Gibbons are apes in the family Hylobatidae (pron.: //). The family historically contained one genus, but now is split into four genera. Gibbons occur in tropical and subtropical rainforests from northeast India to Indonesia and north to southern China, including the islands of Sumatra, Borneo, and Java.
The northern white-cheeked gibbon (Nomascus leucogenys) is a species of gibbon native to South East Asia. It is closely related to the southern white-cheeked gibbon (Nomascus siki), with which it was previously considered conspecific. The females of the two species are virtually indistinguishable in appearance.
The genome of N. leucogenys was sequenced and published in 2011.
A "substantial" population of 455 critically endangered northern white-cheeked crested gibbons (Nomascus leucogenys) have been recently found living in the Pu Mat National Park in Nghe An province, northern Vietnam, near the border with Laos. Conservation International report they are living at high altitudes, and far from human settlements. This population, representing two thirds of the total known in Vietnam are, apparently, the "only confirmed viable population" of this variety in the world.