,1565]" italics="true" pageId="5" pageNumber="31">Tyrannosaurus</emphasis>
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</taxonomicName>
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is the possibility of ontogenetic variation, the chance that characters become altered as an individual matures into adulthood. While the size, orientation, and depth of cranial fossa and such openings as the orbits in tyrannosaurs, as well as tooth count and morphology, have been interpreted to be ontogenetically variable (
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<bibRefCitation id="EFE4B2D0F05EFFA3FAB1F944FA32F951" author="Carr, T. D." box="[1385,1487,1686,1705]" journalOrPublisher="Journal of Vertebrate Paleontology" pageId="5" pageNumber="31" pagination="497 - 520" part="19" refId="ref5906" refString="Carr, T. D., 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology 19, 497 - 520." title="Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria)" type="journal article" year="1999">Carr, 1999</bibRefCitation>
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), these interpretations have been questioned (
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<bibRefCitation id="EFE4B2D0F05EFFA3FAD8F960FA76F93D" author="Currie, P. J." box="[1280,1419,1714,1733]" journalOrPublisher="Acta Palaeontologica Polonica" pageId="5" pageNumber="31" pagination="191 - 226" part="48" refId="ref6096" refString="Currie, P. J., 2003 a. Cranial anatomy of tyrannosaurid dinosaus from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48, 191 - 226." title="Cranial anatomy of tyrannosaurid dinosaus from the Late Cretaceous of Alberta, Canada" type="journal article" year="2003">Currie, 2003a</bibRefCitation>
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;
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<bibRefCitation id="EFE4B2D0F05EFFA3FA4DF960FC87F919" author="Larson, P." editor="Parrish, J. M. & Molnar, R. E. & Currie, P. J. & Koppelhus, E. B." journalOrPublisher="Indiana University Press, Bloomington, Indiana" pageId="5" pageNumber="31" pagination="14 - 53" refId="ref6938" refString="Larson, P., 2013 a. The case for Nanotyrannus. In: Parrish, J. M., Molnar, R. E., Currie, P. J., Koppelhus, E. B. (Eds.), Tyrannosaurid Paleobiology. Indiana University Press, Bloomington, Indiana, pp. 14 - 53." title="The case for Nanotyrannus" type="book chapter" volumeTitle="Tyrannosaurid Paleobiology" year="2013">Larson, 2013a</bibRefCitation>
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). The argument that the dentary groove is an ontogenetically variable character is unappealing for several reasons. First, if this feature corresponds to a system of nerves enervating the mandible, a dramatic change (e.g., metamorphosis) would need to be invoked to explain the loss of this feature through maturation. Second, there are other undisputed
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<taxonomicName id="4C75B4A2F05EFFA3FBCDF88AFBBAF894" authorityName="Osborn" authorityYear="1905" box="[1045,1095,1880,1900]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="5" pageNumber="33" phylum="Chordata" rank="species" species="rex">
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<emphasis id="B9011333F05EFFA3FBCDF88AFBBAF894" box="[1045,1095,1880,1900]" italics="true" pageId="5" pageNumber="31">T. rex</emphasis>
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</taxonomicName>
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specimens, representing juvenile (
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<materialsCitation id="3B1DC57CF05EFFA3FA47F88BFC81F870" ID-GBIF-Occurrence="2960701315" collectionCode="LACM" pageId="5" pageNumber="31" specimenCode="LACM 28471">LACM 28471</materialsCitation>
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,
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<materialsCitation id="3B1DC57CF05EFFA3FC50F8A7FBF6F870" ID-GBIF-Occurrence="2960701313" box="[904,1035,1909,1928]" collectionCode="LACM" pageId="5" pageNumber="31" specimenCode="LACM 23845">LACM 23845</materialsCitation>
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) and subadult (
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<materialsCitation id="3B1DC57CF05EFFA3FB77F8A7FAC1F870" ID-GBIF-Occurrence="2960701308" box="[1199,1340,1909,1928]" collectionCode="LACM" pageId="5" pageNumber="31" specimenCode="LACM 150167">LACM 150167</materialsCitation>
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,
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<materialsCitation id="3B1DC57CF05EFFA3FA90F8A7FA2BF870" ID-GBIF-Occurrence="2960701309" box="[1352,1494,1909,1928]" collectionCode="KUVP" pageId="5" pageNumber="31" specimenCode="KUVP 155809">KUVP 155809</materialsCitation>
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) stages, that lack this groove. The adult form (e.g.,
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<materialsCitation id="3B1DC57CF05EFFA3FA98F843FA28F85C" ID-GBIF-Occurrence="2960701302" box="[1344,1493,1937,1956]" collectionCode="FMNH" pageId="5" pageNumber="31" specimenCode="FMNH PR2081">FMNH PR2081</materialsCitation>
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) lacks this groove.
