Systematics and paleobiology of new bison occurrences from the Late Pleistocene of central Mexico

Abstract

This study presents new findings of bison remains associated with alluvial plains in central Mexico dating back to the Late Pleistocene. These discoveries encompass eight sites in Hidalgo (Conejos, Ventoquipa, Barranca del Berrendo, Barranca Jagüey Viejo, Las Cajas, El Barrio, Monte Alegre, and San Gabriel Azteca) and two sites in Puebla (Barranca Policarpio and Barranca Xocoa). Biometrical analysis was conducted on the herein studied material, consisting of a horn core fragment, a skull fragment, two mandible fragments, five isolated teeth, and several postcranial remains. A comparative study with selected specimens indicates the presence of Bison antiquus and B. cf. latifrons. The record represents the first reported occurrences of these species for the states of Hidalgo and Puebla respectively. Furthermore, the analysis of carbon (δ13C) and oxygen (δ18O) isotopes in tooth enamel apatite from the material of Hidalgo and Puebla was used to characterize the bison's diet and habitat, providing evidence of the flexible dietary regime observed in Pleistocene bison populations and that were common inhabitants of mixed environments. Body mass estimation of some individuals (average weight ≈ 450 kg) is in the lower limit of B. antiquus populations from the Late Pleistocene of North America. New knowledge about the geographical presence of Bison antiquus and B. cf. latifrons in central Mexico is provided. Comparison with another bison record of these species from North America suggests a biochronological delay between them, representing a younger time interval for Bison antiquus (maximum age at 50 ka), allowing us to biostratigraphically constrain some Mexican localities containing bison remains.