Anatomy, possible sexual dimorphism, and phylogenetic affinities of a new mylodontine sloth from the late Pleistocene of intertropical Brazil

Abstract

Glossotherium phoenesis sp. nov. from the late Pleistocene of intertropical Brazil is described and compared with Glossotherium robustum and Glossotherium tropicorum. Compared to these two species, the main differences occur in the shape of the nasal region and pterygoids, proportionate narrowing of the skull, length and arrangement of the tooth rows, degree of projection and form of the mandibular symphysis, height at various points along the dentary, and proportions of the radius, among others described. Clear differences in two well-preserved skulls of the new species are interpreted as representing sexual dimorphism, as occurs in other ground sloths such as Paramylodon and Eremotherium. Other notable features are described for osteoderms and for the ontogenetic developments of the mandible and dentition. The new species G. phoenesis appears to be one of the most derived Mylodontidae, sister taxon of G. tropicorum, and closely related to Pleurolestodon.