Lockwood C A, Tobias P V
Institute of Human Origins, Arizona State University, Tempe, AZ 85287-4101, USA.
J Hum Evol. 1999 Jun;36(6):637-85. doi: 10.1006/jhev.1999.0299.
Stw 505 is the most complete hominin cranium discovered in Sterkfontein Member 4 since Broom'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 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. In many respects, Stw 505 highlights similarities between A. africanus and early Homo. 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.
Stw 505是自布鲁姆发掘以来在斯泰克方丹4号成员遗址发现的最完整的古人类颅骨。它于1989年在4号成员角砾岩中被原位发现，总体上比斯泰克方丹其他具有可比部位的颅骨都要大。破损导致的移位以及塑性变形在几个区域影响了Stw 505，尤其是面部和颅顶。不过，该标本仍有丰富的诊断性形态特征。在几个区域——明显的前支柱、颧骨笔直的下缘、鼻牙槽斜坡上的嵴纹模式、颞骨的基部——Stw 505与非洲南方古猿标本的形态特征紧密匹配，且与其他古人类不同。一些孤立的特征与其他群体有重叠，主要是早期人类和/或粗壮南方古猿。然而，只有非洲南方古猿的模式标本能容纳整套形态特征。在某些情况下，Stw 505给斯泰克方丹样本引入了更多变异。例如，明显的眉弓占据眶上区域的内侧部分，并向内延伸至一个强烈突出的眉间丘。这些特征可能归因于两性异形。在许多方面，Stw 505凸显了非洲南方古猿和早期人类之间的相似性。与其他物种的比较表明，非洲南方古猿的雄性并未表现出粗壮南方古猿那些雌性所没有的衍生特征，而且阿法南方古猿和非洲南方古猿之间的颅骨差异，如果有的话，可能被低估了。
