This genus is characterized by a diploid chromosome number of 52. Northern white-cheeked gibbon. The male cheek patches connect under a black chin and extend up to the top of the ear. Females can have brown-black genitals and black hairs on the tips of fingers and toes. A trace of the crown patch can extend between the scapulae.
Females are sometimes larger than are males.
Nomascus l. leucogenys is nearly extinct in southern Yunnan and northern Vietnam, although they can be found in a small portion of Laos. We currently house two pairs, one of which has two offspring. Southern white-cheeked gibbon. Males have small white cheek patches that extend as far up as the eye's corner, and thin white hair partially encircles the upper lip and totally encircles the lower lip, terminating in a black chin. Males have small, light buff cheek patches that extend to the bottom of the orbital ridge and can be slightly separated at the throat.