Onager, Hemione, Asiatic wild ass
Value of species
The specific name is Ancient Greek ἡμίονος (hēmíonos), from ἡμι- (hēmi-), half, and ὄνος (ónos), donkey; thus, half-donkey or mule. In Persian the archaic word gur preserves the second syllable of the common Indo-European term that includes ona/ono (donkey) and ger/gur (swift).
The species was commonly known as Asian wild ass, in which case the term "onager" was reserved for the E. h. onager subspecies, more specifically 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 a subspecies of the onager as E. hemionus kiang, but recent molecular studies indicate it to be a distinct species, having diverged from the closest relative of the Mongolian wild ass's ancestor less than 500,000 years ago.
A sixth possible subspecies, the Gobi khulan (E. h. luteus, also called the chigetai or dziggetai) has been proposed, but may be synonymous with E. h. hemionus. Debates over the taxonomic identity of the onager occurred until in 1980. As of today, four living subspecies and one extinct subspecies of the Asiatic wild ass have been recognized. The Persian onager was formerly known as Equus onager, as it was thought to be a distinct species. Syrian wild ass (E. h. hemippus), Persian onager (E. h. onager), Indian wild ass (E. h. khur), Turkmenian kulan (E. h. kulan), Mongolian wild ass (E. h. hemionus).