Siamang

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.
The Siamang is different form other gibbons. In Siamangs, two fingers on each hand are fused together, that's where the name "syndactylus" is from. Siamangs have large "gular sacs". These can be found in both males and females. The gular sac is a throat pouch that can be inflated to the size of its head. This allows the Siamang to make loud resonating calls or songs.
There may be two subspecies of the Siamang. If so, they are the nominate Sumatran Siamang ("S. s. syndactylus") and the Malaysian Siamang ("S. s. continentis", in peninsular Malaysia). Otherwise, the Malaysian individuals are only a population. The Siamang is the only gibbon which occurs sympatrically with other gibbons; its two ranges are entirely within the combined ranges of the Agile Gibbon and the Lar Gibbon.
The Siamang can live over 30 years in captivity.
While the illegal buying and selling of pets takes a toll on wild populations, the main threat to the Siamang is habitat loss in both Malaysia and Sumatra. Palm oil production is clearing lots of forest, reducing the habitat of the Siamang, along with that of other species such as the Sumatran Tiger.