Cebidae in the context of Squirrel monkey

New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboidea (/səˈbɔɪdi.ə/), the only extant superfamily in the parvorder Platyrrhini (/plætɪˈraɪnaɪ/).

Platyrrhini is derived from the Greek for "broad 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.

The Callitrichidae (also called Arctopitheci or Hapalidae) are a family of New World monkeys, including marmosets, tamarins, and lion tamarins. At times, this group of animals has been regarded as a subfamily, called the Callitrichinae, of the family Cebidae.

This taxon was traditionally thought to be a primitive lineage, from which all the larger-bodied platyrrhines evolved. However, some works argue that callitrichids are actually a dwarfed lineage.

The Atelidae are one of the five families of New World monkeys now recognised. It was formerly included in the family Cebidae. Atelids are generally larger monkeys; the family includes the howler, spider, woolly, and woolly spider monkeys (the latter being the largest of the New World monkeys). They are found throughout the forested regions of Central and South America, from Mexico to northern Argentina.