Allenopithecus nigroviridis

The Allen's swamp monkey's head and body length range from 17.7 to 18 inches, and its tail length is about 19.5 inches. Its weight ranges from 7.7 to 13 pounds, with males being heavier than females. The hair is slightly longer on the nape and shoulders than on the back, and scant on the underparts, hands and feet. The skin of the face is dark grayish brown to black, but lighter around the eyes. The hairs on the sides of the face extend outward to form a ruff from the ears to the mouth. The hair is flattened on the crown. General coloration above is grayish to almost black, sometimes with a yellowish tinge, and the underparts are light gray or whitish, sometimes speckled with black and yellow. The tail is dark above and lighter below. The body is rather heavy in appearance and anatomically bears some resemblance to the baboons. (The Genus was formerly Cercopithecus. It was changed to Allenopithecus because of periodic perineal swelling.)