StW 505 is the most complete
hominin
The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas).
The ...
cranium discovered in
Sterkfontein Member 4 since
Broom
A broom (also known in some forms as a broomstick) is a cleaning tool consisting of usually stiff fibers (often made of materials such as plastic, hair, or corn husks) attached to, and roughly parallel to, a cylindrical handle, the broomstick. I ...
's excavations. It was found ''in situ'' in 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 term zygoma generally refers to the zygomatic bone, a bone of the human skull commonly referred to as the cheekbone or malar bone, but it may also refer to:
* The zygomatic arch, a structure in the human skull formed primarily by parts of the ...
, the pattern of cresting on the naso-alveolar clivus, the basal aspect of the temporal bone-Stw 505 closely matches the morphology of specimens of ''
Australopithecus africanus'' and is distinct from other hominins. Some isolated characters overlap with other groups, mainly early Homo and/or ''
A. robustus''. However, only the hypodigm of ''A. africanus'' can 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
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
. In many respects, Stw 505 highlights similarities between ''A. africanus'' and early ''
Homo
''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either ancestral to or closely relat ...
''. Comparison with other species suggests that males of ''A. africanus'' do not show derived features of ''A. robustus'' that are not also present in females, and that cranial differences between ''
A. afarensis'' and ''A. africanus'' have, if anything, been understated.
See also
*
List of human evolution fossils
The following tables give an overview of notable finds of hominin fossils and remains relating to human evolution, beginning with the formation of the tribe Hominini (the divergence of the human and chimpanzee lineages) in the late Miocene, roug ...
*
STS 14
STS 14 is a fossilized partial skeleton of the species '' Australopithecus africanus''. It was discovered at Sterkfontein, South Africa by Robert Broom and John T. Robinson in August 1947, and is estimated to be about 2.5 million years old.
Som ...
References
Bibliography
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External links
*{{commonscat-inline, Stw 505
Australopithecus fossils
Archaeological discoveries in South Africa
1989 archaeological discoveries
Archaeology of Southern Africa