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</paragraph>
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</subSubSection>
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<subSubSection id="C36F9CAAF05EFFA0FBC0F87FFE23FE72" lastPageId="6" lastPageNumber="32" pageId="5" pageNumber="31" type="nomenclature">
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<paragraph id="8BCACF21F05EFFA0FBC0F87FFE23FE72" blockId="5.[831,1501,1211,1984]" lastBlockId="6.[88,758,179,1733]" lastPageId="6" lastPageNumber="32" pageId="5" pageNumber="31">
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As all
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<taxonomicName id="4C75B4A2F05EFFA3FBB6F879FAD2F847" authorityName="Osborn" authorityYear="1905" box="[1134,1327,1963,1983]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="5" pageNumber="33" phylum="Chordata" rank="species" species="rex">
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<emphasis id="B9011333F05EFFA3FBB6F879FAD2F847" box="[1134,1327,1963,1983]" italics="true" pageId="5" pageNumber="31">Tyrannosaurus rex</emphasis>
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</taxonomicName>
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specimens we investigated lack a dentary groove, even in juvenile and subadult individuals, and all
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<taxonomicName id="4C75B4A2F05DFFA0FEE1FF1CFE3FFF1A" authorityName="Bakker et al." authorityYear="1988" box="[313,450,206,226]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FEE1FF1CFE3FFF1A" box="[313,450,206,226]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
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specimens we investigated possess a dentary groove, this seems to suggest that the groove is not variable in a single species and that it does not change during ontogeny. The presence or absence of a groove may further be sufficient to diagnose one taxon from another taxon. The most reasonable explanation for this data is that
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<taxonomicName id="4C75B4A2F05DFFA0FDDCFE8BFD82FE95" baseAuthorityName="Gilmore" baseAuthorityYear="1946" box="[516,639,345,365]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="species" species="lancensis">
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<emphasis id="B9011333F05DFFA0FDDCFE8BFD82FE95" box="[516,639,345,365]" italics="true" pageId="6" pageNumber="32">N. lancenesis</emphasis>
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</taxonomicName>
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is a distinct taxon and not a juvenile form of
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<taxonomicName id="4C75B4A2F05DFFA0FE7DFEA7FE24FE71" authorityName="Osborn" authorityYear="1905" box="[421,473,373,393]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="33" phylum="Chordata" rank="species" species="rex">
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<emphasis id="B9011333F05DFFA0FE7DFEA7FE24FE71" box="[421,473,373,393]" italics="true" pageId="6" pageNumber="32">T. rex</emphasis>
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</taxonomicName>
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.
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</paragraph>
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</subSubSection>
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<subSubSection id="C36F9CAAF05DFFA0FFAFFE40FBCCFD20" pageId="6" pageNumber="32" type="description">
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<paragraph id="8BCACF21F05DFFA0FFAFFE40FEFCFB4A" blockId="6.[88,758,179,1733]" pageId="6" pageNumber="32">
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The dentary groove is such a phylogenetically conservative character (i.e., only five losses outside of Tyrannoraptora) that the presence or absence of the groove in tyrannosaurids seems a useful taxonomic character.
