PaleoBios

Leptarctus is a morphologically distinctive carnivoran mammal occurring in Miocene deposits of North America and East Asia. In North American Leptarctus is mostly known from the Great Plains and Florida, but the single occurrence in China and recent description of well-preserved specimens in Oregon indicate that the western North American distribution of the genus is understudied. Here I document previously unreported specimens of Leptarctus and review other leptarctines housed in the collections of the University of California Museum of Paleontology (UCMP). Dental materials of at least four species of Leptarctus are present in the UCMP collections, encompassing occurrences from the Hemingfordian to Hemphillian North American Land Mammal Ages, adding to known records in the Great Plains, and expanding the paleogeographic range of L. wortmani into Nevada. Materials representing the genus in California are fragmentary but confirm the presence of L. wortmani in the Black Hawk Ranch locality in the coastal ranges of northern California, and L. ancipidens in the Cajon Valley in the southern Great Basin region of southern California.