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Fossils of amphibians and squamates are relatively common in Pliocene–Pleistocene sediments in the southeastern Atlantic coast of Buenos Aires Province (Argentina), particularly in the southern slope of the Tandilia mountain system. These taxa are less known in the northern slope, which in the county of Mar Chiquita are solely represented by one anuran record. Here, new herpetofaunal material is described from Mar Chiquita county in the northern slope of the Tandilia mountain system. These specimens, while few, present an interesting taxonomical and morphological diversity. From the Ensenadan outcrops, amphibians are represented by cf. Rhinella. On the other hand, Stenocercus, an indeterminate tropidurid, Colubroides, and an indeterminate snake account for the Ensenadan squamates. In the Bonaerian outcrops, squamates are represented by the viperid Bothrops and an indeterminate Pleurodont. These latter taxa are also present in the Lujanian with an indeterminate snake. These are the first fossil records of squamates from Mar Chiquita and together with the new and previous amphibian records constitute a herpetological assemblage (Ceratophrys ornata, cf. Rhinella, Stenocercus, and Bothrops) that suggests that the paleoclimatic conditions during the Pleistocene of the Pampean region would have been similar to those of the present day. This inference should be considered with caution, since it contradicts those suggested by the mammalian record, which is richer and presents taxonomic identifications that are more precise. Mammalian fossil records indicate a cold and dry glacial Pleistocene interspersed with short, warmer, and more humid periods.

Middle and Late Pleistocene large and mega-mammal records of the Argentine Pampas, belonging to the Bonaerian and Lujanian Stages/Ages, have not yet been adequately dated by standard numerical radiometric methods. Reference timescales for Argentina and other South American fossil sites are mainly based on the mammalian faunal content (biostratigraphic units or biozones). We have recently dated three Middle and Late Pleistocene faunal sites located in the Buenos Aires Province using Electron Spin Resonance (ESR), U-series, Optically Stimulated Luminescence (OSL) and radiocarbon dating. The geographically distant sites (Salto de Piedra, Campo Spósito and Cascada de Paleolama) have yielded fossil assemblages representative of the Lujanian and Bonaerian Stages/Ages. Salto de Piedra, systematically excavated, records one of the most complete fossil sequences and our results indicate that it deposited between at least 127.4 ka (minimum age; Late Pleistocene, MIS 5) and 4.8–4.3 cal ka BP (Middle Holocene, MIS 1). Campo Spósito lower level (corresponding to 'El Tala' unit) was dated to >188 ka via ESR/U-series dating of teeth. Finally, Cascada de Paleolama Unit D, towards the base of the sequence, produced an age of 143 ± 20 ka (Late Pleistocene, MIS 5/6). The new dating results provide a crucial additional age control for the Bonaerian and Lujanian Stages/Ages, and allowed us to better identify and calibrate the limits of Equus neogeus, Megatherium americanum biozones, as well as to better constrain other index taxa that are used to construct local biostratigraphical frameworks. Our results indicate the need for a revision of the biozone schemes established for the Quaternary of Pampean region. • Three Pampean sites have been dated and fossil assemblages taxonomically revised. • Our dating results yielded a robust framework for Pleistocene Pampean sites. • Our revision confirmed index fossils from different biozones overlapped. • Our results advise strong revision of the biozones of the Pampean Quaternary. [ABSTRACT FROM AUTHOR]