New World monkeys are the five families of primates that are found in the tropical regions of Central and South America and Mexico : Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboidea, the only extant superfamily in the parvorder Platyrrhini. Platyrrhini means flat-nosed, and their noses are flatter than those of other simians, with sideways-facing nostrils. Monkeys in the family Atelidae, such as the spider monkey, are the only primates to have prehensile tails. New World monkeys ' closest relatives are the other simians, the Catarrhini (" down -nosed," comprising Old World monkeys and apes). New World monkeys descend from African simians that colonized South America, a line that split off about 40 million years ago.
