Sexual dimorphism in Ramapithecinae.

The Ramapithecinae are an extinct, mainly Miocene group of hominoids comprising the genera Sivapithecus and Gigantopithecus. Ouranopithecus and Ramapithecus are other included genera, here regarded as invalid. Cladistically, ramapithecines are hominid, although, in most aspects of their anatomy, they remain very primitive or ape-like. Miocene ramapithecines show reduced sexual dimorphism in canine size. In this respect they resemble Pliocene/Recent hominids, not extant great apes (which have highly dimorphic canines). Reduced dimorphism in canine size is an important shared derived feature indicating the hominid status of ramapithecines. Among living anthropoids, a significant association has been observed between a monogamous social structure and low canine dimorphism. This supports the inference that ramapithecines may have been monogamous.