Late Oligocene Megatherioidea Fauna (Edentata: Xenarthra) from Salla-Luribay (Bolivia): new data on basal sloth radiation and Cingulata-Phyllophaga split

PUJOS, F.; DE IULIIS, G.

JOURNAL OF VERTEBRATE PALEONTOLOGY

The Society of Vertebrate Paleontology

Lugar: Lawrence; Año: 2007 vol. 27 p. 132 - 144

0272-4634

    The origins of the distinct sloth lineages are not well documented. The Deseadan SALMA site of Salla-Luribay presents four Tardigrada and constitutes one of the two oldest sloth assemblages. The peculiar glypto-sloth Pseudoglyptodon sallaensis is found together with two orophodontoid taxa and a Megalonychidae. The study of the P. sallaensis remains confirms that is effectively a sloth with various glyptodontoid convergences easily explicable by a grazing way of life. The orophodontids exhibit a common dental pattern with Octodontotherium from Patagonia. Except for the presence of Pseudoglyptodon, the Salla-Luribay Xenarthra assemblage closely resembles the La Flecha site from Santa Cruz province, Argentina. The Megalonychidae are also recorded, which increases the paleogeographic distribution of this clade in the late Oligocene. The phylogenetic status of Pseudoglyptodon remains doubtful and additional material is necessary to resolve it. Two species of Peltephilinae, a Glyptodontidae closely related to Eocoleophorus and Glyptatelus complete the xenarthran assemblage. All of the Bolivian specimens are considerably smaller than the Patagonian forms, a difference that may reflect distinct diets, latitudinal cline, and environments during the end of the Oligocene.    The existence of Pseudoglyptodon, four Orophodontidae and two Megalonychidae at the end of the Oligocene (25.65 and 29.4 Ma) in South America is surprising and implies an early diversification of sloths and a Cingulata/ Tardigrada split, probably before the Casamayoran, which would be in agreement with predictions based on molecular evidence.