Cranial anatomy ofEnnatosaurus tecton(Synapsida: Caseidae) from the Middle Permian of Russia and the evolutionary relationships of Caseidae

New material of Alierasaurus ronchii (Synapsida, Caseidae) from the Permian of Sardinia (Italy), and its phylogenetic affinities

“…Romano and Nicosia (2015) conducted a phylogenetic analysis of Caseidae including for the first time the fragmentary taxa 'Casea' nicholsi and Caseoides sanangeloensis. The general topology was largely consistent with the results of Maddin et al (2008) and Benson (2012), with issues still to be discussed and resolved such as the position of 'Casea' halselli and Trichasaurus (the latter considered a caseid in Benson, 2012) falling outside caseids, and 'Casea' nicholsi making once again the genus Casea paraphyletic, forming a sister group with Caseopsis agilis. Taking into account the position assumed by 'Casea' halselli in the topology and the very fragmentary nature of the holotype (FMNH UR 117), Romano and Nicosia (2015) regarded this species as nomen dubium.…”

“…Caseids, together with the varanopids, represent one of two primitive clades that co-exist with the more derived therapsid synapsids (Dilkes and Reisz, 1996;Reisz and Laurin, 2001;Maddin et al, 2008;Reisz and Fröbisch, 2014). The youngest known occurrence of caseids may be represented by a still undescribed large caseid from the La Lieude Formation of the Lodève Basin, a rock unit tentatively assigned to an early Lopingian age by some authors (Schneider et al, 2006;Lopez et al, 2008) while other authors ascribe this formation to the Wordian (Gand and Durand, 2006;Michel et al, 2015).…”

“…According to Reisz, the occurrence of this small caseid in upland environment indicates that the initial evolutionary history of this group of synapsids could have occurred far from the typical floodplain depositional environments inhabited by more derived species. Maddin et al (2008) re-described in detail the cranial material of Ennatosaurus tecton from the Middle Permian of Russia, performing the first 'modern' cladistic analysis of Caseidae. The analysis confirmed the basal position of Oromycter within caseids, and suggested the paraphyly of the genus Casea, with 'Casea' rutena being the sister taxon of the clade made by E. tecton, Cotylorhynchus romeri, and Angelosaurus dolani.…”

“…Although being an immature individual, R. russellorum is characterized by several autapomorphies in the post-cranium which justify the validity of a new taxon. Furthermore, based on the topology provided by Maddin et al (2008), Reisz et al (2011) moved 'Casea' rutena to the new genus Euromycter, with the new combination E. rutenus. Ronchi et al (2011) and Romano and Nicosia (2014) described the first skeletal material referable to non-therapsid synapsid from Italy, the caseid Alierasaurus ronchii from the Permian Cala del Vino Formation (Alghero, Nurra, northwest Sardinia).…”

“…Although cranial characters support the traditional conception of Caseasauria as the most basal clade within nontherapsid synapsids, the postcranial ones and the full dataset lead the clade of Ophiacodontidae +Varanopidae to occupy this basal position. With respect to the work by Maddin et al (2008), Benson (2012) included for the first time in the cladistic analysis the taxa Angelosaurus romeri, Caseopsis agilis, Cotylorhynchus bransoni, Cotylorhynchus hancocki, and Trichasaurus texensis (the latter alternatively attributed to caseids, edaphosaurids, or to "Pelycosauria" incertae sedis; see Romano and Nicosia [2015] and references therein for a detailed overview).…”