The first Eocardiidae (Rodentia) in the Colhuehuapian (early Miocene) of Bryn Gwyn (Northern Chubut, Argentina) and the early evolution of the peculiar cavioid rodents

PÉREZ, MARÍA ENCARNACIÓN; VUCETICH, MARÍA GUIOMAR; KRAMARZ, ALEJANDRO

JOURNAL OF VERTEBRATE PALEONTOLOGY

Society of Vertebrate Paleontology

Año: 2010 vol. 30 p. 528 - 534

0272-4634

ABSTRACT—Caviidae and Hydrochoeridae (extant Cavioidea s.s.), probably the mostpeculiar among rodents, are characterized by their evergrowing heart-shapedcheekteeth. They have classically been rooted in eocardiids, which ranges fromDeseadan to “Colloncuran” (late Oligocene- middle Miocene) in Patagonia, although inthe Deseadan and Colhuehuapian (early Miocene) remains are very scanty. For theColhuehuapian, only one species coming from the southern cliff of the Colhué HuapiLake (Gran Barranca, Chubut, Argentina) was so far known. In this paper, the firstColhuehuapian eocardiids from outside Gran Barranca, are reported: Luantus minor sp.nov. and Chubutomys? leucoresbios sp. nov. They are represented by two fragmentarymandibles and a few isolated cheek teeth, from the Trelew Member of the SarmientoFormation at Bryn Gwyn, lower valley of the Chubut River, Chubut. The new speciesenlarge the knowledge of eocardiid diversity, and reinforce the hypothesis of a basaldichotomy for the group. L. minor represents one of the smallest species of the seriesAsteromys + Luantus + Phanomys + Eocardia, which would have gave rise to modernCavioidea s.s. C? leucoresbios pertains to a group of species with precocioushypsodonty and apparently low diversity, but without modern descendant.