Fig. 5From: Apes and Tricksters: The Evolution and Diversification of Humans’ Closest RelativesComparison of an orangutan (left) and a cast of Sivapithecus indicus (GSP 15000). Discovery of this particular fossil confirmed for most researchers that Sivapithecus belongs in the lineage that gave rise to orangutans. Some of their shared features include: tall, oval-shaped eye sockets; a very narrow region between the eyes; a small, discontinuous brow “ridge” or “rib”; and an upwardly directed palate. The few limb bones that are known from Sivapithecus are very different from the modern orangutan, however, which has led a few researchers to conclude that this fossil is actually a primitive ape rather than an ancestral orangutan. Photo courtesy of Eric DelsonBack to article page