This paper deals with the detailed taxonomic study of the first mammal remains from the Marinio Formation in the Divisadero Largo area, Mendoza, central west Argentina. This area was well-known by the fossils recovered from the Triassic levels and particularly by the faunal assemblage from the Cenozoic levels corresponding to the Divisadero Largo Formation. Until recently, no mammal remains had been accurately reported for the Marinio Formation, Miocene in age. The specimen consists in an almost complete upper jugal series (teeth found separated from the maxillary bone except the M3) of a small Mesotheriidae (Notoungulata), which was preliminary identified as Mesotheriinae indet. The main characteristic of these teeth is their small size, significatively lesser than that of the Miocene genera Eu ypotherium, Typotheriopsis and Pseudotypotherium, being closer to Alycrotypotherium from Bolivia and the Chilean species from the Chucal Formation. The direct comparison with these latter forms has allowed a more detailed Study and the recognition of the material here described as cf. Altiopotherium chucalensis, with all cautions inherent to the incompleteness of the material. (c) 2007 Elsevier Masson SAS. All rights reserved.