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<taxonomicName id="4C75B4A2F05DFFA0FEA4FE37FDF5FE01" authorityName="Bakker et al." authorityYear="1988" box="[380,520,485,505]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FEA4FE37FDF5FE01" box="[380,520,485,505]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
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has been suggested to be similar to
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<taxonomicName id="4C75B4A2F05DFFA0FF32FDD3FE9BFDED" baseAuthorityName="Gilmore" baseAuthorityYear="1946" box="[234,358,513,533]" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FF32FDD3FE9BFDED" box="[234,358,513,533]" italics="true" pageId="6" pageNumber="32">Gorgosaurus</emphasis>
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</taxonomicName>
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, based on the presence of numerous cranial and dental characteristics (
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<bibRefCitation id="EFE4B2D0F05DFFA0FE10FDCCFDA5FDC9" author="Larson, P." box="[456,600,542,561]" editor="Parrish, J. M. & Molnar, R. E. & Currie, P. J. & Koppelhus, E. B." journalOrPublisher="Indiana University Press, Bloomington, Indiana" pageId="6" pageNumber="32" pagination="14 - 53" refId="ref6938" refString="Larson, P., 2013 a. The case for Nanotyrannus. In: Parrish, J. M., Molnar, R. E., Currie, P. J., Koppelhus, E. B. (Eds.), Tyrannosaurid Paleobiology. Indiana University Press, Bloomington, Indiana, pp. 14 - 53." title="The case for Nanotyrannus" type="book chapter" volumeTitle="Tyrannosaurid Paleobiology" year="2013">Larson, 2013a</bibRefCitation>
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). Interestingly, CMNH 7531 was originally described as a species of
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<taxonomicName id="4C75B4A2F05DFFA0FDA1FDEBFF01FD91" baseAuthorityName="Gilmore" baseAuthorityYear="1946" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FDA1FDEBFD08FDB5" box="[633,757,569,589]" italics="true" pageId="6" pageNumber="32">Gorgosaurus</emphasis>
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(
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<bibRefCitation id="EFE4B2D0F05DFFA0FFB8FD84FF0EFD91" author="Gilmore, C. W." box="[96,243,598,617]" journalOrPublisher="Smithsonian Miscellaneous Collections" pageId="6" pageNumber="32" pagination="1 - 19" part="106" refId="ref6594" refString="Gilmore, C. W., 1946. A new carnivorous dinosaur from the Lance formation of Montana. Smithsonian Miscellaneous Collections 106 (13), 1 - 19." title="A new carnivorous dinosaur from the Lance formation of Montana" type="journal article" year="1946">Gilmore, 1946</bibRefCitation>
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)
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</taxonomicName>
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. The presence of the dentary groove in
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<taxonomicName id="4C75B4A2F05DFFA0FD60FD86FF4DFD7C" authorityName="Bakker et al." authorityYear="1988" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FD60FD86FF4DFD7C" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
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seems to further confirm its affinity with
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<taxonomicName id="4C75B4A2F05DFFA0FDADFDA0FF7EFD58" authorityName="Osborn" authorityYear="1905" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Albertosaurinae">Albertosaurinae</taxonomicName>
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rather than
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<taxonomicName id="4C75B4A2F05DFFA0FED2FD5FFE45FD58" authorityName="Matthew & Brown" authorityYear="1922" box="[266,440,653,672]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Tyrannosaurinae">Tyrannosaurinae</taxonomicName>
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.
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<taxonomicName id="4C75B4A2F05DFFA0FE1DFD5FFD95FD58" authorityName="Osborn" authorityYear="1905" box="[453,616,653,672]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Albertosaurinae">Albertosaurinae</taxonomicName>
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is defined as the tyrannosaurs possessing: an antorbital cavity that reaches the nasomaxillary suture, lateral surface of nasal excluded from the antorbital vacity, and a dorsally-oriented, triangular corneal process of the lacrimal (
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<bibRefCitation id="EFE4B2D0F05DFFA0FEEAFD2FFE57FCE8" author="Holtz, T. R." box="[306,426,765,784]" editor="Weishampel, D. B. & Dodson, P. & Osmolska, H." journalOrPublisher="University of California Press, Los Angeles, California" pageId="6" pageNumber="32" pagination="111 - 136" refId="ref6741" refString="Holtz, T. R., 2004. Tyrannosauroidea. In: Weishampel, D. B., Dodson, P., Osmolska, H. (Eds.), The Dinosauria. University of California Press, Los Angeles, California, pp. 111 - 136." title="Tyrannosauroidea" type="book chapter" volumeTitle="The Dinosauria" year="2004">Holtz, 2004</bibRefCitation>
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).
