Sivapithecus includes a great diversity of Miocene ape species from South Asia. Fossils are known from between 10 and 7 million years ago, with many fossils recovered from the Siwalik region of Pakistan, but fossils assigned to Sivapithecus are found as far as China and Turkey. Sivapithecus represents the large radiation of the fossil Asian apes, and one or more forms are ancestral both to living orangutans as well as many fossil apes, including Lufengpithecus and Gigantopithecus.
The cranial morphology of at least one specimen of Sivapithecus clearly shows its relation to living orangutans. Like orangutans, Sivapithecus had a concave face, with projecting incisors and large canines. The face curves markedly upward in profile, a condition called airorhynchy. Also, the orbits are shaped like elongated ovals, tall from top to bottom, and with a similar orientation of the tear ducts in the inner corners of the orbits.
There are dental differences between Sivapithecus and living orangutans. Both apes have thick molar enamel, but in orangutans, the enamel of orangutans is wrinkled into complicated tooth surfaces. In contrast, the surfaces of Sivapithecus teeth are basically uncomplicated and similar in form to Dryopithecus. This primitive molar form is also similar to early hominids, and some of the earliest-known specimens of Sivapithecus were once believed by many paleoanthropologists to be hominid ancestors (see Ramapithecus). From later discoveries, it has become clear that Sivapithecus was already removed from the line of descent of the living African apes and humans.