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Thoracic vertebral count and thoracolumbar transition in Australopithecus afarensis

Ward, CV; Nalley, TK; Spoor, F; Tafforeau, P; Alemseged, Z; (2017) Thoracic vertebral count and thoracolumbar transition in Australopithecus afarensis. Proceedings of the National Academy of Sciences of the United States of America , 114 (23) pp. 6000-6004. 10.1073/pnas.1702229114. Green open access

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Abstract

The evolution of the human pattern of axial segmentation has been the focus of considerable discussion in paleoanthropology. Although several complete lumbar vertebral columns are known for early hominins, to date, no complete cervical or thoracic series has been recovered. Several partial skeletons have revealed that the thoracolumbar transition in early hominins differed from that of most extant apes and humans. Australopithecus africanus, Australopithecus sediba, and Homo erectus all had zygapophyseal facets that shift from thoracic-like to lumbar-like at the penultimate rib-bearing level, rather than the ultimate rib-bearing level, as in most humans and extant African apes. What has not been clear is whether Australopithecus had 12 thoracic vertebrae as in most humans, or 13 as in most African apes, and where the position of the thoracolumbar transitional element was. The discovery, preparation, and synchrotron scanning of the Australopithecus afarensis partial skeleton DIK-1-1, from Dikika, Ethiopia, provides the only known complete hominin cervical and thoracic vertebral column before 60,000 years ago. DIK-1-1 is the only known Australopithecus skeleton to preserve all seven cervical vertebrae and provides evidence for 12 thoracic vertebrae with a transition in facet morphology at the 11th thoracic level. The location of this transition, one segment cranial to the ultimate rib-bearing vertebra, also occurs in all other early hominins and is higher than in most humans or extant apes. At 3.3 million years ago, the DIK-1-1 skeleton is the earliest example of this distinctive and unusual pattern of axial segmentation.

Type: Article
Title: Thoracic vertebral count and thoracolumbar transition in Australopithecus afarensis
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1073/pnas.1702229114
Publisher version: http://doi.org/10.1073/pnas.1702229114
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Australopithecus afarensis, Dikika, segmentation, thoracic, vertebrae
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Anthropology
URI: https://discovery.ucl.ac.uk/id/eprint/1557400
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