Geometric morphometrics in postcranial bone elements of Late Pleistocene horses in Mexico: taxonomic and ecomorphological implications

Abstract

The genus Equus is the last member of the Equidae family whose evolutionary history is about 55 million years. This horse is abundant in Mexican Pleistocene deposits. Elements of the distal extremities (third metacarpals and metatarsals, first and second phalanx of the third digit) of three horse species (Equus cedralensis, E. conversidens and E. mexicanus) from three localities of Mexican Rancholabrean (0.21–0.16 a 0.095 Ma) were analyzed using geometric morphometric techniques. The aim is know whether the shape of each element studied differs between species of horses and also find some ecomorphological connection (form vs. substrate). The results prove the existence of three different groups related with the three species of horse registered in the localities studied; also, the existence of diagnostic elements for the differentiation of the three species of the late Pleistocene horse in Mexico. Based on the three diverse morphotypes is deduced that the species could live in different microhabitats and therefore be able to coexist in the same macrohabitat. Finally, the diversity of morphotypes suggests heterogeneous environments in the study localities.