As you read the abstract,
bear in mind the only thing wrong here is the author’s insistence that Ennatosaurus is a pelycosaur and a synapsid. It is neither, as the addition of taxa to a cladistic analysis would have informed the Romano team. Ennatosaurus was derived from the similarly built milllerettids. This was demonstrated several years ago in the large reptile tree by the simple addition of taxa to the inclusion set.
From the abstract:
The Russian caseid Ennatosaurus tecton (Synapsida Caseasauria) is an important member of the group, being among the few “pelycosaurs” occurring in the Middle Permian, thus making caseids among the longest-surviving groups of non-therapsid synapsids. Although the cranial skeleton has been recently restudied in detail, the descriptions currently available for the postcranium are essentially limited to the original short account on the holotype provided by the original description from the 1950s. This contribution represents a new analysis of the postcranium of this taxon, using several different approaches. The postcranium of Ennatosaurus is informative with respect to both the taxonomy and phylogeny, with autapomorphic characters present particularly in the vertebral column. In addition, we conducted eight principal component analyses to investigate the position of the various appendicular elements of Ennatosaurus within the caseid morphospace. Members of all major groups of “pelycosaurs” were included in the morphometric analysis (along with selected outgroup taxa), allowing us to make some broader preliminary inferences regarding postcranial morphospace occupation of these basal synapsids for each individually-considered element. From the results of the principal component analyses, a major decoupling among the morphological patterns of stylopodial and zeugopodial elements is detected. Whereas femora and humeri exhibit a shared common pattern (with a wider overlap in their respective morphospace), the ulnae, radii, tibiae and fibulae show well-separated regions of morphospaces in the different clades. This result indicates the importance of such long bones also for taxonomic differentiation (in addition to their use for classical functional and biomechanical studies). Finally, a 3D photogrammetric model of the mounted specimen at the Paleontological Institute of Moscow has been used to obtain the first in vivo reconstruction of Ennatosaurus tecton, providing for the first time a potentially realistic picture of the Russian caseid in life.
For all this great work
resistance to taxon inclusion doomed any conclusions drawn. Sadly this basic problem is similar to workers who resist adding fenestrasaurs to pterosaurs studies, thalattosaurs to Vancleavea studies, tenrecs and desmostylians to whale studies, etc. etc…
Romano M, Brocklehurst N and Fröbisch J 2017. Redescription of the postcranial skeleton of Ennatosaurus tecton (Synapsida, Caseasauria, Caseidae) and its first in vivo restoration. Abstrcts from the 2917 meeting of the Society of Vertebrate Paleontology in Calgary.