CONICET | Buscador de Institutos y Recursos Humanos

Pleistocene outcrops exposed in Pampean region ofArgentina represent one of the most informative sources about the Quaternary periodin South America. Here, we report preliminary results obtained from a newfossil site with exceptional preservation located in cliffs of the Salado river(Buenos Aires province). Part of this site was recovered in a paleontologicalrescue that comprised a large-scale excavation of 1200 m2. Fossil-bearing strata consist of sandy-clayed levelswith abundant organic matter, gypsum and carbonatic concretions that weredeposited in a small pond environment filled partially by aeolian sediments. Accordingto 14 C dating ofbone collagen, these strata can be constrained between 13,400 ± 200 - 12,380 ± 190 14 C years BP.We recovered several plant macrofossils including three different types ofseeds, herbivore dung, freshwater mollusks, arthropods (cladoceran ephippia,ostracods, insects) and vertebrates. Insects constitute the most numerousspecimens recovered with more than 400 specimens including coleopterans,orthopterans, hymenopterans and dipterans. Also, we excavated carcasses and disarticulatedskeletal remains that belong to five species of extinct mammals. Remarkably,nearly all recovered bones of herbivore taxa exhibit conspicuous bonemodifications (furrows, pits, punctures, striations and crenulated margins)attributed to medium-largecarnivore activity. Of the recovered mammal bones, we have successfullyextracted and sequenced largely complete mitochondrial genomes for both extinctmammals Glyptodon and Hippidion (?70%/12kb and ?90%/14.7kb, respectively). Theseunexpected results for an open fossil site located in mid-latitudes enhance thevalue of this site as a resource for obtaining molecular data from extinctmegafauna in a subtropical region. Preliminary results including informationgiven by all recovered organisms indicate a climatic amelioration during thedeposition of the paleopond sediments. This inference coincides with previous studies,which stressed the environmental improvement occurred slightly previous to thePleistocene-Holocene transition in Pampean region.

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