Adult Neandertal clavicles from the El Sidrón site (Asturias, Spain) in the context of Homo pectoral girdle evolution.
We undertook a three-dimensional geometric morphometric (3DGM) analysis on 12 new Neandertal clavicle specimens from the El Sidrón site (Spain), dated to 49,000 years ago. The 3DGM methods were applied in a comparative framework in order to improve our understanding of trait polarity in features related to Homo pectoral girdle evolution, using other Neandertals, Homo sapiens, Pan, ATD6-50 (Homo antecessor), and KNM-WT 15000 (Homo ergaster/erectus) in the reference collection. Twenty-nine homologous landmarks were measured for each clavicle. Variation and morphological similarities were assessed through principal component analysis, conducted separately for the complete clavicle and the diaphysis. On average, Neandertal clavicles had significantly larger muscular entheses, double dorsal curvature, clavicle torsion, and cranial orientation of the acromial end than non-Neandertal clavicles; the El Sidrón clavicles fit this pattern. Variation within the samples was large, with extensive overlap between Homo species; only chimpanzee specimens clearly differed from the other specimens in morphometric terms. Taken together, our morphometric analyses are consistent with the following phylogenetic sequence. The primitive condition of the clavicle is manifest in the cranial orientation of both the acromial and sternal ends. The derived condition expressed in the H. sapiens + Neandertal clade is defined by caudal rotation of both the sternal and acromial ends, but with variation in the number of acromia remaining in a certain cranial orientation. Finally, the autapomorphic Neandertal condition is defined by secondarily acquired primitive cranial re-orientation of the acromial end, which varies from individual to individual. These results suggest that the pace of phylogenetic change in the pectoral girdle does not seem to follow that of other postcranial skeletal features.
Group of Paleoanthropology MNCN-CSIC, Department of Paleobiology, Museo Nacional de Ciencias Naturales-CSIC, Calle José Gutiérrez Abascal 2, 28006 Madrid, Spain. Electronic address: arosas@mncn.csic.es.
Antonio
A
Rosas
Group of Paleoanthropology MNCN-CSIC, Department of Paleobiology, Museo Nacional de Ciencias Naturales-CSIC, Calle José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Francisco Javier
FJ
Rodriguez-Perez
Group of Paleoanthropology MNCN-CSIC, Department of Paleobiology, Museo Nacional de Ciencias Naturales-CSIC, Calle José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Markus
M
Bastir
Group of Paleoanthropology MNCN-CSIC, Department of Paleobiology, Museo Nacional de Ciencias Naturales-CSIC, Calle José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Almudena
A
Estalrrich
Institut Català de Paleoecologia Humana i Evolució Social (IPHES), Campus Sescelades URV (Edifici W3), Unidad Asociada al CSIC, 43007 Tarragona, Spain; Universitat Rovira i Virgili, Avda. Catalunya, 35, 43002 Tarragona, Spain.
Rosa
R
Huguet
Group of Paleoanthropology MNCN-CSIC, Department of Paleobiology, Museo Nacional de Ciencias Naturales-CSIC, Calle José Gutiérrez Abascal 2, 28006 Madrid, Spain.
Antonio
A
García-Tabernero
Museo Anatómico, departamento de Anatomía Humana, Universidad de Valladolid, Calle Ramón y Cajal 7, 47005 Valladolid, Spain.
Juan Francisco
JF
Pastor
Área de Prehistoria, Department of History, Universidad de Oviedo, Calle Teniente Alfonso Martínez s/n, 33011 Oviedo, Spain.
Marco
M
de la Rasilla
D000818:Animals; D005075:Biological Evolution; D002968:Clavicle / Q000033:anatomy & histology*; D005260:Female; D005580:Fossils / Q000033:anatomy & histology*; D008297:Male; D059125:Neanderthals / Q000033:anatomy & histology*; D010802:Phylogeny; D012782:Shoulder / Q000033:anatomy & histology; D013030:Spain
Collarbone morphology; Geometric morphometrics; H. neanderthalensis; Pleistocene; Trait polarity