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<bibRefCitation id="EFE4B2D0F05DFFA0FE18FD2FFDA4FCE8" author="Currie, P. J." box="[448,601,765,784]" journalOrPublisher="Canadian Journal of Earth Sciences" pageId="6" pageNumber="32" pagination="651 - 665" part="40" refId="ref6129" refString="Currie, P. J., 2003 b. Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences 40, 651 - 665." title="Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia" type="journal article" year="2003">Currie (2003b)</bibRefCitation>
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defined
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<taxonomicName id="4C75B4A2F05DFFA0FD6EFD2FFF39FCD4" authorityName="Osborn" authorityYear="1905" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Albertosaurinae">Albertosaurinae</taxonomicName>
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as possessing, in contrast to
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<taxonomicName id="4C75B4A2F05DFFA0FDDCFCCBFD4FFCD4" authorityName="Matthew & Brown" authorityYear="1922" box="[516,690,793,812]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Tyrannosaurinae">Tyrannosaurinae</taxonomicName>
|
|
, short and low skulls, shorter ilia, longer tibiae, longer metatarsals and longer toes, a definition
|
|
<taxonomicName id="4C75B4A2F05DFFA0FEB5FC9DFE04FC9B" authorityName="Bakker et al." authorityYear="1988" box="[365,505,847,867]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FEB5FC9DFE04FC9B" box="[365,505,847,867]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
meets.
|
|
<bibRefCitation id="EFE4B2D0F05DFFA0FD8FFC83FD08FC9C" author="Larson, P." box="[599,757,849,868]" editor="Parrish, J. M. & Molnar, R. E. & Currie, P. J. & Koppelhus, E. B." journalOrPublisher="Indiana University Press, Bloomington, Indiana" pageId="6" pageNumber="32" pagination="14 - 53" refId="ref6938" refString="Larson, P., 2013 a. The case for Nanotyrannus. In: Parrish, J. M., Molnar, R. E., Currie, P. J., Koppelhus, E. B. (Eds.), Tyrannosaurid Paleobiology. Indiana University Press, Bloomington, Indiana, pp. 14 - 53." title="The case for Nanotyrannus" type="book chapter" volumeTitle="Tyrannosaurid Paleobiology" year="2013">Larson (2013a)</bibRefCitation>
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|
presented more than 30 skeletal characters that separate
|
|
<taxonomicName id="4C75B4A2F05DFFA0FD60FCB9FF4DFC63" authorityName="Bakker et al." authorityYear="1988" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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|
<emphasis id="B9011333F05DFFA0FD60FCB9FF4DFC63" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
from
|
|
<taxonomicName id="4C75B4A2F05DFFA0FED9FC55FE6EFC63" authorityName="Osborn" authorityYear="1905" box="[257,403,903,923]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FED9FC55FE6EFC63" box="[257,403,903,923]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
|
|
</taxonomicName>
|
|
, with the following characters possibly uniting
|
|
<taxonomicName id="4C75B4A2F05DFFA0FED2FC71FE6BFC4F" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[266,406,931,951]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FED2FC71FE6BFC4F" box="[266,406,931,951]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
and the albertosaurines: greater dentary tooth counts, contact of the maxillary fenestra with the rostral margin of the antorbital fossa, a medial post-orbital fossa and an ectopterygoid pneumatic foramina bounded by a thick lip. Albertosaurines may also be regarded as having more circular than ovoid orbits. We propose that the presence of the dentary groove be added to the list of diagnostic albertosaurine characters, as it is a character that is lost in
|
|
<taxonomicName id="4C75B4A2F05DFFA0FE6BFBBAFD9CFB83" authorityName="Matthew & Brown" authorityYear="1922" box="[435,609,1128,1147]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Tyrannosaurinae">Tyrannosaurinae</taxonomicName>
|
|
. We therefore propose that
|
|
<taxonomicName id="4C75B4A2F05DFFA0FF3EFB50FE8FFB6E" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[230,370,1154,1174]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FF3EFB50FE8FFB6E" box="[230,370,1154,1174]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
should be regarded as a member of
|
|
<taxonomicName id="4C75B4A2F05DFFA0FF80FB4DFF03FB4A" box="[88,254,1183,1202]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Albertosaurinae">Albertosaurinae</taxonomicName>
|
|
.
|
|
</paragraph>
|
|
<paragraph id="8BCACF21F05DFFA0FFAFFB69FF0DF93D" blockId="6.[88,758,179,1733]" pageId="6" pageNumber="32">
|
|
<figureCitation id="134ED3A4F05DFFA0FFAFFB69FF50FB37" box="[119,173,1211,1231]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3</figureCitation>
|
|
shows three potential interpretations of the phylogeny of Tyrannosauroidea.
