Onager known as the Persian onager. Until this day, the species share the same name, "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. The Asiatic wild ass, among Old World equids, existed for more than 4 million years. The oldest divergence of "Equus" was the onager followed by the zebras and onwards. A new species called the kiang ("E. kiang"), a Tibetan relative, was previously considered to be
Onager (weapon) could be winched back again. The onagers of the Roman Empire were mainly used for besieging forts or settlements. They would often be armed with large stones that could be covered with a combustible substance and set alight. The onager was used from the 4th century AD until the 6th century AD. The late-fourth century author Ammianus Marcellinus describes 'onager' as a neologism for scorpions and relates various incidents in which the engines fire both rocks and arrow-shaped missiles. The late-fourth or early-fifth century military writer Vegetius stipulates that a legion ought to field ten onagers, one for each cohort.