Fossil history of the marsh rats of the genus Holochilus and Lundomys (Cricetidae, Sigmodontinae) in southern South America

The sister genera Holochilus and Lundomys, plus the extinct forms Carletonomys and Noronhomys and the living Pseudoryzomys, constitute a small clade of amphibious sigmodontine rodents that inhabits in tropical and subtropical environments of the Neotropics. Based on almost all the available fossil evidence recovered in Argentina, Bolivia, southeastern Brazil, and Uruguay we revised the paleontological record of Holochilus and Lundomys in southern South America. Past distributions and chronologies indicate the following occurrences [biochrons] for the study area: Holochilus brasiliensis (Middle Pleistocene-Recent in Argentina, Late Pleistocene-Recent in Brazil), H. chacarius (Late Holocene-Recent in Argentina, Early Holocene-Recent in Bolivia), dagger H. primigenius (Middle Pleistocene in Bolivia), and Lun-domys molitor (Middle Pleistocene- Late Pleistocene in Argentina, Late Pleistocene- Recent in Uruguay). Taking into account the present distributions and environmental requirements of these rodents we hypothesize several expansion/retraction episodes of their populations triggered by the occurrence of moist/dry climatic pulses during Pleistocene-Holocene times.