Mario T. Alberdi and Jose L. Prado discuss the presence of Hippidion in the New World from 13,000 to 8,000 Before Present.
Mario T. Alberdi and Jose L. Prado, “Review of the Genus Hippidion Owen, 1869 (Mammalia Perissodactyla) from the Pleistocene of South America,” Zoological Journal of the Linnean Society 108 (1993): 1–23
Abstract
This review of Hippidion is based on a multivariate analysis of the foot, and some morphological characteristics of the skull and dentition. We recognize only one genus (Hippidion) including all the hippidiform horses, with three different species: H. principale, H. devillei and H. saldiasi . The latter species is stratigraphically and geographically restricted to the period from 13000 to 8000 years BP in the southern part of South America. Hippidion principale and H. devillei have a large geographical distribution (Argentina, Bolivia, Chile, Perú, Uruguay, Brazil) through the Upper Pliocene-Upper Pleistocene. Both species show some morphometric variations across their geographic range; these features may result from the environmental characteristics.