The first occurrence of a toxodont (Mammalia, Notoungulata) in the United States

Abstract

Toxodonts were a group of large-sized notoungulates of South American origin. They were diverse and widespread in South America in deposits ranging in age from late Oligocene to late Pleistocene. Sparse remains have been found from the Pleistocene of isolated regions of Central America. All of the Central American specimens have been referred to the genus Mixotoxodon (Van Frank, 1950). They were not previously known north of the southern Mexican states of Michoacan and Veracruz, except for an unconfirmed report of an occurrence in Tamaulipas (Arroyo-Cabrales et al., 2010). Here we report the occurrence of a single toxodont tooth, a left upper third molar, from late Pleistocene deposits in Harris County, Texas (30◦N). This is the first record of toxodonts, or any notoungulate, in the United States and extends the geographic range of this group 1600 km north of their previously known localities at Hihuitlán, Michoacan (18◦52' 3"0 N, 103◦24' 14 "W) and La Estribera, Veracruz (18◦07 '01.27" N, 94◦53 '15.59W) (Polaco et al., 2004) to latitude 30◦N.