A New Early Miocene Chinchilloid Hystricognath Rodent; an Approach to the Understanding of the Early Chinchillid Dental Ev olution

KRAMARZ, A.; VUCETICH, MARÍA GUIOMAR; ARNAL, M.

JOURNAL OF MAMMALIAN EVOLUTION

SPRINGER

Lugar: Berlin; Año: 2012

1064-7554

Chinchilloidea is an emblematical group of caviomorph rodentscharacterized by euhypsodont, laminated cheek teeth. Recentmolecular analyses proposed that the extant Dinomys (andimplicitly its fossil allies) is also part of this group. Theirrelationships with fossil caviomorphs with less derived dentalfeatures are still obscured by the deficiency of the fossil recorddocumenting its early dental evolution. The new genus and speciesGarridomys curunuquem, from the early Miocene deposits of theCerro Bandera Formation, northern Patagonia, is here described. Itis represented by numerous mandible and maxillary remains withdentition. This species has protohypsodont cheek teeth with threetransverse crests in all ontogenetic stages arranged in a transitoryS-shaped pattern, resembling putative early dinomyids. Garridomyscurunuquem is here interpreted as the sister group of the cladeincluding the living and fossil chinchillids; both chinchillas andviscaccias would have diverged from a Garridomys-like ancestor andacquired hypsodonty independently. Garridomys and otherchinchilloids would have diverged from the lineage leading tochinchillids in pre-Oligocene times, suggesting a very early, stillpoorly documented chinchilloid radiation.