title: The relevance of the first ribs of the El Sidrón site (Asturias, Spain) for the understanding of the Neandertal thorax.
abstract: Reconstructing the morphology of the Neanderthal rib cage not only provides information about the general evolution of human body shape but also aids understanding of functional anatomy and energetics. Despite this paleobiological importance there is still debate about the nature and extent of variations in the size and shape of the Neandertal thorax. The El Sidrón Neandertals can be used to contribute to this debate, providing new costal remains ranging from fully preserved and undistorted ribs to highly fragmented elements. Six first ribs are particularly well preserved and offer the opportunity to analyze thorax morphology in Neandertals. The aims of this paper are to present this new material, to compare the ontogenetic trajectories of the first ribs between Neandertals and modern humans, and, using geometric morphometrics, to test the hypothesis of morphological integration between the first rib and overall thorax morphology. The first ribs of the El Sidrón adult Neandertals are smaller in centroid size and tend to be less curved when compared with those of modern humans, but are similar to Kebara 2. Our results further show that the straightening of the first ribs is significantly correlated with a straightening of the ribs of the upper thorax (R = 0.66; p < 0.0001) in modern humans, suggesting modularity in the upper and lower thorax units as reported in other hominins. It also supports the hypothesis that the upper thorax of Neandertals differs in shape from modern humans with more anteriorly projecting upper ribs during inspiration. These differences could have biomechanical consequences and account for stronger muscle attachments in Neandertals. Different upper thorax shape would also imply a different spatial arrangement of the shoulder girdle and articulation with the humerus (torsion) and its connection to the upper thorax. Future research should address these inferences in the context of Neandertal overall body morphology.
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain. Electronic address: mbastir@mncn.csic.es.
authors.forename: Markus
authors.initials: M
authors.lastname: Bastir
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: García-Martínez
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain.
authors.forename: Almudena
authors.initials: A
authors.lastname: Estalrrich
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: García-Tabernero
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain; Institut Català de Paleoecologia Humana i Evolució Social (IPHES), C/ Marcel.lí Domingo s/n e Campus Sescelades URV (Edifici W3), 43007 Tarragona, Spain; Àrea de Prehistòria, Universitat Rovira i Virgili (URV), Avinguda de Catalunya 35, 43002 Tarragona, Spain; Unidad asociada al CSIC, Departamento de Paleobiología, Museo Nacional de Ciencias Naturales, Calle José Gutierrez Abascal, 2. 28006 Madrid, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Huguet
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain; Sociedad de Ciencias Aranzadi-Aranzadi Zientzia Elkartea, Alto de Zorroaga Bidea, 11, 20014, Donostia, Gipuzkoa, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Ríos
authors.affiliation: Faculty of Medicine in the Galilee, Bar Ilan University, Henrietta Szold, 8, P.O.B 1589, 1311502, Zefat, Israel.
authors.forename: Alon
authors.initials: A
authors.lastname: Barash
authors.affiliation: Department of Radiology, Medical University Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Recheis
authors.affiliation: Department of History, University of Oviedo, Campus del Milán, C/ Teniente Alfonso Martínez s/n, 33011, Oviedo, Spain.
authors.forename: Marco
authors.initials: M
authors.lastname: de la Rasilla
authors.affiliation: Paleoanthropology Group, Museo Nacional de Ciencias Naturales (CSIC), J. G. Abascal 2, 28006, Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Rosas
mesh_terms: D000328:Adult; D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D006801:Humans; D059125:Neanderthals / Q000033:anatomy & histology*; D012272:Ribs / Q000033:anatomy & histology*; D013030:Spain; D013909:Thorax / Q000033:anatomy & histology
keywords: Body shape; Costal skeleton; Homo neanderthalensis; Integration; Semilandmarks