treatments-xml/data/DE/7C/30/DE7C305BFF9EFA5AF9F8FDD3B023EF81.xml

<document id="015A1B4F1EB575B4045EA965CFF48295" ID-CLB-Dataset="3537" ID-DOI="10.1046/j.1096-3642.2002.00015.x" ID-GBIF-Dataset="33418eac-3f41-4da6-94aa-eafa33222a2e" ID-ISSN="0024-4082" ID-Zenodo-Dep="4687167" IM.materialsCitations_approvedBy="felipe" IM.metadata_approvedBy="felipe" IM.taxonomicNames_approvedBy="felipe" checkinTime="1618408764460" checkinUser="carolina" docAuthor="Muizon, Christian de &amp; Domning, Daryl P." docDate="2002" docId="DE7C305BFF9EFA5AF9F8FDD3B023EF81" docLanguage="en" docName="ZoolJLinnSoc.134.423-452.pdf" docOrigin="Zoological Journal of the Linnean Society 134 (4)" docSource="https://academic.oup.com/zoolinnean/article-lookup/doi/10.1046/j.1096-3642.2002.00015.x" docStyle="DocumentStyle:0DD8C314D74634CE09062A86991413F8.2:ZoolJLinnSoc.2002-2009.journal_article" docStyleId="0DD8C314D74634CE09062A86991413F8" docStyleName="ZoolJLinnSoc.2002-2009.journal_article" docStyleVersion="2" docTitle="Odobenocetops LEPTODON MUIZON, DOMNING &amp; PARRISH 1999" docType="treatment" docVersion="8" lastPageNumber="432" masterDocId="22454823FF9CFA53F959FFF8B422EA62" masterDocTitle="The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications" masterLastPageNumber="452" masterPageNumber="423" pageNumber="425" updateTime="1698936361855" updateUser="ExternalLinkService" zenodo-license-document="CC-BY-4.0" zenodo-license-figures="CC-BY-4.0">
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<mods:title id="5712846736E8B52F851C020017D7CDC0">The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications</mods:title>
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<mods:namePart id="9E983FA98CD1B39C8D5E68C1A2201225">Muizon, Christian de</mods:namePart>
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<treatment id="DE7C305BFF9EFA5AF9F8FDD3B023EF81" ID-DOI="http://doi.org/10.5281/zenodo.5700703" ID-GBIF-Taxon="190302703" ID-Zenodo-Dep="5700703" LSID="urn:lsid:plazi:treatment:DE7C305BFF9EFA5AF9F8FDD3B023EF81" httpUri="http://treatment.plazi.org/id/DE7C305BFF9EFA5AF9F8FDD3B023EF81" lastPageId="9" lastPageNumber="432" pageId="2" pageNumber="425">
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<paragraph id="566A814DFF9EFA51F9F8FDD3B63BE801" blockId="2.[161,745,555,643]" pageId="2" pageNumber="425">
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<taxonomicName id="91D5FACEFF9EFA51F9F8FDD3B63BE801" authority="LEPTODON MUIZON, DOMNING &amp; PARRISH, 1999" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9EFA51F9F8FDD3B5C5E820" box="[161,487,555,579]" italics="true" pageId="2" pageNumber="425">ODOBENOCETOPS LEPTODON</emphasis>
<bibRefCitation id="3244FCBCFF9EFA51F8B6FDD3B63BE801" author="de Muizon C &amp; Domning DP &amp; Parrish M" pageId="2" pageNumber="425" pagination="449 - 455" refId="ref23136" refString="de Muizon C, Domning DP, Parrish M. 1999. Dimorphic tusks and adaptive strategies in a new species of walrus-like dolphin (Odobenocetopsidae) from the Pliocene of Peru. Comptes-rendus de l'Academie des Sciences, Paris, Sciences de la Terre et des Planetes 329: 449 - 455." type="journal article" year="1999">MUIZON, DOMNING &amp; PARRISH, 1999</bibRefCitation>
</taxonomicName>
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<paragraph id="566A814DFF9EFA51F844FD93B64FE8E1" blockId="2.[161,745,555,643]" box="[285,621,619,643]" pageId="2" pageNumber="425">
(
<figureCitation id="CEEE9DC8FF9EFA51F87CFD93B5BCE8E1" box="[293,414,619,643]" captionStart-0="Figure 1" captionStart-1="Figure 2" captionStart-10="Figure 11" captionStart-11="Figure 12" captionStart-2="Figure 3" captionStart-3="Figure 4" captionStart-4="Figure 5" captionStart-5="Figure 6" captionStart-6="Figure 7" captionStart-7="Figure 8" captionStart-8="Figure 9" captionStart-9="Figure 10" captionStartId-0="3.[823,902,1340,1361]" captionStartId-1="4.[145,224,1254,1275]" captionStartId-10="13.[159,238,1854,1875]" captionStartId-11="15.[159,238,1854,1875]" captionStartId-2="5.[159,238,932,953]" captionStartId-3="6.[145,224,1088,1109]" captionStartId-4="7.[159,238,713,734]" captionStartId-5="10.[145,224,1211,1232]" captionStartId-6="11.[159,238,1422,1443]" captionStartId-7="12.[145,224,832,853]" captionStartId-8="12.[145,224,1201,1222]" captionStartId-9="12.[809,888,1388,1409]" captionTargetBox-0="[842,1419,198,1308]" captionTargetBox-1="[308,1262,197,1223]" captionTargetBox-10="[330,1266,1399,1825]" captionTargetBox-11="[355,1254,935,1823]" captionTargetBox-2="[172,1434,196,900]" captionTargetBox-3="[156,757,200,1057]" captionTargetBox-4="[194,777,156,678]" captionTargetBox-5="[150,757,196,1179]" captionTargetBox-6="[328,1271,198,1389]" captionTargetBox-7="[329,1247,198,798]" captionTargetBox-8="[156,751,965,1169]" captionTargetBox-9="[818,1418,964,1357]" captionTargetId-0="figure-576@3.[836,1445,193,1316]" captionTargetId-1="figure-331@4.[305,1265,195,1234]" captionTargetId-10="figure-608@13.[319,1279,1391,1850]" captionTargetId-11="figure-378@15.[315,1275,916,1842]" captionTargetId-2="figure-533@5.[167,1448,190,916]" captionTargetId-3="figure-707@6.[153,762,195,1063]" captionTargetId-4="figure-812@7.[167,777,154,713]" captionTargetId-5="figure-595@10.[149,757,196,1179]" captionTargetId-6="figure-173@11.[320,1281,185,1397]" captionTargetId-7="figure-241@12.[323,1284,192,803]" captionTargetId-8="figure-248@12.[153,762,963,1172]" captionTargetId-9="figure-255@12.[815,1424,959,1365]" captionTargetPageId-0="3" captionTargetPageId-1="4" captionTargetPageId-10="13" captionTargetPageId-11="15" captionTargetPageId-2="5" captionTargetPageId-3="6" captionTargetPageId-4="7" captionTargetPageId-5="10" captionTargetPageId-6="11" captionTargetPageId-7="12" captionTargetPageId-8="12" captionTargetPageId-9="12" captionText-0="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." captionText-1="Figure 2. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views." captionText-10="Figure 11. Odobenocetops leptodon, holotype (SMNK PAL 2492). Atlas in anterior (A), posterior (B), dorsal (C), ventral (D), lateral right (E), and lateral left (F) views." captionText-11="Figure 12. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Left forelimb in lateral (A) and medial (B) views." captionText-2="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." captionText-3="Figure 4. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in lateral left (A) and lateral right (B) views." captionText-4="Figure 5. Reconstruction of the dorsal view of the rostrum of Odobenocetops leptodon. Abbreviations: Fps, fossa for the premaxillary sac; Fr, frontal; Mx, maxilla; NaF, narial fossa; Pmx, premaxilla; Sb, supplementary bone." captionText-5="Figure 6. Auditory region of Odobenocetops leptodon, holotype (SMNK PAL 2492). Lateral view (A) and posterolateral view showing the tympanic aperture (B). On B, the outline of the tympanic aperture has been enhanced with a white line.Abbreviations:Ap, anterior process of the periotic; Bo, basioccipital; Cho, choanae; Eam, external auditory meatus; Fo, foramen ovale; Gf, glenoid fossa; Llpt, lateral lamina of the pterygoid; Oc, occipital condyle; Pa, palatine; Ptc, pterygoid crest; Ptp, post-tympanic process of the squamosal; po, paroccipital process of the exoccipital; Pts, pterygoid sinus; Sp, sigmoid process of the tympanic; Tym, tympanic." captionText-6="Figure 7. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Periotic in dorsal (A), lateral (B), ventral (C), and medial (D) views. Abbreviations: ac, aqueductus cochleae; ap, anterior process; av, aqueductus vestibuli; dfc, dorsal opening of the facial canal; ef, fovea epitubaria; fc, fenestra cochleae; fi, fossa incudis; fm, fossa mallei (= epitympanic recess); iam, internal auditory meatus; pbf, posterior bullar facet; pc, pars cochlearis (= promontorium); pp, posterior process; slf, sulcus facialis; so, supernumerary ossicles; st, stapes; stf, fossa for stapedial muscle; ts, tractus spiralis; vfc, ventral opening of the facial canal; vr, ventral rim of the anterior process." captionText-7="Figure 8. Odobenocetops cf. leptodon, referred specimen (MNHN PPI 249). Periotic in dorsal (A), lateral (B), ventral (C), and medial (D) views." captionText-8="Figure 9. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Partial tympanic in ventral (A) and medial (B) views." captionText-9="Figure 10 Odobenocetops leptodon, referred specimen (MNHN SAO 202). Malleus in posteromedial view (A); incus in ventral view (B). Abbreviations: ast, articular facet for the stapes; cb, crus breve; cl, crus longum; icf, articular facets for the incus; mn, manubrium; pm, processus muscularis; tu, tuberculum." figureDoi-0="http://doi.org/10.5281/zenodo.4687171" figureDoi-1="http://doi.org/10.5281/zenodo.4687175" figureDoi-10="http://doi.org/10.5281/zenodo.4687205" figureDoi-11="http://doi.org/10.5281/zenodo.4687207" figureDoi-2="http://doi.org/10.5281/zenodo.4687177" figureDoi-3="http://doi.org/10.5281/zenodo.4687181" figureDoi-4="http://doi.org/10.5281/zenodo.4687183" figureDoi-5="http://doi.org/10.5281/zenodo.4687189" figureDoi-6="http://doi.org/10.5281/zenodo.4687193" figureDoi-7="http://doi.org/10.5281/zenodo.4687195" figureDoi-8="http://doi.org/10.5281/zenodo.4687199" figureDoi-9="http://doi.org/10.5281/zenodo.4687201" httpUri-0="https://zenodo.org/record/4687171/files/figure.png" httpUri-1="https://zenodo.org/record/4687175/files/figure.png" httpUri-10="https://zenodo.org/record/4687205/files/figure.png" httpUri-11="https://zenodo.org/record/4687207/files/figure.png" httpUri-2="https://zenodo.org/record/4687177/files/figure.png" httpUri-3="https://zenodo.org/record/4687181/files/figure.png" httpUri-4="https://zenodo.org/record/4687183/files/figure.png" httpUri-5="https://zenodo.org/record/4687189/files/figure.png" httpUri-6="https://zenodo.org/record/4687193/files/figure.png" httpUri-7="https://zenodo.org/record/4687195/files/figure.png" httpUri-8="https://zenodo.org/record/4687199/files/figure.png" httpUri-9="https://zenodo.org/record/4687201/files/figure.png" pageId="2" pageNumber="425">FIGS 1–12</figureCitation>
, 
<tableCitation id="1B57B4F6FF9EFA51F8F2FD93B63AE8E1" box="[427,536,619,643]" captionStart="Table 1" captionStartId="2.[145,209,1038,1059]" captionText="Table 1. Measurements of the holotype of Odobenocetops leptodon (SMNK PAL 2492) in mm. (e = estimated)" pageId="2" pageNumber="425">TABLES 1</tableCitation>
AND 
<tableCitation id="1B57B4F6FF9EFA51FB0FFD93B646E8E1" box="[598,612,619,643]" captionStart="Table 2" captionStartId="2.[809,873,1273,1294]" captionText="Table 2. Measurments of the ear bones of Obobenocetops leptodon (referred specimen, MNHN SAO 202) in mm (e = estimated)" pageId="2" pageNumber="425">2</tableCitation>
)
</paragraph>
<paragraph id="566A814DFF9EFA51F9C8FD5BB697E977" blockId="2.[145,761,675,789]" pageId="2" pageNumber="425">
<materialsCitation id="E6BD8B10FF9EFA51F9C8FD5BB697E977" ID-GBIF-Occurrence="3403400301" collectionCode="SMNK" pageId="2" pageNumber="425" specimenCode="PAL 2492" specimenCount="1" typeStatus="holotype">
<emphasis id="64A15D5FFF9EFA51F9C8FD5BB4D7E8DA" box="[145,245,675,696]" italics="true" pageId="2" pageNumber="425">
<typeStatus id="896E3FEFFF9EFA51F9C8FD5BB4D7E8DA" box="[145,245,675,696]" pageId="2" pageNumber="425" type="holotype">Holotype</typeStatus>
</emphasis>
: 
<collectionCode id="30C41988FF9EFA51F857FD5BB57EE8DA" box="[270,348,675,696]" country="Germany" httpUri="http://grbio.org/cool/tc3a-fmpc" name="Staatliches Museum fuer Naturkunde Karlsruhe (State Museum of Natural History)" pageId="2" pageNumber="425">SMNK</collectionCode>
<specimenCode id="06732936FF9EFA51F836FD5BB5CEE8DA" box="[367,492,675,696]" collectionCode="SMNK" country="Germany" httpUri="http://grbio.org/cool/tc3a-fmpc" name="Staatliches Museum fuer Naturkunde Karlsruhe (State Museum of Natural History)" pageId="2" pageNumber="425">PAL 2492</specimenCode>
, an incomplete skull (lacking most of the dorsal and right sides of the braincase, right orbit, and right side of the right alveolar sheath), with the right ear bones and the atlas.
</materialsCitation>
</paragraph>
<paragraph id="566A814DFF9EFA51F9C8FCD5B07AEBF0" blockId="2.[145,761,813,958]" lastBlockId="2.[809,1425,197,403]" pageId="2" pageNumber="425">
<emphasis id="64A15D5FFF9EFA51F9C8FCD5B543E921" box="[145,353,813,835]" italics="true" pageId="2" pageNumber="425">Referred specimen</emphasis>
: MNHN SAO 202, partial skeleton with partial skull lacking the right tusk and with the alveolar sheaths very damaged. Most of the braincase has been weathered away but the left periotic and a partial tympanic are preserved 
<emphasis id="64A15D5FFF9EFA51FB50FC50B677E9DF" box="[521,597,936,957]" italics="true" pageId="2" pageNumber="425">in situ</emphasis>
. The postcranial skeleton is very poorly preserved, comprising only a few hyoid fragments, 26 partial vertebrae, several rib fragments, the distal half of the left humerus, most of the left radius, a proximal portion of the ulna lacking the olecranon, and fragments of carpals and metacarpals. MNHN PPI 249, a right periotic is referred to 
<taxonomicName id="91D5FACEFF9EFA51FAF2FE86B076EBF0" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[939,1108,381,403]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9EFA51FAF2FE86B7E4EBF1" box="[939,966,382,403]" italics="true" pageId="2" pageNumber="425">O.</emphasis>
cf. 
<emphasis id="64A15D5FFF9EFA51FAA9FE85B076EBF0" box="[1008,1108,381,402]" italics="true" pageId="2" pageNumber="425">leptodon</emphasis>
</taxonomicName>
<emphasis id="64A15D5FFF9EFA51FD0DFE85B07AEBF0" box="[1108,1112,381,402]" italics="true" pageId="2" pageNumber="425">.</emphasis>
</paragraph>
<paragraph id="566A814DFF9EFA51FA70FE53B09FEB9C" blockId="2.[809,1425,427,510]" pageId="2" pageNumber="425">
<emphasis id="64A15D5FFF9EFA51FA70FE53B0BEEBA3" box="[809,1180,427,449]" italics="true" pageId="2" pageNumber="425">Etymology of the species name</emphasis>
: from Greek: 
<emphasis id="64A15D5FFF9EFA51FC09FE53B1B3EBA2" box="[1360,1425,427,448]" italics="true" pageId="2" pageNumber="425">leptos</emphasis>
(thin) and 
<emphasis id="64A15D5FFF9EFA51FAFAFE32B7F8EBBD" box="[931,986,458,479]" italics="true" pageId="2" pageNumber="425">odon</emphasis>
(tooth), in reference to the needle-like morphology of the large right tusk.
