Przewalski's horse is one of three known subspecies of "Equus ferus", the others being the domesticated horse, "Equus ferus caballus" and the extinct tarpan, "Equus ferus ferus". Przewalski's horse is the only remaining truly wild "horse" in the world. There are still a number of other wild equines, including three species of zebra and various subspecies of the African wild ass, onager (including the Mongolian wild ass) and kiang.