MODERN FIELD WORK IN THE UINTA BASIN

Despite its importance in the biostratigraphic and paleoecological framework of mammalian evolution in the Eocene, field work in the Uinta Basin was patchy throughout much of the 20^th century. Although various museums sent crews to collect representative samples of the fauna, no continuous, focused work was done on the sediments until the 1990’s. It was then that yearly field crews based out of Washington University in St. Louis began to systematically collect mammals from the type sediments of the Uintan and Duchesnean North American Land Mammal ages. The focus of these expeditions was on small mammals, which were missing from many of the early collections, which focused on large, museum-grade specimens. The work led to expanding the sample of small to medium-sized mammals, both taxonomically and in terms of numbers of individuals, including members of the mammalian orders Primates, Rodentia, Artiodactyla, Carnivora, and Lipotyphla. With the addition of fine stratigraphic work in the eastern basin, these collections have allowed for better biostratigraphic controls on faunal ranges and investigations of the evolution of taxa through this under-sampled time in North American mammalian evolution. The work continues to this day, with field crews from Midwestern University, College of Charleston, Lamar University, UCLA, and the San Diego Museum of Natural History. Most recently, work has focused on better stratigraphic control and tying together the Uinta and Duchesne River Formations, as well as screen-washing for better collections of the smallest, but biostratigraphically important, taxa. In addition, field work has expanded to the poorly sampled western Basin, comparisons have been made to other similar aged taxa across North America, and an effort has been made to tie the fauna to global climate changes that were occurring at this time.