A RANCHOLABREAN VERTEBRATE FAUNA FROM MURRIETA, CALIFORNIA

Mitigation projects in the city of Murrieta, in southwestern Riverside County, California, have recovered numerous vertebrate fossils, primarily from the Irvingtonian Pauba Formation. A collection recovered in 2003 from an unnamed sandstone unit overlying the Pauba Formation in the Harveston neighborhood of northern Murrieta appears to represent the first Rancholabrean fauna from the city, based on the presence of Bison antiquus. In addition to Bison, the Harveston fauna includes numerous remains of Equus occidentalis, and much rarer remains of Equus conversidens. Other taxa include Mammuthus columbi, Camelops hesternus, Paramylodon harlani, Paleolama sp., an antilocaprid comparable in size to Antilocapra, Odocoileus cf. O. virginianus, and Microtus sp.. The possible presence of Odocoileus virginianus is interesting, as this taxon is not currently found in Southern California and the larger O. hemionus which lives today in the region has not been identified in the Harveston fauna. The presence of Equus, Bison, Mammuthus, and Microtus in the Harveston fauna, along with the absence of Mammut and Tapirus (both of which are known from the Pauba Formation in Murrieta), suggests that the Murrieta area may have shifted to a more open and perhaps drier habitat between the Irvingtonian and Rancholabrean.