</paragraph>
<paragraph id="566A814DFF9EFA51FA70FDEFB073E9FE" blockId="2.[809,1425,534,924]" pageId="2" pageNumber="425">
<emphasis id="64A15D5FFF9EFA51FA70FDEFB7BBE84E" box="[809,921,535,556]" italics="true" pageId="2" pageNumber="425">Diagnosis</emphasis>
: 
<taxonomicName id="91D5FACEFF9EFA51FAE9FDEEB0EAE849" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[944,1224,534,555]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9EFA51FAE9FDEEB0EAE849" box="[944,1224,534,555]" italics="true" pageId="2" pageNumber="425">Odobenocetops leptodon</emphasis>
</taxonomicName>
differs from 
<taxonomicName id="91D5FACEFF9EFA51FC2EFDEFB78AE829" authorityName="Muizon" authorityYear="1993" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9EFA51FC2EFDEFB78AE829" italics="true" pageId="2" pageNumber="425">O. peruvianus</emphasis>
</taxonomicName>
in the morphology of the snout, which is more rounded and wider in dorsal view; in the lack of large premaxillary foramina; in the presence of small depressions for premaxillary sacs in the premaxillae, anterior to the bony nares; in the presence of supplementary rostral bones at the anterodorsal apex of the snout; in the broader, deeper, and longer palate; in the anterior border of the palate, which is more U-shaped, while it is more V-shaped in 
<taxonomicName id="91D5FACEFF9EFA51FC6AFCD3B757E93D" authorityName="Muizon" authorityYear="1993" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9EFA51FC6AFCD3B757E93D" italics="true" pageId="2" pageNumber="425">O. peruvianus</emphasis>
</taxonomicName>
; and in the straight (or slightly concave) anterodorsal border of the orbit, which is deeply concave in 
<taxonomicName id="91D5FACEFF9EFA51FAF0FC7FB068E9FE" authorityName="Muizon" authorityYear="1993" box="[937,1098,903,924]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9EFA51FAF0FC7FB068E9FE" box="[937,1098,903,924]" italics="true" pageId="2" pageNumber="425">O. peruvianus</emphasis>
</taxonomicName>
.
</paragraph>
<paragraph id="566A814DFF9EFA50FA70FC4CB52CEBD0" blockId="2.[809,1425,948,1216]" lastBlockId="3.[159,775,197,434]" lastPageId="3" lastPageNumber="426" pageId="2" pageNumber="425">
<emphasis id="64A15D5FFF9EFA51FA70FC4CB079E9A8" box="[809,1115,948,970]" italics="true" pageId="2" pageNumber="425">Locality, Horizon and Age</emphasis>
: the 
<typeStatus id="896E3FEFFF9EFA51FDC5FC4CB0DFE9A8" box="[1180,1277,948,970]" pageId="2" pageNumber="425" type="holotype">holotype</typeStatus>
and MNHN SAO 202 are from the SAO level of the Pisco Formation in 
<collectingCountry id="2EC2C1DDFF9EFA51FA21FC0AB78DEE65" box="[888,943,1010,1031]" name="Peru" pageId="2" pageNumber="425">Peru</collectingCountry>
(at approximately km 540 of the Panamerican Highway south of 
<collectingRegion id="94114FAFFF9EFA51FD67FBE8B05CEE44" box="[1086,1150,1040,1062]" country="Peru" name="Lima" pageId="2" pageNumber="425">Lima</collectingRegion>
). The SAO horizon has been defined by 
<bibRefCitation id="3244FCBCFF9EFA51FA84FBD7B12BEE27" author="de Muizon C &amp; Bellon H" box="[989,1289,1071,1093]" pageId="2" pageNumber="425" pagination="1063 - 1066" refId="ref22988" refString="de Muizon C, Bellon H. 1980. L'age mio-pliocene de la Formation Pisco (Perou). Comptes Rendus de l'Academie des Sciences, ser. D 290: 1063 - 1066." type="journal article" year="1980">de Muizon &amp; Bellon (1980)</bibRefCitation>
but see also 
<bibRefCitation id="3244FCBCFF9EFA51FA70FBB6B7CDEE06" author="de Muizon C" box="[809,1007,1102,1124]" pageId="2" pageNumber="425" pagination="1 - 160" refId="ref22636" refString="de Muizon C. 1981. Les vertebres fossiles de la formation Pisco (Perou). Premiere partie: Deux nouveaux Monachinae (Phocidae, Mammalia) du Pliocene de Sud-Sacaco. Travaux de l'Institut Francais d'Etudes Andines 22: 1 - 160." type="journal article" year="1981">de Muizon (1981)</bibRefCitation>
, 
<bibRefCitation id="3244FCBCFF9EFA51FAA3FBB6B118EE06" author="de Muizon C &amp; DeVries TJ" box="[1018,1338,1102,1124]" pageId="2" pageNumber="425" pagination="547 - 563" refId="ref23064" refString="de Muizon C, DeVries TJ. 1985. Geology and paleontology of late Cenozoic marine deposits in the Sacaco area (Peru). Geologisches Rundschau 74: 547 - 563." type="journal article" year="1985">de Muizon &amp; DeVries (1985)</bibRefCitation>
, and 
<bibRefCitation id="3244FCBCFF9EFA51FC2FFBB6B01DEEE0" author="de Muizon C &amp; Bellon H" pageId="2" pageNumber="425" pagination="1401 - 1404" refId="ref23023" refString="de Muizon C, Bellon H. 1986. Nouvelles donnees sur l'age de la Formation Pisco (Perou). Comptes Rendus des Seances de l'Academie des Sciences, Ser. II (303): 1401 - 1404." type="journal article" year="1986">de Muizon &amp; Bellon (1986)</bibRefCitation>
. Its age spans approximately from 4 to 3 Ma; therefore, the specimens are early Pliocene in age. The SAO level of the Pisco Formation is slightly younger than the SAS level (5–4 Ma), which yielded the 
<typeStatus id="896E3FEFFF9FFA50F875FF1CB5AFEA98" box="[300,397,228,250]" pageId="3" pageNumber="426" type="holotype">holotype</typeStatus>
of 
<taxonomicName id="91D5FACEFF9FFA50F8E1FF1CB67EEA9B" authorityName="Muizon" authorityYear="1993" box="[440,604,228,249]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50F8E1FF1CB67EEA9B" box="[440,604,228,249]" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
</taxonomicName>
and the third specimen referred to here as a female of 
<taxonomicName id="91D5FACEFF9FFA50FBFDFEFBB4C9EB55" authorityName="Muizon" authorityYear="1993" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50FBFDFEFBB4C9EB55" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
</taxonomicName>
. MNHN PPI 249, an isolated periotic, is from beds of the Pisco Formation located at 
<emphasis id="64A15D5FFF9FFA50FB3BFEB9B64FEB34" box="[610,621,321,342]" italics="true" pageId="3" pageNumber="426">c</emphasis>
. 
<quantity id="912D2CA8FF9FFA50FB25FEB8B691EB34" box="[636,691,320,342]" metricMagnitude="3" metricUnit="m" metricValue="3.0" pageId="3" pageNumber="426" unit="km" value="3.0">3 km</quantity>
east of Yauca (these beds may be slightly younger than those of the SAO horizon and may belong to the late Pliocene).
</paragraph>
<caption id="02AAD1C5FF9EFA51F9C8FBF6B68CEE23" pageId="2" pageNumber="425" startId="2.[145,209,1038,1059]">
<paragraph id="566A814DFF9EFA51F9C8FBF6B68CEE23" blockId="2.[145,761,1038,1090]" pageId="2" pageNumber="425">
<emphasis id="64A15D5FFF9EFA51F9C8FBF6B4CFEE41" bold="true" box="[145,237,1038,1059]" pageId="2" pageNumber="425">Table 1.</emphasis>
Measurements of the holotype of 
<taxonomicName id="91D5FACEFF9EFA51FB39FBF6B594EE23" authority="(SMNK PAL 2492)" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9EFA51FB39FBF6B4C8EE23" italics="true" pageId="2" pageNumber="425">Odobenocetops leptodon</emphasis>
(SMNK PAL 2492)
</taxonomicName>
in mm. (e = estimated)
</paragraph>
</caption>
<paragraph id="566A814DFF9EFA51F9C8FB9EB4EBEE19" blockId="2.[145,758,1126,1881]" box="[145,201,1126,1147]" pageId="2" pageNumber="425">Skull</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFB7CB598EEFB" blockId="2.[145,758,1126,1881]" box="[167,442,1156,1177]" pageId="2" pageNumber="425">Basicondylar length: 415e</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFB59B637EED4" blockId="2.[145,758,1126,1881]" box="[167,533,1184,1207]" pageId="2" pageNumber="425">Bizygomatic width: 150 ¥ 2 = 300e</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFB46B59FEE93" blockId="2.[145,758,1126,1881]" pageId="2" pageNumber="425">Minimum width of the skull posterior to the postorbital processes: 70 ¥ 2 = 140e</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFB01B6EBEF6C" blockId="2.[145,758,1126,1881]" box="[167,713,1273,1294]" pageId="2" pageNumber="425">Maximum width between the postorbital processes:</paragraph>
<caption id="02AAD1C5FF9EFA51FA70FB01B7BAEF2B" pageId="2" pageNumber="425" startId="2.[809,873,1273,1294]">
<paragraph id="566A814DFF9EFA51FA70FB01B7BAEF2B" blockId="2.[809,1425,1273,1353]" pageId="2" pageNumber="425">
<emphasis id="64A15D5FFF9EFA51FA70FB01B7A7EF6C" bold="true" box="[809,901,1273,1294]" pageId="2" pageNumber="425">Table 2.</emphasis>
Measurments of the ear bones of 
<emphasis id="64A15D5FFF9EFA51FDA0FB01B7A0EF4E" italics="true" pageId="2" pageNumber="425">
Obobenocetops 
<taxonomicName id="91D5FACEFF9EFA51FA70FAEFB7A0EF4E" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[809,898,1303,1324]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="2" pageNumber="425" phylum="Chordata" rank="species" species="leptodon">leptodon</taxonomicName>
</emphasis>
(referred specimen, MNHN SAO 202) in mm (e = estimated)
</paragraph>
</caption>
<paragraph id="566A814DFF9EFA51F9E7FAEEB56CEF49" blockId="2.[145,758,1126,1881]" box="[190,334,1301,1324]" pageId="2" pageNumber="425">130 ¥ 2 = 260</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFACCB63EEF2B" blockId="2.[145,758,1126,1881]" box="[167,540,1332,1353]" pageId="2" pageNumber="425">Maximum width of both nares: 59e</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFAA9B66DEF04" blockId="2.[145,758,1126,1881]" box="[167,591,1361,1382]" pageId="2" pageNumber="425">
Maximum length of the left naris: 
<geoCoordinate id="33E1E78AFF9EFA51FB41FAA9B66DEF04" box="[536,591,1361,1382]" degrees="53.5" direction="east" orientation="longitude" pageId="2" pageNumber="425" precision="5555" value="53.5">53.5e</geoCoordinate>
</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFA96B59FEFE1" blockId="2.[145,758,1126,1881]" box="[167,445,1390,1411]" pageId="2" pageNumber="425">Width of the choanae: 104</paragraph>
<paragraph id="566A814DFF9EFA51FA70FA97B758EFE6" blockId="2.[809,1411,1391,1881]" box="[809,890,1391,1412]" pageId="2" pageNumber="425">Periotic</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFA74B5D1EFDC" blockId="2.[145,758,1126,1881]" pageId="2" pageNumber="425">Maximum width of the skull at the level of the exoccipitals: 123.5 ¥ 2 = 257e</paragraph>
<paragraph id="566A814DFF9EFA51FA66FA74B057EFC3" blockId="2.[809,1411,1391,1881]" box="[831,1141,1420,1441]" pageId="2" pageNumber="425">
Anteroposterior length: 
<geoCoordinate id="33E1E78AFF9EFA51FD64FA74B057EFC3" box="[1085,1141,1420,1441]" degrees="77.5" direction="east" orientation="longitude" pageId="2" pageNumber="425" precision="5555" value="77.5">77.5e</geoCoordinate>
</paragraph>
<paragraph id="566A814DFF9EFA51FA66FA51B109EFBE" blockId="2.[809,1411,1391,1881]" pageId="2" pageNumber="425">Maximum width (measured ventrally, approximately perpendicular to anteroposterior length: 42e</paragraph>
<paragraph id="566A814DFF9EFA51F9FEFA3EB4C1EC74" blockId="2.[145,758,1126,1881]" pageId="2" pageNumber="425">Maximum width between the pterygoid crests: 142 Width between the apices of the hamular processes: 112</paragraph>
<paragraph id="566A814DFF9EFA51FA66FA1CB0E3EC56" blockId="2.[809,1411,1391,1881]" pageId="2" pageNumber="425">Length of pars cochlearis from contact with anterior process anteriorly to medial edge of aqueductus cochleae (measured dorsally): 29.5</paragraph>
<paragraph id="566A814DFF9EFA51F9C8F9E6B4DAEC51" blockId="2.[145,758,1126,1881]" box="[145,248,1566,1587]" pageId="2" pageNumber="425">Tympanic</paragraph>
<paragraph id="566A814DFF9EFA51F9FEF9C4B4EAEC0C" blockId="2.[145,758,1126,1881]" pageId="2" pageNumber="425">Length of the lateral lobe of the left tympanic: 54.2 Atlas</paragraph>
<paragraph id="566A814DFF9EFA51FA66F9C4B7A0EC0C" blockId="2.[809,1411,1391,1881]" pageId="2" pageNumber="425">Maximum width of the pars cochlearis in medial view: 30.8</paragraph>
<paragraph id="566A814DFF9EFA51F9FEF98EB628ECE9" blockId="2.[145,758,1126,1881]" box="[167,522,1654,1675]" pageId="2" pageNumber="425">Maximum width of the atlas: 174</paragraph>
<paragraph id="566A814DFF9EFA51FA66F98FB0D3ECEE" blockId="2.[809,1411,1391,1881]" box="[831,1265,1655,1676]" pageId="2" pageNumber="425">Length of internal auditory meatus: 14.3</paragraph>
<paragraph id="566A814DFF9EFA51F9FEF96CB4EAED63" blockId="2.[145,758,1126,1881]" pageId="2" pageNumber="425">Maximum height of the atlas at sagittal plane: 106 Maximum vertical diameter of neural canal: 64.5 Maximum horizontal diameter of neural canal: 56.5 Limb</paragraph>
<paragraph id="566A814DFF9EFA51FA70F96CB7B2ECCB" blockId="2.[809,1411,1391,1881]" box="[809,912,1684,1705]" pageId="2" pageNumber="425">Tympanic</paragraph>
<paragraph id="566A814DFF9EFA51FA66F949B75FEC86" blockId="2.[809,1411,1391,1881]" pageId="2" pageNumber="425">Length of the involucrum (measured medially): 58.8 Malleus</paragraph>
<paragraph id="566A814DFF9EFA51FA66F914B7A3ED7C" blockId="2.[809,1411,1391,1881]" pageId="2" pageNumber="425">
Maximum length in posteromedial view (cf. 
<figureCitation id="CEEE9DC8FF9EFA51FC4DF914B153ED63" box="[1300,1393,1772,1793]" captionStart="Figure 10" captionStartId="12.[809,888,1388,1409]" captionTargetBox="[818,1418,964,1357]" captionTargetId="figure-255@12.[815,1424,959,1365]" captionTargetPageId="12" captionText="Figure 10 Odobenocetops leptodon, referred specimen (MNHN SAO 202). Malleus in posteromedial view (A); incus in ventral view (B). Abbreviations: ast, articular facet for the stapes; cb, crus breve; cl, crus longum; icf, articular facets for the incus; mn, manubrium; pm, processus muscularis; tu, tuberculum." figureDoi="http://doi.org/10.5281/zenodo.4687201" httpUri="https://zenodo.org/record/4687201/files/figure.png" pageId="2" pageNumber="425">Fig. 10A</figureCitation>
): 11.4
</paragraph>
<paragraph id="566A814DFF9EFA51F9FEF8F1B63DED7C" blockId="2.[145,758,1126,1881]" box="[167,543,1801,1822]" pageId="2" pageNumber="425">Maximum length of the radius: 117</paragraph>
<paragraph id="566A814DFF9EFA51F9FEF8DEB681ED3B" blockId="2.[145,758,1126,1881]" pageId="2" pageNumber="425">Anteroposterior length of distal end of humerus: 60.1 Mediolateral width of distal end of humerus: 43</paragraph>
<paragraph id="566A814DFF9EFA51FA66F8DFB7A0ED3B" blockId="2.[809,1411,1391,1881]" pageId="2" pageNumber="425">
Maximum width in posteromedial view (cf. 
<figureCitation id="CEEE9DC8FF9EFA51FC54F8DFB148ED5E" box="[1293,1386,1831,1852]" captionStart="Figure 10" captionStartId="12.[809,888,1388,1409]" captionTargetBox="[818,1418,964,1357]" captionTargetId="figure-255@12.[815,1424,959,1365]" captionTargetPageId="12" captionText="Figure 10 Odobenocetops leptodon, referred specimen (MNHN SAO 202). Malleus in posteromedial view (A); incus in ventral view (B). Abbreviations: ast, articular facet for the stapes; cb, crus breve; cl, crus longum; icf, articular facets for the incus; mn, manubrium; pm, processus muscularis; tu, tuberculum." figureDoi="http://doi.org/10.5281/zenodo.4687201" httpUri="https://zenodo.org/record/4687201/files/figure.png" pageId="2" pageNumber="425">Fig. 10A</figureCitation>
): 6.05
</paragraph>
<paragraph id="566A814DFF9FFA50F828FE1FB616EB9D" blockId="3.[369,564,487,511]" box="[369,564,487,511]" pageId="3" pageNumber="426">DESCRIPTION</paragraph>
<paragraph id="566A814DFF9FFA50F9C6FDEEB664E8EA" blockId="3.[159,775,534,648]" pageId="3" pageNumber="426">
The following description focuses on the differences between the two species of 
<taxonomicName id="91D5FACEFF9FFA50F88DFDCDB659E828" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[468,635,565,586]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9FFA50F88DFDCDB659E828" box="[468,635,565,586]" italics="true" pageId="3" pageNumber="426">Odobenocetops</emphasis>
</taxonomicName>
. We refer to 
<bibRefCitation id="3244FCBCFF9FFA50F9C6FDACB58EE808" author="de Muizon C &amp; Domning DP &amp; Ketten DR" box="[159,428,596,618]" pageId="3" pageNumber="426" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF9FFA50F87BFDADB577E80B" box="[290,341,596,618]" italics="true" pageId="3" pageNumber="426">et al</emphasis>
. (2002)
</bibRefCitation>
for the aspects of the cranial anatomy common to the two species.
