Fossil murids: Taxonomy, Paleoecology, and Paleoenvironments

PARDIÑAS, U.F.J.

Quaternary of South America & Antarctic Peninsula

Año: 1999 vol. 12 p. 225 - 254

ABSTRACT: The Pleistocene-Holocene record of Sigmodontine rodents from the Southern cone of South America (Argentina, Chile, Uruguay and southern Brazil) is discussed, especially regarding the development of the communities inhabiting the Pampean region (Argentina) and their relation to climatic fluctuations. Sanandresian faunas (Late Pliocene-Early Pleistocene) are scarcely known, but they have a unique assemblage of microherbivore phyllotines probably related with colder and dryer than present climatic conditions. A major part of the species still living in the area are first recorded during the Ensenadan Stage (Early-Middle Pleistocene). "No-analogue assemblages" are recorded, with sympatry of subtropical (Nectomys squamipes, Akodon cf. A. cursor, Lundomys molitor, Clyomys sp.) and Patagonian-Central micromammals (Akodon cf. A. iniscatus, Eligmodontia sp., Lestodelphys sp.), showing environmental conditions with no modern analogues. In the Lujanian Stage (Late Pleistocene), in contrast to the megafauna, the records of sigmodontines are isolated. These rodents show a significant decrease in their specific diversity, revealing non-glacial environments related to the Last Glacial Maximum. During the last 10 ka significant corologic fluctuations occurred of subtropical (Pseudoryzomys simplex, Bibimys cf. B. torresi) and Patagonian-Central taxa (Eligmodontia typus, Phyllotis cf. P. xanthopygus). Towards the latest Holocene, warmer conditions can be inferred from the maximal specific diversity observed in the "no-analogue assemblages” of southeastern Buenos Aires Province. The quantitative and qualitative taxonomic structure of modern communities may have been established a few hundreds years ago as a result of the interaction between the present temperate climatic conditions and human impact (development of farming ecosystems, foraging, etc.). The murid fossil record outside the Argentine pampas is virtually nonexistent, being restricted to the Late Pleistocene-Holocene. The construction of a large data base firmly established on taxonomy and taphonomy is strongly recommended.