The Monkey In general, any member of the mammalian order Primates, with the exception of the tree shrews, the lemurs and their allies, the gibbons and apes, and Monkeys are arranged into two main groups: those of the Old World tropics, the catarrhines, with two families, Cercopithecidae (monkeys with cheek pouches) and Colobidae (leaf monkeys); and those of the New World tropics, the platyrrhines, also with two families, Callitrichidae (marmoset) and Cebidae. Monkeys live in tropical forests, where they move about by using all four limbs. Except for the largest, such as the baboon and drills, monkeys are predominantly arboreal, leaping from limb to limb in their travels among the trees. On the grou