CONICET | Buscador de Institutos y Recursos Humanos

The age of the Río Mendoza Formation of Potrerillos, Cuyo Basin, was assigned previously to the Lower Triassic because of its tetrapods contents. Many authors considered this as controversial and currently a Middle Triassic age is though for this unit due to it rests unconformably upon Choiyoi Group. The tetrapod remains formerly recovered come from thick tuffaceous beds (pink, grey, green), and violete and reddish mudstones herein attributed at the middle upper section of the Cerro de Las Cabras Formation. New material of kannemeyerid dicynodonts and indeterminate cynodonts in the northern side of Cerro Bayo of Potrerillos and detailed stratigraphy indicate that the fossils come from the lower and mid section of the Cerro de Las Cabras Formation instead the Río Mendoza Formation. Therefore, the age of the oldest amniotes recorded from Cuyana Basin could not be earlier than Late mid-Triassic given the microfloristic assemblage yielded by Cerro de Las Cabras Formation.