The Siamang ("Symphalangus syndactylus") is a tailless, black furred gibbon native to the forests of Malaysia, Thailand, and Sumatra. It lives in trees, that's why it is called arboreal. The Siamang is the largest of the lesser apes. It can grow to be twice the size of other gibbons. Siamangs grow to about 1 m in height, and weigh up to 23 kg. The Siamang is the only species in the genus Symphalangus.