Prolapsus, A Large Sciuravid Rodent: And New Eomyids From the Late Eocene of Trans-Pecos Texas

The questionably hystricognathous and hystricomorphous rodent Prolapsus is assigned, on the basis of its dental characters, to the Family Sciuravidae. The complete dentition of Prolapsus sibilamoris is now known but P. junctionis is still represented by isolated teeth only. Prolapsus sp. of Wood(1973) is now identified as a species of Pauronys. Prolapsus is found in the early Uintan Whistler Squat local fauna and late Uintan Serendipity local fauna at several localities in Trans-Pecos Texas and is closely related to a new emoyid genus, Aguafriamys, here described, that occurs in sediments of Duchesnean age in the same area. If Prolapsus is interpreted as being truly hystricognathous it follows that this character has evolved more than once. A new species of Yoderimys is described from the Coffee Cup local fauna Chadronian age.