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 of the modern wild horse, including the domestic horse, "Equus caballus". Controversy still surrounds "E. lambei" and the divergence of other similar extinct horse species. Through examinations of the bones and teeth of "Equus lambei", many similarities can be seen with the modern horse "Equus caballus". There is also a strong resemblance to "E. lambei" in the metapodials of "E. caballus przewalskii" and the phalanges of "E. caballus lenensis" "." Metrical and morphological studies of horse teeth from the Bluefish Caves confirm the close similarity between "Equus lambei" with wild and domestic horses alive today. "E. lambei" is a "caballus"