A NEW GENUS OF ORYZOMYINE RODENT (CRICETIDAE: SIGMODONTINAE) FROM THE PLEISTOCENE OF ARGENTINA

摘要

Based on a right maxinary with 1st molar recovered in Pleistocene (Ensenadan) deposits from south-central Buenos Aires Province, Argentina, a new genus and species of Oryzomyini (Rodentia, Cricetidae) is named and described. The new taxon is one of the largest known extinct or extant sigmodontines, morphologically related to the marsh rats Holochilus, dagger Noronhomys, and Pseudoryzomys. It can be differentiated from these taxa by the combination of several traits in the 1st upper molar, in particular a well-developed mesoloph and the free connection of both para- and protoflexus. The occurrence of this sigmodontine suggests wanner and probably rnoister conditions dUrino deposition titnes, a hypothesis reinforced by other vertebrates exhUrned together (e.g., turtles, coypus, and the giant armadino dagger Propraopus).