Proboscidea from the Big Cypress Creek fauna, Deweyville Formation, Harris County, Texas

In 2008 a rich accumulation of vertebrate bones and teeth was discovered in a small tributary drainage to Big Cypress Creek near the town of Hockley in Harris County, Texas. The fossils were recovered from sandy sediments of fluvial origin, interspersed with contemporaneous spring boil deposits, attributed to the Deweyville Formation and the recovered remains consist entirely of disarticulated and dissociated skeletal elements and teeth. Distinct stratigraphic horizons are limited in extent in the fossiliferous sections along the drainage, and the fossils are generally concentrated in close association with gravel lag deposits. Two radiocarbon dates on wood suggest that the fauna may have accumulated about 24,000 years ago but presence of spring deposits, association with lag deposits, and the aerial extent (approximately 125 m of exposed section along the length of the tributary) could indicate significant time averaging during the Rancholabrean (Bison occurs in the fauna). The unique faunal character of the site is emphasized by a single tooth of Mixotoxodon, a notoungulate mammal, that provides the first evidence of this taxon from the United States. The fauna is dominantly composed of herbivorous megafauna with two proboscideans (Mammuthus and Cuvieronius). Mammut americanum has not yet been found in the fauna. Isotopic analyses of the proboscideans and some of the other megafauna suggest that an open environment with scattered woodland habitat existed in southeastern Texas at the end of the last glacial period.