The Hemphillian (~8Ma) Thousand Creek Fauna of northwestern Nevada contains three species of closely related antilocaprids in two genera, Ilingoceros alexandrae, Ilingoceros schizoceras, and Sphenophalos nevadanus. These species were diagnosed on the basis of their distinct horn morphology, but the little work done comparing their dental or postcranial morphology showed no clear separation between the species, leading to a hypothesis that the two Ilingoceros were age classes and that Ilingoceros and Sphenophalos represented sexual morphs within one species. We used multivariate morphometric comparison of eight linear dimensions of >200 antilocaprid astragali from Thousand Creek to find out if there is enough variation to support the presence of more than one species.
Preliminary results have been presented by Dr. Edward Davis at the annual meeting of the Society of Vertebrate Paleontology in Austin (2007). The results of this research project are published in Palaeontologia Electronica.
Davis, E. B., and Calede, J.2012. Multivariate analysis of Hemphillian (Late Miocene) and recent antilocaprid astragali indicates little divergence between Ilingoceros and Sphenophalos in the Thousand Creek Formation, Nevada. Paleontologia Electronica 15.1.1A.
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Collaborator: Edward Davis