Onager recognized. The Persian onager was formerly known as "Equus onager", as it was thought to be a distinct species. Onagers are the most horse-like of wild asses. They are short-legged compared to horses, and their coloring varies depending on the season. They are generally reddish-brown in color during the summer, becoming yellowish-brown or grayish-brown in the winter. They have a black stripe bordered in white that extends down the middle of the back. The belly, the rump, and the muzzle are white in most onagers, except for the Mongolian wild ass that has a broad black dorsal stripe bordered with
Onager ancestor of all modern equids (members of the genus "Equus") lived around 5.6 (3.9–7.8) million years ago (Mya). Direct paleogenomic sequencing of a 700,000-year-old middle Pleistocene horse metapodial bone from Canada implies a more recent 4.07 Mya for the most recent common ancestor within the range of 4.0 to 4.5 Mya. The oldest divergencies are the Asian hemiones (subgenus "E. (Asinus)", including the kulan, onager, and kiang), followed by the African zebras (subgenera "E. (Dolichohippus)", and "E. (Hippotigris)"). All other modern forms including the domesticated horse (and many fossil Pliocene and Pleistocene forms) belong to the subgenus "E. (Equus)" which