</paragraph>
<paragraph id="566A814DFF9FFA50F839FD3DB664E8B9" blockId="3.[352,582,709,733]" box="[352,582,709,733]" pageId="3" pageNumber="426">GENERAL FEATURES</paragraph>
<paragraph id="566A814DFF9FFA50F9C6FD15B507EF49" blockId="3.[159,775,749,1446]" pageId="3" pageNumber="426">
The general morphology of the skull of 
<taxonomicName id="91D5FACEFF9FFA50FB39FD15B522E943" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50FB39FD15B522E943" italics="true" pageId="3" pageNumber="426">Odobenocetops leptodon</emphasis>
</taxonomicName>
is similar to that of 
<taxonomicName id="91D5FACEFF9FFA50F8BFFCF4B6A4E943" authorityName="Muizon" authorityYear="1993" box="[486,646,780,801]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50F8BFFCF4B6A4E943" box="[486,646,780,801]" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
</taxonomicName>
in its basic pattern (
<figureCitation id="CEEE9DC8FF9FFA50F85BFCD2B547E923" box="[258,357,810,833]" captionStart-0="Figure 1" captionStart-1="Figure 2" captionStart-2="Figure 3" captionStart-3="Figure 4" captionStartId-0="3.[823,902,1340,1361]" captionStartId-1="4.[145,224,1254,1275]" captionStartId-2="5.[159,238,932,953]" captionStartId-3="6.[145,224,1088,1109]" captionTargetBox-0="[842,1419,198,1308]" captionTargetBox-1="[308,1262,197,1223]" captionTargetBox-2="[172,1434,196,900]" captionTargetBox-3="[156,757,200,1057]" captionTargetId-0="figure-576@3.[836,1445,193,1316]" captionTargetId-1="figure-331@4.[305,1265,195,1234]" captionTargetId-2="figure-533@5.[167,1448,190,916]" captionTargetId-3="figure-707@6.[153,762,195,1063]" captionTargetPageId-0="3" captionTargetPageId-1="4" captionTargetPageId-2="5" captionTargetPageId-3="6" captionText-0="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." captionText-1="Figure 2. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views." captionText-2="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." captionText-3="Figure 4. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in lateral left (A) and lateral right (B) views." figureDoi-0="http://doi.org/10.5281/zenodo.4687171" figureDoi-1="http://doi.org/10.5281/zenodo.4687175" figureDoi-2="http://doi.org/10.5281/zenodo.4687177" figureDoi-3="http://doi.org/10.5281/zenodo.4687181" httpUri-0="https://zenodo.org/record/4687171/files/figure.png" httpUri-1="https://zenodo.org/record/4687175/files/figure.png" httpUri-2="https://zenodo.org/record/4687177/files/figure.png" httpUri-3="https://zenodo.org/record/4687181/files/figure.png" pageId="3" pageNumber="426">Figs 1–4</figureCitation>
). However, in dorsal view, the former differs from the latter in the morphology of the snout, which is much wider and more blunt. In anterior view the snout was more massive. Furthermore, if a melon was actually present, as hypothesized below, it is likely that the head of 
<taxonomicName id="91D5FACEFF9FFA50F8F1FC3CB609E9BB" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[424,555,964,985]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50F8F1FC3CB609E9BB" box="[424,555,964,985]" italics="true" pageId="3" pageNumber="426">O. leptodon</emphasis>
</taxonomicName>
was more rounded than that of 
<taxonomicName id="91D5FACEFF9FFA50F86EFC1BB5F8E99A" authorityName="Muizon" authorityYear="1993" box="[311,474,995,1016]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50F86EFC1BB5F8E99A" box="[311,474,995,1016]" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
</taxonomicName>
. The skull of 
<taxonomicName id="91D5FACEFF9FFA50FBDBFC1BB725E995" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[642,775,994,1016]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50FBDBFC1BB725E995" box="[642,775,994,1016]" italics="true" pageId="3" pageNumber="426">O. leptodon</emphasis>
</taxonomicName>
has the same bilobate outline as is observed in 
<emphasis id="64A15D5FFF9FFA50FBF5FBFAB4D0EE57" italics="true" pageId="3" pageNumber="426">
<taxonomicName id="91D5FACEFF9FFA50FBF5FBFAB4CCEE57" authorityName="Muizon" authorityYear="1993" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
which is unique in a Neogene odontocete (
<bibRefCitation id="3244FCBCFF9FFA50F9FEFBC6B59EEE37" author="de Muizon C &amp; Domning DP &amp; Ketten DR" box="[167,444,1086,1109]" pageId="3" pageNumber="426" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF9FFA50F869FBC7B544EE31" box="[304,358,1086,1108]" italics="true" pageId="3" pageNumber="426">et al</emphasis>
., 2002
</bibRefCitation>
). This condition, where the frontals and maxillae do not overhang the temporal fossa, is found in primitive odontocetes such as 
<taxonomicName id="91D5FACEFF9FFA50F9C6FB62B507EECD" authorityName="Kellogg" authorityYear="1923" box="[159,293,1178,1199]" class="Mammalia" family="Remingtonocetidae" genus="Xenorophus" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9FFA50F9C6FB62B507EECD" box="[159,293,1178,1199]" italics="true" pageId="3" pageNumber="426">Xenorophus</emphasis>
</taxonomicName>
, 
<taxonomicName id="91D5FACEFF9FFA50F861FB62B598EECD" authorityName="Cope" authorityYear="1895" box="[312,442,1178,1199]" class="Mammalia" family="Agorophiidae" genus="Agorophius" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9FFA50F861FB62B598EECD" box="[312,442,1178,1199]" italics="true" pageId="3" pageNumber="426">Agorophius</emphasis>
</taxonomicName>
and 
<taxonomicName id="91D5FACEFF9FFA50F8A7FB62B68EEECD" authorityName="Allen" authorityYear="1921" box="[510,684,1178,1199]" class="Mammalia" family="Remingtonocetidae" genus="Archaeodelphis" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9FFA50F8A7FB62B68EEECD" box="[510,684,1178,1199]" italics="true" pageId="3" pageNumber="426">Archaeodelphis</emphasis>
</taxonomicName>
and in archaeocetes because of the lesser telescoping of the skull (
<bibRefCitation id="3244FCBCFF9FFA50F9BCFB20B5A0EE8C" author="Kellogg, AR" box="[229,386,1240,1262]" pageId="3" pageNumber="426" pagination="1 - 366" refId="ref22423" refString="Kellogg, AR. 1936. A review of the Archaeoceti. Carnegie Institute of Washington Publication 482: 1 - 366." type="journal article" year="1936">Kellogg, 1936</bibRefCitation>
; 
<bibRefCitation id="3244FCBCFF9FFA50F8D4FB20B60DEE8C" author="Fordyce RE" box="[397,559,1240,1262]" pageId="3" pageNumber="426" pagination="1028 - 1045" refId="ref21922" refString="Fordyce RE. 1981. Systematics of the odontocete Agorophius pygmaeus and the family Agorophiidae (Mammalia: Cetacea). Journal of Paleontology 55: 1028 - 1045." type="journal article" year="1981">Fordyce, 1981</bibRefCitation>
). In 
<taxonomicName id="91D5FACEFF9FFA50FB39FB20B725EE8F" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[608,775,1240,1261]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9FFA50FB39FB20B725EE8F" box="[608,775,1240,1261]" italics="true" pageId="3" pageNumber="426">Odobenocetops</emphasis>
</taxonomicName>
it is regarded as a reversal of this typically cetacean telescoping.
</paragraph>
<paragraph id="566A814DFF9FFA50F9E1FACCB677EFC4" blockId="3.[159,775,749,1446]" pageId="3" pageNumber="426">
In general, the skull of 
<taxonomicName id="91D5FACEFF9FFA50F897FACCB671EF2B" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[462,595,1332,1353]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50F897FACCB671EF2B" box="[462,595,1332,1353]" italics="true" pageId="3" pageNumber="426">O. leptodon</emphasis>
</taxonomicName>
is very heavily built and the bone is much denser, thicker, and more solid than in other delphinoids, being almost osteosclerotic in its posteroventrolateral angle.
</paragraph>
<caption id="02AAD1C5FF9FFA50FA6EFAC4B11DEFE9" ID-DOI="http://doi.org/10.5281/zenodo.4687171" ID-Zenodo-Dep="4687171" httpUri="https://zenodo.org/record/4687171/files/figure.png" pageId="3" pageNumber="426" startId="3.[823,902,1340,1361]" targetBox="[842,1419,198,1308]" targetPageId="3">
<paragraph id="566A814DFF9FFA50FA6EFAC4B11DEFE9" blockId="3.[823,1439,1340,1419]" pageId="3" pageNumber="426">
<emphasis id="64A15D5FFF9FFA50FA6EFAC4B792EF33" bold="true" box="[823,944,1340,1361]" pageId="3" pageNumber="426">Figure 1.</emphasis>
<taxonomicName id="91D5FACEFF9FFA50FAE2FAC4B0E1EF33" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[955,1219,1340,1361]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50FAE2FAC4B0E1EF33" box="[955,1219,1340,1361]" italics="true" pageId="3" pageNumber="426">Odobenocetops leptodon</emphasis>
</taxonomicName>
, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B).
</paragraph>
</caption>
<paragraph id="566A814DFF9FFA50F8D2FA1AB639EF98" blockId="3.[395,539,1506,1530]" box="[395,539,1506,1530]" pageId="3" pageNumber="426">PREMAXILLA</paragraph>
<paragraph id="566A814DFF9FFA57F9C6F9F2B7B9EFA6" blockId="3.[159,775,1546,1906]" lastBlockId="4.[809,1425,1393,1906]" lastPageId="4" lastPageNumber="427" pageId="3" pageNumber="426">
The premaxillae of 
<taxonomicName id="91D5FACEFF9FFA50F8D8F9F3B627EC7D" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[385,517,1546,1568]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50F8D8F9F3B627EC7D" box="[385,517,1546,1568]" italics="true" pageId="3" pageNumber="426">O. leptodon</emphasis>
</taxonomicName>
are built on the same pattern as those of 
<taxonomicName id="91D5FACEFF9FFA50F8D0F9D2B4C0EC3C" authority="(de Muizon et al., 2002)" baseAuthorityName="de Muizon" baseAuthorityYear="2002" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50F8D0F9D2B60FEC5D" box="[393,557,1578,1599]" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
(
<bibRefCitation id="3244FCBCFF9FFA50FB66F9D1B4F8EC3C" author="de Muizon C &amp; Domning DP &amp; Ketten DR" pageId="3" pageNumber="426" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF9FFA50FB9CF9D2B6DBEC5C" box="[709,761,1577,1599]" italics="true" pageId="3" pageNumber="426">et al</emphasis>
., 2002
</bibRefCitation>
)
</taxonomicName>
. They both present a large alveolar process housing one tusk, the right tusk (of the presumed male, which is the only sex represented) being much larger than the left. Since the left alveolar process is not preserved on the 
<typeStatus id="896E3FEFFF9FFA50F8F9F93AB623ECBA" box="[416,513,1730,1752]" pageId="3" pageNumber="426" type="holotype">holotype</typeStatus>
of 
<taxonomicName id="91D5FACEFF9FFA50FB72F93BB6ECECBA" box="[555,718,1731,1752]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50FB72F93BB6ECECBA" box="[555,718,1731,1752]" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
</taxonomicName>
(the only specimen known when this species was first described) and because there are no other mammals which exhibit pronounced cranial asymmetry, it was hypothesized that the processes sheathing the tusks were both of the same size and that, consequently, the left tusk (which was judged to be shorter than the right sheath) was not erupted. The 
<typeStatus id="896E3FEFFF9FFA50FDADFA14B177EC60" box="[1268,1365,1516,1538]" pageId="3" pageNumber="426" type="holotype">holotype</typeStatus>
of 
<emphasis id="64A15D5FFF9FFA50FCDCFA14B7BCEC7D" italics="true" pageId="3" pageNumber="426">
<taxonomicName id="91D5FACEFF9FFA50FCDCFA14B7B8EC7D" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">O. leptodon</taxonomicName>
,
</emphasis>
however, indicates that the left sheath was clearly smaller than the right and that the left tusk was actually erupted. It is therefore probable that the condition of 
<taxonomicName id="91D5FACEFF9FFA50FD52F99FB0B5EC19" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1035,1175,1638,1660]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50FD52F99FB0B5EC19" box="[1035,1175,1638,1660]" italics="true" pageId="3" pageNumber="426">O. leptodon</emphasis>
</taxonomicName>
was also present in 
<taxonomicName id="91D5FACEFF9FFA50FA6EF97EB7FAECF9" box="[823,984,1670,1691]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9FFA50FA6EF97EB7FAECF9" box="[823,984,1670,1691]" italics="true" pageId="3" pageNumber="426">O. peruvianus</emphasis>
</taxonomicName>
. In the 
<typeStatus id="896E3FEFFF9FFA50FD6CF97DB0B4ECF9" box="[1077,1174,1669,1691]" pageId="3" pageNumber="426" type="holotype">holotype</typeStatus>
of 
<taxonomicName id="91D5FACEFF9FFA50FDE3F97EB11FECF8" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1210,1341,1669,1691]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="3" pageNumber="426" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9FFA50FDE3F97EB11FECF8" box="[1210,1341,1669,1691]" italics="true" pageId="3" pageNumber="426">O. leptodon</emphasis>
</taxonomicName>
, the left sheath is transversely flattened and lies almost in a parasagittal plane (it diverges only slightly laterally). The right sheath is thicker because of the larger size of the tusk and diverges more markedly laterally. The region of the sheaths anterior to the tusks is strongly flattened and forms a posteriorly bent U-shaped lamina which borders the palate anteriorly. The anteroventral edge of this lamina is 
<quantity id="912D2CA8FF98FA57FB13FA89B68FEFE5" box="[586,685,1393,1415]" metricMagnitude="-3" metricUnit="m" metricValue="7.5" metricValueMax="10.0" metricValueMin="5.0" pageId="4" pageNumber="427" unit="cm" value="0.75" valueMax="1.0" valueMin="0.5">0.5–1 cm</quantity>
thick, and presents longitudinal irregular ridges of bone to which was firmly attached the strong upper lip that was very probably present in 
<taxonomicName id="91D5FACEFF98FA57F885FA36B67FEF80" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[476,605,1485,1507]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF98FA57F885FA36B67FEF80" box="[476,605,1485,1507]" italics="true" pageId="4" pageNumber="427">O. leptodon</emphasis>
</taxonomicName>
as in 
<taxonomicName id="91D5FACEFF98FA57FBC7FA36B4FFEC63" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF98FA57FBC7FA36B4FFEC63" italics="true" pageId="4" pageNumber="427">O. peruvianus</emphasis>
</taxonomicName>
. The anterior and anterolateral side of each premaxillary sheath is a broad convex surface bearing several large grooves and foramina. These structures indicate an extensive vascularization of the anterior region of the skull, which is regarded here as related to the presence of a thick, muscular upper lip. In anterior view, in the sagittal plane, the snout is more elevated than in 
<taxonomicName id="91D5FACEFF98FA57F83CF93BB629ECBA" box="[357,523,1731,1752]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF98FA57F83CF93BB629ECBA" box="[357,523,1731,1752]" italics="true" pageId="4" pageNumber="427">O. peruvianus</emphasis>
</taxonomicName>
and the surface of attachment of the upper lip is larger. Furthermore, the snout is wider in anterior view, and the anterior edge of the palate is grossly U-shaped rather than more Vshaped as in 
<taxonomicName id="91D5FACEFF98FA57F872F8C6B5EEED31" box="[299,460,1854,1875]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF98FA57F872F8C6B5EEED31" box="[299,460,1854,1875]" italics="true" pageId="4" pageNumber="427">O. peruvianus</emphasis>
</taxonomicName>
. Therefore it is clear that the upper lip of 
<taxonomicName id="91D5FACEFF98FA57F814F8A4B5F3ED13" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[333,465,1884,1905]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF98FA57F814F8A4B5F3ED13" box="[333,465,1884,1905]" italics="true" pageId="4" pageNumber="427">O. leptodon</emphasis>
</taxonomicName>
was much larger than in 
<emphasis id="64A15D5FFF98FA57FA70FA8AB7FBEFE5" box="[809,985,1394,1415]" italics="true" pageId="4" pageNumber="427">
<taxonomicName id="91D5FACEFF98FA57FA70FA8AB7F7EFE5" box="[809,981,1394,1415]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
indicating a larger vibrissal array and/or better suction ability in the former than in the latter.
