DOI: 10.1127/0077-7749/2007/0245-0309 0077-7749/07/0245-0309 $ 1.25 ©2007 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart N. Jb. Geol. Paläont. Abh. 2007, vol. 245/3, p. 309–313, Stuttgart, September 2007, published online 2007 A new species of Gashternia (Marsupialia) from Itaboraí (Brazil) Francisco J. Goin, La Plata and Edison V. Oliveira, Uruguaiana With 1 figure GOIN, F. J. & OLIVEIRA, E. V. (2007): A new species of Gashternia (Marsupialia) from Itaboraí (Brazil). – N. Jb. Geol. Paläont. Abh., 245: 309 – 313; Stuttgart. Abstract: We describe Gashternia carioca sp. nov. (Marsupialia, Polydolopimorphia, Bonapartherii- formes, Bonapartherioidea, Gashterniidae), from Late Paleocene levels (Itaboraian Age) of São José de Itaboraí, Rio de Janeiro, Brazil. It differs from the type species of the genus, G. ctalehor Simpson, in being slightly smaller and in having a proportionally larger P3. The new species constitutes the first record of a gashterniid polydolopimorphian in Brazil. In comparable parts, it differs slightly from still undescribed specimens from the Las Flores Formation, in central Patagonia; this adds new evidence on the contemporaneity of the Itaboraí and the Las Flores faunas. Key words: Marsupialia, Polydolopimorphia, Gashterniidae, Gashternia carioca sp. nov., Brazil, Itaboraian Age. 1. Introduction Gashternia ctalehor was first described by SIMPSON (1935) on the basis of a single specimen (AMNH 28533), consisting in a dentary fragment preserving the first two molars. Specimen AMNH 28533 was collected at Cañadón Hondo (Chubut Province, Argentina), in levels traditionally referred to the Late Paleocene (Riochican SALMA). Later SIMPSON (1948), even though bearing doubts about its marsu- pial condition, stated that representatives of Carolo- ameghinia (Caroloameghiniidae) were “…remotely similar, but very different in detail.” (SIMPSON 1948: 69). CLEMENS (1966) and ARCHER (1976) suggested afinnities between Gashternia and didelphoids. MARSHALL (1987) regarded it as the type genus of a new Family Gastherniidae (Superfamily Argyrola- goidea, Order Polydolopimorphia). MARSHALL et al. (1990) excluded gastherniids from their list of living and extinct metatherians. SZALAY (1994) considered the Gastherniidae as the basalmost group for groe- beriids, argyrolagids and patagoniids, and included it within the Infraorder Simpsonitheria (Suborder Sudameridelphia, Order Didelphia). CANDELA et al. (1995) reported on new specimens of Gashternia exhumed from Itaboraian-aged levels of the Las Flores Formation, in Central Patagonia. These speci- mens consisted mostly in isolated upper and lower molars. The new evidence supported the marsupial condition of Gashternia and its polydolopimorphian affinities as well (see also GOIN 2003). Finally GOIN & CANDELA (2004, see also CASE et al. 2005) pro- posed a new classification of the Polydolopimorphia, in which gastherniids were regarded as belonging to the Suborder Bonapartheriiformes, Superfamily Bonapartherioidea. In turn, this superfamily includes