Rediscovering a forgotten rodent of Patagonia and its phylogenetic implications

Cephalomyidae is an enigmatic caviomorph ‘family’ recorded in the Deseadan–Colhuehuapian SALMAs (South American Land Mammal Age) of Bolivia and Argentina. The validity and phylogenetic relationships of this group remain unconfirmed. Litodontomys chubutensis is one of the most poorly known cephalomyids, recorded only by a partial mandible with the complete dental series. Here we present a new specimen of Litodontomys from the same Deseadan locality as the holotype (Cabeza Blanca, Chubut, Argentina). It is a more complete and better preserved specimen from a larger and older individual. A phylogenetic analysis, performed to test the position of the genus and the validity and relationships of the family Cephalomyidae, recovered Litodontomys as the sister taxon of Cephalomys and confirmed the monophyly of the clade for the first time in an updated matrix and broader phylogenetic context.