The simians (infraorder Simiiformes, Anthropoidea) are the monkeys, cladistically including the apes: The New World monkeys or platyrrhines, and the catarrhine clade consisting of the Old World monkeys and apes.

The simian line and the tarsier line diverged about 60 million years ago (during the Cenozoic era). Forty million years ago, simians from Africa colonized South America, giving rise to the New World monkeys. The remaining simians (catarrhines) split 25 million years ago into apes and Old World monkeys.

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