|
|
<taxonomicName id="4C75B4A2F05DFFA0FEC0FB04FE5CFB12" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[280,417,1238,1258]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FEC0FB04FE5CFB12" box="[280,417,1238,1258]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
has been previously suggested to be either (1) a valid taxon distinct from
|
|
<taxonomicName id="4C75B4A2F05DFFA0FDDDFB20FD69FAFE" authorityName="Osborn" authorityYear="1905" box="[517,660,1266,1286]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FDDDFB20FD69FAFE" box="[517,660,1266,1286]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
|
|
</taxonomicName>
|
|
(
|
|
<figureCitation id="134ED3A4F05DFFA0FD7EFB21FD0CFAFE" box="[678,753,1267,1286]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3A</figureCitation>
|
|
;
|
|
<bibRefCitation id="EFE4B2D0F05DFFA0FF80FADDFF21FADA" author="Larson, P." box="[88,220,1295,1314]" editor="Larson, P. & Carpenter, K." journalOrPublisher="Indiana University Press, Bloomington, Indiana" pageId="6" pageNumber="32" pagination="102 - 128" refId="ref6886" refString="Larson, P., 2008. Variation and sexual dimorphism in Tyrannosaurus rex. In: Larson, P., Carpenter, K. (Eds.), Tyrannosaurus Rex: The Tyrant King. Indiana University Press, Bloomington, Indiana, pp. 102 - 128." title="Variation and sexual dimorphism in Tyrannosaurus rex" type="book chapter" volumeTitle="Tyrannosaurus Rex: The Tyrant King" year="2008">Larson, 2008</bibRefCitation>
|
|
;
|
|
<bibRefCitation id="EFE4B2D0F05DFFA0FF3EFADDFE92FADA" author="Larson, P." box="[230,367,1295,1314]" editor="Parrish, J. M. & Molnar, R. E. & Currie, P. J. & Koppelhus, E. B." journalOrPublisher="Indiana University Press, Bloomington, Indiana" pageId="6" pageNumber="32" pagination="14 - 53" refId="ref6938" refString="Larson, P., 2013 a. The case for Nanotyrannus. In: Parrish, J. M., Molnar, R. E., Currie, P. J., Koppelhus, E. B. (Eds.), Tyrannosaurid Paleobiology. Indiana University Press, Bloomington, Indiana, pp. 14 - 53." title="The case for Nanotyrannus" type="book chapter" volumeTitle="Tyrannosaurid Paleobiology" year="2013">Larson, 2013a</bibRefCitation>
|
|
), (2) the sister taxon to
|
|
<taxonomicName id="4C75B4A2F05DFFA0FDB9FADCFD0DFADA" authorityName="Osborn" authorityYear="1905" box="[609,752,1294,1314]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FDB9FADCFD0DFADA" box="[609,752,1294,1314]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
|
|
</taxonomicName>
|
|
, either as
|
|
<taxonomicName id="4C75B4A2F05DFFA0FF60FAF8FE5AFAC6" authorityName="Currie et al." authorityYear="2005" baseAuthorityName="Gilmore" baseAuthorityYear="1946" box="[184,423,1322,1342]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FF60FAF8FE5AFAC6" box="[184,423,1322,1342]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus lancensis</emphasis>
|
|
</taxonomicName>
|
|
(
|
|
<bibRefCitation id="EFE4B2D0F05DFFA0FE6FFAF9FD92FAC6" author="Currie, P. J. & Henderson, M. & Horner, J. R. & Williams, S. A." box="[439,623,1323,1342]" journalOrPublisher="Abstracts" pageId="6" pageNumber="32" pagination="19" refId="ref6209" refString="Currie, P. J., Henderson, M., Horner, J. R., Williams, S. A., 2005. On tyrannosaur teeth, tooth positions and the taxonomic status of Nanotyrannus lancensis. In: The Origin, Systematics, and Paleobiology of Tyrannosauridae Symposium. Abstracts: 19." title="On tyrannosaur teeth, tooth positions and the taxonomic status of Nanotyrannus lancensis" type="proceedings" volumeTitle="The Origin, Systematics, and Paleobiology of Tyrannosauridae Symposium" year="2005">Currie et al., 2005</bibRefCitation>
|
|
) or as
|
|
<taxonomicName id="4C75B4A2F05DFFA0FD61FAF8FF53FAA2" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FD61FAF8FF53FAA2" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
(
|
|
<figureCitation id="134ED3A4F05DFFA0FF64FA95FEFEFAA2" box="[188,259,1351,1370]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3B</figureCitation>
|
|
;
|
|
