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.