The Panaca Formation is exposed in Lake, Meadow, and Spring Valleys, Lincoln County, southeastern Nevada, USA (Figure 1), and represents basin-fill deposition. The caprine remains reported here are from Meadow Valley, a feature formed during middle to late Miocene crustal extension (Bartley et al. 1988). Phoenix (1948) estimated the total thickness of the Panaca Formation to be approximately 427 m. Sedimentological studies by Pederson et al. (1999) indicate that the deposit consists of horizontally stratified siltstones, sandstones, and mudstones, with occasional small artesian spring-formed lacustrine deposits (see review in Lindsay et al. 2002).
Stock (1921) first recovered and briefly described fossils from the Panaca Formation. White (1987, 1991) reported the leporids Hypolagus edensis, Lepoides lepoides, Pewelagus dawsoni, and Nekrolagus progressus and considered them characteristic taxa of the Blancan. Repenning (1987) placed the fauna in the early Blancan, based on his study of Repomys panacaensis and arvicolid (microtine) rodents Mimomys (Ophiomys) magilli and Pliopotamys meadensis. Mou (1997) described the primitive arvicolid Mimomys panacaensis from UALP locality 8197, a site correlative with and adjacent to Stock’s AMNH Limestone Corner locality (Lindsay et al. 2002). The caprine specimens reported here were recovered from the Limestone Corner locality in 1940 and reportedly were recovered as a single cluster of skeletal elements, implying that they are related and represent a single individual (a premise followed here). This concept is consistent with the state of preservation and age of growth for various skeletal elements. All the small mammals and the artiodactyls from the Panaca Formation in Meadow Valley are more characteristic of the Blancan than of the previous Hemphillian Age and are part of the Rodent Ravine section of Lindsay et al. (2002).
The stratigraphic interval preserved in Meadow Valley spans about one million years, from approximately 5.5 Ma (upper part of chron C3r GPTS [Geomagnetic Polarity Time Scale]) to about 4.5 Ma (chron C3n.2n GPTS), as interpreted by Lindsay et al. (2002). Their work places the fauna of the Panaca Formation in Blancan I of Repenning (1987), its base in eastern Nevada being approximately 4.95 Ma. The age of the caprine remains reported here are between approximately 4.95 and 4.50 Ma (chron C3n.3r GPTS), immediately above the Hemphillian/Blancan NALMA boundary (Lindsay et al. 2002).
AMNH, American Museum of Natural History, New York, USA; GRCA, Grand Canyon National Park; NAUQSP, Northern Arizona University Quaternary Sciences Program, Laboratory of Quaternary Paleontology; PLWZM UM, Philip L. Wright Zoological Museum, University of Montana; UALP, University of Arizona Laboratory of Paleontology, Tucson, Arizona, USA.