Did the megafauna range to 4300 BP in South America?

A date of 4300 +/- 90 BP for extinct megafauna in Argentina is discussed. T he fossil remains come from the Guerrero Member (area) of the Lujan Formati on near the city of Lujan, Buenos Aires Province. The age of the top of the Guerrero Member is constrained by more than 60 radiocarbon dates obtained from the overlying Rio Salado Member of Lujan Formation, Las Escobas Format ion, and Puesto Callejon Viejo Soil, most of them older than 4300 BP. In vi ew of its low collagen content, the C-14 measurement of bone sample from Lu jan should not be accepted uncritically. Because of the poor bone preservat ion and the possible introduction of "young" contaminants that were not com pletely eliminated, the C-14 date of 4300 +/- 90 BP is not reliable. Both b iostratigraphic and C-14 dating evidence indicates that the date of 4300 BP for the last representative of extinct megafauna in South America is unsup ported.