School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa; Department of Anatomy, University of Pretoria, PO Box 2034, Pretoria, 0001, South Africa.
Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA; Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, WITS, Johannesburg, 2050, South Africa.
J Hum Evol. 2018 Aug;121:204-220. doi: 10.1016/j.jhevol.2018.04.004. Epub 2018 May 21.
The Sterkfontein Caves site is one of the richest early hominin fossil localities in Africa. More specifically, the fossiliferous deposits within the lower-lying Jacovec Cavern have yielded valuable hominin remains; prominent among them is the Australopithecus partial cranium StW 578. Due to the fragmentary nature of the braincase, the specimen has not yet been formally assigned to a species. In this context, we employ microtomography to quantify cranial thickness and composition of StW 578 in order to assess its taxonomic affinity. As comparative material, we investigate 10 South African hominin cranial specimens from Sterkfontein (StW 505, Sts 5, Sts 25, Sts 71), Swartkrans (SK 46, SK 48, SK 49) and Makapansgat (MLD 1, MLD 10, MLD 37/38), attributed to either Australopithecus or Paranthropus, as well as 10 extant human and 10 extant chimpanzee crania. Thickness variation in and structural arrangement of the inner and outer cortical tables and the diploë are automatically assessed at regular intervals along one parasagittal and one coronal section. Additionally, topographic cranial vault thickness distribution is visualized using color maps. Comparisons highlight an absolutely and relatively thickened condition of the StW 578 cranial vault versus those of other South African Plio-Pleistocene hominins. Moreover, in StW 578, as well as in the Australopithecus specimens Sts 5 and Sts 71 from Sterkfontein, the diploic layer contributes substantially to cumulative vault thickness (i.e., >60%). Within the comparative sample investigated here, StW 505 and Sts 71 from Sterkfontein Member 4, both attributed to Australopithecus, most closely resemble StW 578 in terms of cranial vault thickness values, tissue proportions, and two- and three-dimensional distributions. Including additional Plio-Pleistocene Australopithecus and Paranthropus crania from South and East Africa in future studies would further help establish morphological variability in these hominin taxa.
斯特克方丹洞穴遗址是非洲最丰富的早期人类化石产地之一。更具体地说，较低的雅科夫洞穴内的化石沉积物提供了有价值的人类遗骸；其中最著名的是南方古猿部分颅骨 StW 578。由于颅腔的破碎性质，该标本尚未被正式分配到一个物种。在这种情况下，我们使用微断层扫描来量化 StW 578 的颅腔厚度和组成，以评估其分类学亲缘关系。作为比较材料，我们研究了来自斯特克方丹（StW 505、Sts 5、Sts 25、Sts 71）、斯瓦特克朗斯（SK 46、SK 48、SK 49）和马卡潘斯盖特（MLD 1、MLD 10、MLD 37/38）的 10 个南非人类化石标本，这些标本归因于南方古猿或傍人，以及 10 个现生人颅骨和 10 个现生黑猩猩颅骨。内、外皮质表和脑膜层的厚度变化和结构排列在一个正中矢状面和一个冠状面的规则间隔处自动评估。此外，使用彩色地图可视化颅顶厚度的地形分布。比较突出了 StW 578 颅顶与其他南非上新世至更新世人类的绝对和相对增厚条件。此外，在 StW 578 中，以及在斯特克方丹的南方古猿标本 Sts 5 和 Sts 71 中，脑膜层对累积颅顶厚度有很大贡献（即>60%）。在所研究的比较样本中，斯特克方丹 4 号成员的 StW 505 和 Sts 71 都归因于南方古猿，在颅顶厚度值、组织比例以及二维和三维分布方面最接近 StW 578。在未来的研究中纳入来自南非和东非的额外上新世至更新世南方古猿和傍人颅骨将进一步帮助确定这些人类分类群的形态变异性。
