Paper No. 7
Presentation Time: 9:00 AM-6:30 PM
PROGRESS REPORT ON THE FIRST UINTA C MICRO-MAMMAL FAUNA FROM THE UINTA BASIN AND ITS COMPARISON WITH THE CASA BLANCA MAMMAL COMMUNITY FROM LAREDO, TEXAS
Since 2007, our collaborative team has focused on the collection of micro-mammal remains from the WU-26 locality in Uintah County, Utah. This is the first micro-mammal site discovered in the Uinta C Member of the Uinta Formation. So far we have excavated and screen-washed 20 tons of bulk sample and examined the fine concentrate with binocular microscopes. Most recovered mammal specimens are isolated cheek teeth ranging in size between 1-2 mm. The sample size now exceeds 300 mammal specimens identifiable to genus or species. The more common taxa are beginning to be represented by statistically significant sample sizes. WU-26 is stratigraphically located in the uppermost portion of the Uinta C member of the late middle Eocene Uinta Formation and lies 40 m below the base of the Brennan Basin Member of the Duchesne River Formation. The Uinta Formation is the type locality for mammalian specimens, which define the Uintan North American Land Mammal age. WU-26 provides a unique glimpse into the mammal community which inhabited the Uinta Basin near the end of deposition of the Uinta Formation and indicates that several micro-mammal species thought to be restricted to the Uinta B Member actually continued to inhabit the Uinta Basin throughout the time during which most of the Uinta C Member was deposited.
The WU-26 sample size is beginning to be large enough to make meaningful comparisons with micro-mammal communities outside the Uinta Basin. More than 1000 micro-mammal specimens have been collected at the Uinta C correlate Casa Blanca locality, TMM 42486, from the tropical and parallic, late middle Eocene, Laredo Formation, at Laredo, Texas. The two faunas display many similarities at the ordinal level, including having five species of primates. Taxa common to both faunas include Herpetotherium, Microsyops, Mytonius, Epihippus, Protoreodon, Mytonomys, Microparamys, and Pauromys, indicating that although geographically disjunct, both environments shared habitats compatible for these genera. However, it appears that the two communities shared few species as Protoreodon parvus is the only species so far recognized to be present in both faunas.