Su Anne, Carlson Kristian J
School of Health Sciences, Cleveland State University, Cleveland, OH 44115, USA.
Department of Cell & Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA; Evolutionary Studies Institute, University of the Witwatersrand, WITS 2050 Johannesburg, South Africa.
J Hum Evol. 2017 May;106:1-18. doi: 10.1016/j.jhevol.2016.12.006. Epub 2017 Mar 15.
Tali of several hominin taxa are preserved in the fossil record and studies of the external morphology of these often show a mosaic of human-like and ape-like features. This has contributed to a growing recognition of variability characterizing locomotor kinematics of Australopithecus. In contrast, locomotor kinematics of another Plio-Pleistocene hominin, Paranthropus, are substantially less well-documented, in part, because of the paucity of postcranial fossils securely attributed to the genus. Since the talus transmits locomotor-based loads through the ankle and its internal structure is hypothesized to reflect accommodation to such loads, it is a cornerstone structure for reconstructing locomotor kinematics. Here we quantify and characterize trabecular bone morphology within tali attributed to Australopithecus africanus (StW 102, StW 363, StW 486) and Paranthropus robustus (TM 1517), making quantitative comparisons to modern humans, extant non-human apes, baboons, and a hominin talus attributed to Paranthropus boisei (KNM-ER 1464). Using high-resolution images of fossil tali (25 μm voxels), nine trabecular bone subregions of interest beneath the articular surface of the talar trochlea were segmented to quantify localized patterns in distribution and primary strut orientation. It was found that trabecular strut orientation and shape, in some cases, can discriminate amongst species characterized by different locomotor foot kinematics. Discriminant function analyses using standard trabecular bone structural properties align TM 1517 with Pan and Gorilla, while other hominin tali structurally most resemble those of baboons. In primary strut orientation, Paranthropus tali (KNM-ER 1464 and TM 1517) resemble the human condition in the anterior-medial subregion, where strut orientation appears positioned to distribute compressive loads medially and distally toward the talar head. In A. africanus tali (particularly StW 486), primary strut orientation in this region resembles that of apes. These results suggest that Paranthropus may have had a human-like medial weight shift during the last half of stance phase but Australopithecus did not.
几种古人类类群的距骨保存在化石记录中，对这些距骨外部形态的研究常常显示出类人特征和类猿特征的混合。这使得人们越来越认识到南方古猿运动学特征的变异性。相比之下，另一种上新世-更新世古人类傍人属的运动学特征记录得要少得多，部分原因是明确归属于该属的颅后化石数量稀少。由于距骨通过脚踝传递基于运动的负荷，并且假设其内部结构反映了对这种负荷的适应，因此它是重建运动学特征的基石结构。在这里，我们对归属于非洲南方古猿（StW 102、StW 363、StW 486）和粗壮傍人（TM 1517）的距骨内小梁骨形态进行量化和特征描述，并与现代人类、现存非人类猿类、狒狒以及归属于鲍氏傍人的一具古人类距骨（KNM-ER 1464）进行定量比较。利用化石距骨的高分辨率图像（体素为25微米），对距骨滑车关节面下方的九个小梁骨感兴趣子区域进行分割，以量化分布的局部模式和主要支柱方向。研究发现，小梁支柱的方向和形状在某些情况下可以区分具有不同运动足部运动学特征的物种。使用标准小梁骨结构特性进行的判别函数分析将TM 1517与黑猩猩和大猩猩归为一类，而其他古人类距骨在结构上最类似于狒狒的距骨。在主要支柱方向上，傍人属距骨（KNM-ER 1464和TM 1517）在前内侧子区域类似于人类的情况，在该区域支柱方向似乎是为了将压缩负荷向内侧和远端朝距骨头分布。在非洲南方古猿距骨（特别是StW 486）中，该区域的主要支柱方向类似于猿类。这些结果表明，傍人在站立阶段的后半段可能具有类似人类的内侧重心转移，而南方古猿则没有。
