Una nueva localidad fosilífera en Oaxaca (México) y el registro más austral de Bison latifrons. Implicaciones paleobiogeográficas, paleoecológicas y paleoambientales

Abstract

We report the southernmost record of Bison latifrons in North America. This is the first record for the species in Oaxaca (Mexico), and for the Transmexican Volcanic Belt morphotectonic province; the known geographic distribution range of Bison latifrons is extended in more than 447 km, from Tequixquiac in the State of Mexico to central Oaxaca. This finding comes from a new fossiliferous locality at the municipality of San Dionisio Ocotepec, located in the Central Valleys region of the state of Oaxaca, Mexico. The associated fauna includes: Mammuthus columbi, Equus cf. E. conversidens, and Bison sp. By the presence of bison as well as mammoth, a Rancholabrean land mammal age (Late Pleistocene) is assigned to the fossil fauna. In addition, we performed a proboscidean mesowear analysis as well as a low magnification microwear analysis (35x) to the dental elements of the mammoth. Our findings suggest that the mammoth individual was a grazer. Due to the mammoth's feeding habits and the habitat described for Mexican samples of bison and horses, we concluded that during the Late Pleistocene, San Dionisio Ocotepec was dominated by open grassland in the lowlands. This new fossil site and its fauna contribute to improve the knowledge of the Rancholabrean in southern Mexico, and particularly in the Central Valleys of Oaxaca. This improves our understanding of the biotic and climatic changes during the foundation of the Holocene. © 2018, Instituto de Geologã-a, Universidad Nacional Autãnoma de Mã