title: The vertebrae and ribs of Homo naledi.
abstract: Hominin evolution featured shifts from a trunk shape suitable for climbing and housing a large gut to a trunk adapted to bipedalism and higher quality diets. Our knowledge regarding the tempo, mode, and context in which these derived traits evolved has been limited, based largely on a small-bodied Australopithecus partial skeleton (A.L. 288-1; "Lucy") and a juvenile Homo erectus skeleton (KNM-WT 15000; "Turkana Boy"). Two recent discoveries, of a large-bodied Australopithecus afarensis (KSD-VP-1/1) and two Australopithecus sediba partial skeletons (MH1 and MH2), have added to our understanding of thorax evolution; however, little is known about thorax morphology in early Homo. Here we describe hominin vertebrae, ribs, and sternal remains from the Dinaledi chamber of the Rising Star cave system attributed to Homo naledi. Although the remains are highly fragmented, the best-preserved specimens-two lower thoracic vertebrae and a lower rib-were found in association and belong to a small-bodied individual. A second lower rib may belong to this individual as well. All four of these individual elements are amongst the smallest known in the hominin fossil record. H. naledi is characterized by robust, relatively uncurved lower ribs and a relatively large spinal canal. We expect that the recovery of additional material from Rising Star Cave will clarify the nature of these traits and shed light on H. naledi functional morphology and phylogeny.
authors.affiliation: Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa; New York Consortium in Evolutionary Primatology, New York, NY 10024, USA. Electronic address: sawilliams@nyu.edu.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Williams
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (MNCN-CSIC), J.G. Abascal 6, 28006 Madrid, Spain; Faculty of Sciences, Biology Department, Universidad Autónoma de Madrid, 28049 Madrid, Spain; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Daniel
authors.initials: D
authors.lastname: García-Martínez
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (MNCN-CSIC), J.G. Abascal 6, 28006 Madrid, Spain; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Markus
authors.initials: M
authors.lastname: Bastir
authors.affiliation: Department of Anthropology, Chaffey College, Rancho Cucamonga, CA 91737, USA.
authors.forename: Marc R
authors.initials: MR
authors.lastname: Meyer
authors.affiliation: Department of Human Anatomy and Physiology, Faculty of Health Sciences, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Shahed
authors.initials: S
authors.lastname: Nalla
authors.affiliation: Department of Anthropology, University of Wisconsin-Madison, Madison, WI 53593, USA; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: John
authors.initials: J
authors.lastname: Hawks
authors.affiliation: Anthropological Institute and Museum, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Peter
authors.initials: P
authors.lastname: Schmid
authors.affiliation: Department of Evolutionary Anthropology, Box 90383, Duke University, Durham, NC 27708, USA; Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Churchill
authors.affiliation: Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa.
authors.forename: Lee R
authors.initials: LR
authors.lastname: Berger
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology*; D015186:Hominidae / Q000033:anatomy & histology*; D012272:Ribs / Q000033:anatomy & histology*; D013019:South Africa; D013131:Spine / Q000033:anatomy & histology*
keywords: Australopithecus; Bipedalism; Ribcage; Thorax; Trunk; Vertebral column