SMALL RODENTS OF THE UINTA FORMATION

Recent screen-washing efforts in the Uinta Formation of northeastern Utah have produced evidence of a number of small-bodied mammals (>500g), particularly rodents, which has increased the sample size of known taxa and expanded the temporal range of others. Well-known small rodents from the Uinta Formation include multiple species of the cylindrodontid Pareumys, the sciuravid Sciuravus, and the protoptychid Protoptychus. While these are certainly small-bodied taxa, they have primarily been recovered via surface collection. Prior to screen-washing, much smaller micro-rodents were a rare occurrence in our collections. All of the specimens come from the high Uinta C locality, WU-26 and include the taxa: Janimus sp., Pauromys sp., Pareumys sp., and Microparamys sp. Janimus was only known from the Uinta Formation by the type specimen initially described by Dawson (1966), this current report expands the known hypodigm. The temporal range of Pauromys extends from the early Eocene Wasatchian North American Land Mammal Age (NALMA) to the latest Uintan NALMA of Texas. The new finding of Pauromys in the late Uintan of Utah lends support to the idea that the provinciality of middle Eocene mammalian communities in North America may not be very strong. Additionally, the range of Microparamys is expanded into the late Uintan (Ui3) by its presence at WU-26. These tiny rodents in the late Uintan also suggests that there was greater taxonomic and ecological homogeneity in middle Eocene faunas than previously thought.