A nearly complete skeleton, including most of the thoracic member bones of the sloth Mylodon darwinii, have been found in Upper Pleistocene strata from Anisacate River, Argentina. The thoracic member bones resemble their homologues in Glossotherium robustum, Paramylodon harlani, and Mylodonopsis ibseni in the following traits: (1) the olecranon is mediolaterally compressed; (2) the radius has an acute styloid process; (3) the radial diaphysis medial border is straight for two thirds of its length; (4) the radial shaft medial border forms an angle with the medial border of the styloid process. The radius presents a distinctive, mostly proximally facing articular circumference. The unfused epiphyses and feeble muscle attachment ridges indicate a sub-adult ontogenetic stage. Deviation of the olecranon and weak M. teres major origin and insertion, suggest a low fossorial specialization. The structure of the thoracic limb bones does not support climbing habits, because pronation-related features are reduced and the humeral head is not prominent. The structure of the radius suggests graviportal adaptations: the proximal head is mediolaterally expanded and the diaphysis straight. A phylogenetic analysis adding thoracic member characters recovers M. darwinii as part of a clade that includes Glossotherium robustum and Paramylodon harlani, but excludes Lestodon armatus. This contrasts with the results of previous analyses focusing on the head skeleton, highlighting the relevance of sampling postcranial characters in phylogenetic analyses of mylodontine sloths. © 2017 Paläontologische Gesellschaft
Documento: | Artículo |
Título: | Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications |
Autor: | Haro, J.A.; Tauber, A.A.; Krapovickas, J.M. |
Filiación: | Museo de Paleontología, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sarsfield 249, Córdoba, Argentina Cátedra de Paleontología, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sarsfield 1611, Córdoba, Argentina Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina Museo Provincial de Ciencias Naturales “Dr. Arturo Umberto Illía”, Poeta Lugones 395, Córdoba, Argentina |
Palabras clave: | Late Pleistocene; Mylodon darwinii; Mylodontinae; Osteology; Phylogeny |
Año: | 2017 |
Página de inicio: | 1 |
Página de fin: | 19 |
DOI: | http://dx.doi.org/10.1007/s12542-017-0350-z |
Título revista: | Palaontologische Zeitschrift |
Título revista abreviado: | Palaontologische Z. |
ISSN: | 00310220 |
Registro: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00310220_v_n_p1_Haro |