A hominin first rib discovered at the Sterkfontein Caves, South Africa

  • Gaokgatlhe Tawane Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa
  • Daniel García-Martínez 1. Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa 2. Palaeoanthropology Group, National Museum of Natural Sciences (MNCN-CSIC), Madrid, Spain 3. Biology Department, Faculty of Sciences, Autonomous University of Madrid, Madrid, Spain
  • Jennifer Eyre 1. Center for the Study of Human Origins, Department of Anthropology, New York University, New York, New York, USA 2. New York Consortium in Evolutionary Primatology, New York, New York, USA
  • Markus Bastir 1. Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa 2. Palaeoanthropology Group, National Museum of Natural Sciences (MNCN-CSIC), Madrid, Spain
  • Lee Berger Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa
  • Peter Schmid 1. Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa 2. Anthropological Institute and Museum, University of Zurich, Zurich, Switzerland
  • Shahed Nalla 1. Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa 2. Department of Human Anatomy and Physiology, Faculty of Health Sciences, University of Johannesburg, Johannesburg, South Africa
  • Scott A. Williams 1. Evolutionary Studies Institute and Centre for Excellence in Palaeosciences, University of the Witwatersrand, Johannesburg, South Africa 2. Center for the Study of Human Origins, Department of Anthropology, New York University, New York, New York, USA 3. New York Consortium in Evolutionary Primatology, New York, New York, USA
Keywords: upper thorax, rib cage, Australopithecus africanus, geometric morphometrics, Gauteng Province

Abstract

First ribs – the first or most superior ribs in the thorax – are rare in the hominin fossil record, and when found, have the potential to provide information regarding the upper thorax shape of extinct hominins. Here, we describe a partial first rib from Member 4 of the Sterkfontein Caves, South Africa. The rib shaft is broken away, so only the head and neck are preserved. The rib is small, falling closest to small-bodied Australopithecus first ribs (AL 288-1 and MH1). Given that it was recovered near the StW 318 femur excavation, which also represents a small individual, we suggest that the two may be associated. Three-dimensional geometric morphometric analyses were used to quantify the rib fragment morphology and compare it to extant hominoid and other fossil hominin ribs. While only the proximal end is preserved, our analyses show that South African Australopithecus share derived features of the proximal first rib more closely resembling A. afarensis and later hominins than great apes.

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Published
2016-05-26