A new Megatheriinae skull (Xenarthra, Tardigrada) from the Pliocene of Northern Venezuela ? implications for a giant sloth dispersal to Central and North America

CARLINI, A. A.; BRANDONI, D.; SÁNCHEZ, R.; SÁNCHEZ-VILLAGRA M.

PALAEONTOLOGIA ELECTRONICA

COQUINA PRESS

Lugar: New York; Año: 2018 p. 1 - 12

1094-8074

A skull of a ground sloth from the Pliocene San Gregorio Formation documents anorthern neotropical occurrence of a megatheriine that addresses issues on intraspecificvariation and biogeography. The new specimen is broadly similar in size and morphologyto that of Proeremotherium eljebe from the underlying Codore Formation inthe Urumaco Sequence, differing in several features such as a longer basicranial areaand a more posteriorly projected basioccipital between the condyles. The living slothsspecies of Bradypus and Choloepus do not have unequivocal anatomical features thatindicate sexual dimorphism. Nevertheless, fossil sloths may have shown such dimorphism,and speculations on this subject are part of the considerations that can bemade when allocating fragmentary fossils (e.g., in the new skull the presence of a longsagittal crest could indicate a male individual and the absence of an extended crest inProeremotherium eljebe a female one). We speculate that as early as the late middleMiocene, two main lines of Megatheriinae had clearly separated in two geographicareas, one in the rising Andean area and one at low latitudes on the lowlands of centraland northern South America.