Pleistocene Equidae of Texas

Pleistocene-age fossil horses of Texas belong to at least three faunal assemblages. The oldest contains Hippotigris (= Plesippus) which disappeared before Yarmouthian time. The second contains Equus scotti and Onager semiplicatus (= Equus (Asinus) calobatus) which disappeared before Sangamon time. Both these groups are found on the High Plains but not on the Coastal Plain or along the central Texas rivers, where a later fauna, probably of Sangamon age, is found which contains remains of Equus, Asinus, and Onager but no Hippotigris. The Texas Onager material is referable to the Asiatic group and in addition to O. semiplicatus contains O. lambei, O. littoralis, O. fraternus, O. complicatus, and others; one new form is described herein. Post-Pleistocene horses of the Texas High Plains region contain Equus caballus, both the draft and pony-horse types. These are treated as subspecies, Equus c. caballus for the larger and Equus c. laurentius for the smaller form. E. laurentius was described by Hay (1913a) and the type has subsequently been considered a“feral” horse that somehow became fossilized. It seems doubtful that fossilization could have taken place in less than 400 years, the maximum time available for a “feral” horse. Also, E. laurentius is inseparable from E. niobrarensis alaskae and the Texas materials. Two new species are described, five species are transferred to Onager, and additional species are reconsidered.