</paragraph>
<caption id="02AAD1C5FF98FA57F9C8FB1EB4F1EF7B" ID-DOI="http://doi.org/10.5281/zenodo.4687175" ID-Zenodo-Dep="4687175" httpUri="https://zenodo.org/record/4687175/files/figure.png" pageId="4" pageNumber="427" startId="4.[145,224,1254,1275]" targetBox="[308,1262,197,1223]" targetPageId="4">
<paragraph id="566A814DFF98FA57F9C8FB1EB4F1EF7B" blockId="4.[145,1425,1254,1305]" pageId="4" pageNumber="427">
<emphasis id="64A15D5FFF98FA57F9C8FB1EB4D9EE99" bold="true" box="[145,251,1254,1275]" pageId="4" pageNumber="427">Figure 2.</emphasis>
<taxonomicName id="91D5FACEFF98FA57F85EFB1EB623EE99" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[263,513,1254,1275]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF98FA57F85EFB1EB623EE99" box="[263,513,1254,1275]" italics="true" pageId="4" pageNumber="427">Odobenocetops leptodon</emphasis>
</taxonomicName>
, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views.
</paragraph>
</caption>
<paragraph id="566A814DFF98FA56FA18FA35B5A9EC1E" blockId="4.[809,1425,1393,1906]" lastBlockId="5.[159,775,1056,1906]" lastPageId="5" lastPageNumber="428" pageId="4" pageNumber="427">
Dorsally, the morphology of the premaxillae of 
<taxonomicName id="91D5FACEFF98FA57FC2EFA35B7A8EC63" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF98FA57FC2EFA35B7A8EC63" italics="true" pageId="4" pageNumber="427">O. leptodon</emphasis>
</taxonomicName>
presents the major characters which differentiate this species from 
<taxonomicName id="91D5FACEFF98FA57FD09F9F3B0D0EC42" box="[1104,1266,1547,1568]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF98FA57FD09F9F3B0D0EC42" box="[1104,1266,1547,1568]" italics="true" pageId="4" pageNumber="427">O. peruvianus</emphasis>
</taxonomicName>
. These bones are much wider than in 
<emphasis id="64A15D5FFF98FA57FD1CF9D1B0CCEC5D" box="[1093,1262,1577,1599]" italics="true" pageId="4" pageNumber="427">
<taxonomicName id="91D5FACEFF98FA57FD1CF9D1B0C8EC5D" box="[1093,1258,1577,1599]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
and the right premaxilla is more expanded laterally because of the greater size of the tusk (
<figureCitation id="CEEE9DC8FF98FA57FD14F99EB08AEC1E" box="[1101,1192,1638,1660]" captionStart="Figure 2" captionStartId="4.[145,224,1254,1275]" captionTargetBox="[308,1262,197,1223]" captionTargetId="figure-331@4.[305,1265,195,1234]" captionTargetPageId="4" captionText="Figure 2. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687175" httpUri="https://zenodo.org/record/4687175/files/figure.png" pageId="4" pageNumber="427">Figs 2A</figureCitation>
and 
<figureCitation id="CEEE9DC8FF98FA57FDBFF99FB12BEC1F" box="[1254,1289,1639,1661]" captionStart="Figure 3" captionStartId="5.[159,238,932,953]" captionTargetBox="[172,1434,196,900]" captionTargetId="figure-533@5.[167,1448,190,916]" captionTargetPageId="5" captionText="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="4" pageNumber="427">3A</figureCitation>
). There are no enlarged premaxillary foramina as are observed in the other odontocetes, including 
<taxonomicName id="91D5FACEFF98FA57FDF0F95CB16FECDB" box="[1193,1357,1700,1721]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF98FA57FDF0F95CB16FECDB" box="[1193,1357,1700,1721]" italics="true" pageId="4" pageNumber="427">O. peruvianus</emphasis>
</taxonomicName>
. This absence is regarded as a loss in 
<taxonomicName id="91D5FACEFF98FA57FDC5F93BB13DECB5" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1180,1311,1730,1752]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF98FA57FDC5F93BB13DECB5" box="[1180,1311,1730,1752]" italics="true" pageId="4" pageNumber="427">O. leptodon</emphasis>
</taxonomicName>
which, in this respect, is more derived than 
<taxonomicName id="91D5FACEFF98FA57FDECF919B174EC95" box="[1205,1366,1761,1783]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="4" pageNumber="427" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF98FA57FDECF919B174EC95" box="[1205,1366,1761,1783]" italics="true" pageId="4" pageNumber="427">O. peruvianus</emphasis>
</taxonomicName>
. The premaxillary foramina transmit branches of the internal maxillary artery and maxillary nerve from the infraorbital foramen (internal to the orbit) to parts of the nasofacial muscles anteriorly and posteriorly on the rostrum (see e.g. 
<bibRefCitation id="3244FCBCFF99FA56F8D7FBD8B676EE57" author="Schenkkan EJ" box="[398,596,1056,1078]" pageId="5" pageNumber="428" pagination="127 - 159" refId="ref23287" refString="Schenkkan EJ. 1973. On the comparative anatomy and function of the nasal tracts in odontocetes (Mammalia, Cetacea). Bijdragen tot de Dierkunde 43: 127 - 159." type="journal article" year="1973">Schenkkan, 1973</bibRefCitation>
: fig. 5, on 
<taxonomicName id="91D5FACEFF99FA56FB9CFBD8B560EE31" baseAuthorityName="Sowerby" baseAuthorityYear="1804" class="Mammalia" family="Hyperoodontidae" genus="Mesoplodon" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="bidens">
<emphasis id="64A15D5FFF99FA56FB9CFBD8B560EE31" italics="true" pageId="5" pageNumber="428">Mesoplodon bidens</emphasis>
</taxonomicName>
). In 
<taxonomicName id="91D5FACEFF99FA56F8DAFBC6B608EE31" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[387,554,1086,1107]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF99FA56F8DAFBC6B608EE31" box="[387,554,1086,1107]" italics="true" pageId="5" pageNumber="428">Odobenocetops</emphasis>
</taxonomicName>
these vessels and nerves are probably related to the irrigation and innervation of the strong upper lips and associated musculature as well as the possible vibrissae. In 
<taxonomicName id="91D5FACEFF99FA56FBB4FB63B522EEAC" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF99FA56FBB4FB63B522EEAC" italics="true" pageId="5" pageNumber="428">O. leptodon</emphasis>
</taxonomicName>
the canals conducting the nerves and vessels do not open dorsally but are clearly present. This is observed on the referred skull MNHN SAO 202 (
<figureCitation id="CEEE9DC8FF99FA56FB82FB0EB4E3EF49" captionStart="Figure 3" captionStartId="5.[159,238,932,953]" captionTargetBox="[172,1434,196,900]" captionTargetId="figure-533@5.[167,1448,190,916]" captionTargetPageId="5" captionText="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="5" pageNumber="428">Fig. 3A</figureCitation>
), in which the apex of the snout is eroded above the pulp cavity of the tusks. The canals passed above the proximal extremities of the tusks and apparently (clearly observable on the right side) divided into several smaller canals perforating the premaxillae to reach the upper lip anteriorly. Ramifications of the premaxillary canals are also observable on the lateral side of the premaxilla at the level of the antorbital notch, where several large foramina are present. It is likely that irrigation and innervation for the pulp cavities of the tusks were also transported by the premaxillary canals.
</paragraph>
<caption id="02AAD1C5FF99FA56F9C6FC5CB514E9B4" ID-DOI="http://doi.org/10.5281/zenodo.4687177" ID-Zenodo-Dep="4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="5" pageNumber="428" startId="5.[159,238,932,953]" targetBox="[172,1434,196,900]" targetPageId="5">
<paragraph id="566A814DFF99FA56F9C6FC5CB514E9B4" blockId="5.[159,1439,932,982]" pageId="5" pageNumber="428">
<emphasis id="64A15D5FFF99FA56F9C6FC5CB52AE9DB" bold="true" box="[159,264,932,953]" pageId="5" pageNumber="428">Figure 3.</emphasis>
<emphasis id="64A15D5FFF99FA56F84DFC5CB636E9DB" box="[276,532,932,953]" italics="true" pageId="5" pageNumber="428">
<taxonomicName id="91D5FACEFF99FA56F84DFC5CB62DE9DB" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[276,527,932,953]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="leptodon">Odobenocetops leptodon</taxonomicName>
,
</emphasis>
referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views.
</paragraph>
</caption>
<paragraph id="566A814DFF99FA56F9E1F97DB0F9EE8C" blockId="5.[159,775,1056,1906]" lastBlockId="5.[823,1439,1056,1906]" pageId="5" pageNumber="428">
The premaxillae of 
<taxonomicName id="91D5FACEFF99FA56F8CAF97DB637ECF8" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[403,533,1669,1690]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF99FA56F8CAF97DB637ECF8" box="[403,533,1669,1690]" italics="true" pageId="5" pageNumber="428">O. leptodon</emphasis>
</taxonomicName>
bear a small concave area, anterior to the bony nares, where lay the premaxillary sacs of the air sac system (
<bibRefCitation id="3244FCBCFF99FA56FB34F93AB6D9ECBA" author="Mead JG" box="[621,763,1730,1752]" pageId="5" pageNumber="428" pagination="1 - 72" refId="ref22579" refString="Mead JG. 1975. Anatomy of the external nasal passages and facial complex in the Delphinidae (Mammalia, Cetacea). Smithsonian Contributions to Zoology 207: 1 - 72." type="journal article" year="1975">Mead, 1975</bibRefCitation>
). These fossae for the premaxillary sacs are limited medially by the medial border of the premaxilla which overhangs the vomerian gutter; they are limited anteromedially by the suture with the rostral supplementary bone (see below); and anterolaterally they are medial to the posterior edge of each tusk alveolus (
<figureCitation id="CEEE9DC8FF99FA56FC34FBD8B77BEE31" captionStart="Figure 2" captionStartId="4.[145,224,1254,1275]" captionTargetBox="[308,1262,197,1223]" captionTargetId="figure-331@4.[305,1265,195,1234]" captionTargetPageId="4" captionText="Figure 2. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687175" httpUri="https://zenodo.org/record/4687175/files/figure.png" pageId="5" pageNumber="428">Figs 2A</figureCitation>
, 
<figureCitation id="CEEE9DC8FF99FA56FA3DFBC6B7A1EE31" box="[868,899,1086,1107]" captionStart="Figure 3" captionStartId="5.[159,238,932,953]" captionTargetBox="[172,1434,196,900]" captionTargetId="figure-533@5.[167,1448,190,916]" captionTargetPageId="5" captionText="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="5" pageNumber="428">3A</figureCitation>
and 
<figureCitation id="CEEE9DC8FF99FA56FAE3FBC6B7EBEE36" box="[954,969,1086,1108]" captionStart="Figure 5" captionStartId="7.[159,238,713,734]" captionTargetBox="[194,777,156,678]" captionTargetId="figure-812@7.[167,777,154,713]" captionTargetPageId="7" captionText="Figure 5. Reconstruction of the dorsal view of the rostrum of Odobenocetops leptodon. Abbreviations: Fps, fossa for the premaxillary sac; Fr, frontal; Mx, maxilla; NaF, narial fossa; Pmx, premaxilla; Sb, supplementary bone." figureDoi="http://doi.org/10.5281/zenodo.4687183" httpUri="https://zenodo.org/record/4687183/files/figure.png" pageId="5" pageNumber="428">5</figureCitation>
). Fossae for premaxillary sacs are absent in 
<emphasis id="64A15D5FFF99FA56FA0EFBA5B022EE11" box="[855,1024,1117,1139]" italics="true" pageId="5" pageNumber="428">
<taxonomicName id="91D5FACEFF99FA56FA0EFBA5B7DEEE11" box="[855,1020,1117,1139]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
where the space between the large premaxillary foramina and the anterior edge of the nares is so reduced that it was supposed that the premaxillary sacs were either very reduced or absent in this species (
<bibRefCitation id="3244FCBCFF99FA56FA92FB20B0EDEE8C" author="de Muizon C &amp; Domning DP &amp; Ketten DR" box="[971,1231,1240,1262]" pageId="5" pageNumber="428" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF99FA56FD15FB20B05CEE8F" box="[1100,1150,1240,1261]" italics="true" pageId="5" pageNumber="428">et al</emphasis>
., 2002
</bibRefCitation>
).
</paragraph>
<paragraph id="566A814DFF99FA56FA09FB0EB0B8EC3C" blockId="5.[823,1439,1056,1906]" pageId="5" pageNumber="428">
On the dorsal face of the skull the premaxillae of 
<taxonomicName id="91D5FACEFF99FA56FA6EFAEDB79AEF48" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[823,952,1301,1322]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF99FA56FA6EFAEDB79AEF48" box="[823,952,1301,1322]" italics="true" pageId="5" pageNumber="428">O. leptodon</emphasis>
</taxonomicName>
extend further posteriorly than in 
<taxonomicName id="91D5FACEFF99FA56FC1AFAEDB7A1EF2B" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF99FA56FC1AFAEDB7A1EF2B" italics="true" pageId="5" pageNumber="428">O. peruvianus</emphasis>
</taxonomicName>
. The posterior extremity of the left premaxilla is damaged on MNHN SAO 202, but it is clear that it lay slightly posterior to the posterior border of the nares. The posterior extremity of the right premaxilla lies about 
<quantity id="912D2CA8FF99FA56FAF5FA56B7FDEFA6" box="[940,991,1454,1476]" metricMagnitude="-2" metricUnit="m" metricValue="5.0" pageId="5" pageNumber="428" unit="cm" value="5.0">5 cm</quantity>
posterior to the nares. On the 
<typeStatus id="896E3FEFFF99FA56FC67FA56B1BDEFA6" box="[1342,1439,1454,1476]" pageId="5" pageNumber="428" type="holotype">holotype</typeStatus>
of 
<emphasis id="64A15D5FFF99FA56FA0EFA35B020EF81" box="[855,1026,1485,1507]" italics="true" pageId="5" pageNumber="428">
<taxonomicName id="91D5FACEFF99FA56FA0EFA35B7DCEF81" box="[855,1022,1485,1507]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
the posterior extremity of the left premaxilla is located half-way between the anterior and posterior limits of the naris and on the right side (as well as on both sides of SMNK PAL 2491) it reaches the posterior edge of the naris.
</paragraph>
<paragraph id="566A814DFF99FA55FA09F99EB5D1EF49" blockId="5.[823,1439,1056,1906]" lastBlockId="6.[145,761,1240,1906]" lastPageId="6" lastPageNumber="429" pageId="5" pageNumber="428">
The Pmx-Mx suture is external to the nares, the border of which is formed by the maxillae only, in contrast to the condition of 
<taxonomicName id="91D5FACEFF99FA56FD02F95CB0DDECDB" box="[1115,1279,1700,1721]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF99FA56FD02F95CB0DDECDB" box="[1115,1279,1700,1721]" italics="true" pageId="5" pageNumber="428">O. peruvianus</emphasis>
</taxonomicName>
in which the Pmx-Mx suture is internal to the nares in the anterior two-thirds of their length. In their dorsal portions the premaxillae of 
<taxonomicName id="91D5FACEFF99FA56FABCF8F8B04BED77" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[997,1129,1792,1813]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF99FA56FABCF8F8B04BED77" box="[997,1129,1792,1813]" italics="true" pageId="5" pageNumber="428">O. leptodon</emphasis>
</taxonomicName>
are relatively flat and not as salient as is observed in 
<taxonomicName id="91D5FACEFF99FA56FD31F8E7B125ED56" box="[1128,1287,1823,1844]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="5" pageNumber="428" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF99FA56FD31F8E7B125ED56" box="[1128,1287,1823,1844]" italics="true" pageId="5" pageNumber="428">O. peruvianus</emphasis>
</taxonomicName>
. This feature is clearly observed on the lateral edges of the nares and at the level of the antorbital notch, where the premaxillae markedly overhang the maxillae in 
<taxonomicName id="91D5FACEFF9AFA55FB86FB20B532EF6E" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55FB86FB20B532EF6E" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
, whereas the relief of these regions is much smoother in 
<taxonomicName id="91D5FACEFF9AFA55F830FAEEB5CFEF48" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[361,493,1301,1323]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9AFA55F830FAEEB5CFEF48" box="[361,493,1301,1323]" italics="true" pageId="6" pageNumber="429">O. leptodon</emphasis>
</taxonomicName>
.
</paragraph>
<caption id="02AAD1C5FF9AFA55F9C8FBB8B517EEF2" ID-DOI="http://doi.org/10.5281/zenodo.4687181" ID-Zenodo-Dep="4687181" httpUri="https://zenodo.org/record/4687181/files/figure.png" pageId="6" pageNumber="429" startId="6.[145,224,1088,1109]" targetBox="[156,757,200,1057]" targetPageId="6">
<paragraph id="566A814DFF9AFA55F9C8FBB8B517EEF2" blockId="6.[145,761,1088,1168]" pageId="6" pageNumber="429">
<emphasis id="64A15D5FFF9AFA55F9C8FBB8B524EE37" bold="true" box="[145,262,1088,1109]" pageId="6" pageNumber="429">Figure 4.</emphasis>
<emphasis id="64A15D5FFF9AFA55F848FBB8B63FEE37" box="[273,541,1088,1109]" italics="true" pageId="6" pageNumber="429">
<taxonomicName id="91D5FACEFF9AFA55F848FBB8B63AEE37" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[273,536,1088,1109]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="leptodon">Odobenocetops leptodon</taxonomicName>
,
</emphasis>
referred specimen (MNHN SAO 202). Skull in lateral left (A) and lateral right (B) views.
