It is in fact, not a big chimp, but a Siamang: a black gibbon (Hylobates syndactylus) of Sumatra and the Malay Peninsula that is the largest of the gibbons. The siamang resembles other gibbons but is more robust. The siamang is also distinguished by the webbing between its second and third toes and by a dilatable hairless air sac in its throat. If you've been to the Nashville Zoo, or live nearby, you know all about the air sac.