<bibRefCitation id="EFE4B2D0F05DFFA0FED5FA95FE3FFAA2" author="Currie, P. J. & Hurum, J. H. & Sabath, K. L." box="[269,450,1351,1370]" journalOrPublisher="Acta Palaeontologica Polonica" pageId="6" pageNumber="32" pagination="227 - 234" part="48" refId="ref6169" refString="Currie, P. J., Hurum, J. H., Sabath, K. L., 2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 48, 227 - 234." title="Skull structure and evolution in tyrannosaurid dinosaurs" type="journal article" year="2003">Currie et al., 2003</bibRefCitation>
|
|
), or (3) even a juvenile
|
|
<taxonomicName id="4C75B4A2F05DFFA0FD6DFA94FF4DFA8E" authorityName="Osborn" authorityYear="1905" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FD6DFA94FF4DFA8E" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
|
|
</taxonomicName>
|
|
(
|
|
<figureCitation id="134ED3A4F05DFFA0FF1AFAB1FEF1FA8E" box="[194,268,1379,1398]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3C</figureCitation>
|
|
;
|
|
<bibRefCitation id="EFE4B2D0F05DFFA0FEC1FAB1FE14FA8E" author="Brusatte, S. L. & Norell, M. A. & Carr, T. D. & Erickson, G. M. & Hutchinson, J. R. & Balanoff, A. M. & Bever, G. S. & Choiniere, J. N. & Makovicky, P. J. & Xu, X." box="[281,489,1379,1398]" journalOrPublisher="Science" pageId="6" pageNumber="32" pagination="1481 - 1485" part="329" refId="ref5776" refString="Brusatte, S. L., Norell, M. A., Carr, T. D., Erickson, G. M., Hutchinson, J. R., Balanoff, A. M., Bever, G. S., Choiniere, J. N., Makovicky, P. J., Xu, X., 2010. Tyrannosaur paleobiology: new research on ancient exemplar organisms. Science 329, 1481 - 1485." title="Tyrannosaur paleobiology: new research on ancient exemplar organisms" type="journal article" year="2010">Brusatte et al., 2010</bibRefCitation>
|
|
). The most parsimonious distribution of the dentary groove found in this study (
|
|
<figureCitation id="134ED3A4F05DFFA0FD7DFAADFD13FA6A" box="[677,750,1407,1426]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3A</figureCitation>
|
|
) places
|
|
<taxonomicName id="4C75B4A2F05DFFA0FF47FA4BFED5FA55" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[159,296,1433,1453]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FF47FA4BFED5FA55" box="[159,296,1433,1453]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
as sister to the
|
|
<taxonomicName id="4C75B4A2F05DFFA0FE0FFA49FD8AFA56" box="[471,631,1435,1454]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Albertosaurinae">Albertosaurinae</taxonomicName>
|
|
(
|
|
<taxonomicName id="4C75B4A2F05DFFA0FD51FA4BFF93FA31" baseAuthorityName="Gilmore" baseAuthorityYear="1946" class="Reptilia" family="Tyrannosauridae" genus="Gorgosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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|
<emphasis id="B9011333F05DFFA0FD51FA4BFF93FA31" italics="true" pageId="6" pageNumber="32">Gorgosaurus</emphasis>
|
|
</taxonomicName>
|
|
+
|
|
<taxonomicName id="4C75B4A2F05DFFA0FF5FFA67FEF1FA31" authorityName="Osborn" authorityYear="1905" box="[135,268,1461,1481]" class="Reptilia" family="Tyrannosauridae" genus="Albertosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FF5FFA67FEF1FA31" box="[135,268,1461,1481]" italics="true" pageId="6" pageNumber="32">Albertosaurus</emphasis>
|
|
</taxonomicName>
|
|
). The
|
|
<taxonomicName id="4C75B4A2F05DFFA0FE96FA67FE2AFA31" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[334,471,1461,1481]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FE96FA67FE2AFA31" box="[334,471,1461,1481]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
+
|
|
<taxonomicName id="4C75B4A2F05DFFA0FE29FA67FD7CFA31" authorityName="Osborn" authorityYear="1905" box="[497,641,1461,1481]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FE29FA67FD7CFA31" box="[497,641,1461,1481]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
|
|
</taxonomicName>
|
|
hypothesis (
|
|
<figureCitation id="134ED3A4F05DFFA0FFB8FA00FF59FA1D" box="[96,164,1490,1510]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3B</figureCitation>
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|
) requires five additional independent losses of the dentary groove, more than the tree which places
