Donkey the environment. They may compete with livestock and native animals for resources, spread weeds and diseases, foul or damage watering holes and cause erosion. Few species of ass exist in the wild. The African wild ass, "Equus africanus", has two subspecies, the Somali wild ass, "Equus africanus somaliensis", and the Nubian wild ass, "Equus africanus africanus", the principal ancestor of the domestic donkey. Both are critically endangered. Extinct species include the European ass, "Equus hydruntinus", which became extinct during the Neolithic, and the North African wild ass, "Equus africanus atlanticus", which became extinct in Roman times. There are five subspecies
Equus lambei horse, not an ass. The closest resemblance to "E." "lambei" is shown by the Mongolian horse, "E. caballus przewalskii", now believed to be extinct in the wild. In size and proportions, "E. lambei" resembles "E. caballus przewalskii". Among living horses, perhaps the Yukon horse most closely resembles the Przewalski's horse ("Equus caballus przewalskii") from Mongolia . The upper foot bones (metapodials) of "Equus lambei" are slender compared to Przewalski's horse. The bones of "E. lambei" also closely resemble the proximal phalanges of "E. caballus lenensis", an extinct species from the late Pleistocene of Siberia . Along with steppe bison ("Bison