Odobenocetops, MUIZON, 1993

Muizon, Christian de & Domning, Daryl P., 2002, The anatomy of Odobenocetops (Delphinoidea, Mammalia), the walrus-like dolphin from the Pliocene of Peru and its palaeobiological implications, Zoological Journal of the Linnean Society 134 (4), pp. 423-452 : 424

ODOBENOCETOPS MUIZON, 1993

Type species: Odobenocetops peruvianus Muizon, 1993 . Emended diagnosis: delphinoid cetacean which does not possess the elongated rostrum present in all other cetaceans. The rostrum is short, rounded, and blunt; it is formed by the premaxillae which are greatly enlarged and have large, asymmetrical ventral alveolar sheaths holding sexually dimorphic tusks. The right tusk of the male is large and can reach one metre or more in length. It is cylindrical and its section is mediolaterally compressed (the long axis measures c. 4–5 cm). The left tusk of the male was only between 20 and 25 cm long, of which a few cm were erupted. Its section is also mediolaterally compressed. Both tusks are straight. In the female, the right tusk is only slightly larger than the left and both protruded only a few cm from the gum. Premaxillary sheaths and tusks form an angle of approximately 60–70° with the dorsal plane of the skull. The bony nares have been displaced anteriorly and are anteroposteriorly elongated. The palate is very deep and arched, and its anterior border (which is formed by the anterior edges of the alveolar sheaths) is U- to V-shaped. On the palate the vomer is very large and the premaxillae and the pterygoids are in contact with it. The maxillae have been excluded from the palate and relegated to a small triangular area on the lateral side of the rostrum and an elongated strip on the dorsal face of the skull. The postorbital processes are large and lateral to the posterior end of the nares. The orbits face anterolaterally and dorsally. The portions of the frontals and maxillae which cover the temporal fossae in the other odontocetes have been reduced and narrowed in such a way that the temporal fossae are opened dorsally. Ventrally, the crest of the hamular processe of the pterygoid is strong and rounded and the choanae are very wide. The basioccipital is extremely wide and long. The glenoid cavity of the squamosal is an anteroposteriorly elongated groove. The occipital condyles are very salient and more convex than in any other Pliocene or living cetacean.