</paragraph>
</caption>
<paragraph id="566A814DFF9AFA55F9F0FACCB071EBB2" blockId="6.[145,761,1240,1906]" lastBlockId="6.[809,1425,197,1323]" pageId="6" pageNumber="429">
The anterior sides of the premaxillae of 
<taxonomicName id="91D5FACEFF9AFA55FB2FFACCB544EF0B" authority="(SMNK PAL 2492)" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9AFA55FB2FFACCB6DBEF2B" box="[630,761,1332,1353]" italics="true" pageId="6" pageNumber="429">O. leptodon</emphasis>
(SMNK PAL 2492)
</taxonomicName>
bear strong foramina and grooves, which indicates an abundant vascularization related to the development of the upper lip. The premaxillae are much broader and much more elevated than in 
<taxonomicName id="91D5FACEFF9AFA55F9C8FA36B510EF81" box="[145,306,1486,1507]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55F9C8FA36B510EF81" box="[145,306,1486,1507]" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
, again indicating a larger and stronger upper lip (
<figureCitation id="CEEE9DC8FF9AFA55F85EFA14B57CEC63" box="[263,350,1516,1538]" captionStart="Figure 1" captionStartId="3.[823,902,1340,1361]" captionTargetBox="[842,1419,198,1308]" captionTargetId="figure-576@3.[836,1445,193,1316]" captionTargetPageId="3" captionText="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." figureDoi="http://doi.org/10.5281/zenodo.4687171" httpUri="https://zenodo.org/record/4687171/files/figure.png" pageId="6" pageNumber="429">Figs 1B</figureCitation>
and 
<figureCitation id="CEEE9DC8FF9AFA55F8CEFA14B59BEC60" box="[407,441,1516,1538]" captionStart="Figure 3" captionStartId="5.[159,238,932,953]" captionTargetBox="[172,1434,196,900]" captionTargetId="figure-533@5.[167,1448,190,916]" captionTargetPageId="5" captionText="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="6" pageNumber="429">3C</figureCitation>
). The premaxillary sheaths, which house the tusks, are partly preserved on SMNK PAL 2492. The right is complete and the left is broken, apparently no more than 2 or 
<quantity id="912D2CA8FF9AFA55FB50F9B0B61EEC3F" box="[521,572,1608,1629]" metricMagnitude="-2" metricUnit="m" metricValue="3.0" pageId="6" pageNumber="429" unit="cm" value="3.0">3 cm</quantity>
from the apex. Contrary to what was hypothesized in the case of 
<emphasis id="64A15D5FFF9AFA55F9C8F97EB519ECF9" box="[145,315,1670,1691]" italics="true" pageId="6" pageNumber="429">
<taxonomicName id="91D5FACEFF9AFA55F9C8F97EB515ECF9" box="[145,311,1670,1691]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
the sheaths are not identical in size; the left one is clearly smaller and shorter than the right and reflects the size difference between the tusks. In lateral view, the right alveolar process forms an angle of 
<emphasis id="64A15D5FFF9AFA55F846F8F9B508ED74" box="[287,298,1793,1814]" italics="true" pageId="6" pageNumber="429">c</emphasis>
. 60° with the dorsal plane of the skull (from the vertex to the anterodorsal tip of the rostrum). The anteroventral edges of the sheaths (which include the anterior edge of the palate) are thickened and corrugated, as is observed in 
<taxonomicName id="91D5FACEFF9AFA55FC6BFF3DB757EA9B" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55FC6BFF3DB757EA9B" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
, which indicates attachments for strong, possibly horny, connective tissue for the attachment of the upper lip. This narrow edge also bears (in both species) a series of foramina, which could have been related to a fringe of vibrissae. In the style of feeding we have hypothesized, these could have allowed the animal to detect when the front edges of the sheaths were in contact with the sea floor.
</paragraph>
<paragraph id="566A814DFF9AFA55FA18FE21B031EE11" blockId="6.[809,1425,197,1323]" pageId="6" pageNumber="429">
The anteroventral crest of the premaxillae (
<figureCitation id="CEEE9DC8FF9AFA55FC61FE21B1B3EB8C" box="[1336,1425,473,495]" captionStart="Figure 1" captionStartId="3.[823,902,1340,1361]" captionTargetBox="[842,1419,198,1308]" captionTargetId="figure-576@3.[836,1445,193,1316]" captionTargetPageId="3" captionText="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." figureDoi="http://doi.org/10.5281/zenodo.4687171" httpUri="https://zenodo.org/record/4687171/files/figure.png" pageId="6" pageNumber="429">Figs 1B</figureCitation>
and 
<figureCitation id="CEEE9DC8FF9AFA55FA04FE00B75EE86C" box="[861,892,504,526]" captionStart="Figure 3" captionStartId="5.[159,238,932,953]" captionTargetBox="[172,1434,196,900]" captionTargetId="figure-533@5.[167,1448,190,916]" captionTargetPageId="5" captionText="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="6" pageNumber="429">3C</figureCitation>
) has a very wide U-shape whereas it is more V-shaped in 
<taxonomicName id="91D5FACEFF9AFA55FA98FDEFB045E84E" box="[961,1127,535,556]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55FA98FDEFB045E84E" box="[961,1127,535,556]" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
. This morphology is the result of the widening of the snout and is possibly related to the presence of the supplementary bones described below. The U-shaped anterior border of the palate is not perpendicular to the sagittal plane. In other words, in anterior view, if the sagittal plane is positioned vertically (based on pterygoids, basioccipital and vomerian groove), the plane of the anterior crest of the palate dips towards the right side of the skull. This is because the anteroventral edge of the smaller and less laterally divergent left sheath is dorsal to (more elevated than) that of the right sheath. This condition implies that when the animal was feeding (i.e. with the anterior border of the palate parallel to the sea floor; see 
<bibRefCitation id="3244FCBCFF9AFA55FD29FC3CB119E9B8" author="de Muizon C" box="[1136,1339,964,986]" pageId="6" pageNumber="429" pagination="671 - 683" refId="ref22909" refString="de Muizon C. 1993 b. Odobenocetops peruvianus, una remarcable convergencia de adaptacion alimentaria. Bulletin de l'Institut Francais d'Etudes Andines 22: 671 - 683." type="journal article" year="1993">de Muizon, 1993b</bibRefCitation>
and 
<bibRefCitation id="3244FCBCFF9AFA55FC2FFC3CB02DE99B" author="de Muizon C &amp; Domning DP &amp; Ketten DR" pageId="6" pageNumber="429" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF9AFA55FAD0FC1BB79FE995" box="[905,957,994,1016]" italics="true" pageId="6" pageNumber="429">et al</emphasis>
., 2002
</bibRefCitation>
), the sagittal plane was inclined toward the left side of the animal (i.e. dipping toward the right side). Therefore, because of the asymmetry of the premaxillae, 
<taxonomicName id="91D5FACEFF9AFA55FD4AFBC7B0B8EE31" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1043,1178,1086,1108]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9AFA55FD4AFBC7B0B8EE31" box="[1043,1178,1086,1108]" italics="true" pageId="6" pageNumber="429">O. leptodon</emphasis>
</taxonomicName>
was feeding slightly inclined on left side.
</paragraph>
<paragraph id="566A814DFF9AFA55FA18FB84B014EF49" blockId="6.[809,1425,197,1323]" pageId="6" pageNumber="429">
The premaxillae form the anterior region of the palate as is observed in 
<taxonomicName id="91D5FACEFF9AFA55FD1EFB63B0CBEED2" box="[1095,1257,1179,1200]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55FD1EFB63B0CBEED2" box="[1095,1257,1179,1200]" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
. Although the palate of 
<taxonomicName id="91D5FACEFF9AFA55FACBFB41B036EEAC" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[914,1044,1209,1230]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9AFA55FACBFB41B036EEAC" box="[914,1044,1209,1230]" italics="true" pageId="6" pageNumber="429">O. leptodon</emphasis>
</taxonomicName>
is much broader than in 
<taxonomicName id="91D5FACEFF9AFA55FC6CFB41B757EE8F" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55FC6CFB41B757EE8F" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
, the area occupied by the premaxillae in this part of the skull is only slightly larger than in 
<taxonomicName id="91D5FACEFF9AFA55FC2EFB0FB78AEF49" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9AFA55FC2EFB0FB78AEF49" italics="true" pageId="6" pageNumber="429">O. peruvianus</emphasis>
</taxonomicName>
(see below).
</paragraph>
<paragraph id="566A814DFF9AFA55FD59FA9FB09BEF1C" blockId="6.[1024,1209,1383,1407]" box="[1024,1209,1383,1407]" pageId="6" pageNumber="429">ROSTRAL BONES</paragraph>
<paragraph id="566A814DFF9AFA54FA70FA68B6ADEC3C" blockId="6.[809,1425,1424,1906]" lastBlockId="7.[159,775,902,1906]" lastPageId="7" lastPageNumber="430" pageId="6" pageNumber="429">
One of the most striking differentiating characters of 
<taxonomicName id="91D5FACEFF9AFA55FA70FA57B791EFA1" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[809,947,1454,1476]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="6" pageNumber="429" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9AFA55FA70FA57B791EFA1" box="[809,947,1454,1476]" italics="true" pageId="6" pageNumber="429">O. leptodon</emphasis>
</taxonomicName>
is the presence of two supplementary bones (one on each side) anterior to the premaxillae at the anterodorsal apex of the snout. These bones are apparently appressed against the medial edges of the premaxillae and lie partly on the dorsal part of the skull and partly on the anterior slope of the snout. The dorsal portion is narrower than long but broadens anteriorly. It is limited posteriorly by the fossa for the premaxillary sac of the premaxilla, while medially it has a small contact with the medial portion of the maxilla on the dorsal face of the rostrum (
<figureCitation id="CEEE9DC8FF9AFA55FC5CF919B17CEC94" box="[1285,1374,1761,1783]" captionStart="Figure 1" captionStartId="3.[823,902,1340,1361]" captionTargetBox="[842,1419,198,1308]" captionTargetId="figure-576@3.[836,1445,193,1316]" captionTargetPageId="3" captionText="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." figureDoi="http://doi.org/10.5281/zenodo.4687171" httpUri="https://zenodo.org/record/4687171/files/figure.png" pageId="6" pageNumber="429">Figs 1B</figureCitation>
, 
<figureCitation id="CEEE9DC8FF9AFA55FC32F919B1AFEC94" box="[1387,1421,1761,1782]" captionStart="Figure 2" captionStartId="4.[145,224,1254,1275]" captionTargetBox="[308,1262,197,1223]" captionTargetId="figure-331@4.[305,1265,195,1234]" captionTargetPageId="4" captionText="Figure 2. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687175" httpUri="https://zenodo.org/record/4687175/files/figure.png" pageId="6" pageNumber="429">2A</figureCitation>
, 
<figureCitation id="CEEE9DC8FF9AFA55FA70F8F8B76AED77" box="[809,840,1792,1813]" captionStart="Figure 3" captionStartId="5.[159,238,932,953]" captionTargetBox="[172,1434,196,900]" captionTargetId="figure-533@5.[167,1448,190,916]" captionTargetPageId="5" captionText="Figure 3. Odobenocetops leptodon, referred specimen (MNHN SAO 202). Skull in dorsal (A), ventral (B), and anteroventral (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687177" httpUri="https://zenodo.org/record/4687177/files/figure.png" pageId="6" pageNumber="429">3A</figureCitation>
and 
<figureCitation id="CEEE9DC8FF9AFA55FAD3F8F8B7BBED74" box="[906,921,1792,1814]" captionStart="Figure 5" captionStartId="7.[159,238,713,734]" captionTargetBox="[194,777,156,678]" captionTargetId="figure-812@7.[167,777,154,713]" captionTargetPageId="7" captionText="Figure 5. Reconstruction of the dorsal view of the rostrum of Odobenocetops leptodon. Abbreviations: Fps, fossa for the premaxillary sac; Fr, frontal; Mx, maxilla; NaF, narial fossa; Pmx, premaxilla; Sb, supplementary bone." figureDoi="http://doi.org/10.5281/zenodo.4687183" httpUri="https://zenodo.org/record/4687183/files/figure.png" pageId="6" pageNumber="429">5</figureCitation>
). Within the vomerian groove, the rostral supplementary bone is bordered by the medial portion of the maxilla, but the edge of the groove is formed by the rostral bone itself. The lateral suture is directed anteroposteriorly and is located just medial to the tusk alveoli. The anterior portion is not observable on MNHN SAO 202 but it is in relatively good condition on the left side of SMNK PAL 2492. It is also relatively narrow and forms a strip of bone overlying the premaxilla, tapering ventrally, and reaching (or almost reaching) the ventromedial border of the premaxilla at the anterior edge of the palate. Its medial suture is with the vomer. These supplementary bones are in fact wedged (as far as the dorsal portion is concerned) between the tusks laterally and the vomer and maxilla medially. They are partly responsible for the breadth of the snout in 
<taxonomicName id="91D5FACEFF9BFA54F80FFB0FB5F9EF69" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[342,475,1270,1292]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54F80FFB0FB5F9EF69" box="[342,475,1270,1292]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
and tend to separate the proximal extremities of the tusks and alveoli (i.e. the premaxillae). As a probable consequence of their presence, the tusks are less divergent distally than in 
<taxonomicName id="91D5FACEFF9BFA54FBB4FAABB53CEFE5" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FBB4FAABB53CEFE5" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
and the anterior border of the palate is Ushaped in 
<taxonomicName id="91D5FACEFF9BFA54F843FA68B5BCEFC7" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[282,414,1424,1445]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54F843FA68B5BCEFC7" box="[282,414,1424,1445]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
rather than more V-shaped as in 
<taxonomicName id="91D5FACEFF9BFA54F9E5FA57B579EFA6" box="[188,347,1455,1476]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54F9E5FA57B579EFA6" box="[188,347,1455,1476]" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
. Apparently, as is observed on the left premaxilla of SMNK PAL 2492, the rostral bones were anterodorsally protruding, forming an elevated prominence at the apex of the snout. This condition is not observable on MNHN SAO 202 since the bones have been partly eroded in their apical portions.
</paragraph>
<caption id="02AAD1C5FF9BFA54F9C6FD31B686E954" ID-DOI="http://doi.org/10.5281/zenodo.4687183" ID-Zenodo-Dep="4687183" httpUri="https://zenodo.org/record/4687183/files/figure.png" pageId="7" pageNumber="430" startId="7.[159,238,713,734]" targetBox="[194,777,156,678]" targetPageId="7">
<paragraph id="566A814DFF9BFA54F9C6FD31B686E954" blockId="7.[159,775,713,822]" pageId="7" pageNumber="430">
<emphasis id="64A15D5FFF9BFA54F9C6FD31B524E8BC" bold="true" box="[159,262,713,734]" pageId="7" pageNumber="430">Figure 5.</emphasis>
Reconstruction of the dorsal view of the rostrum of 
<taxonomicName id="91D5FACEFF9BFA54F9E7FD1EB59EE899" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[190,444,742,763]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54F9E7FD1EB59EE899" box="[190,444,742,763]" italics="true" pageId="7" pageNumber="430">Odobenocetops leptodon</emphasis>
</taxonomicName>
. Abbreviations: Fps, fossa for the premaxillary sac; Fr, frontal; Mx, maxilla; NaF, narial fossa; Pmx, premaxilla; Sb, supplementary bone.
</paragraph>
</caption>
<paragraph id="566A814DFF9BFA54F9E1F99EB149E84E" blockId="7.[159,775,902,1906]" lastBlockId="7.[823,1439,197,1170]" pageId="7" pageNumber="430">
These supplementary bones could be ossa prenasalia, cartilage bones which appear late in development (mainly in postnatal life) and which are not uncommon in mammals. They are paired or unpaired bones which articulate with the nasals or premaxillae and which are always related to the presence of a rhinarium (
<taxonomicName id="91D5FACEFF9BFA54F87DF8E6B5D0ED56" authority=", Sus" authorityName="Sus" box="[292,498,1822,1844]" class="Mammalia" family="Macroscelididae" genus="Rhynchocyon" kingdom="Animalia" order="Macroscelidea" pageId="7" pageNumber="430" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9BFA54F87DF8E6B598ED51" box="[292,442,1822,1843]" italics="true" pageId="7" pageNumber="430">Rhynchocyon</emphasis>
, 
<emphasis id="64A15D5FFF9BFA54F891F8E7B5D0ED56" box="[456,498,1823,1844]" italics="true" pageId="7" pageNumber="430">Sus</emphasis>
</taxonomicName>
, 
<taxonomicName id="91D5FACEFF9BFA54FB59F8E6B6EEED56" authority=", Chiroptera" authorityName="Chiroptera" box="[512,716,1822,1844]" class="Mammalia" family="Talpidae" genus="Talpa" kingdom="Animalia" order="Soricomorpha" pageId="7" pageNumber="430" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9BFA54FB59F8E6B660ED51" box="[512,578,1822,1843]" italics="true" pageId="7" pageNumber="430">Talpa</emphasis>
, Chiroptera
</taxonomicName>
) or a proboscis (
<bibRefCitation id="3244FCBCFF9BFA54F84FF8C5B588ED31" author="Starck D" box="[278,426,1853,1875]" pageId="7" pageNumber="430" pagination="405 - 549" refId="ref23389" refString="Starck D. 1967. Le crane des mammiferes. In: Grasse, PP, ed. Traite de Zoologie. Paris: Masson, 405 - 549." type="book chapter" year="1967">Starck, 1967</bibRefCitation>
). In the case of 
<taxonomicName id="91D5FACEFF9BFA54FB03F8C5B6F9ED30" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[602,731,1853,1874]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FB03F8C5B6F9ED30" box="[602,731,1853,1874]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
the supplementary bones present at the anterodorsal apex of the snout could be related to the thick and powerful upper lip used by 
<taxonomicName id="91D5FACEFF9BFA54FD6CFF1CB0FEEA9B" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[1077,1244,228,249]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF9BFA54FD6CFF1CB0FEEA9B" box="[1077,1244,228,249]" italics="true" pageId="7" pageNumber="430">Odobenocetops</emphasis>
</taxonomicName>
to forage on the bottom in search of food (
<bibRefCitation id="3244FCBCFF9BFA54FD26FEFAB17FEB7A" author="de Muizon C" box="[1151,1373,258,280]" pageId="7" pageNumber="430" pagination="745 - 748" refId="ref22882" refString="de Muizon C. 1993 a. Walrus-like feeding adaptation in a new cetacean from the Pliocene of Peru. Nature 365: 745 - 748." type="journal article" year="1993">de Muizon, 1993a</bibRefCitation>
;b; 
<bibRefCitation id="3244FCBCFF9BFA54FCDDFEFAB03CEB55" author="de Muizon C &amp; Domning DP &amp; Ketten DR" pageId="7" pageNumber="430" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF9BFA54FACEFEDAB7E9EB54" box="[919,971,289,311]" italics="true" pageId="7" pageNumber="430">et al</emphasis>
., 2002
</bibRefCitation>
). They could also indicate of the presence of a very sensitive tactile organ, with or without vibrissae (see 
<bibRefCitation id="3244FCBCFF9BFA54FD62FEA6B12BEB17" author="de Muizon C" box="[1083,1289,350,373]" pageId="7" pageNumber="430" pagination="745 - 748" refId="ref22882" refString="de Muizon C. 1993 a. Walrus-like feeding adaptation in a new cetacean from the Pliocene of Peru. Nature 365: 745 - 748." type="journal article" year="1993">de Muizon, 1993a</bibRefCitation>
), much more developed in 
<taxonomicName id="91D5FACEFF9BFA54FA88FE85B077EBF0" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[977,1109,381,402]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FA88FE85B077EBF0" box="[977,1109,381,402]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
than in 
<taxonomicName id="91D5FACEFF9BFA54FDE5FE85B17DEBF1" box="[1212,1375,381,403]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FDE5FE85B17DEBF1" box="[1212,1375,381,403]" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
. It is likely that strong muscles for the upper lip of 
<taxonomicName id="91D5FACEFF9BFA54FC0AFE64B754EBAD" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FC0AFE64B754EBAD" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
were attaching on the (?)prenasalia. However, it is noteworthy that the prenasalia of other mammals are generally not tightly articulated with the premaxillae and/or the nasals, and not distinctly paired.
