Date of this Version
A new genus of sciurid, Cynomyoides, is named. The new genus includes a new species from the late Clarendonian of Nebraska, C. vatis (type species), and an unnamed species from the early Barstovian of Montana. The dental and mandibular morphology of Cynomyoides is reminiscent of that of the latest Tertiary to Recent prairie dog Cynomys and is believed to be part of the lineage leading to Cynomys. The recognition of a Miocene genus of prairie dog extends the known record of these ground squirrels well back into the Tertiary and makes it much less likely that Cynomys was derived from a species of the ground squirrel Spermophilus in the latest Tertiary, as has been suggested by previous authors. A new scheme for the classification of nearctic marmotines is proposed.