Further information on the new monkey species,Cercopithecus salongo Thys van den Audenaerde, 1977

Abstract

In 1977,T. Kano obtained a curious monkey's skin in the central part of the Zaire Basin, andThys van den Audenaerde identified it as a newCercopithecus species designating it asC. salongo.Thys van den Audenaerde described the skin, concluding that the species might be a central African representative of the west African diana monkey. In the present paper, we supplement his description of this new species with subsequently obtained photos and information, correct some misstatements regarding its ecology, and examine its phylogenic relationship to the diana monkey based on this information including the cranial morphology. C. salongo has a black face fringed with a white forehead band, white to creamy white whiskers and beard. The general frontal appearance resembles the diana monkey except for a very shortly projecting beard. The distal parts of all limbs are black. The head, back, side and anterior parts of the thighs are greyish chestnut in color. The belly and throat are white. The peri-anal region is white to light blue, and the testicles are also light blue. The tail is dirty white in its ventral parts, and grey in the mid-dorsal part. There is a pure black spot of inverted V-shape on the ventral base area of the tail, which represents a unique marking of this species. The extremity of the tail is covered with black hairs. This color pattern differs from all known Cercopithecines in at least two or three different color markings. C. salongo is one of the smallest-sized guenons. Its tail seems to be a little shorter than that of ordinary guenons. Its population density is low around Wamba where it was found. The monkey's habitat is secondary forest mainly, but a small number of them also inhabit swamp forest. They utilize the lower stratum and frequently forage on the ground. They feed on fruits supplemented with young leaves and shoots. Such a terrestrial tendency cannot be seen in diana monkeys which occupy the higher strata of primary forest.C. salongo's common troop size ranges from 2 to 15 individuals but sometimes the species can be observed in troops of about 30 monkeys. It also forms mixed groups with other guenons. The skull size is the smallest among guenons. It is characterized by relatively large jaws, a deeply constricted frontal bone, and narrow and small incisors. These traits are different from those of ordinary guenons as well as of the diana monkey. The pattern of tooth wear is also characteristic; all incisors are only slightly worn while the third molars expose dentine, which is a reverse of the pattern of ordinary Cercopithecines. Thys van den Audenaerde suggested a close relationship betweenC. salongo andC. diana based on the resemblance of the frontal area and the existance of a peri-anal light colored area. However, this is not supported from the viewpoint of the ecology and cranial morphology. There are also some different points in the respective color patterns. It seems better, therefore, to leave the position of this species as undetermined at this stage.