Sistemática y antigüedad de Paramyocastor diligens (Ameghino, 1888) (Rodentia, Caviomorpha, Myocastoridae)

Diego H. Verzi, Cecilia M. Deschamps, María Guiomar Vucetich

Abstract


Materials (including the holotypes) of the nominal species of the myocastorids Myopotamus (= Myocastor) diligens Ameghino, Paramyocastor intactus Ameghino, lsomvopotamus affinis Rovereto and Isomyopotamus albaniri Reig, are analyzed. We propose that differences in molar morphology among these species represent individual and, especially, ontogenetic variability. Consequently, these taxa are considered synonymous, being Paramyocastor diligens (Ameghino) the correct combination. A new specimen found in the lower levels of the Monte Hermoso F¿rmation confirms the record of P. diligens in sediments of Montehermosan Age. Therefore, the biochron of this myocastorid is Montehermosan-Upper Chapadmalalan (Late Miocene- Late Pliocene).

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