There are five specimens from the same pit
that were assigned to the varanid taxon Ascendonanus. Spindler et al. 2018 thought they were all conspecific.
Given their distinct proportions
(Fig. 1) and the phylogenetic differences recovered in 2 of the 5 so far (earlier one nested as a basal iguanid), we’re going to need some new generic names for at least one of the referred specimens. The others have not yet been tested in the large reptile tree (LRT, 1179 taxa).
remains Ascendonanus, but here it’s no longer a varanopid synapsid. Here it nests as a derived prodiapsid and the basalmost tested diapsid (Fig. 2), a little younger than the oldest diapsid, Petrolacosaurus.
Some of these specimens
(Fig. 1) have an occiput/acetabulum length distinct from the others, ranging from 3x to 5x the skull length, the first clue to their distinct morphologies.
Spindler et al. 2018
did not include several taxa typically included in pelycosaur studies and should not have included any caseasaurs, despite their traditional inclusion. Spindler et al. did not include any diapsids nor did they understand the role of the former varanopids now nesting as ancestors to the Diapsida (sans Lepidosauriformes).
The holotype 0924 specimen has more of a varanopid skull
than the 1045 specimen we looked at earlier. Prodiapsid sisters include varanopids ancestral to synapsids. Prodiapsids, as their name suggests, are late-surviving ancestors to diapsids like the coeval Araeoscelis (Early Permian) and the earlier Spinoaequalis (Late Carboniferous).
Not sure yet
where the other three specimens assigned to Ascendonanus nest. Enough muck stirred for the moment.
Rößler R, Zierold T, Feng Z, Kretzschmar R, Merbitz M, Annacker V and Schneider JW 2012. A snapshot of an early Permian ecosystem preserved by explosive volcanism:
New results from the Chemnitz Petrified Forest, Germany. PALAIOS, 2012, v. 27, p. 814–834.
Spindler F, Werneburg R, Schneider JW, Luthardt L, Annacker V and Räler R 2018. First arboreal ‘pelycosaurs’ (Synapsida: Varanopidae) from the early Permian Chemnitz Fossil Lagerstätte, SE Germany, with a review of varanopid phylogeny. DOI: https://doi.org/10.1007/s12542-018-0405-9