NEW WORLD MONKEY

also called Platyrrhine, any of certain anthropoid primates of the New World, as distinguished from the Old World forms (catarrhines). The term, in use since about 1812, covers the members of the families Callitrichidae (marmosets and tamarins) and Cebidae (capuchins, spider monkeys, and others). Characteristics include large, broadly separated nostrils; three premolars in each half of each jaw; relatively unopposable thumbs; and long, sometimes prehensile, tails.