Several changes have been made in the species-level classification followed in the original action plan, although the classification (Table 1) retains its conservative approach and a moderate bias towards splitting rather than lumping. Sixty-four species are listed, compared with 63 in the earlier plan. The changes and their rationale are as follows:
The angwantibo (Arctocebus) is divided into two species, A. calabarensis north of the Sanaga River and A. aureus to the south, following Maier (1980) and Groves (1989). As this plan went to press, a new potto-like taxon, Pseudopotto martini, was named by Schwartz (1996) on the basis of two skeletal specimens in a Zurich museum. The specimens originated in western equatorial Africa.
The angwantibo (Arctocebus calabarensis) is a short-tailed, careful climber, related to the potto and the Asian lorises. It is one of the rarest of African prosimians.
P. Jewll
Because of uncertainties about galago systematics at the time of publication of the original plan, all the galagos were placed in the genus Galago. There is now a much broader consensus, which is followed here, that the greater galagos should be placed in their own genus, Otolemur; that the dwarf galagos also belong in their own genus, Galagoides; and that the western (but not eastern) needle-clawed galagos should be placed in Euoticus (see Groves 1989 and Bearder et al. 1995).
Some additional galago species are recognized based on studies by Olson (1979), the review by Groves (1989), and the continuing research by Bearder et al. (1995) on vocalizations. In addition to acknowledging the distinctiveness of Galagoides thomasi from G. demidoff (the correct name for G. demidovii), as in the original plan, G. gallarum and G. moholi are regarded as distinct from G. senegalensis, following Olson (1979), Groves (1989) and Nash et al. (1989). Two species of Euoticus are recognized: E. elegantulus south of the Sanaga River and E. pallidus to the north and on Bioko (Groves 1989). Galago inustus is given its correct name of G. matschiei (Groves 1989; Nash et al. 1989).
The vocalization studies of Bearder et al. (1995) suggest that there are three, or even four, different kinds of Allen's galago. Pending a thorough taxonomic review, we retain a single-species classification here, but we recognize that there is probably more than one valid species in this group. Bearder et al. have also argued that vocal evidence suggests the presence of several previously unrecognized galago species in Tanzania and Malawi; they have drawn attention to three forms of dwarf galago in Tanzania (the Matundu, Rondo and Amani dwarf galagos) that appear to merit species status based on their calls, and to two small galagos from Tanzania (Newala) and Malawi (Kalwe) that have similarities to G. zanzibaricus, but also have vocal differences. Because of the state of flux in galago taxonomy, these “new” galagos are not formally recognized here, but such diversity clearly needs to be acknowledged in future planning.
Table 1 Classification of African Primates
We have retained a 5-species classification of the baboons (Papio). Although Jolly (1993) has argued forcefully that the baboons are best regarded as a single species, a five-species arrangement is still widely used and has some support in recent research (Hayes et al. 1990).
The mangabeys are divided into two genera, Cercocebus (including galeritus, atys and torquatus) and Lophocebus (including albigena and aterrimus), following Groves (1978, 1989). Molecular data apparently support this generic split (T. Disotell, personal comm.). Groves regards galeritus on the Tana River as a species distinct from Central African agilis; we have not followed this arrangement here, and await further research and a clarification of the status of the Udzungwa population in Tanzania. Groves also unites albigena and aterrimus in one species (L. albigena), but also says that to recognize one species or three (albigena, aterrimus and opden-boschi) “is a somewhat arbitrary division”. Pending further study, we retain the more familiar two-species classification used by Napier (1981).
A young mountain gorilla (Gorilla gorilla beringei).
Amy Vedder/Bill Weber
The study of Colyn et al. (1991) has concluded that the central Zairean guenons Cercopithecus salongo and C. dryas are the same species. The name dryas has priority. This new plan therefore replaces “C. ?salongo” with Cercopithecus dryas. “Cercopithecus?sp.” from Gabon has now been formally named Cercopithecus solatus (Harrison 1988). Cercopithecus sclateri was provisionally accepted as a distinct species in the first plan; it is now fully accepted, in light of new information (Oates et al., 1992). Cercopithecus wolfi (including the subspecies wolfi, pyrogaster, elegans) is now treated as a full species, distinct from C. pogonias. This follows the conclusions of several studies reported in the benchmark volume on the guenons, edited by Gautier-Hion et al. (1988), and by the phylogenetic analysis of Gooder (1991). Gooder notes three derived cranial and dental characters separating wolfi from pogonias. Struhsaker (personal communication) does not agree that wolfi should be split from pogonias, citing their identical vocalizations; on the other hand, Gautier (1988) considers their high-pitched binary alarm calls to be probably convergent.
We have not followed Lernould (1988) in separating Cercopithecus aethiops into four species, aethiops, pygerythrus, sabaeus and tantalus; this division was favored by Dandelot (1971) but is yet to be widely accepted. Groves (1989) argues that C. aethiops is so divergent from other Cercopithecus that it should be referred to its own genus Chlorocebus, but again this view has, as yet, little support. We retain Allenopithecus, Miopithecus and Erythrocebus as genera, rather than relegating them to subgeneric status as Lernould did. There appears to have been no progress since the publication of the original plan in resolving the question of whether the northern and southern forms of talapoin are the same or different species.
Cercopithecus aethiops is a wide-ranging species, typical of riverine forests throughout the savanna zone of Africa. It has invaded parts of the rain forest zone where the vegetation has been opened up by farming.
Russell A. Mittermeier
A northern talapoin monkey (Miopithecus sp.). The smallest Old World monkey, the talapoin's prefered habitat is low, dense growth, including tangled lianas, near rivers or in inundated forest.
Noel Rowe
The taxonomy of red colobus monkeys remains very poorly resolved. In the original plan we provisionally recognized five species: Procolobus badius, P. pennantii, P. rufomitratus, P. gordonorum and P. kirkii. Although there are strong grounds for regarding this arrangement as reflecting a real biological pattern, it is not a widely-accepted arrangement and can cause confusion. Until a thorough reanalysis of red colobus relationships is undertaken, ideally using new genetic information, it seems best to revert to the traditional view that there is one red colobus species (Procolobus badius) with many subspecies. The subspecies are discussed below.
Insufficient data are yet available to support the recent suggestion by Morin et al. (1994) that West African chimpanzees should be elevated to full species rank. Ruvolo et al. (1994) have found a greater difference in one mitochondrial gene between eastern and western gorilla subspecies than exists between common and pygmy chimpanzees for the same gene; this raises the possibility that two species of gorilla might eventually be recognized (Morell 1994).