of the Viala Formation yielded a radiometric age of 290.96 ± 0.19 Ma corresponding to the late Sakmarian. It has also been determined that the M1 and M2 megasequences of the Rodez basin are equivalent to the Rabéjac Formation of the Lodève basin (and also of the Combret Member of the Saint-Pierre Formation of the Saint-Affrique basin in southern Aveyron). Above the Rabéjac Formation, the lower two-thirds of the Octon Member of the Salagou Formation yielded four tuff horizons radiometrically dated. The oldest tuff horizon provided an age of 284.40 ± 0.07 Ma corresponding to the latest Artinskian. Based on this dating, the Rabéjac Formation and the correlative M1 and M2 megasequences of the Grès Rouge Group can be dated to the late Artinskian. A conclusion consistent with the magnetostratigraphy which suggests that the entire Grès Rouge Group (members M1 to M5) would have an age between the late Artinskian and the early Wordian. Classification The first phylogenetic analysis of the caseids containing Ruthenosaurus was made by Romano & Nicosia in 2015. In their most parsimonious analysis including nearly all caseids (to the exclusion of the very fragmentary Alierasaurus ronchi from Sardinia), Ruthenosaurus is found very close to Cotylorhynchus and most specifically to the giant Cotylorhynchus hancocki. However, Romano & Nicosia have concluded that given the large body size of the two taxa and considering the absence of cranial material for Ruthenosaurus, it is possible that their close similarity is size related. Below the most parsimonious phylogenetic analysis published by Romano & Nicosia in 2015. A phylogenetic analysis published in 2022 by Werneburg and colleagues suggests a possible close relationship between Ruthenosaurus and Caseopsis. Ruthenosaurus is also recovered as the sister taxon to a clade containing the genera Alierasaurus, Cotylorhynchus and Lalieudorhynchus. Below is the cladogram published by Werneburg and colleagues in 2022. References Caseasaurs Prehistoric synapsid genera Fossils of France Fossil taxa described in 2011 Permian synapsids of Europe Taxa named by Robert R. Reisz