The siamang (Symphalangus syndactylus) is an arboreal, black-furred gibbon native to the forests of Indonesia, Malaysia, and Thailand. The largest of the gibbons, the siamang can be twice the size of other gibbons, reaching 1 m in height, and weighing up to 14 kg. Its arms are incredibly long with a span sometimes twice as long as body length. It is the only species in the genus Symphalangus. Siamangs can be differentiated from other gibbons in two major ways: A naked throat sac (also called a gular sac) that can expand to the size of a siamang’s head when inflated prior to making calls; webbing between its second and third toes which provides the siamang with its scientific name, Symphalangus syndactylus – Ancient Greek for together phalanx + united finger.
