The Late Oligocene Xenarthran fauna of Quebrada Fiera (Mendoza, Argentina) and its implications for sloth origins and the diversity of Paleogene cingulates

PUJOS, F.; CIANCIO, MARTÍN; FORASIEPI, ANALÍA; PUJOS, MICHEL; CANDELA, ADRIANA; VERA, BÁRBARA; REGUERO, MARCELO; COMBINA, A. M.; CERDEÑO, ESPERANZA

SPECIAL PAPERS IN PALAEONTOLOGY SERIES

PALAEONTOLOGICAL ASSOC

Lugar: Londres; Año: 2021 vol. 7 p. 1613 - 1656

0038-6804

The late Oligocene mammalian fauna of Quebrada Fiera is one of the most diverseof the Deseadan SALMA. We describe its endemic xenarthran assemblage, represented by 13 species, including two stem sloths and 11 armored cingulates. The rare folivoran remainscomplete the knowledge of Octodontotherium, one of the first mylodontids, and suggest theexistence of new a small megatherioid non-megalonychid Similhapalops nivis gen. et sp. nov.Octodontotherium sp. lumbar vertebrae provide the oldest evidence of xenarthry for the order.The presence at the knee joint of an ossified meniscus and cyamo-fabella strongly suggests aplantigrade ancestral condition in Mylodontidae. Armored xenarthrans are represented byarmadillos Eutatini (Meteutatus sp., M. lagenaformis, and Stenotatus ornatus), anundetermined Euphractinii, the ?horned? peltephilids Peltephilus sp. and P. undulatus, and thepalaeopeltid Palaeopeltis inornatus; an undetermined Glyptodontidae, the glyptatelinesGlyptatelus cf. tatusinus and Clypeotherium sp., and an undetermined propalaeohoplophorine.The xenarthrans represent a third of the mammals of the Quebrada Fiera fauna, one of themost varied at the end of the Paleogene in South America. This vertebrate fauna isrepresented by a mix of endemic taxa with other species of high latitude (Patagonian) origin,but few from low latitude faunas. A detailed study of this mammalian assemblagecomplemented by detailed geological and petrographical studies suggest the existence ofstrong volcanic activity, the presence of braided rivers, lagoonal environments in openhabitats under a temperate or hot climate with savannas and/or grasslands and isolated forestsduring the late Oligocene at the foot of the proto-Andes.