Museo Nacional de Ciencias Naturales (CSIC), Department of Paleobiology, Paleoanthropology Group, J.G. Abascal 2, 28006, Madrid, Spain; Universidad Autónoma de Madrid, Faculty of Sciences, Department of Biology, Darwin 2, 28049, Madrid, Spain.
Museo Nacional de Ciencias Naturales (CSIC), Department of Paleobiology, Paleoanthropology Group, J.G. Abascal 2, 28006, Madrid, Spain.
J Hum Evol. 2020 Dec;149:102897. doi: 10.1016/j.jhevol.2020.102897. Epub 2020 Nov 1.
The first cervical vertebra (atlas, C1) is an important element of the vertebral column because it connects the cranial base with the cervical column, thus helping to maintain head posture and contributing to neck mobility. However, few atlases are preserved in the fossil record because of the fragility of this vertebra. Consequently, only eight well-preserved atlases from adult Neandertals have been recovered and described. Here, we present nine new atlas remains from the El Sidrón Neandertal site (Asturias, Spain), two of which (SD-1643 and SD-1605/1595) are sufficiently well preserved to allow for a detailed comparative and three-dimensional geometric morphometric analysis. We compared standard linear measurements of SD-1643 and SD-1605/1595 with those of other Neandertal atlases and carried out three-dimensional geometric morphometric analyses to compare size and shape of SD-1643 and SD-1605/1595 with those of 28 Pan (Pan troglodytes and Pan paniscus), a broad comparative sample of 55 anatomically modern humans from African and European populations, and other fossil hominins (Neandertals, Homo antecessor, Paranthropus boisei). The El Sidrón atlas fossils show typical features of the Neandertal atlas morphology, such as caudal projection of the anterior tubercle, gracility of both the posterior tubercle and the tuberosity for the insertion of the transverse ligament, and an anteroposteriorly elongated neural canal. Furthermore, when compared with atlases from the other taxa, Neandertals exhibit species-specific features of atlas morphology including a relatively lower lateral mass height, relatively narrower transverse foramina, and flatter and more horizontally oriented articular facets. Some of these features fit with previous suggestions of shorter overall length of the cervical spine and potential differences in craniocervical posture and mobility. Our results may support a different spinopelvic alignment in this species, as the atlas morphology suggests reduced cervical lordosis.
第一颈椎（寰椎，C1）是脊柱的重要组成部分，因为它连接颅底与颈椎，有助于维持头部姿势并增加颈部活动度。然而，由于该椎骨易碎，因此在化石记录中很少保存寰椎。因此，只有 8 个保存完好的成年尼安德特人寰椎被发现并描述。在这里，我们展示了来自西班牙埃尔西多恩（El Sidrón）尼安德特人遗址的 9 个新的寰椎遗骸，其中 2 个（SD-1643 和 SD-1605/1595）保存得足够完好，可以进行详细的比较和三维几何形态测量分析。我们比较了 SD-1643 和 SD-1605/1595 的标准线性测量值与其他尼安德特人寰椎的测量值，并进行了三维几何形态测量分析，比较了 SD-1643 和 SD-1605/1595 的大小和形状与来自非洲和欧洲人群的 28 个现生人类（Pan troglodytes 和 Pan paniscus）、55 个解剖学现代人类的广泛比较样本以及其他化石人类（尼安德特人、Homo antecessor、Paranthropus boisei）的样本。埃尔西多恩的寰椎化石具有尼安德特人寰椎形态的典型特征，例如前结节的尾侧突出、后结节和横韧带附着的结节的纤细、以及前后拉长的神经管。此外，与其他分类群的寰椎相比，尼安德特人具有寰椎形态的种特异性特征，包括相对较低的侧块高度、相对较窄的横突孔以及更平坦和更水平的关节面。这些特征中的一些与之前提出的颈椎总长度较短以及潜在的颅颈姿势和活动度差异的假设相符。我们的结果可能支持该物种不同的脊柱骨盆排列，因为寰椎形态表明颈椎前凸减少。