|
|
<taxonomicName id="4C75B4A2F05DFFA0FDD2FA3FFD6EF9F9" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[522,659,1517,1537]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FDD2FA3FFD6EF9F9" box="[522,659,1517,1537]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
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closer to Albertosauriane. The hypothesis that
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<taxonomicName id="4C75B4A2F05DFFA0FE39F9DBFD97F9E5" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[481,618,1545,1565]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FE39F9DBFD97F9E5" box="[481,618,1545,1565]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
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is a juvenile
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<taxonomicName id="4C75B4A2F05DFFA0FF80F9F7FF1AF9C1" authorityName="Osborn" authorityYear="1905" box="[88,231,1573,1593]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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|
<emphasis id="B9011333F05DFFA0FF80F9F7FF1AF9C1" box="[88,231,1573,1593]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
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</taxonomicName>
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(
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<figureCitation id="134ED3A4F05DFFA0FF2CF9F4FECBF9C1" box="[244,310,1574,1593]" captionStart="Fig" captionStartId="4.[88,113,1624,1638]" captionTargetBox="[222,1339,180,1594]" captionTargetId="figure@4.[221,1340,178,1595]" captionTargetPageId="4" captionText="Fig. 3. Proposed phylogenetic relationships of Nanotyrannus within Tyrannosauroidea with distribution of the theropod dentary groove on trees indicated with thickened bars. (A) Most parsimonious cladogram proposed by this study placing Nanotyrannus as sister to the Albertosaurinae.(B) Relationship sensu Currie (2003a) placing Nanotyrannus as sister to Tyrannosaurus. This tree requires 5 more independent losses of the dentary groove than the tree proposed in this study. (C) Relationship proposed by Brusatte et al. (2010) placing Nanotyrannus as a juvenile Tyrannosaurus. This tree requires 4 more independent losses than the tree proposed in this study and a loss of the dentary groove through ontogeny in Tyrannosaurus." figureDoi="http://doi.org/10.5281/zenodo.3890529" httpUri="https://zenodo.org/record/3890529/files/figure.png" pageId="6" pageNumber="32">Fig. 3C</figureCitation>
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) requires four additional independent losses, as well as requiring an ontogenetic explanation for why juvenile
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<taxonomicName id="4C75B4A2F05DFFA0FF80F98EFF71F988" authorityName="Osborn" authorityYear="1905" box="[88,140,1628,1648]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="33" phylum="Chordata" rank="species" species="rex">
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<emphasis id="B9011333F05DFFA0FF80F98EFF71F988" box="[88,140,1628,1648]" italics="true" pageId="6" pageNumber="32">T. rex</emphasis>
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</taxonomicName>
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possesses the character absent in adults. The fact that there are specimens interpreted as juvenile and subadult
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<taxonomicName id="4C75B4A2F05DFFA0FDBCF9AAFD6AF974" authorityName="Osborn" authorityYear="1905" box="[612,663,1656,1676]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="33" phylum="Chordata" rank="species" species="rex">
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<emphasis id="B9011333F05DFFA0FDBCF9AAFD6AF974" box="[612,663,1656,1676]" italics="true" pageId="6" pageNumber="32">T. rex</emphasis>
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</taxonomicName>
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that lack the dentary groove should render that hypothesis completely unsupportable.
