PALEOECOLOGY OF THE MID-MIOCENE TONOPAH LOCAL FAUNA OF SOUTHWESTERN NEVADA

The Tonopah Local Fauna (TLF) is a Barstovian fauna from the western slope of the San Antonio Mountains, a few miles north of Tonopah, Nevada. Formation terminology is unsettled; the fauna has been variously referred to the Siebert Formation, the Tonopah Formation, and the Esmeralda Formation. A very diverse assemblage of herbivores and carnivores is present within this fauna, including canids, felids, rhinocerotids, camelids, equids, antilocaprids, insectivores, rodents, and lagomorphs. The fauna is curiously rich in carnivores, with four canid taxa, one felid, and one mustelid.

We are engaged in a study of the sedimentology and paleoecology of this assemblage, which lived just prior to the Mid-Miocene Climate Optimum (MMCO), a 3-4 million year-long interval of anomalously high temperatures. Comparison of the TLF with other Great Basin Miocene communities, such as the Coal Valley, Stewart Springs, and Barstow Formation faunas, will improve our understanding of how mammal communities responded to long-term climate change in the Miocene. The Coal Valley assemblage, for example, also of southwestern Nevada, was deposited just after the MMCO, providing an opportunity to examine how the MMCO impacted Great Basin mammal communities. Paleoecological aspects to be compared include community structure, diversity, and food web complexity.