A large male hominin cranium from Sterkfontein, South Africa, and the status ofAustralopithecus africanus


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June 1999


Stw 505 is the most complete hominin cranium discovered in Sterkfontein Member 4 since Broom's excavations. It was foundin situin Member 4 breccia in 1989 and is larger, on the whole, than any other cranium from Sterkfontein that has comparable parts. Displacement due to breakage, as well as plastic deformation, has affected Stw 505 in several areas, especially the face and the vault. Diagnosticmorphology is nevertheless abundant in the specimen. In several areas—the distinct anterior pillar, the straight inferior border of the zygoma, the pattern of cresting on the naso-alveolar clivus, the basal aspect of the temporal bone—Stw 505 closely matches the morphology of specimens ofAustralopithecus africanusand is distinct from other hominins. Some isolated characters overlap with other groups, mainly earlyHomoand/orA. robustus. However, only the hypodigm ofA. africanuscan accommodate the entire suite of morphology. In some cases, Stw 505 introduces more variation into the Sterkfontein sample. For example, prominent superciliary eminences occupy the medial portions of the supraorbital region and flow medially into a strongly protruding glabellar mound. These characteristics are probably attributable to sexual dimorphism. In many respects, Stw 505 highlights similarities betweenA. africanusand earlyHomo. Comparison with other species suggests that males ofA. africanusdo not show derived features ofA. robustusthat are not also present in females, and that cranial differences betweenA. afarensisandA. africanushave, if anything, been understated.


Australopithecus, Hominids, Systematics, Variation, Sexual Dimorphism

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Journal of Human Evolution, Vol. 36, no. 6 (1999-6).