New Late Pleistocene megafaunal assemblage with well-supported chronology from the Pampas of southern South America

摘要

Late Pleistocene outcrops exposed in Buenos Aires province, Argentina, represent one of the most informative sources about the paleoecology of South American megafauna. However, there are no records of an accurately dated carnivore-herbivore taphocenosis. This paper presents preliminary results of a recent excavation at the margins of the Salado River, on sediments attributed to the Lujan Formation (Late Pleistocene-Early Holocene). The fossiliferous strata consist of greenish brown sandy-clays deposited in a small paleopond environment that was filled by fluvial sediments, exhibiting abundant organic matter, gypsum and carbonate concretions. Fieldwork yielded an association of extinct large-sized mammals that include the horse Hippidion principale, the saber-tooth cat Smilodon populator (at least one adult and one juvenile associated specimen), a giant ground sloth Megatherium americanum, and the glyptodont Doedicurus clavicaudatus. Four ~(14)C dates were performed on organic matter (12,100 ± 100 ~(14)C BP), a femur of S. populator (13,400 ± 200 ~(14)C BP), and a cervical vertebra of Hippidion principale (12,860 ± 120 ~(14)C BP), and a pelvis of D. clavicaudatus (12,380 ± 190 ~(14)C BP) situating the site within 12,500 and 13,500 years, approximately. Remarkably, some of the recovered specimens exhibit conspicuous bone modifications (narrows, pits, punctures, striations and crenulated margins) attributed to the activity of a medium-large carnivore. The association between bones of herbivore mammals with conspicuous modifications produced by a large carnivore, and the presence of cub and adult remains of Smilodon, link this felid with at least part of the excavated association.