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</paragraph>
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<paragraph id="8BCACF21F05DFFA0FF80F93BFF0BF904" blockId="6.[88,246,1769,1788]" box="[88,246,1769,1788]" pageId="6" pageNumber="32">
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<heading id="D082784DF05DFFA0FF80F93BFF0BF904" bold="true" box="[88,246,1769,1788]" fontSize="8" level="2" pageId="6" pageNumber="32" reason="0">
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<emphasis id="B9011333F05DFFA0FF80F93BFF0BF904" bold="true" box="[88,246,1769,1788]" pageId="6" pageNumber="32">5. Conclusions</emphasis>
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</heading>
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</paragraph>
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<paragraph id="8BCACF21F05DFFA0FFAFF8F3FBCCFD20" blockId="6.[88,757,1825,1984]" lastBlockId="6.[805,1475,179,728]" pageId="6" pageNumber="32">
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The occurrence of the dentary groove in theropod dinosaurs serves as a useful feature for determining relationships and inferring the validity of the disputed taxon
|
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<taxonomicName id="4C75B4A2F05DFFA0FDEBF88AFD42F894" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[563,703,1880,1900]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FDEBF88AFD42F894" box="[563,703,1880,1900]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
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. The groove appears early in the theropod record and is a ubiquitous character for the duration of the Jurassic and Early Cretaceous. For the 92 theropod taxa investigated in this study, 48 possess this feature. As 80% of basal theropods possess this groove, it could be considered a defining character of theropod dinosaurs, lost in only a handful of lineages. While loss of the groove did not appear to result from the evolution of beaks in different theropod clades, it may have been one of many evolutionary changes that occurred which strengthened the jaws of tyrannosaurids. This feature has also proved useful for interpreting relationships among tyrannosauroids, which have a mosaic distribution of this character.
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<taxonomicName id="4C75B4A2F05DFFA0FCFDFE43FC4CFE5D" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[805,945,401,421]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
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<emphasis id="B9011333F05DFFA0FCFDFE43FC4CFE5D" box="[805,945,401,421]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
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</taxonomicName>
|
|
clearly presents the dentary groove, whereas
|
|
<taxonomicName id="4C75B4A2F05DFFA0FCFDFE7FFC22FE39" authorityName="Osborn" authorityYear="1905" box="[805,991,429,449]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="33" phylum="Chordata" rank="species" species="rex">
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|
<emphasis id="B9011333F05DFFA0FCFDFE7FFC22FE39" box="[805,991,429,449]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus rex</emphasis>
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|
</taxonomicName>
|
|
lacks this feature. Without a modern analog that demonstrates the loss of such a groove through maturation, accepting that this feature is lost through ontogeny is speculative. “Jane”, and the other specimens referred to
|
|
<taxonomicName id="4C75B4A2F05DFFA0FB33FDD3FA8AFDED" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[1259,1399,513,533]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FB33FDD3FA8AFDED" box="[1259,1399,513,533]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
, therefore would not be examples of juvenile
|
|
<taxonomicName id="4C75B4A2F05DFFA0FB67FDCFFAAFFDC9" authorityName="Osborn" authorityYear="1905" box="[1215,1362,541,561]" class="Reptilia" family="Tyrannosauridae" genus="Tyrannosaurus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FB67FDCFFAAFFDC9" box="[1215,1362,541,561]" italics="true" pageId="6" pageNumber="32">Tyrannosaurus</emphasis>
|
|
</taxonomicName>
|
|
, and stand alone as a distinct genus.
|
|
<taxonomicName id="4C75B4A2F05DFFA0FB87FDEBFB16FDB5" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[1119,1259,569,589]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FB87FDEBFB16FDB5" box="[1119,1259,569,589]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
should further be considered sister to the
|
|
<taxonomicName id="4C75B4A2F05DFFA0FBFDFD84FB37FD91" box="[1061,1226,598,617]" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Albertosaurinae">Albertosaurinae</taxonomicName>
|
|
, rather than the
|
|
<taxonomicName id="4C75B4A2F05DFFA0FAA7FD84FC65FD7D" authorityName="Matthew & Brown" authorityYear="1922" class="Reptilia" family="Tyrannosauridae" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="subFamily" subFamily="Tyrannosaurinae">Tyrannosaurinae</taxonomicName>
|
|
, as they are the only other clade of large tyrannosaurs to possess this groove. This feature, in addition to many other cranial characters, makes an alignment of
|
|
<taxonomicName id="4C75B4A2F05DFFA0FB00FD7AFA99FD44" authority="Bakker et al., 1988" authorityName="Bakker et al." authorityYear="1988" box="[1240,1380,680,700]" class="Reptilia" family="Tyrannosauridae" genus="Nanotyrannus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Dinosauria" pageId="6" pageNumber="32" phylum="Chordata" rank="genus">
|
|
<emphasis id="B9011333F05DFFA0FB00FD7AFA99FD44" box="[1240,1380,680,700]" italics="true" pageId="6" pageNumber="32">Nanotyrannus</emphasis>
|
|
</taxonomicName>
|
|
with the albertosaurines preferred.
|
|
</paragraph>
|
|
</subSubSection>
|
|
</treatment>
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</document> |