Horse
Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus".
Onager
The onager is a member of the subgenus "Asinus", belonging to the genus "Equus" and is classified under the family Equidae. The species was described and given its binomial name "Equus hemionus" by German zoologist Peter Simon Pallas in 1775.