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 niobrarensis Equus niobrarensis Equus niobrarensis (or commonly, Niobrara horse) is an extinct species of "Equus", the genus that includes the horse. "E. niobrarensis" may be synonymous with "Equus scotti". It was "stout-legged" and belonged to the "big horses" category as defined by M. C. Winans. The skull of the horse was noted as being broader than Equus caballus. "E. niobrarensis" was native to North America and commonly found in western North America and dates to the late Pleistocene. Fossils of "E. niobrarensis" were discovered at Dry Cave in Wisconsin. Another mention of an "E. niobrarensis" discovery was in Skeleton Cave, Oregon.