Horse
The horse adapted to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not. Horses and other equids are odd-toed ungulates of the order Perissodactyla, a group of mammals that was dominant during the Tertiary period. In the past, this order contained 14 families, but only three—Equidae (the horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)—have survived to the present day.
Onager
The onager (; "Equus hemionus"), also known as hemione or Asiatic wild ass, is a species of the family Equidae (horse family) native to Asia. A member of the subgenus "Asinus", the onager was described and given its binomial name by German zoologist Peter Simon Pallas in 1775. Five subspecies have been recognized, one of which is extinct.