NEW FOSSIL CERCOPITHECID REMAINS FROM THE HUMPATA-PLATEAU, SOUTHERN ANGOLA

The aim of the present investigation was to describe and identify the well-preserved cranial remains of a fossil cercopithecid recently reco vered from sites on the Humpata Plateau in southern Angola. In the pas t, papionin fossils recovered from the Angolan site of Tchiua (Leba) h ave been referred to various taxa, including Dinopithecus ingens, Para papio sp., and Papio (Dinopithecus) quadratirostris, Comparison of the new Angolan papionin cranial remains with those previously described from the Humpata Plateau and a large range of living and fossil Papion ini revealed that the range of metrical and morphological variation pr esent in the Humpata papionin sample was consistent with that found in a single extant papionin species. The Humpata cranial remains bear th e largest number of similarities to Theropithecus baringensis R. Leake y, 1969, and it is to this species that the remains are hereby referre d. This assignment is based on a suite of 11 shared attributes of the Humpata papionin fossils and the type specimen of T. baringensis, KNM BC2, which include: large molar teeth of relatively low relief with pi nched cusps and with a prominent distal fovea on M(3); a small, low cr anial vault with little mid-parietal expansion; a bow-shaped supraorbi tal torus; trapezoidal, inferiorly tapering orbits; a functional compl ex related to the presence of a large and vertically oriented anterior temporalis muscle; a large infratemporal fossa with an anteromedially oriented posterior border; a long muzzle with a steep interorbital dr op, shallow incisive are, flattened dorsum, and rounded maxillary ridg es; nasal bones that extend across the breadth of the posterior margin of the nasal aperture and then taper markedly as they approach nasion ; prominent, inferiorly divergent mental ridges; and relatively shallo w mandibular fossae that are long, elliptical in shape, and extend to the level of the M(3). The results of the current study suggest that T . baringensis (now including the Humpata papionin sample) and T. quadr atirostris occupy a position at the base of the Theropithecus radiatio n very close to the origin of Dinopithecus ingens and Gorgopithecus ma jor. The species of the genera Theropithecus (including its Humpata re presentatives) and Papio, along with D. ingens and G. major, form a cl uster of taxa that are more closely related to each other than they ar e to other extant or extinct papionins. (C) 1994 Wiley-Liss, Inc.