Alouatta: A genus of the subfamily ALOUATTINAE, family ATELIDAE, inhabiting the forests of Central and South America. Howlers travel in groups and define their territories by howling accompanied by vigorously shaking and breaking branches.Cebidae: A family of New World monkeys in the infraorder PLATYRRHINI, consisting of nine subfamilies: ALOUATTINAE; AOTINAE; Atelinae; Callicebinae; CALLIMICONINAE; CALLITRICHINAE; CEBINAE; Pithecinae; and SAIMIRINAE. They inhabit the forests of South and Central America, comprising the largest family of South American monkeys.Focal Epithelial Hyperplasia: Hyperplasia of the mucous membrane of the lips, tongue, and less commonly, the buccal mucosa, floor of the mouth, and palate, presenting soft, painless, round to oval sessile papules about 1 to 4 mm in diameter. The condition usually occurs in children and young adults and has familial predilection, lasting for several months, sometimes years, before running its course. A viral etiology is suspected, the isolated organism being usually the human papillomavirus. (Jablonski, Illustrated Dictionary of Dentistry; Belshe, Textbook of Human Virology, 2d ed, p954)Platyrrhini: An infraorder of New World monkeys, comprised of the families AOTIDAE; ATELIDAE; CEBIDAE; and PITHECIIDAE. They are found exclusively in the Americas.Monkey Diseases: Diseases of Old World and New World monkeys. This term includes diseases of baboons but not of chimpanzees or gorillas (= APE DISEASES).