Resumen

CERDENO, Esperanza; GONZALEZ RIGA, Bernardo  y  BORDONARO, Osvaldo. First discovery of mammals from Mariño Formation (Miocen) in Divisadero Largo (Mendoza, Argentina). Ameghiniana [online]. 2006, vol.43, n.1, pp.205-214. ISSN 1851-8044.

This paper deals with the first mammal remains found in the Mariño Formation outcropping in the Divisadero Largo area, Mendoza, Argentina. The Cenozoic levels in this zone are well known by the faunal assemblage of the Divisadero Largo Formation, which allowed the establishment of the Divisaderan Land Mammal Age (Late Eocene-Early Oligocene), but until now no vertebrate fossils had been described from the overlying Mariño Formation (Miocene). This formation also outcrops in the localities of Potrerillos and Cacheuta, Southwest Mendoza city, where some paleobotanical remains and ichnites have been recently found. The specimen studied in this paper is the first accurate datum of fossil mammals from the Mariño Formation, and it could probably constitutes a new taxon for Argentina within the notoungulates Mesotheriidae Mesotheriinae. The specimen consists of a maxillary fragment with right M3 and, separated from the maxillary, the almost complete M2, a labial fragment of M1, the P4 and a P3 fragment. These teeth belong to an adult individual and are characterized by their small size, clearly lesser than that of known Miocene genera Eutypotherium , Typotheriopsis , and Pseudotypotherium . This material presents size similarities with the genus Microtypotherium from Bolivia and the very recently described species from the Chucal Formation (Chile).

Palabras clave : Mesotheriidae; Notoungulata; Mariño Formation; Miocene; Mendoza; Argentina.