Gibbons are the small apes in the family Hylobatidae. The family is divided into four genera based on their
diploid chromosome number: Hylobates , Hoolock , Nomascus , and Symphalangus. They occur in tropical and subtropical rainforests from northeast India to Indonesia and north to southern China, including the islands of
Sumatra, Borneo and Java. The extinct Bunopithecus sericus is an extinct gibbon or gibbon-like ape which, until recently, was thought to be closely related to the Hoolock
gibbons.