The last important –and possibly the most spectacular– turnover in South American mammal history occurred around the Pleistocene-Holocene boundary, when 100% of megamammal species and about 80% of large mammal species became extinct. In this paper, we consider as “megamammals” those with body mass over 1,000 kg, and “large mammals” those over 44 kg. With the exception of a few smaller mammals, no other animal or plant disappeared. Consequently, this extinction event was distinct from mass extinctions.