The Atelidae are one of the five families of New World monkeys now recognised. It was formerly included in the family Cebidae. Atelids are generally larger monkeys; the family includes the howler, spider, woolly, and woolly spider monkeys (the latter being the largest of the New World monkeys). They are found throughout the forested regions of Central and South America, from Mexico to northern Argentina. Atelid monkeys are small to moderate in size, ranging from 34 to 72 cm in head-body length, with the howler monkeys being the largest members of the group, and the spider monkeys being the smallest. They have long prehensile tails with a sensitive, almost hairless, tactile pad on the underside of the distal part. The tail is frequently used as 'fifth limb' while moving through the trees where they make their homes. They also have nails on their fingers and toes, enabling them to climb. Most species have predominantly dark brown, grey, or black fur, often with paler markings. These are arboreal and diurnal animals, with most species restricted to dense rain forest, although some howler monkey species are found in drier forests, or wooded savannah. They mainly eat fruit and leaves, although the smaller species, in particular, may also eat some small insects. They have the dental formula: 2.1.3.32.1.3.3 Females give birth to a single infant (or, rarely, twins) after a gestation period of 180 to 225 days. In most species, individuals give birth every one to three years, and there is little, if any, seasonal peak in the number of births. Atelid monkeys are typically polygamous, and live in social groups with anything up to twenty five adults, depending on species. Where groups are relatively small, as is common amongst the howler monkeys, a single male monopolises a 'harem' of females, but larger groups will contain several males, with a clear hierarchy of dominance. Currently, 29 species of atelid monkey are recognized, grouped into five genera, and two subfamilies. FAMILY ATELIDAE