Aside from humans (genus Homo), the macaques are the most widespread primate genus, ranging from Japan to Afghanistan and, in the case of the barbary macaque, to North Africa. Twenty-two macaque species are currently recognised, and they include some of the monkeys best known to non-zoologists, such as the rhesus macaque, Macaca mulatta, and the barbary macaque, M. sylvanus, a colony of which lives on theRock of Gibraltar. Although several species lack tails, and their common names therefore refer to them as apes, these are true monkeys, with no greater relationship to the true apes than any other Old World monkeys.
Squirrel monkeys live in the tropical forests of Central and South America in the canopy layer. Most species have parapatric or allopatric ranges in the Amazon, while S. oerstedii is found disjunctly in Costa Rica and Panama.

