New postcranial remains of ground sloths (Xenarthra, Folivora, Mylodontidae) from Southern Brazil
DOI:
https://doi.org/10.4072/rbp.2023.1.04Abstract
Diagnoses of Mylodontidae species are generally based on skull, mandibular, and tooth characteristics, and rarely on postcranial morphology, due to the lack of postcranial material associated with the cranial material. The studies of postcranial anatomy have generally a biomechanical focus and reflect a set of functions of skeletal structures, but their interpretation in phylogenetic analysis is still limited. In Pleistocene deposits of Rio Grande do Sul State, Brazil, an important set of postcranial specimens was collected, belonging to Mylodontidae. They were morphologically and morphometrically analyzed, allowing us to observe some diagnostic characters such as the humeral entepicondylar foramen and crests, shape of the radial shaft, angle of distal articulation of the tibia, as well as the angle of proximal articulation of the astragalus. The material was also compared with specimens from other South American localities. Most of the remains were assigned to Glossotherium robustum and Lestodon armatus. In addition, a new Scelidotheriinae was recorded for Rio Grande do Sul State. The study indicated significant differences in the postcranial morphology, which allowed the recognition of some specific diagnostic characters.
Keywords: Mylodontinae, Scelidotheriinae, hindlimb, forelimb, Pleistocene, Rio Grande do Sul.
RESUMO – As diagnoses de espécies de Mylodontidae são baseadas principalmente em características cranianas, mandibulares e dentárias e, raramente, em morfologia pós-craniana, devido à falta de esqueletos completos associados a material craniano. Os estudos de anatomia pós-craniana têm se limitado, em geral, a biomecânica, com foco nas funções das estruturas esqueléticas, mas suas interpretações filogenéticas ainda são poucas. Nos depósitos pleistocênicos do Estado do Rio Grande do Sul, Brasil, um importante conjunto de espécimes pós-cranianos pertencentes a Mylodontidae foi morfológica e morfometricamente analisado, o que nos permitiu observar algumas características diagnósticas como o forame entepicondilar e as cristas do úmero, formato da diáfise do rádio, ângulo da articulação distal da tíbia, bem como o ângulo da articulação proximal do astrágalo. Os materiais também foram comparados com espécimes de outras localidades da América do Sul. A maioria do material foi atribuída a Glossotherium robustum e Lestodon armatus. Ademais, um novo Scelidotheriinae é registrado para o Rio Grande do Sul. O estudo indicou diferenças significativas na morfologia pós-craniana, que permitiram o reconhecimento de caracteres diagnósticos específicos.
Palavras-chave: Mylodontinae, Scelidotheriinae, membro anterior, membro posterior, Pleistoceno, Rio Grande do Sul.
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