CONCEPTUAL CHALLENGES FOR THE PALEOECOLOGICAL RECONSTRUCTION OF THE PLEISTOCENE PAMPEAN MEGAFAUNA AND THE CONSEQUENCES OF ITS EXTINCTION

The Pleistocene Pampean Megafauna (PPM) may be considered as the assemblage consisting mainly of large mammals (i.e., bodymass ≥ 45 kg) that inhabited what is currently considered the Pampean Region during the Pleistocene and became extinct near the Pleistocene–Holocene transition. This contribution addresses several conceptual issues that may guide future efforts in its reconstruction and to consider potential consequences of its extinction. First, we approach the concept of megafauna by urging its explicit definition and contextualization in every investigation as a means of avoiding conceptual ambiguity. Second, we call attention to the risks of succumbing too readily to the temptation of employing a simplistic approach that assumes that extinct taxa had virtually the same biological requirements as those of their extant counterparts. We claim that within the PPM the abundance of taxa distantly related to or markedly distinct morphologically from their living counterparts poses significant challenges for understanding their paleobiology. Paleobiological interpretations need not be rigidly phylogenetically restricted, and phylogenetically based interpretations require critical assessment before their application. Third, we consider the paleoecology of the PPM from a metabolic perspective: as it was clearly dominated by allegedly hypometabolic megaherbivores (xenarthrans), there is no clear counterpart among living faunas. Fourth, we call attention to the fact that the loss of the PPM may have left in its wake an enduring but little-recognized legacy on the functioning of the contemporary ecosystem of the Pampean Region. Extinction of the PPM opened an enormous ecological chasm in the herbivore guild during the Holocene that persisted for about 6000 years, until it was filled, at least in part, by herds of cattle introduced since the sixteenth century.