The Siamang (Symphalangus syndactylus) is an arboreal, black furred gibbon native to the forests of Malaysia, Thailand, and Sumatra. The largest of the lesser apes, the siamang can be twice the size of other gibbons, reaching 1 m in height, and weighing up to 23 kg. The Siamang is the only species in the genus Symphalangus.