Equus (genus) Equus (genus) Equus is a genus of mammals in the family Equidae, which includes horses, donkeys, and zebras. Within Equidae, "Equus" is the only recognized extant genus, comprising seven living species. The term equine refers to any member of this genus, including horses. Like Equidae more broadly, "Equus" has numerous extinct species known only from fossils. The genus most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes (erect in most subspecies), and long tails. All species are herbivorous, and mostly grazers, with simpler
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