Equus fraternus

Equus fraternus is a possibly dubious extinct species of Equus that lived in North America during the Pleistocene. Fossils have been reported from Irvingtonian and Rancholabrean deposits in Alberta, Canada and in Florida, Illinois, Mississippi, Nebraska, Pennsylvania, South Carolina and Texas, with a possible record from Costa Rica. Its holotype is a single isolated second premolar kept at the American Museum of Natural History, and in 1985 Melissa Winans argued that the tooth characters used to diagnose it could result from wear and that the holotype contained more than one individual. Augusto Azzaroli nevertheless assigned skulls and other bones to it and saw it as a close relative of the Mexican and South American horses. Its taxonomic status remains unclear.