</paragraph>
<paragraph id="566A814DFF9BFA54FA09FDCDB796E99A" blockId="7.[823,1439,197,1170]" pageId="7" pageNumber="430">
If these supplementary bones are not prenasalia, another alternative which could explain the condition of 
<taxonomicName id="91D5FACEFF9BFA54FA0AFD8BB7F4E8E5" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[851,982,626,648]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FA0AFD8BB7F4E8E5" box="[851,982,626,648]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
is the presence of septomaxillae. These bones are present in crossopterygians, lissamphibians, squamates, in all nonmammalian therapsids, and in all the nontherian mammals except multituberculates. The septomaxilla is absent in marsupials and placentals except in Xenarthra (
<bibRefCitation id="3244FCBCFF9BFA54FDF3FCF4B116E943" author="Wible JR" box="[1194,1332,780,802]" pageId="7" pageNumber="430" pagination="183 - 205" refId="ref23419" refString="Wible JR. 1990. Petrosals of Late Cretaceous marsupials from North America, and a cladistic analysis of the petrosal in therian mammals. Journal of Vertebrate Paleontology 10: 183 - 205." type="journal article" year="1990">Wible, 1990</bibRefCitation>
; 
<bibRefCitation id="3244FCBCFF9BFA54FC18FCF4B7BCE923" author="Zeller U &amp; Wible JR &amp; Elsner M" pageId="7" pageNumber="430" pagination="31 - 46" refId="ref23454" refString="Zeller U, Wible JR, Elsner M. 1993. New ontogenetic evidence on the septomaxilla of Tamandua and Choloepus (Mammalia, Xenarthra), with a re-evaluation of the homology of the mammalian septomaxilla. Journal of Mammalian Evolution 1: 31 - 46." type="journal article" year="1993">
Zeller 
<emphasis id="64A15D5FFF9BFA54FCD2FCF4B76FE95D" italics="true" pageId="7" pageNumber="430">et al</emphasis>
., 1993
</bibRefCitation>
). However, we are reluctant to interpret the supplementary bones of 
<taxonomicName id="91D5FACEFF9BFA54FD16FCB1B0F0E93C" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1103,1234,841,862]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FD16FCB1B0F0E93C" box="[1103,1234,841,862]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
as septomaxillae, since the study of the development of the nasal capsule of odontocetes (
<bibRefCitation id="3244FCBCFF9BFA54FABEFC7EB126E9FE" author="Klima M &amp; van Bree PJ" box="[999,1284,902,924]" pageId="7" pageNumber="430" pagination="131 - 178" refId="ref22522" refString="Klima M, van Bree PJ. 1985. Uberzahlige Skeletelemente im Nasenschadel von Phocoena phocoena und die Entwicklung der Nasenregion bei den Zahnwalen. Gegenbaurs Morphologisches Jahrbuch 131: 131 - 178." type="journal article" year="1985">Klima &amp; Van Bree, 1985</bibRefCitation>
; 
<bibRefCitation id="3244FCBCFF9BFA54FC48FC7EB752E9D9" author="Klima M &amp; Seel M &amp; Deimer P" pageId="7" pageNumber="430" pagination="245 - 284" refId="ref22490" refString="Klima M, Seel M, Deimer P. 1986. Die Entwicklung des hochspezialisierten Nasenschadels beim Pottwal (Physeter macrocephalus). Gegenbaurs Morphologisches Jahrbuch 132: 245 - 284." type="journal article" year="1986">
Klima 
<emphasis id="64A15D5FFF9BFA54FC06FC7FB1B3E9F9" box="[1375,1425,902,924]" italics="true" pageId="7" pageNumber="430">et al</emphasis>
., 1986
</bibRefCitation>
; 
<bibRefCitation id="3244FCBCFF9BFA54FA24FC5DB02BE9D9" author="Klima M" box="[893,1033,933,955]" pageId="7" pageNumber="430" pagination="105 - 121" refId="ref22446" refString="Klima M. 1987. Morphogenesis of the nasal structures of the skull in toothed whales (Odontoceti). In: Kuhn H-J, Zeller U, eds. Morphogenesis of the Mammalian Skull. Mammalia Depicta 13: 105 - 121." type="journal article" year="1987">Klima, 1987</bibRefCitation>
) does not show any indication that such bones are present at any developmental stage in this group.
</paragraph>
<paragraph id="566A814DFF9BFA54FA09FBF9B0CEEEF3" blockId="7.[823,1439,197,1170]" pageId="7" pageNumber="430">
A third alternative is to regard the supplementary bones of 
<taxonomicName id="91D5FACEFF9BFA54FAC3FBD8B03EEE57" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[922,1052,1056,1077]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FAC3FBD8B03EEE57" box="[922,1052,1056,1077]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
as neomorphic elements different from prenasalia and septomaxillae, possibly related to the muscle attachment of the lip, which was probably much stronger than in 
<taxonomicName id="91D5FACEFF9BFA54FD1AFB84B0C6EEF3" box="[1091,1252,1148,1169]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FD1AFB84B0C6EEF3" box="[1091,1252,1148,1169]" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
.
</paragraph>
<paragraph id="566A814DFF9BFA54FD1FFB36B0B2EE84" blockId="7.[1094,1168,1230,1254]" box="[1094,1168,1230,1254]" pageId="7" pageNumber="430">TUSKS</paragraph>
<paragraph id="566A814DFF9BFA5BFA6EFB0EB614EED2" blockId="7.[823,1439,1270,1906]" lastBlockId="8.[145,762,197,1906]" lastPageId="8" lastPageNumber="431" pageId="7" pageNumber="430">
The tusks of 
<taxonomicName id="91D5FACEFF9BFA54FA80FB0FB042EF69" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[985,1120,1270,1292]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FA80FB0FB042EF69" box="[985,1120,1270,1292]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
are similar to those of 
<taxonomicName id="91D5FACEFF9BFA54FCDCFB0FB794EF49" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FCDCFB0FB794EF49" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
(
<figureCitation id="CEEE9DC8FF9BFA54FA92FAEDB063EF49" box="[971,1089,1301,1323]" captionStart="Figure 1" captionStartId="3.[823,902,1340,1361]" captionTargetBox="[842,1419,198,1308]" captionTargetId="figure-576@3.[836,1445,193,1316]" captionTargetPageId="3" captionText="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." figureDoi="http://doi.org/10.5281/zenodo.4687171" httpUri="https://zenodo.org/record/4687171/files/figure.png" pageId="7" pageNumber="430">Figs 1A,B</figureCitation>
). They are much better preserved in SMNH PAL 2492 than in the 
<typeStatus id="896E3FEFFF9BFA54FC59FACCB143EF28" box="[1280,1377,1332,1354]" pageId="7" pageNumber="430" type="holotype">holotype</typeStatus>
of 
<taxonomicName id="91D5FACEFF9BFA54FCDCFACCB794EF0A" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FCDCFACCB794EF0A" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
. The large right tusk is a straight, cylindrical, needle-like tooth. Its erupted portion (broken and worn during life) is 
<quantity id="912D2CA8FF9BFA54FD0EFA68B087EFC7" box="[1111,1189,1424,1445]" metricMagnitude="0" metricUnit="m" metricValue="1.0699999999999998" pageId="7" pageNumber="430" unit="cm" value="107.0">107 cm</quantity>
long and its alveolar portion (as preserved) is approximately 
<quantity id="912D2CA8FF9BFA54FC43FA57B179EFA6" box="[1306,1371,1455,1476]" metricMagnitude="-1" metricUnit="m" metricValue="2.8" pageId="7" pageNumber="430" unit="cm" value="28.0">28 cm</quantity>
long. Before the loss of its original tip, it could easily have been 
<quantity id="912D2CA8FF9BFA54FA2DFA14B797EC63" box="[884,949,1516,1537]" metricMagnitude="-1" metricUnit="m" metricValue="3.0" pageId="7" pageNumber="430" unit="cm" value="30.0">30 cm</quantity>
longer. Therefore, the right tusk of 
<taxonomicName id="91D5FACEFF9BFA54FC0AFA14B754EC7D" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FC0AFA14B754EC7D" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
is much longer than what was estimated for 
<taxonomicName id="91D5FACEFF9BFA54FCDCF9F3B794EC5D" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FCDCF9F3B794EC5D" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
, in which we suggested that it was possibly no longer than 
<quantity id="912D2CA8FF9BFA54FAABF9B0B010EC3F" box="[1010,1074,1608,1630]" metricMagnitude="-1" metricUnit="m" metricValue="5.5" pageId="7" pageNumber="430" unit="cm" value="55.0">55 cm</quantity>
with a 
<quantity id="912D2CA8FF9BFA54FDCFF9B0B0DDEC3F" box="[1174,1279,1608,1630]" metricMagnitude="-1" metricUnit="m" metricValue="1.75" metricValueMax="2.0" metricValueMin="1.5" pageId="7" pageNumber="430" unit="cm" value="17.5" valueMax="20.0" valueMin="15.0">15–20 cm</quantity>
long erupted portion. It is therefore probable that the long tusk of 
<taxonomicName id="91D5FACEFF9BFA54FA6EF97EB7F8ECF9" box="[823,986,1670,1691]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF9BFA54FA6EF97EB7F8ECF9" box="[823,986,1670,1691]" italics="true" pageId="7" pageNumber="430">O. peruvianus</emphasis>
</taxonomicName>
was longer than previously suspected (but see below). In 
<taxonomicName id="91D5FACEFF9BFA54FD52F95CB0AEECDB" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1035,1164,1700,1721]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FD52F95CB0AEECDB" box="[1035,1164,1700,1721]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
as in 
<emphasis id="64A15D5FFF9BFA54FD97F95CB156ECDB" box="[1230,1396,1700,1721]" italics="true" pageId="7" pageNumber="430">
<taxonomicName id="91D5FACEFF9BFA54FD97F95CB152ECDB" box="[1230,1392,1700,1721]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
the section of the tusk is elliptical and the diameters diminish towards the apex. At the alveolar border the diameters are 
<quantity id="912D2CA8FF9BFA54FAB8F8F8B00FED77" box="[993,1069,1792,1814]" metricMagnitude="-2" metricUnit="m" metricValue="5.0" pageId="7" pageNumber="430" unit="mm" value="50.0">50 mm</quantity>
and 
<emphasis id="64A15D5FFF9BFA54FD32F8F9B054ED74" box="[1131,1142,1793,1814]" italics="true" pageId="7" pageNumber="430">c</emphasis>
. 
<quantity id="912D2CA8FF9BFA54FDDEF8F8B0F7ED77" box="[1159,1237,1792,1814]" metricMagnitude="-2" metricUnit="m" metricValue="3.6" pageId="7" pageNumber="430" unit="mm" value="36.0">36 mm</quantity>
, whereas at 
<quantity id="912D2CA8FF9BFA54FC35F8F8B1BDED77" box="[1388,1439,1792,1813]" metricMagnitude="-2" metricUnit="m" metricValue="8.0" pageId="7" pageNumber="430" unit="cm" value="8.0">8 cm</quantity>
from the broken and worn apex the diameters are 
<quantity id="912D2CA8FF9BFA54FA6EF8C5B7A0ED31" box="[823,898,1853,1875]" metricMagnitude="-2" metricUnit="m" metricValue="3.0" pageId="7" pageNumber="430" unit="mm" value="30.0">30 mm</quantity>
and 
<quantity id="912D2CA8FF9BFA54FA9DF8C5B030ED31" box="[964,1042,1853,1875]" metricMagnitude="-2" metricUnit="m" metricValue="2.5" pageId="7" pageNumber="430" unit="mm" value="25.0">25 mm</quantity>
. The large tusk of 
<taxonomicName id="91D5FACEFF9BFA54FDA2F8C6B1A3ED30" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1275,1409,1853,1875]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="7" pageNumber="430" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF9BFA54FDA2F8C6B1A3ED30" box="[1275,1409,1853,1875]" italics="true" pageId="7" pageNumber="430">O. leptodon</emphasis>
</taxonomicName>
is made of dentine only (it has no enamel) and bears longitudinal striae as in 
<taxonomicName id="91D5FACEFF94FA5BF8DDFF3EB606EAB9" box="[388,548,198,219]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BF8DDFF3EB606EAB9" box="[388,548,198,219]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
. At the apex of the tusk is a long wear facet which faces ventrally. It is 
<quantity id="912D2CA8FF94FA5BF9C8FEFBB4E6EB7A" box="[145,196,259,280]" metricMagnitude="-2" metricUnit="m" metricValue="8.0" pageId="8" pageNumber="431" unit="cm" value="8.0">8 cm</quantity>
long and convex ventrally. The facet is strongly oblique and its posterior edge does not present a marked limit with the ventral border of the tusk. The pulp cavity is wide open at the proximal extremity of the tooth, which indicates continuous growth. At the proximal extremity of the erupted portion (
<quantity id="912D2CA8FF94FA5BFB27FE64B693EBD3" box="[638,689,412,433]" metricMagnitude="-2" metricUnit="m" metricValue="2.0" pageId="8" pageNumber="431" unit="cm" value="2.0">2 cm</quantity>
distal to the alveolar border) the diameters of the pulp cavity are 
<quantity id="912D2CA8FF94FA5BF99CFE21B532EB8D" box="[197,272,473,495]" metricMagnitude="-2" metricUnit="m" metricValue="2.4" pageId="8" pageNumber="431" unit="mm" value="24.0">24 mm</quantity>
and 
<quantity id="912D2CA8FF94FA5BF800FE21B585EB8D" box="[345,423,473,495]" metricMagnitude="-2" metricUnit="m" metricValue="1.3" pageId="8" pageNumber="431" unit="mm" value="13.0">13 mm</quantity>
. Considering that the pulp cavity is almost as wide as the tooth itself at the proximal extremity of the tusk, and if (as in 
<taxonomicName id="91D5FACEFF94FA5BFB08FDEFB6D2E84E" box="[593,752,535,556]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFB08FDEFB6D2E84E" box="[593,752,535,556]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
) the cavity was conical, the pulp cavity of 
<taxonomicName id="91D5FACEFF94FA5BFB2CFDCEB6DBE828" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[629,761,565,587]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BFB2CFDCEB6DBE828" box="[629,761,565,587]" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
should have been approximately 
<quantity id="912D2CA8FF94FA5BFB49FDACB672E80B" box="[528,592,596,618]" metricMagnitude="-1" metricUnit="m" metricValue="6.0" pageId="8" pageNumber="431" unit="cm" value="60.0">60 cm</quantity>
long, which is more than twice the length measured in 
<taxonomicName id="91D5FACEFF94FA5BFB03FD8BB6DAE8EA" box="[602,760,627,648]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFB03FD8BB6DAE8EA" box="[602,760,627,648]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
(
<quantity id="912D2CA8FF94FA5BF9C0FD69B4FCE8C5" box="[153,222,657,679]" metricMagnitude="-1" metricUnit="m" metricValue="2.3" pageId="8" pageNumber="431" unit="cm" value="23.0">23 cm</quantity>
). 
