THE SKULL OF ANCHITHERIOMYS AND A NEW SUBFAMILY OF BEAVERS (CASTORIDAE, RODENTIA)

A nearly complete skull of Anchitheriomys from the Miocene of Nebraska allows description of the cranial foramina. In skull characters, Anch itheriomys most closely resembles Agnotocastor and Neatocastor among c astorids; it retains primitive features that it shares with eutypomyid s (position of the posterior palatine foramina, smooth palatal surface , nearly parallel tooth rows, retention of dP3) combined with derived features (elongate rostrum, procumbent incisors) that are shared only with Agnotocastor and Neatocastor. A new subfamily, Agnotocastorinae, is erected for this group of primitive beavers.