Megafauna extinction in South America: A new chronology for the Argentine Pampas José L. Prado a, ⁎, Cayetana Martinez-Maza b , María T. Alberdi b a INCUAPA CONICET, Universidad Nacional del Centro de la provincia de Buenos Aires, Del Valle 5737, B7400JWI Olavarría, Argentina b Departamento de Paleobiología, MuseoNacional de CienciasNaturales, CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain abstract article info Article history: Received 1 September 2014 Received in revised form 10 February 2015 Accepted 18 February 2015 Available online 28 February 2015 Keywords: Megafauna extinction South America Pampas Radiocarbon date Late Pleistocene The megafauna extinction in South America was one of the most profound events, with the loss of 50 genera (~83%). Three orders disappeared (Notoungulata, Proboscidea, Litopterna), as did all large xenarthrans, but how this fits into global extinction is uncertain, mainly due to the lack of chronological resolution. In recent years there has been an increase in the number of radiocarbon dating at archeological and paleontological sites, but this information varies greatly from area to area in South America, and few data can be considered to constitute a taxon-date. The timing of the late Pleistocene extinction in the Pampas is poorly established. Most taxa only appear in the bio- stratigraphic context and many reported 14 C dates do not meet rigorous criteria for accepting dates, including re- ports suggesting survival of megafauna into the Holocene. In the present paper, we evaluate the published radiocarbon dates in the pampas and present 20 new radiocarbon dates for paleontological sites in order to es- tablish a more accurate “extinction window” for the key taxa. These new dates are sufficiently robust to assess correspondences among last-appearance records of megafauna, first-appearance records of humans, and the Younger Dryas to Holocene climatic transition in the Argentine Pampas. These results highlight the need for greater effort in taxa selection for dating. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Extinctions of mammal species, genera and in some cases at the fam- ily level have been detected since the middle Miocene in the Pampa of Argentina. These extinctions are most related to environmental climate changes and affected some large mammals, especially native ungulates and marsupials. However, at the end of the Pleistocene extinction there was a particularly extraordinary event and more species of mega- mammals (over 1000 kg) and most large mammals (over 44 kg) were lost than in any other extinction event (Cione et al., 2009). The mammal communities in the Pampas had included at least some large mammals since the late Miocene, but mega-mammals appeared and became widespread during the Pleistocene (Alberdi et al., 1995; Pascual et al., 1996). The late Pleistocene extinction in this region was attributed to cold, changes in mammal distributions, epidemics or human activities (Cione et al., 2003). The only difference with regard to the preceding event was the arrival of human beings to the continent around 11,000 14 C BP, when a consistent archeological signal appears, most of the earliest occupation evidence being found in the eastern Pampas (Steele and Politis, 2009; Prates et al., 2013). It would appear that the last representa- tives of the megafauna disappeared from South America approximately 7000 years ago (Politis and Messineo, 2008), and the extinction process therefore seems to have been extended by several thousand years. The ar- gument for a primary human role in the extinction of megafauna has been based upon the presumption that the arrival of humans to the Pampas was synchronous with their disappearance, but if climate was the cause of extinction, the megafauna should have disappeared during the biggest climate changes, not necessarily coinciding with the first human arrivals. But for other authors (Braje and Erlandson, 2013), the defined date is less important than understanding that the last current extinction was an event that developed over many millennia and one of the most interest- ing aspects involves understanding how humans have modified the earth's ecosystems over time. The late Pleistocene in the pampas is first characterized by rapid cooling around 14,000 yrs BP. This cold phase may have begun even ear- lier than the classical Younger Dryas (Krohling and Iriondo, 1999), followed by rapid warming at the start of the Holocene. Analysis of mammal diversity in the Pampas (Prado et al., 2001) shows a maximum peak around 14,000 yrs BP, after which it declines. This analysis also suggests that Last Appearance Events for large and mega-mammals was a process that began before human arrival and which continued during the coexistence period with humans. Barnosky and Lindsey (2010) recently proposed a hypothesis involving synergy between the two causes and suggests that this hypothesis implied that extinction began after humans first arrived, but accelerated dramatically with the Palaeogeography, Palaeoclimatology, Palaeoecology 425 (2015) 41–49 ⁎ Corresponding author. Tel.: +54 2284 450331x209. E-mail address: jprado@soc.unicen.edu.ar (J.L. Prado). http://dx.doi.org/10.1016/j.palaeo.2015.02.026 0031-0182/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo