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a group of catarrhine monkeys of the family Cercopithecidae. The group comprises three genera.
The genus Nasalis has one species, the true proboscis monkey (N. larvatus), which is found on the island of Borneo (Kalimantan). The true proboscis monkey has a long nose. Its body length is 55–75 cm, and its tail length 65–75 cm.
The genus Rhinopithecus has two species: the snub-nosed langur (R. roxellanae) —with three subspecies, which are distributed in southern and western China—and the Tonkin snub-nosed langur (R. avunculus), which is distributed in northern Vietnam. Both species have snub noses that curve upward in old individuals. The body length measures 55–85 cm, and the tail length 60–95 cm. The hairs, as in Nasalis, are long and of various colors.
The genus Simias has one species, the pig-tailed langur (S. concolor), which is found on the islands of Siberut, Sipora, and South Pagi and in southwestern Sumatra. The nose is snub but less developed than that of Rhinopithecus. The body length is about 55 cm, and the tail length 13–15 cm. The coloration is dusky brown.
Proboscis monkeys are arboreal animals and live in groups of 20 or more individuals. The numbers of snub-nosed and pig-tailed langurs are sharply decreasing.
T. D. GLADKOVA