LAUSR

Abstract We present two new Paleogene fossiliferous sites that provide the first mammal remains for the Malargue Group in the Neuquen basin of southeastern Mendoza Province, Argentina. Identified taxa from Agua de Flores-Agua de Isaac: Kibenikhoria sp., Oldfieldthomasiidae indet., ?Henricosborniidae indet., and a large Notoungulata probably related to the Isotemnidae. Taxa from Liu Malal: cf. Kibenikhoria and Notopithecidae gen. et sp. nov. Based on facies composition and geological distribution, we consider that the Cenozoic deposits from these fossiliferous localities correspond to the already defined Puesto Fortunata Formation. This unit is correlated to the Coihueco Formation, the top of the Malargue Group in the northern Neuquen basin, and its mammal content supports the proposed hiatus between the ~40 Ma and 20 Ma based on chronostratigraphy. The presence of Kibenikhoria in the local faunas of southeastern Mendoza extends the geographic range of this genus so far known in Patagonia to central-west areas of Argentina and supports an early-middle Eocene age for the fossil-bearing levels of the Puesto Fortunata Formation.