Dietary evaluation of a hipparionin horse population from the middle Miocene of Oaxaca, southeastern Mexico

Abstract

The first paleodietary interpretation of a hipparionin horse population from the middle Miocene El Camarón Formation (late early Barstovian, K-Ar dated 15.0 ± 0.8 to 16.7 ± 0.71 Ma) of Oaxaca, southeastern Mexico is presented. The species is formally referred to Cormohipparion aff. C. quinni and its dietary behavior were evaluated by the extended mesowear analysis method. A cluster analysis compared the Oaxacan species with 23 selected extant species and fossil hipparionins from the Neogene of North America, Europe, and Africa. The mesowear pattern of the Oaxacan hipparionin is comparable to that of the mixed feeder Cormohipparion quinni from the late Barstovian of northern Great Plains. These species display a combination of high relief and round cusps characteristic of a relatively high-abrasion diet. This suggests that the population of C. aff. C. quinni was a mixed feeder that incorporated abrasive food items into the diet (grass and/or extrinsic grit). The results provide evidence for the existence of local grazing habitats in southern tropical North America during the early middle Miocene (ca. 15 Ma), and give additional support that savanna-like habitats were present in high and low latitudes of North America during the mid Miocene (~18–12 Ma).