<bibRefCitation id="3244FCBCFF94FA5BF9A8FD6AB625E8C5" author="Hay KA &amp; Mansfield AW" box="[241,519,657,679]" pageId="8" pageNumber="431" pagination="145 - 176" refId="ref22195" refString="Hay KA, Mansfield AW. 1989. Narwhal, Monodon monoceros Linnaeus, 1758. In: Ridgway, SH, Harrison R, eds. Handbook of Marine Mammals, Vol. 4: River Dolphins and the Larger Toothed Whales. London: Academic Press, 145 - 176." type="book chapter" year="1989">Hay &amp; Mansfield (1989)</bibRefCitation>
stated that the pulp cavity of the narwhal tusk is conical at the root. However, ‘ 
<quantity id="912D2CA8FF94FA5BF85CFD37B54DE886" box="[261,367,719,740]" metricMagnitude="-1" metricUnit="m" metricValue="1.5" metricValueMax="2.0" metricValueMin="1.0" pageId="8" pageNumber="431" unit="cm" value="15.0" valueMax="20.0" valueMin="10.0">10–20 cm</quantity>
from the base it narrows to a canal 
<quantity id="912D2CA8FF94FA5BF9C8FD15B4FAE961" box="[145,216,749,771]" metricMagnitude="-3" metricUnit="m" metricValue="5.0" pageId="8" pageNumber="431" unit="cm" value="0.5">0.5 cm</quantity>
in diameter which passes nearly to the tip of the tusk’ (
<bibRefCitation id="3244FCBCFF94FA5BF859FCF4B61CE940" author="Hay KA &amp; Mansfield AW" box="[256,574,780,802]" pageId="8" pageNumber="431" pagination="145 - 176" refId="ref22195" refString="Hay KA, Mansfield AW. 1989. Narwhal, Monodon monoceros Linnaeus, 1758. In: Ridgway, SH, Harrison R, eds. Handbook of Marine Mammals, Vol. 4: River Dolphins and the Larger Toothed Whales. London: Academic Press, 145 - 176." type="book chapter" year="1989">Hay &amp; Mansfield, 1989: 160</bibRefCitation>
). These authors, citing 
<bibRefCitation id="3244FCBCFF94FA5BF98EFCD2B55AE923" author="Porsild MP" box="[215,376,810,833]" pageId="8" pageNumber="431" pagination="8 - 13" refId="ref23268" refString="Porsild MP. 1922. Scattered observations on narwhals. Journal of Mammalogy 3: 8 - 13." type="journal article" year="1922">Porsild (1922)</bibRefCitation>
, also stated that in very old males the pulp canal is nearly occluded. Therefore, if the age of the animal is unknown, the length of the pulp cavity is probably not a good criterion to estimate the length of the right tusk of 
<taxonomicName id="91D5FACEFF94FA5BF831FC5DB625E9D9" box="[360,519,933,955]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BF831FC5DB625E9D9" box="[360,519,933,955]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
. The apex of the tusk of the 
<typeStatus id="896E3FEFFF94FA5BF986FC3CB562E9B8" box="[223,320,964,986]" pageId="8" pageNumber="431" type="holotype">holotype</typeStatus>
of 
<taxonomicName id="91D5FACEFF94FA5BF830FC3CB5CDE9BB" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[361,495,964,985]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BF830FC3CB5CDE9BB" box="[361,495,964,985]" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
shows an open cavity. Since the wear facet clearly indicates the apex of the tooth, this canal had to be separated from the pulp cavity. In fact, a radiograph of the tusk shows that 
<quantity id="912D2CA8FF94FA5BF9C8FBC6B4F3EE36" box="[145,209,1086,1108]" metricMagnitude="-1" metricUnit="m" metricValue="3.5" pageId="8" pageNumber="431" unit="cm" value="35.0">35 cm</quantity>
from the apex, this apical canal is probably closed by dentine. It is likely that when the tooth was unworn the pulp cavity extended almost to the apex, as is observed in the living narwhal.
</paragraph>
<paragraph id="566A814DFF94FA5BF9F0FB41B094EB16" blockId="8.[145,762,197,1906]" lastBlockId="8.[809,1425,197,372]" pageId="8" pageNumber="431">
The small tusk is not complete in either specimen of 
<emphasis id="64A15D5FFF94FA5BF9C8FB20B539EE8F" box="[145,283,1240,1261]" italics="true" pageId="8" pageNumber="431">
<taxonomicName id="91D5FACEFF94FA5BF9C8FB20B535EE8F" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[145,279,1240,1261]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">O. leptodon</taxonomicName>
,
</emphasis>
but its apex is preserved on SMNK PAL 2492, although separated from the intra-alveolar portion of the tooth. Therefore, on the specimen (
<figureCitation id="CEEE9DC8FF94FA5BF9C0FACCB528EF28" box="[153,266,1332,1354]" captionStart="Figure 2" captionStartId="4.[145,224,1254,1275]" captionTargetBox="[308,1262,197,1223]" captionTargetId="figure-331@4.[305,1265,195,1234]" captionTargetPageId="4" captionText="Figure 2. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: dorsal (A), ventral (B), and lateral (left side) (C) views." figureDoi="http://doi.org/10.5281/zenodo.4687175" httpUri="https://zenodo.org/record/4687175/files/figure.png" pageId="8" pageNumber="431">Figs 2B,C</figureCitation>
) the reconstructed length of the tusk is an estimate, although probably relatively close to the actual length. The total length of the tusk was approximately 
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and the intra-alveolar portion approximately 
<quantity id="912D2CA8FF94FA5BF81BFA57B5A4EFA6" box="[322,390,1455,1476]" metricMagnitude="-1" metricUnit="m" metricValue="2.0" pageId="8" pageNumber="431" unit="cm" value="20.0">20 cm</quantity>
. It is unlikely that more than 
<quantity id="912D2CA8FF94FA5BF9C8FA35B4E6EF81" box="[145,196,1485,1507]" metricMagnitude="-2" metricUnit="m" metricValue="5.0" pageId="8" pageNumber="431" unit="cm" value="5.0">5 cm</quantity>
of the tusk were erupted. The eruption of the small tusk is corroborated by the presence, at the apex, of a small wear facet, which is grossly parallel to the anterior U-shaped border of the palate and therefore to the sea bottom in feeding position. The section of the small tusk is also oval and the diameters at its proximal extremity are 
<quantity id="912D2CA8FF94FA5BFB46F97DB648ECF9" box="[543,618,1669,1691]" metricMagnitude="-2" metricUnit="m" metricValue="2.2" pageId="8" pageNumber="431" unit="mm" value="22.0">22 mm</quantity>
and 
<quantity id="912D2CA8FF94FA5BFBFEF97DB6D7ECF9" box="[679,757,1669,1691]" metricMagnitude="-2" metricUnit="m" metricValue="1.8" pageId="8" pageNumber="431" unit="mm" value="18.0">18 mm</quantity>
. At the extremity of the preserved portion of the alveolar part of the tusk (which is close to the alveolar border) the diameters are 
<quantity id="912D2CA8FF94FA5BF8E7F919B628EC95" box="[446,522,1761,1783]" metricMagnitude="-2" metricUnit="m" metricValue="1.8" pageId="8" pageNumber="431" unit="mm" value="18.0">18 mm</quantity>
and 
<quantity id="912D2CA8FF94FA5BFB1DF919B685EC95" box="[580,679,1761,1783]" metricMagnitude="-2" metricUnit="m" metricValue="1.45" pageId="8" pageNumber="431" unit="mm" value="14.5">14.5 mm</quantity>
. At the level of the proximal extremity of the wear facet (approximately 
<quantity id="912D2CA8FF94FA5BF810F8E7B55EED56" box="[329,380,1823,1844]" metricMagnitude="-2" metricUnit="m" metricValue="1.0" pageId="8" pageNumber="431" unit="cm" value="1.0">1 cm</quantity>
from the apex of the tusk), the diameters are 
<quantity id="912D2CA8FF94FA5BF865F8C5B5AAED31" box="[316,392,1853,1875]" metricMagnitude="-2" metricUnit="m" metricValue="1.0" pageId="8" pageNumber="431" unit="mm" value="10.0">10 mm</quantity>
and 
<quantity id="912D2CA8FF94FA5BF89EF8C5B636ED31" box="[455,532,1853,1875]" metricMagnitude="-2" metricUnit="m" metricValue="1.1" pageId="8" pageNumber="431" unit="mm" value="11.0">11 mm</quantity>
. The pulp cavity of the tusk is similar to that observed in 
<taxonomicName id="91D5FACEFF94FA5BFB09F8A4B6D0ED13" box="[592,754,1884,1905]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFB09F8A4B6D0ED13" box="[592,754,1884,1905]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
: it is small, conical, and approximately 
<quantity id="912D2CA8FF94FA5BFDBDFF3DB135EAB9" box="[1252,1303,197,219]" metricMagnitude="-2" metricUnit="m" metricValue="1.0" pageId="8" pageNumber="431" unit="cm" value="1.0">1 cm</quantity>
deep, partially filled with a knot of irregular dentine on MNHN SAO 202. In the narwhal such a knot on the unerupted small tusk (right in the male, and both in the female) is produced when the growth of the tooth stops, generally prior to sexual maturity.
</paragraph>
<paragraph id="566A814DFF94FA5BFD70FE49B0B2EBAB" blockId="8.[1065,1168,433,457]" box="[1065,1168,433,457]" pageId="8" pageNumber="431">MAXILLA</paragraph>
<paragraph id="566A814DFF94FA5BFA70FE21B111E961" blockId="8.[809,1425,473,771]" pageId="8" pageNumber="431">
The maxilla is reduced as in 
<emphasis id="64A15D5FFF94FA5BFDD6FE22B119EB8D" box="[1167,1339,474,495]" italics="true" pageId="8" pageNumber="431">
<taxonomicName id="91D5FACEFF94FA5BFDD6FE22B115EB8D" box="[1167,1335,474,495]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
and is basically similar to that of this species. It does not participate in the construction of the bony palate, which has no teeth other than the tusks. In MNHN SAO 202, as is observed in 
<taxonomicName id="91D5FACEFF94FA5BFAA4FDACB083E80B" box="[1021,1185,596,617]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFAA4FDACB083E80B" box="[1021,1185,596,617]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
, the portions of the maxillae posterior to the nares are narrow strips of bone and the right is wider than the left. A slight asymmetry of the bones of the face (especially the maxillae) is characteristic of odontocetes, in which the right bones are more developed than the left.
</paragraph>
<paragraph id="566A814DFF94FA5BFD7BFCC7B0B5E935" blockId="8.[1058,1175,831,855]" box="[1058,1175,831,855]" pageId="8" pageNumber="431">FRONTALS</paragraph>
<paragraph id="566A814DFF94FA5BFA70FC90B78DEEF3" blockId="8.[809,1425,872,1169]" pageId="8" pageNumber="431">
The frontals of 
<taxonomicName id="91D5FACEFF94FA5BFA86FC90B046E91F" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[991,1124,872,893]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BFA86FC90B046E91F" box="[991,1124,872,893]" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
also have the same basic pattern observed in 
<taxonomicName id="91D5FACEFF94FA5BFD40FC7FB09EE9FE" box="[1049,1212,903,924]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFD40FC7FB09EE9FE" box="[1049,1212,903,924]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
. The supraorbital process is a large triangular plate overhanging an anterolaterally orientated orbit. The dorsal border of the orbit differs from that of 
<taxonomicName id="91D5FACEFF94FA5BFD9AFC1BB149E99A" box="[1219,1387,995,1016]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFD9AFC1BB149E99A" box="[1219,1387,995,1016]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
in being only slightly concave instead of deeply notched. The condition of 
<taxonomicName id="91D5FACEFF94FA5BFD53FBD8B0BAEE57" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1034,1176,1056,1077]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BFD53FBD8B0BAEE57" box="[1034,1176,1056,1077]" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
probably precluded (certainly reduced) the dorsal binocular vision that was hypothesized by 
<bibRefCitation id="3244FCBCFF94FA5BFD70FBA5B11DEE11" author="de Muizon C &amp; Domning DP &amp; Ketten DR" box="[1065,1343,1117,1139]" pageId="8" pageNumber="431" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF94FA5BFDE9FBA6B0C7EE10" box="[1200,1253,1117,1139]" italics="true" pageId="8" pageNumber="431">et al</emphasis>
. (2002)
</bibRefCitation>
for 
<taxonomicName id="91D5FACEFF94FA5BFC2EFBA6B78AEEF3" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFC2EFBA6B78AEEF3" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
.
</paragraph>
<paragraph id="566A814DFF94FA5BFA80FB36B0C3EE87" blockId="8.[985,1249,1230,1254]" box="[985,1249,1230,1254]" pageId="8" pageNumber="431">PALATINES AND VOMER</paragraph>
<paragraph id="566A814DFF94FA5BFA70FB0FB7D4ED10" blockId="8.[809,1425,1270,1906]" pageId="8" pageNumber="431">
On the palate the vomer of 
<taxonomicName id="91D5FACEFF94FA5BFD3FFB0FB0CBEF69" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1126,1257,1270,1292]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BFD3FFB0FB0CBEF69" box="[1126,1257,1270,1292]" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
is more developed than in 
<taxonomicName id="91D5FACEFF94FA5BFA89FAEEB057EF49" box="[976,1141,1302,1323]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFA89FAEEB057EF49" box="[976,1141,1302,1323]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
, in which it is already much larger than in the other odontocetes. It extends further posteriorly on the palate than in 
<emphasis id="64A15D5FFF94FA5BFC74FAABB759EFE5" italics="true" pageId="8" pageNumber="431">
<taxonomicName id="91D5FACEFF94FA5BFC74FAABB75AEFE5" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">O. peruvianus</taxonomicName>
,
</emphasis>
and as a consequence the palate is wider in its median region and its lateral edges are not so deeply notched. In the posterior region of the palate of the 
<typeStatus id="896E3FEFFF94FA5BFA70FA35B7AFEF81" box="[809,909,1485,1507]" pageId="8" pageNumber="431" type="holotype">holotype</typeStatus>
, the palatines are not in contact medially (as is observed in 
<taxonomicName id="91D5FACEFF94FA5BFA8AFA14B054EC63" box="[979,1142,1516,1537]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFA8AFA14B054EC63" box="[979,1142,1516,1537]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
); as a result, the vomer is visible continuously in the middle of the palate from the anterior crest to the basisphenoid. However, on the referred specimen MNHN SAO 202 the palatines are almost in contact and the condition of the 
<typeStatus id="896E3FEFFF94FA5BFC69F99EB1B3EC1E" box="[1328,1425,1638,1660]" pageId="8" pageNumber="431" type="holotype">holotype</typeStatus>
may be an individual variation. The palate of 
<taxonomicName id="91D5FACEFF94FA5BFC1DF97EB74AECDB" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BFC1DF97EB74AECDB" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
is longer than in 
<taxonomicName id="91D5FACEFF94FA5BFD62F95CB0FEECDB" box="[1083,1244,1700,1721]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFD62F95CB0FEECDB" box="[1083,1244,1700,1721]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
. This condition is mainly due to the fact that the posterior edge of the palate (between the apices of the pterygoid hamuli) is convex posteriorly in the former while it is deeply concave in the latter. Consequently, the palate in 
<taxonomicName id="91D5FACEFF94FA5BFC2EF8E7B7A8ED30" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF94FA5BFC2EF8E7B7A8ED30" italics="true" pageId="8" pageNumber="431">O. leptodon</emphasis>
</taxonomicName>
is much larger than in 
<taxonomicName id="91D5FACEFF94FA5BFDC1F8C6B11AED31" box="[1176,1336,1854,1875]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="8" pageNumber="431" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF94FA5BFDC1F8C6B11AED31" box="[1176,1336,1854,1875]" italics="true" pageId="8" pageNumber="431">O. peruvianus</emphasis>
</taxonomicName>
in both length and width.
</paragraph>
<paragraph id="566A814DFF95FA5AF8D5FF3CB638EABE" blockId="9.[396,538,196,220]" box="[396,538,196,220]" pageId="9" pageNumber="432">PTERYGOIDS</paragraph>
<paragraph id="566A814DFF95FA5AF9C6FF14B5A9E810" blockId="9.[159,775,236,1086]" pageId="9" pageNumber="432">
The pterygoids have a large ventrolateral crest as in 
<taxonomicName id="91D5FACEFF95FA5AF9C6FEF3B566EB43" box="[159,324,267,289]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AF9C6FEF3B566EB43" box="[159,324,267,289]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
, probably for attachment of the pars lateralis of the pterygoid muscle. However, the apex of the pterygoid hamulus is smaller and not as salient posteriorly as in 
<taxonomicName id="91D5FACEFF95FA5AF83DFE9FB624EB1F" box="[356,518,359,381]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AF83DFE9FB624EB1F" box="[356,518,359,381]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
(see below). The apex of the pterygoid hamulus contacts the medial lamina of the pterygoid. The latter is greatly thickened and incorporated into the basioccipital crest as in 
<taxonomicName id="91D5FACEFF95FA5AFBF3FE3BB4C9EB95" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFBF3FE3BB4C9EB95" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
(see below, the description of SMNK PAL 2491, referred to 
<taxonomicName id="91D5FACEFF95FA5AF87DFDF9B5E4E874" box="[292,454,513,534]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AF87DFDF9B5E4E874" box="[292,454,513,534]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
). This contact of the pterygoid hamulus with the enlarged medial lamina of the pterygoid forms a large foramen through which passes the eustachian tube.
