The oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora): Late Miocene faunal turnover in central Argentina and the Great American Biotic Interchange

VERZI, D.H.; MONTALVO, C.I.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2008 vol. 267 p. 284 - 291

0031-0182

The discovery of a rich fauna from the late Miocene Cerro Azul Formation in Caleufú, central Argentina, is reported. This fauna includes vertebrate Holarctic immigrants, among which are the oldest South American records of mammals of the families Cricetidae (Rodentia) and Mustelidae (Carnivora). Stratigraphic, biochronological and taphonomic evidence indicates that the faunal assemblage from Caleufú is confidently synchronous and represents the late Huayquerian (Zone of Xenodontomys elongatus; late Miocene). Thus, this fauna supports hypotheses of the arrival of cricetids and mustelids prior to the Pliocene completion of the Panamanian isthmus. However, the new records do not permit inferences to be made about precise moments of entry of these groups into South America. Representation of the GABI in the fossil record is here interpreted as a major event integrated by a nested pattern of events, including geographically more restricted turnovers (implying particular taphonomic and geographic biases) and associated environmental changes. In such a hierarchical context, the record of Caleufú represents a local turnover different from those occurring with arrivals of these taxa, or their ancestors, into the continent. In accordance with biochronological data, the turnover recorded in Caleufú could be coeval with the global-scale glacial event detected for the late Miocene (ca. 5.7-5.8 Ma). In southern South America, this arid and cold pulse would have triggered the distribution drift to central Argentina of fauna previously restricted to western peri-Andean areas. Local turnovers such as the one reported here, and associated physical changes, have to be analyzed in detail as individual events in order to interpret the chronology, dynamics and paleoenvironmental context of hierarchically greater episodes such as the GABI.