Coloration of the body fur is often relatively inconspicuous and occasionally cryptic, generally being darker dorsally and paler ventrally. The face is usually virtually naked, although in some species there is a beard-like tuft of hair on the chin. However, in many cases the fur and skin on the face and sometimes on other areas of the body are conspicuously patterned, notably in various guenons, where species-specific coloration patterns on the head are commonly emphasized by characteristic head movements. Striking color contrasts are also frequently present in the genital region. In males, the scrotum and/or penis are often distinctively colored, while in females of some species there is often a conspicuous sex skin
that changes in color and size over the course of the ovarian cycle. The most colorful species is undoubtedly the mandrill (Mandrillus sphinx). In this species, the faces of males have a bright red nose flanked by blue, ridged paranasal bulges along with white whiskers, and there is a large, orange-yellow beard, while the rump is also colored red and blue and the penis is bright red. Females are similarly, although less brightly, colored; but they also have prominent sexual swellings that are bright red at peak inflation.
In the head, the eyes are always directed directly forwards and the snout is mildly to strongly elongated. In common with other higher primates, a rhinarium (a naked, moist area of skin around the nostrils present in most mammals) is always completely lacking. The nostrils are relatively close-set and point downward. Cheek pouches are consistently present, but the degree of development varies from species to species. The dental formula, which is the same in all Old World monkeys and apes, is (I2/2 C1/1 P2/2 M3/3) X 2 = 32. The canine teeth are typically large, stabbing teeth, and the rear edges of the upper canines are honed against the leading edges of the anterior premolars in the lower jaw. The molars in both upper and lower jaws are bilophodont. Cercopithecine monkeys typically walk and run quadrupedally both in the trees and on the ground, and the arms and legs are of approximately equal length. In the trees, they are agile climbers. On the hand, the thumb is always well developed, and fine manipulative actions are particularly prevalent in terrestrial species. In all Old World monkeys, including leaf-monkeys (colobines), well-developed hardened sitting pads (ischial callosities) are present
on the buttocks, and these are supported by broad, roughened bony flanges (ischial tuberosities) on the pelvis. The tail is very variable in length, being very long in some species and reduced to a small stump in others. As a rule, arboreal species tend to have a relatively long tail, whereas marked reduction of the tail is found in species that spend much of their time on the ground. Head and body length varies from 14 in (35 cm) to 30 in (75 cm), while tail length varies from practically zero to 34 in (86 cm), according to species. Body mass ranges from 2 lb 12 oz (1.25 kg) for the diminutive talapoin (Miop-ithecus talapoin) to 48 lb (31.6 kg) for a male mandrill (Man-drillus sphinx).
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