Petrosal and Basicranial Morphology of Leptoreodon major (Protoceratidae, Artiodactyla)

Abstract

Leptoreodon is a basal member of the Protoceratidae, an extinct group of artiodactyls variably allied with the Camelidae and the Ruminantia. The basicranial morphology of other protoceratids (Leptotragulus, Protoceras, Syndyoceras) is similar to that of ruminants, supporting the hypothesis that the two clades are closely related. However, study of the basicranium of Leptoreodon major has revealed that protoceratid basicranial morphology is more variable than previously thought. Leptoreodon does share morphological features with some, if not all, other protoceratids, but the taxon also has some features not previously documented in the family. These previously undocumented features resemble the basicranial morphology of camelids rather than ruminants, suggesting that previous hypotheses of protoceratid relationships need to be reexamined.