Zanolli Clément, Hublin Jean-Jacques, Kullmer Ottmar, Schrenk Friedemann, Kgasi Lazarus, Tawane Mirriam, Xing Song
Univ. Bordeaux, CNRS, MCC, PACEA, UMR 5199, Pessac F-33600, France; Evolutionary Studies Institute, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg, Johannesburg 2000, South Africa.
Chaire de Paléoanthropologie, CIRB (UMR 7241-U1050), Collège de France, 11, Place Marcelin-Berthelot, Cedex 05, Paris 75231, France.
J Hum Evol. 2025 Mar;200:103634. doi: 10.1016/j.jhevol.2024.103634. Epub 2025 Jan 2.
The hominin mandible SK 15 was discovered in April 1949 in Swartkrans Member 2, dated to ∼1.4 Ma. Albeit distorted on the right side, the left and right corpus of SK 15 are relatively low and thick, even compared to most Early to Middle Pleistocene Homo specimens. It preserves the left molar row and the right M and M that show a distalward increase in mesiodistal diameter. SK 15 was originally attributed to Telanthropus capensis but is now generally attributed to Homo erectus/Homo ergaster, even if it was previously suggested to possibly belong to Australopithecus. Similarities between SK 15 and Homo naledi mandible and tooth morphology were also claimed. To clarify the taxonomy of SK 15, we used X-ray microtomography to investigate aspects of bone and tooth structural organization. Geometric morphometric analyses of the dental arcade shape, mandible symphysis outline, and the M and M enamel-dentine junction shape were conducted. For mandibular symphysis shape, SK 15 exhibits an australopith signal, whereas for both the dental arcade and enamel-dentine junction analyses, the specimen is statistically classified as Paranthropus. Altogether, the results show that SK 15 unambiguously falls outside the variation of H. erectus/H. ergaster and that it is most compatible with the morphology of Paranthropus, albeit showing smaller dimensions and an absence of some dental morphological features (e.g., developed protostylid, distally tapering M, short molar roots) typically found in specimens of Paranthropus aethiopicus, Paranthropus boisei, and Paranthropus robustus. In particular, SK 15 differs markedly in size and morphology from mandibular remains of P. robustus from Swartkrans Member 2. We thus tentatively attribute SK 15 to Paranthropus capensis, a more gracile species of Paranthropus than the other three currently recognized species of this genus and discuss the implications for the existence of another species of Paranthropus in southern Africa during the Early Pleistocene.
南方古猿下颌骨SK 15于1949年4月在斯瓦特克朗斯第2层被发现，年代约为140万年前。尽管右侧有变形，但SK 15的左右下颌体相对较低且厚，即便与大多数早更新世至中更新世的人属标本相比也是如此。它保留了左侧磨牙列以及右侧的M1和M2，其近远中径向远中方向增加。SK 15最初被归为开普远古人，但现在一般被归为直立人/匠人，尽管之前有人认为它可能属于南方古猿。也有人声称SK 15与纳莱迪人下颌骨及牙齿形态存在相似之处。为了厘清SK 15的分类，我们使用X射线显微断层扫描技术来研究骨骼和牙齿结构组织的各个方面。对牙弓形状、下颌联合轮廓以及M1和M2釉牙本质界形状进行了几何形态计量分析。对于下颌联合形状，SK 15呈现出南方古猿的特征信号，而对于牙弓和釉牙本质界分析，该标本在统计学上被归类为傍人。总体而言，结果表明SK 15明显超出了直立人/匠人的变异范围，并且它与傍人的形态最为相符，尽管其尺寸较小且缺少一些在埃塞俄比亚傍人、鲍氏傍人和粗壮傍人标本中通常发现的牙齿形态特征（例如，发达的原尖、向远中逐渐变细的M1、短的磨牙根）。特别是，SK 15在大小和形态上与来自斯瓦特克朗斯第2层的粗壮傍人下颌遗骸有显著差异。因此，我们初步将SK 15归为开普傍人，它是傍人属中比该属目前公认的其他三个物种更为纤细的一个物种，并讨论了这对早更新世时期南非存在另一种傍人物种的意义。
