FAUNAL RECORD AND PALEOENVIRONMENTS OF THE LATE QUATERNARY, LA PAMPA PROVINCE, ARGENTINA. Fossil mammals from the Eastern sector of the Pampean Region (Argentina) provided the basis for the chronological and biostratigraphical continental scheme of the South American late Cenozoic. A new faunal assemblage from the Western area of the region (Santa Rosa, La Pampa Province) is presented along with the analysis of its sedimentary and stratigraphic context, and a paleoenvironmental reconstruction. The mammalian faunal assemblage is the largest and more diverse reported from a single locality in La Pampa province and is composed by Glyptodon clavipes Owen, Doedicurus sp. (Xenarthra, Cingulata), Megatherium americanum Cuvier, Glossotherium robustum (Owen), Scelidotherium sp. (Xenarthra, Folivora), Toxodon sp., (Notoungulata, Toxodontidae), Lama sp. (Artiodactyla, Camelidae), Equus (Amerhippus) sp. and Hippidion sp. (Perissodactyla, Equidae). The fossil bearing levels represent a fluvial-like channel environment that drained the rain water excess towards a nearby topographic depression (Laguna Don Tomás). According to the relative stratigraphic position in the sequence and the correlation with other localities of the region, the fossil bearing levels would have accumulated during the Late Pleistocene. Among taxa recovered at Sitio 1, Glyptodon clavipes, Megatherium americanum and Glossotherium robustum are characteristic species of the Bonaerian and Lujanian Stages-Ages, while Equus (Amerhippus) is an exclusive taxon of the Lujanian. Consequently, this new faunal assemblage is assignable to the Lujanian Stage-Age (Late Pleistocene-Early Holocene). Its presence in the analyzed deposits confirms the chronology proposed from the bearing levels.