THE LATE PLEISTOCENE (RANCHOLABREAN) VIKO VIJIN LOCAL FAUNA FROM LA MIXTECA ALTA, NORTHWESTERN OAXACA, SOUTHERN MEXICO

Paleontological work carried out in the Late Pleistocene floodplain and bar fluvial deposits of northwestern Oaxaca, southern Mexico, resulted in collecting cranial and poscranial material of mammals identified as Glyptotherium, Hemiauchenia, Camelops, Odocoileus, two Equus species, Cuvieronius, Mammuthus and Bison. The presence of Bison in all the localities indicates a Rancholabrean North American Land Mammal age for the faunal assemblage. Also, many mollusk specimens were collected and belong to five families of terrestrial gastropods, three families of freshwater gastropods, and one family of freshwater bivalves. Additionally, several fragments of Rodentia indet., sigmodontine rodents, and scincomorph lizards were also recovered through the screen-washing of sediments. This faunal association was designed herein as the Viko vijin (cold epoch or period in Mixteca language) Local Fauna (L. F.) and shares nine mammalian taxa with the Rancholabrean local faunas of Terapa (Sonora, NW Mexico), Chapala (Jalisco), El Cedazo (Aguascalientes) and Tequixquiac (Mexico), central Mexico. Likewise, five of the eight mollusk families identified are also present in the Late Pleistocene Rancho La Amapola, San Luis Potosi, Central Mexico. The presence of the llama Hemiauchenia in Oaxaca represents the southern-most record of this genus during the Late Pleistocene in North America, while Late Pleistocene scincomorph lizards are recorded for first time in Oaxaca. Similarly, the records of the mollusk families Bulimulidae, Polygyridae and Urocoptidae in the Mixteca Alta Oaxaquenit are the first for Mexico and allow extend their geographic ranges from southern USA to southern Mexico during the Late Pleistocene.