Early Pliocene horses from late Pleistocene fluvial deposits, Gulf Coastal Plain, south Texas

Abstract

Isolated teeth and post-cranial elements of fossil vertebrates were recovered from sand and gravel pits in valley fill and terrace deposits along the Nueces River in San Patricio and Nueces Counties, Texas. A log from the valley fill deposit has been radiocarbon dated at 13,230 ± 110 BP. The fauna is mixed and comprises typical late Pleistocene taxa and relatively abundant remains of early Pliocene (latest Hemphillian) horses. The latter group includes Astrohippus albidens (Mooser), Nannippus spp., Neohipparion eurystyle (Cope), and a derived species of either Calippus or Pseudhipparion. Many of these specimens show little or no evidence of abrasion, in spite of the fact that they may have been transported at least 12–25 km. The source beds for these early Pliocene horses are unknown, but the fossils were probably eroded from older, updip sediments of the upper Goliad Formation during a low stand of sea level at the end of the Pleistocene and deposited during the late Wisconsinan.