Biostratigraphic and palaeoclimatic meaning of the Middle Pleistocene South American rodent Ctenomys kraglievichi (Caviomorpha, Octodontidae)

The systematics and the geographic and stratigraphic distribution of a large and peculiar Pleistocene Ctenomys (Rodentia, Octodontidae) of Argentina are revisited. Based on the geological range of this species, and paleomagnetic and biochronological data of the bearing units, the stratigraphy and chronology of the Bonaerian Stage (Middle Pleistocene) is refined and a new biozone is proposed for the Argentine pampean region. Morphological features of this species and its association with other caviomorph taxa of Brazilian origin suggest that this rodent fauna represents an immigration event triggered by an important warm climatic pulse. We suggest that this warm pulse, the most important so far recorded for southern South America, may be correlated to the Middle Pleistocene OIS 11 recorded worldwide.