Primates are the prosimians — monkeys of the new world and monkeys and apes of the old world. Prosimians are small tree-living creatures that are mostly nocturnal. They include lemurs and aye-aye of Madagascar, lorises and tarsiers. The slow loris and the slender loris are found in India.
New World Monkeys, unlike most prosimians monkeys, are diurnal. They have flatter faces and more developed brains than prosimians. They are different from monkeys of the old world in that they are all arboreal and almost always have prehensile tails. A ‘prehensile’ tail is one that is able to grasp and hold things. They are found only in South and Central America and include capuchin, howler, spider, squirrel and owl monkeys.
Monkeys of the old world, found in Africa and Asia, may once have roamed in Europe as well. Old world monkeys do not have prehensile tails and some of them are terrestrial. They are closely related to apes and humans and include langurs or leaf monkeys and macaques found in India.