</paragraph>
<paragraph id="566A814DFF95FA5AF9E1FD83B64DE92B" blockId="9.[159,775,236,1086]" pageId="9" pageNumber="432">
The pterygoid sinus is extremely reduced when compared to most other odontocetes. It is about one-tenth the size observed in 
<emphasis id="64A15D5FFF95FA5AF8C5FD40B671E8AF" box="[412,595,696,717]" italics="true" pageId="9" pageNumber="432">
<taxonomicName id="91D5FACEFF95FA5AF8C5FD40B66CE8AF" baseAuthorityName="Kasuya" baseAuthorityYear="1973" box="[412,590,696,717]" class="Mammalia" family="Monodontidae" genus="Delphinapterus" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="genus">Delphinapterus</taxonomicName>
,
</emphasis>
and if a functional sinus was actually present it was obviously vestigial. In fact, the lateral side of the 
<taxonomicName id="91D5FACEFF95FA5AFB39FD0EB725E969" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[608,775,758,779]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF95FA5AFB39FD0EB725E969" box="[608,775,758,779]" italics="true" pageId="9" pageNumber="432">Odobenocetops</emphasis>
</taxonomicName>
skull between the apex of the tympanic and the pterygoid hamulus is considerably shortened.
</paragraph>
<paragraph id="566A814DFF95FA5AF9E1FCAAB590EE5C" blockId="9.[159,775,236,1086]" pageId="9" pageNumber="432">A small lateral lamina of the pterygoid is present. However, contrary to the condition in other odontocetes it does not articulate with the squamosal but with the alisphenoid. It forms the anterior border of the foramen ovale on the lateral wall of the skull. This condition is only superficial since internally the foramen ovale is fully enclosed in the alisphenoid as in the other eutherians.</paragraph>
<paragraph id="566A814DFF95FA5AF8DFFB8AB602EEE8" blockId="9.[390,544,1138,1162]" box="[390,544,1138,1162]" pageId="9" pageNumber="432">ALISPHENOID</paragraph>
<paragraph id="566A814DFF95FA5AF9C6FB63B110EB55" blockId="9.[159,775,1179,1906]" lastBlockId="9.[823,1439,197,311]" pageId="9" pageNumber="432">
As in 
<taxonomicName id="91D5FACEFF95FA5AF9B1FB63B5A9EED2" box="[232,395,1179,1200]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AF9B1FB63B5A9EED2" box="[232,395,1179,1200]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
, the alisphenoid is a very thick bone, which contrasts with the condition observed in the other delphinoids. The foramen ovale is well separated from the cranial hiatus and not confluent with it as in the 
<typeStatus id="896E3FEFFF95FA5AF874FAEDB5ACEF49" box="[301,398,1301,1323]" pageId="9" pageNumber="432" type="holotype">holotype</typeStatus>
of 
<taxonomicName id="91D5FACEFF95FA5AF8EFFAEEB67BEF49" box="[438,601,1302,1323]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AF8EFFAEEB67BEF49" box="[438,601,1302,1323]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
, in which it is probably broken (see, below, the description of SMNK PAL 2491, a specimen referred to 
<taxonomicName id="91D5FACEFF95FA5AFB63FAABB6FCEF0A" box="[570,734,1363,1384]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFB63FAABB6FCEF0A" box="[570,734,1363,1384]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
, in which the alisphenoid region is much better preserved than in the 
<typeStatus id="896E3FEFFF95FA5AF86DFA68B5BAEFC4" box="[308,408,1424,1446]" pageId="9" pageNumber="432" type="holotype">holotype</typeStatus>
, USNM 488257). The foramen ovale is enormous (two to three times the size observed in 
<taxonomicName id="91D5FACEFF95FA5AF999FA35B552EF80" baseAuthorityName="Kasuya" baseAuthorityYear="1973" box="[192,368,1485,1506]" class="Mammalia" family="Monodontidae" genus="Delphinapterus" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF95FA5AF999FA35B552EF80" box="[192,368,1485,1506]" italics="true" pageId="9" pageNumber="432">Delphinapterus</emphasis>
</taxonomicName>
), as is observed in 
<taxonomicName id="91D5FACEFF95FA5AFB05FA36B722EF81" box="[604,768,1486,1507]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFB05FA36B722EF81" box="[604,768,1486,1507]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
. The mandibular nerve, which exits the skull through the foramen ovale, has eight branches in the dog (
<bibRefCitation id="3244FCBCFF95FA5AF9FFF9D1B5A2EC5D" author="Miller ME &amp; Christensen GC &amp; Evans HE" box="[166,384,1577,1599]" pageId="9" pageNumber="432" refId="ref22612" refString="Miller ME, Christensen GC, Evans HE. 1964. Anatomy of the dog. Philadelphia: W. B. Saunders." type="book" year="1964">
Miller 
<emphasis id="64A15D5FFF95FA5AF9A1F9D2B50FEC5C" box="[248,301,1577,1599]" italics="true" pageId="9" pageNumber="432">et al</emphasis>
., 1964
</bibRefCitation>
): the pterygoid nerve, the buccal nerve, the deep temporal nerve, the masseteric nerve, the auriculotemporal nerve, the mylohyoid nerve, the mandibular alveolar nerve, and the lingual nerve. It is a mixed nerve, sensory and motor. Of course the condition in 
<taxonomicName id="91D5FACEFF95FA5AF85FF93BB58FECBA" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[262,429,1731,1752]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF95FA5AF85FF93BB58FECBA" box="[262,429,1731,1752]" italics="true" pageId="9" pageNumber="432">Odobenocetops</emphasis>
</taxonomicName>
was not necessarily similar to that in the dog. However, it is noteworthy that these branches totally or partially innervate the tongue, the masticatory and digastricus muscles, the hyoid muscles, the cheeks, and the lips. Therefore, the size of the foramen ovale and the inferred large size of the mandibular nerve are consistent with the large size of the tongue, the upper lip and the jaw muscles as well as with their function as hypothesized by 
<bibRefCitation id="3244FCBCFF95FA5AFC7CFEFAB7A7EB55" author="de Muizon C" pageId="9" pageNumber="432" pagination="745 - 748" refId="ref22882" refString="de Muizon C. 1993 a. Walrus-like feeding adaptation in a new cetacean from the Pliocene of Peru. Nature 365: 745 - 748." type="journal article" year="1993">de Muizon (1993a</bibRefCitation>
,b) and 
<bibRefCitation id="3244FCBCFF95FA5AFA85FED9B0FDEB54" author="de Muizon C &amp; Domning DP &amp; Parrish M" box="[988,1247,289,311]" pageId="9" pageNumber="432" pagination="449 - 455" refId="ref23136" refString="de Muizon C, Domning DP, Parrish M. 1999. Dimorphic tusks and adaptive strategies in a new species of walrus-like dolphin (Odobenocetopsidae) from the Pliocene of Peru. Comptes-rendus de l'Academie des Sciences, Paris, Sciences de la Terre et des Planetes 329: 449 - 455." type="journal article" year="1999">
de Muizon 
<emphasis id="64A15D5FFF95FA5AFD05FEDAB0ACEB54" box="[1116,1166,289,311]" italics="true" pageId="9" pageNumber="432">et al</emphasis>
. (1999
</bibRefCitation>
; 
<bibRefCitation id="3244FCBCFF95FA5AFDB5FED9B105EB55" author="de Muizon C &amp; Domning DP &amp; Ketten DR" box="[1260,1319,289,311]" pageId="9" pageNumber="432" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">2002</bibRefCitation>
).
</paragraph>
<paragraph id="566A814DFF95FA5AFD7FFE8BB092EBE9" blockId="9.[1062,1200,371,395]" box="[1062,1200,371,395]" pageId="9" pageNumber="432">SQUAMOSAL</paragraph>
<paragraph id="566A814DFF95FA5AFA6EFE64B023EF81" blockId="9.[823,1440,412,1507]" pageId="9" pageNumber="432">
The major characteristic of the squamosal of 
<taxonomicName id="91D5FACEFF95FA5AFC6DFE64B759EBB2" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF95FA5AFC6DFE64B759EBB2" italics="true" pageId="9" pageNumber="432">Odobenocetops</emphasis>
</taxonomicName>
is the highly modified glenoid cavity and zygomatic process, described by 
<bibRefCitation id="3244FCBCFF95FA5AFDDDFE21B1B9EB8D" author="de Muizon C &amp; Domning DP &amp; Ketten DR" box="[1156,1435,473,495]" pageId="9" pageNumber="432" refId="ref23097" refString="de Muizon C, Domning DP, Ketten DR. 2002. Odobenocetops peruvianus, the walrus-convergent delphinoid (Cetacea, Mammalia) from the lower Pliocene of Peru. Smithsonian Contribution to Paleobiology 93: in press." type="book" year="2002">
de Muizon 
<emphasis id="64A15D5FFF95FA5AFC53FE22B11DEB8C" box="[1290,1343,473,495]" italics="true" pageId="9" pageNumber="432">et al</emphasis>
. (2002)
</bibRefCitation>
, which forms a large, anteroposteriorly orientated gutter-like cavity (
<figureCitation id="CEEE9DC8FF95FA5AFD7AFDEEB0AAE84E" box="[1059,1160,534,556]" captionStart="Figure 1" captionStartId="3.[823,902,1340,1361]" captionTargetBox="[842,1419,198,1308]" captionTargetId="figure-576@3.[836,1445,193,1316]" captionTargetPageId="3" captionText="Figure 1. Odobenocetops leptodon, holotype (SMNK PAL 2492). Skull: left ventrolateral view (A), anterior view (approximately parallel to the feeding plane) (B)." figureDoi="http://doi.org/10.5281/zenodo.4687171" httpUri="https://zenodo.org/record/4687171/files/figure.png" pageId="9" pageNumber="432">Figs 1B</figureCitation>
and 
<figureCitation id="CEEE9DC8FF95FA5AFD83FDEEB0C8E84E" box="[1242,1258,534,556]" captionStart="Figure 6" captionStartId="10.[145,224,1211,1232]" captionTargetBox="[150,757,196,1179]" captionTargetId="figure-595@10.[149,757,196,1179]" captionTargetPageId="10" captionText="Figure 6. Auditory region of Odobenocetops leptodon, holotype (SMNK PAL 2492). Lateral view (A) and posterolateral view showing the tympanic aperture (B). On B, the outline of the tympanic aperture has been enhanced with a white line.Abbreviations:Ap, anterior process of the periotic; Bo, basioccipital; Cho, choanae; Eam, external auditory meatus; Fo, foramen ovale; Gf, glenoid fossa; Llpt, lateral lamina of the pterygoid; Oc, occipital condyle; Pa, palatine; Ptc, pterygoid crest; Ptp, post-tympanic process of the squamosal; po, paroccipital process of the exoccipital; Pts, pterygoid sinus; Sp, sigmoid process of the tympanic; Tym, tympanic." figureDoi="http://doi.org/10.5281/zenodo.4687189" httpUri="https://zenodo.org/record/4687189/files/figure.png" pageId="9" pageNumber="432">6</figureCitation>
). This region, although following the same basic pattern in the two species, shows some differences in 
<taxonomicName id="91D5FACEFF95FA5AFD9EFDACB168E80B" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[1223,1354,596,617]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF95FA5AFD9EFDACB168E80B" box="[1223,1354,596,617]" italics="true" pageId="9" pageNumber="432">O. leptodon</emphasis>
</taxonomicName>
. In the latter, the glenoid cavity is approximately 15% shorter anteroposteriorly. Furthermore, in lateral view, the posterior border of the glenoid cavity lies 
<quantity id="912D2CA8FF95FA5AFC4DFD48B140E8A7" box="[1300,1378,688,709]" metricMagnitude="-2" metricUnit="m" metricValue="3.5" metricValueMax="4.0" metricValueMin="3.0" pageId="9" pageNumber="432" unit="cm" value="3.5" valueMax="4.0" valueMin="3.0">3–4 cm</quantity>
from the lambdoid crest of the exoccipital, whereas in 
<taxonomicName id="91D5FACEFF95FA5AFCDCFD37B794E961" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFCDCFD37B794E961" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
the posterior edge of the cavity is at the level of the crest. The lateral wall of the glenoid cavity (or gutter), although concave ventrolaterally, is almost horizontal and not strongly recurved ventrally as is observed in 
<taxonomicName id="91D5FACEFF95FA5AFA94FC90B056E91F" box="[973,1140,872,893]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFA94FC90B056E91F" box="[973,1140,872,893]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
. Furthermore, the zygomatic process of the squamosal is apparently located in a higher and more anterior position on the skull. This condition is not easy to observe on the available specimens of 
<emphasis id="64A15D5FFF95FA5AFA8AFC1BB07CE995" box="[979,1118,994,1016]" italics="true" pageId="9" pageNumber="432">
<taxonomicName id="91D5FACEFF95FA5AFA8AFC1BB078E995" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[979,1114,994,1016]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="leptodon">O. leptodon</taxonomicName>
,
</emphasis>
since the roof of the braincase is almost totally lacking in SMNK PAL 2492 and the process is broken in MNHN SAO 202. It is clear, however, that the anterior notch of the glenoid cavity of 
<taxonomicName id="91D5FACEFF95FA5AFAFCFBA5B009EE10" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" box="[933,1067,1117,1138]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF95FA5AFAFCFBA5B009EE10" box="[933,1067,1117,1138]" italics="true" pageId="9" pageNumber="432">O. leptodon</emphasis>
</taxonomicName>
is closer to the lateral ridge of the frontal (the posterior extension of the posterior edge of the supraorbital process) than in 
<taxonomicName id="91D5FACEFF95FA5AFC65FB63B7A1EEAD" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFC65FB63B7A1EEAD" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
. This separation measures 
<emphasis id="64A15D5FFF95FA5AFD9FFB42B0F3EEAD" box="[1222,1233,1210,1231]" italics="true" pageId="9" pageNumber="432">c</emphasis>
. 
<quantity id="912D2CA8FF95FA5AFDB8FB41B10AEEAD" box="[1249,1320,1209,1231]" metricMagnitude="-2" metricUnit="m" metricValue="5.1" pageId="9" pageNumber="432" unit="cm" value="5.1">5.1 cm</quantity>
in SMNK PAL 2492 and 
<emphasis id="64A15D5FFF95FA5AFAB1FB20B7D1EE8F" box="[1000,1011,1240,1261]" italics="true" pageId="9" pageNumber="432">c</emphasis>
. 
<quantity id="912D2CA8FF95FA5AFD5CFB20B06EEE8F" box="[1029,1100,1240,1262]" metricMagnitude="-2" metricUnit="m" metricValue="6.3" pageId="9" pageNumber="432" unit="cm" value="6.3">6.3 cm</quantity>
in MNHN SAO 202 (
<taxonomicName id="91D5FACEFF95FA5AFC08FB20B754EF69" baseAuthorityName="SMNK PAL" baseAuthorityYear="2492" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="leptodon">
<emphasis id="64A15D5FFF95FA5AFC08FB20B754EF69" italics="true" pageId="9" pageNumber="432">O. leptodon</emphasis>
</taxonomicName>
); 
<emphasis id="64A15D5FFF95FA5AFACBFB0FB7BFEF6E" box="[914,925,1271,1292]" italics="true" pageId="9" pageNumber="432">c</emphasis>
. 
<quantity id="912D2CA8FF95FA5AFAE9FB0EB7D5EF6E" box="[944,1015,1270,1292]" metricMagnitude="-2" metricUnit="m" metricValue="9.5" pageId="9" pageNumber="432" unit="cm" value="9.5">9.5 cm</quantity>
in USNM 488257 and 
<emphasis id="64A15D5FFF95FA5AFC4EFB0FB100EF6E" box="[1303,1314,1271,1292]" italics="true" pageId="9" pageNumber="432">c</emphasis>
. 
<quantity id="912D2CA8FF95FA5AFC6CFB0FB15EEF6E" box="[1333,1404,1271,1292]" metricMagnitude="-2" metricUnit="m" metricValue="9.2" pageId="9" pageNumber="432" unit="cm" value="9.2">9.2 cm</quantity>
in SMNK PAL 2491 (
<taxonomicName id="91D5FACEFF95FA5AFD46FAEDB0E4EF49" box="[1055,1222,1301,1323]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFD46FAEDB0E4EF49" box="[1055,1222,1301,1323]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
). The squamosalparietal suture is especially clear on MNHN SAO 202. It is similar to that described for 
<taxonomicName id="91D5FACEFF95FA5AFDB6FAABB1BAEF0A" box="[1263,1432,1363,1384]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="species" species="peruvianus">
<emphasis id="64A15D5FFF95FA5AFDB6FAABB1BAEF0A" box="[1263,1432,1363,1384]" italics="true" pageId="9" pageNumber="432">O. peruvianus</emphasis>
</taxonomicName>
, having the same unusual zig-zag shape. This is likely to represent an adaptation to strong muscular tensions applied to the bones during the suction feeding of 
<taxonomicName id="91D5FACEFF95FA5AFA0DFA35B7D9EF80" authorityName="LEPTODON MUIZON, DOMNING &amp; PARRISH" authorityYear="1999" box="[852,1019,1485,1506]" class="Mammalia" family="Odobenocetopsidae" genus="Odobenocetops" higherTaxonomySource="GBIF" kingdom="Animalia" order="Cetacea" pageId="9" pageNumber="432" phylum="Chordata" rank="genus">
<emphasis id="64A15D5FFF95FA5AFA0DFA35B7D9EF80" box="[852,1019,1485,1506]" italics="true" pageId="9" pageNumber="432">Odobenocetops</emphasis>
</taxonomicName>
.
</paragraph>
</subSubSection>
</treatment>
</document>