Rubidge and Hopson (1990, 1996) got it right.
Patranomodon (Figs. 1–3) is basal to the dicynodonts AND the venjukovamorphs the Therapsid Skull Tree (TST, 68 taxa; Fig. 4).
Rubidge and Hopson (1996) reported, “Patranaomodon is primitive with respect to other anornodonts in having short palatal exposure of the premaxilla, an unreduced tabular, a slit-like interpterygoidal vacuity, a screw-shaped jaw articulation (which precludes fore-aft sliding of the lower jaw), and only three sacral vertebrae. The poorly-known Galechirus and Galepus from the younger Cistecephalus Assemblage Zone appear to be at a comparably primitive evolutionary grade, and the three genera are tentatively united in the family Galechiridae. The taxon Dromasauria is shown to be paraphyletic and therefore should be discarded.”
In the TST
both venjukoviamorphs and dicynodonts are large, terrestrial dromasaurs. Here (Fig. 2) are a set of skulls to scale demonstrating the ancestry of the vejukoviamorphs.
This second set of skulls
(Fig. 3) shows the ancestry of the dicynodonts to scale, according to the TST.
A recent look at dicynodonts
(Kammerer 2019) suggested that Biseridens was basal to the clade Dicynodontia, but that cladogram did not test the taxa shown here (Fig. 4).
We’ll dive deeper
into Kammerer 2019 in the next few days. Currently I am updating all the data for the TST using photos (Fig. 1) to supplement earlier drawings to fine tune the scoring. Yes, it’s okay to correct earlier errors based on less accurate drawings.
Rubidge BS and Hopson JA 1990. A new anomodont therapsid from South Africa and its bearing on the ancestry of Dicynodontia. South African Journal of Science, 86(1), 43-45.
Rubidge BS and Hopson JA 1996. A primitive anomodont therapsid from the base of the Beaufort Group (Upper Permian) of South Africa. Zoological Journal of the Linnean Society, 117: 115–139. Doi:10.1111/j.1096-3642.1996.tb02152.x