Remarks on the paleoecology of Medistylus dorsatus (Ameghino, 1903) and other pachyrukhinae (Notoungulata, Hegetotheriidae) from the Deseadan (Late oligocene) of the Chubut Province, Argentina

DOZO, M. T.; REGUERO, M. A.; CERDEÑO, E.

Plaza Huincul

Congreso; XXI Jornadas Argentinas de Paleontología de Vertebrados; 2005

The pachyrukhinae are small terrestrial herbivorous hegetotheriidae easily recognized by their specialized rabbit-like anterior dentition. They are well known from the Deseadan SALMA, with Prosotherium, Propachyrucos, and Medistylus. Hypsodonty, width of the muzzle and premaxillary shape (PSI) are characters recognized as a good evidence of paleoenvironmental adaptations. Pachyrukhinae are the most hypsodont Deseadan notoungulates. The PSI value of M. dorsatus is more similar to that of grazer feeders. Medistylus and Prosotherium would be the most grazer hervibores during Deseadan times. The occurrence of these three euhipsodont pachyrukhines provides a previously unsuspected early diversity of the subfamily in Patagonia, and suggest a great paleoenvironmental difference between this area and Bolivia and Uruguay during Deseadan SALMA.