African wild ass (Equus)" which diverged ~4.8 (3.2–6.5) million years ago. Different authors consider the African wild ass and the domesticated donkey one or two species; either view is technically legitimate, though the former is phylogenetically more accurate. The species name for the African wild ass is sometimes given as "asinus", from the domestic donkey, whose specific name is older and usually would have priority. But this usage is erroneous since the International Commission on Zoological Nomenclature has conserved the name "Equus africanus" in Opinion 2027. This was done to prevent the confusing situation of the phylogenetic ancestor being taxonomically included in its
Equus conversidens Equus conversidens Equus conversidens (Owen 1869), or the Mexican horse, is a dubious Pleistocene species of horse, now extinct, that inhabited North America. The holotype of "Equus conversidens", a partial palate, was unearthed in Pleistocene deposits northeast of Mexico City, Mexico. In January 1963, a partial skeleton was found in the city of Canyon, Texas in a white clay bed during the excavation of a basement, and was referred to "E. conversidens" by Dalquest and Hughes (1965), who interpreted the species as medium to small-sized, and added additional records of the species from Texas (including a skeleton from Slaton), Arizona,