Nothrotheriops from the Pleistocene of Oklahoma and Paleogeography of the Genus

A small Pleistocene, probably Irvingtonian, fauna collected near Curtis, Oklahoma, has yielded the first record of Nothrotheriops from Oklahoma. Examination of previously known and new specimens shows that all well-documented Rancholabrean records of this genus occur in the mountainous areas of western North America. Definite Irvingtonian occurrences span the continent from the San Francisco area and northwestern Mexico through the Great Plains to Florida. This change in distribution may have resulted from an increasingly variable late Pleistocene climate that restricted Nothrotheriops to areas where it could respond by altitudinal migration and by utilizing cave environments as thermal buffers. Continuing reduction of its range could have resulted in small disjunct mountain populations that finally succumbed to the climatic extremes of the terminal Pleistocene or hunting by paleoindians.