Cranial and dental studies of Glossotherium robustum (Owen, 1842) (Xenarthra: Pilosa: Mylodontidae) from the Pleistocene of southern Brazil

Abstract

Pitana, V.G., Esteban, G.I., Ribeiro, A.M. & Cartelle, C. 2013. Cranial and dental studies of Glossotherium robustum (Owen, 1842) (Xenarthra: Pilosa: Mylodontidae) from the Pleistocene of southern Brazil. Alcheringa, 1–16. ISSN 0311-5518.

Mylodontine ground sloths were studied from several Pleistocene localities of Rio Grande do Sul State: São Gabriel (central region), Quaraí, Uruguaiana and Alegrete (western region) and Santa Vitória do Palmar (coastal region) municipalities. The cranial and mandibular material is assigned to Glossotherium robustum based on the enlargement of the anterior portion of the maxilla, a rounded and ventrolaterally arched fossa for the estylohyal, an elliptical occipital condyle, a spatulate symphyseal region of the mandible, together with the size and degree of lobulation of the teeth. Comparison with specimens from the Pampean region of Argentina, western Uruguay and northeastern Brazil revealed that the Rio Grande do Sul material is most similar morphologically to that of the Pampean region of Argentina and Uruguay. These southern specimens are morphologically distinct from Pleistocene material from tropical Brazil assigned to Glossotherium sp. The Pleistocene records of G. robustum indicate that this taxon was widely distributed between 20°S and 40°S spanning Argentina, Brazil, Bolivia, Chile, Uruguay and Paraguay, whereas Glossotherium sp. was restricted to latitudes <30°S.

在Rio Grande do Sul 的若干更新世地点如: Sa ͂o Gabriel (中区), Quarai ′, Uruguaiana及Alegrete(西区), 以及Santa Vito′ do Palmar(沿海区), 我们研究了Mylodontine地懒。根据颚骨前部分变大, 圆形腹侧向上弓的窝, 椭圆的枕髁, 下颚的匙形沿耻骨联合区, 以及牙齿分叶的范围和程度, 这些颅骨和下颚骨被归为Glossotherium robustum。与采自阿根廷Pampean地区、乌拉圭西部和巴西东北部的标本进行比较, 我们发现Rio Grande do Sul 标本在形态上与阿根廷和乌拉圭的最相似。这些南部标本在形态上与热带巴西的更新世Glossotherium sp.标本有很大差异。G. robustum的更新世记录表示, 这个分类群广泛分布于208S和408S之间, 包括阿根廷、巴西、玻利维亚、智利、乌拉圭和巴拉圭, 而Glossothrium sp. 只局限于纬度5308S。

Key words:

• Glossotherium robustum
• Pleistocene
• Rio Grande do Sul State
• Brazil

Acknowledgements

We thank Marcelo Reguero (Museo de La Plata), Deise R. Henriques (Museu Nacional do Rio de Janeiro), Jaime Powell (Museo Miguel Lillo, San Miguel de Tucumán) and Andrés Rinderknecht (Museo Nacional de Historia Natural de Montevideo) for access to the collections under their care, Jorge Ferigolo for discussions about anatomy and morphology, and the reviewers for comments that greatly improved this work.