Lemurs, lorises, and galagos are not monkeys; instead they are strepsirrhine primates. Like monkeys, tarsiers are haplorhine primates; however, they are also not monkeys. There are two major types of monkey: New World monkeys from South and Central America and Old World monkeys from Africa and Asia. Hominoid apes , which all lack tails, are also catarrhines but are not considered monkeys. Because old world monkeys are more closely related to hominoid apes than to new world monkeys, yet the term monkey excludes these closer relatives, monkeys are referred to as a paraphyletic group. Simians and tarsiers emerged within haplorrhines some 60 million years ago. New world monkeys and catarrhine monkeys emerged within the simians some 35 millions years ago. Old world monkeys and Hominoidea emerged within the catarrhine monkeys some 25 millions years ago. Extinct basal simians such as Aegyptopithecus or Parapithecus are also considered monkeys by primatologists. (source : wikipedia)
