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1 September 2015 New Insights on the Most Primitive Desmostylian from a Partial Skeleton of Behemotops (Desmostylia, Mammalia) from Vancouver Island, British Columbia
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Abstract

A partial articulated skeleton of a desmostylian was found in siltstone of the Sooke Formation in the streambed at the mouth of the Sombrio River in Juan De Fuca Provincial Park, Vancouver Island, British Columbia, Canada. Another exposure of the Sooke Formation southeast of the locality has been dated to Chron C6Cr age, 24.1–24.8 Ma. This specimen includes the left side of the skull, two molars, a premolar, canines, partial scapula, nearly complete humerus, and numerous vertebrae and ribs. Molar characteristics are the same as material of Behemotops proteus from the Pysht Formation of Washington State, which is near the type locality of Behemotops proteus of the upper Oligocene Pysht Formation, Washington State. Previous specimens of B. proteus were limited to lower jaws and portions of the upper and lower postcanine dentitions. The slightly smaller Behemotops katsuiei from Japan is known from more elements, yet its cranial material is limited to the posterior portion of the cranium and a small portion of the zygomatic arch. This new material allows us to see that Behemotops cf. B. proteus had cranial features much like those seen in Cornwallius sookensis of North America. These include a postorbital process of the jugal, with the zygomatic process of the squamosal not dorsally expanded, a concave hard palate, enlarged canine tusks that point ventrally, and a narrow, curved incisor arcade on a narrow rostrum. This is different from specimens previously referred to as Behemotops emlongi and then synonymized with B. proteus, which have a broad symphysis with large tusks. These specimens formerly known as B. emlongi are now referred to a new genus.

© by the Society of Vertebrate Paleontology
Brian Lee Beatty and Thomas C. Cockburn "New Insights on the Most Primitive Desmostylian from a Partial Skeleton of Behemotops (Desmostylia, Mammalia) from Vancouver Island, British Columbia," Journal of Vertebrate Paleontology 35(5), (1 September 2015). https://doi.org/10.1080/02724634.2015.979939
Received: 23 April 2014; Accepted: 1 October 2014; Published: 1 September 2015
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