Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications

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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 ibs...

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Autores principales: Haro, J.A., Tauber, A.A., Krapovickas, J.M.
Formato: JOUR
Materias:
Late Pleistocene
Mylodon darwinii
Mylodontinae
Osteology
Phylogeny
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00310220_v91_n3_p439_Haro
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00310220_v91_n3_p439_Haro2023-10-03T14:41:06Z Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications Haro, J.A. Tauber, A.A. Krapovickas, J.M. Late Pleistocene Mylodon darwinii Mylodontinae Osteology Phylogeny 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. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00310220_v91_n3_p439_Haro
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Late Pleistocene
Mylodon darwinii
Mylodontinae
Osteology
Phylogeny
spellingShingle Late Pleistocene
Mylodon darwinii
Mylodontinae
Osteology
Phylogeny
Haro, J.A.
Tauber, A.A.
Krapovickas, J.M.
Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications
topic_facet Late Pleistocene
Mylodon darwinii
Mylodontinae
Osteology
Phylogeny
description 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.
format JOUR
author Haro, J.A.
Tauber, A.A.
Krapovickas, J.M.
author_facet Haro, J.A.
Tauber, A.A.
Krapovickas, J.M.
author_sort Haro, J.A.
title Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications
title_short Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications
title_full Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications
title_fullStr Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications
title_full_unstemmed Thoracic member (pectoral girdle and forelimb) bones of Mylodon darwinii Owen (Xenarthra, Mylodontidae) from the Late Pleistocene of Central Argentina and their phylogenetic implications
title_sort thoracic member (pectoral girdle and forelimb) bones of mylodon darwinii owen (xenarthra, mylodontidae) from the late pleistocene of central argentina and their phylogenetic implications
url http://hdl.handle.net/20.500.12110/paper_00310220_v91_n3_p439_Haro
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