A STUDY OF PLEISTOCENE EQUUS TEETH

Fossil horses, dating from the Hemphillian North American Stage (Miocene/Pliocene) to the Recent, are common and widespread throughout the state of Texas. Several fossilized horse teeth were recently recovered in Crosby County, Texas in association with the remains of Mammuthus columbi. The mammoth remains were located in situ within a Pleistocene freshwater deposit. However, the horse teeth were discovered within the wash adjacent to the outcrop containing the mammoth. No horse remains have been found in situ at the site. However, a literature survey shows several formations of interest in Crosby County; the Blanco Formation (Pliocene) and the Blackwater Draw Formation (Pleistocene). Fossil horse remains have been well documented from both formations. The assemblage of fossils belonging to Equus consist of disarticulated teeth, including two complete superior premolars/molars and several fragmented superior molars, as well as fragments from two lower molars. Enough features have been preserved to firmly place the teeth within the genera Equus. The advanced morphology of the protocone is inconsistent with a Blancan aged species and most likely places the teeth within the Pleistocene rather than the Pliocene. The dentition of the upper molars is very similar to the modern horse, Equus caballus. The lower molars are inconsistent with E. caballus, as they seem to display characteristics of the subgenera Asinus or Hemionus, respectively. Therefore, the remains can be described as belonging to the genera Equus (Asinus/Hemionus) sp. Qualitative analysis based on the only complete samples collected, the superior molars, is inconclusive in determining the species.