Diptychus

a genus of freshwater fishes of the family Cyprinidae. There are three species, distributed in mountain waters of Middle and Central Asia. Two species are found in the USSR. The scaly osman (Diptychus maculatus), which inhabits high-mountain streams, is up to 50 cm long and weighs up to 1 kg. It feeds on vegetation and invertebrates. The fish spawns in the spring and summer. Its dwarf form, D. maculatus morpha sewerzow, does not exceed 25 cm in length and weighs less than 200 g. The naked osman (D. dybowskii) is found in mountain rivers and lakes. There are two forms: one inhabits rivers, and the other lakes. The naked osman is up to 60 cm long and weighs up to 3 kg. It is most abundant in Lake Issyk-Kul’, where it is a commercial fish.

Fishes of the genus Oreoleuciscus are sometimes called osmans or Altai osmans.