THE LATE OLIGOCENE XENARTHRAN FAUNA OF QUEBRADA FIERA (MENDOZA, ARGENTINA) AND ITS IMPLICATIONS FOR SLOTH ORIGINS AND THE DIVERSITY OF PALAEOGENE CINGULATES

F. PUJOS , M. R. CIANCIO , A. M. FORASIEPI , M. PUJOS, A. M. CANDELA , B. VERA , M. A. REGUERO , A.M. COMBINA AND E. CERDENO

SPECIAL PAPERS IN PALAEONTOLOGY SERIES

PALAEONTOLOGICAL ASSOC

Lugar: Londres; Año: 2021

0038-6804

The late Oligocene mammalian fauna of QuebradaFiera is one of the most diverse of the DeseadanSALMA (South American Land Mammal Age). Wedescribe its endemic xenarthran assemblage, represented by13 species, consisting of 2 stem sloths and 11 armouredcingulates. The rare folivoran material confirms the presenceof Octodontotherium, one of the early knownmylodontids, and suggests the existence of a new, small,non-megalonychid megatherioid, Similhapalops nivis. Thelumbar vertebrae of Octodontotherium sp. provide the oldestevidence of xenarthry for the order. The presence atthe knee joint of an ossified meniscus and cyamo-fabellastrongly suggests a plantigrade ancestral condition inMylodontidae. Armoured xenarthrans are represented bythe armadillos Eutatini (Meteutatus sp., M. lagenaformis,and Stenotatus ornatus), an undetermined Euphractinii, the?horned? peltephilids Peltephilus sp. and P. undulatus, andthe palaeopeltid Palaeopeltis inornatus; an undeterminedGlyptodontidae, the glyptatelines Glyptatelus cf. tatusinusand Clypeotherium sp., and an undetermined propalaehoplophorine.The xenarthrans represent one-third of themammals of the Quebrada Fiera fauna, one of the mostvaried at the end of the Palaeogene in South America.This vertebrate fauna is represented by a mix of endemictaxa and other species of high latitude (Patagonian) origin,but few from low latitude faunas. A detailed study of thismammalian assemblage, complemented by detailed geologicaland petrographical studies, suggests the existence ofstrong volcanic activity, and the presence of braided riversand lagoonal environments in open habitats under a temperateor hot climate, with savannas and/or grasslands andisolated forests during the late Oligocene at the foot ofthe proto-Andes.