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 ( Symphalangus syndactylus ) is a tailless , arboreal , black-furred gibbon native to the forests of Malaysia , Thailand , and Sumatra .