The groups of modern primates

At about the same time as the dinosaurs became extinct, about 65 million years ago, the primitive primates diverged quickly to give rise to two main suborders; the prosimians(meaning “before apes”) and anthropoids(meaning “ape fom”). The prosimians are represented today by lemurs, lorises, and tarsiers, and the anthropoids by monkeys, apes, and humans.

Monkeys are distinguished from apes in having long tails, and the forelimbs are not usually longer than the hindlimbs. They are believed to have evolved from two different groups of lemur-like animals which became isolated when continental drift separated Eurasia from North America. The North American group evolved into New World monkeys which died out in North America but somehow colonised South America. The Eurasia group gave rise to Old World monkeys, from which apes and humans evolved. There are several differences between Old World monkey and New World monkeys which show their separate evolution. For example, the nostrils of monkeys from South America are wide open and far apart, and New World monkeys have a long tail that is prehensile (adapted for grasping branches); the nostrils of monkeys from Africa and Asia are narrow and close together and no old World monkey has a prehensile tail.