Simian

The simians, anthropoids, or higher primates (simian from Latin: simis, lit. 'monkey') are primates of the infraorder Simiiformes (), containing all animals traditionally called monkeys and apes. More precisely, they consist of the parvorders Platyrrhini (New World monkeys) and Catarrhini, the latter of which consists of the family Cercopithecidae (Old World monkeys in the stricter sense) and the superfamily Hominoidea (apes – including humans).

The simians are sister group to the tarsiers (Tarsiiformes), together forming the haplorhines. The radiation occurred about 60 million years ago (during the Cenozoic era); 40 million years ago, simians colonized South America, giving rise to the New World monkeys. The remaining simians (catarrhines) split about 25 million years ago into Cercopithecidae and Hominoidea.

Biological key-features

Biological features common to all or most simians include genetic similarities, similarities in eye location and the muscles close to the eyes, internal similarities between ears, dental similarities, and similarities on foot bone structure. The earliest simians were small primates with varied diets, forward-facing eyes, acute color vision for daytime lifestyles, and brains devoted more to vision and less to smell. Living simians in both the New World and the Old World have larger brains than other primates, but they evolved these larger brains independently.

Simians characteristically have relatively large brains, fused mandibles, binocular and color vision, and the females have a single fused uterus. They also have fewer teeth and are more sexually dimorphic in terms of body size and anatomy.