CONICET | Buscador de Institutos y Recursos Humanos

In this paper new remains of the extinct, mid-sized testudinid Chelonoidis gringorum from northwestern Chubut (Argentina) are described in detail. The specimens were collected in outcrops of the Collón Curá Formation (middle Miocene) and they are represented by postcranial remains mainly carapace and plastron. The taxonomic assignation of these specimens was based on anatomical comparisons with other extant and extinct, mid-sized testudinids from South America. The high intraspecific variation, the lack of a detailed diagnosis of C. gringorum, and the lack of detailed descriptions of extinct mid-sized testudinids from South America in general, made problematic the study of this group. The geographic distribution of the mid-sized testudinids in Argentina during the Miocene shows that there was a displacement towards lower latitudes, which is coincident with the climatic deterioration at the end of the Miocene and that, in turns, had a big impact in Patagonia. Last, but not least, the assignation of these specimens to C. gringorum expands the stratigraphic distribution of this species to the middle Miocene, because before was only known in the early Miocene.