Equus is a genus of mammals in the family Equidae, which includes horses, asses, and zebras. Within Equidae, Equus is the only extant genus. 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. There are seven living species. Equines are medium to large odd-toed ungulates with slender legs, long heads, manes (erect in most subspecies) and long tails. All species are herbivorous with simpler digestive systems than ruminants but are able to subsist on lower quality vegetation.