A species of gibbon that was once widespread in china and Vietnam was named eastern black crested gibbon (Nomascus nasutus).There are 2 subspecie.
In 1950 it became extinct in the Chinese mainland and today only 20 gibbons of the subspecies survive on Hainan Island. In 2002 around 26 individuals of the subspecies Nomascus nasutus (Cao vit Black Crested Gibbon) were rediscovered in the Trung Khanh district of cal bang province in northeast Vietnam.
The Eastern Black Crested Gibbon is the most endangered and is the rarest species in the world. This has been resulted from deforestation of its habitat, encroachment and poaching.