Kammerer 2019 nests a new dicynodont

Figure 1. Partial cladogram of the Anomodontia (including Dromasauria) and Dicynodontia from Kammerer 2019. Blue taxa are proximal outgroups in this cladogram.

In a description of a new dicynodont, Thliptosaurus,
Kammerer 2019 presented a comprehensive cladogram of the dicynodonts, the dromasaurs and several outgroup taxa (Fig. 1), including the dinocephalians, Biseridens (Fig. 2), Archaeosyodon and Titanophoneus.

Figure 2. Biseridens and Phthinosuchus, two related therapsids. According to Kammerer 2019, Biseridens is the proximal outgroup to the Anomodontia, who’s

Unfortunately 
Kammerer 2019 excluded several outgroup and ingroup taxa pertinent to the origin of dicynondonts and anomodonts. In the Therapsid Skull Tree (TST,  67 taxa, Fig. 4), the Anomodontia (dicynodonts, dromasaurus and kin) arise from basalmost therapsids, like Cutleria, Stenocybus (Fig. 3) and Hipposaurus. These appear prior to Biarmosuchus. Elsewhere on the cladogram, Biseridens and Titanophoneus arise from more derived tapinocephalids unrelated to basal Anomodontia, more distant descendants of Biarmosuchus.

Figure 3. The ancestry of dicynodonts includes Patranomodon and Galeops.

Kammerer 2019 was attempting to produce a cladogram
of the clade Anomodontia. I cannot comment on the tree topology of dicynodonts, because the TST includes so few of them. However, Kammerer followed tradition by including Biseridens and Titanophoneus as outgroup taxa, omitting those recovered by the LRT and TST.

So… taxon exclusion
put a small damper on an otherwise comprehensive report. This happens way too often in paleontology.

Figure 4. TST revised with new data on Patranomodon and sister taxa.

Biseridens (Fig. 2) was too distinct
to be the ancestor to the tiny dromasaurs, Suminia and Galepus (Fig. 3) and the rest of the Anomodontia. The taxa shown above (Fig. 3) demonstrate a more gradual accumulation of traits, better modeling deep time events.

Yesterday we looked at the uncontroversial key role
two small dromasaurs, Patranomodon and Galeops (Fig. 3), played in the origin of the Dicynodontia. Kammerer’s tree and the TST are in agreement on that point. Likewise the two trees agree that Eodicynodon is the basalmost dicynodont and that Suminia is closely related to Otsheria + Ulemica, close relatives of Venjukovia.

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References
Kammerer CF 2019. A new dicynodont (Anomodontia: Emydopoidea) from the terminal Permian of KwaZulu-Natal, South Africa. Palaeontologia africana 53: 179–191. ISSN 2410-4418.

Hipposaurus moves to the base of the Anomodontia

New data,
a photograph, of the skull of Hipposaurus (Figs. 1, 2; Haughton 1929; WB123), moved this basal therapsid to the base of the Anomodontia (Fig. 3), one node down (more primitive) in the therapsid skull tree (TST, 67 taxa, Fig. 3) and the same in the large reptile tree (LRT, 1440 taxa).

Figure 1. Hipposaurus skull with colors applied and used to create reconstruction on the right. Note the squamosal is largely missing and splinters of bone fill the orbit. Here those splinters are used to recreate a standard squamosal for this clade.

Wikipedia reports,
Broom 1932 considered Hipposaurus a gorgonopsian in the family ‘Ictidorhinidae’. Ictidorhinus nests between Hipposaurus and the gorgonopsians in the TST (Fig. 3). So, for 1932, and prior to the advent of software-driven cladograms, that was a good assessment.

Figure 2. Published material on Hipposaurus permits one to create a reconstruction like this. Not far removed from its ophiacodont / haptodine / pelycosaur precursors, Hipposaurus had longer, more gracile limbs and a distinct sabertooth canine, like Haptodus or Cutleria on steroids!

Hipposaurus boonstrai (Haughton 1929, skull length 21cm, length 1.2m) Capitanian, Mddle Permian ~260 mya is a basal therapsid. Derived from a sister to  Cutleria, Hipposaurus phylogenetically preceded the Anomodontia and all higher predatory synapsids, including mammals.

Figure 4. TST revised with new data on Patranomodon and sister taxa.

Much larger than its ancestors, 
Hipposaurus kept the small round skull of its ancestors, but had longer, more slender limbs capable of a more erect pose and probably a faster gait.

Earlier we looked at Dimetropus tracks that were originally attributed to a high-walking Dimetrodon, but fits Hipposaurus those tracks much better. The basalmost therapsid, Cutleria (Lewis and Vaughn 1965; Early Permian) is another possibility known from fewer bones.

Figure 4. Hipposaurus to scale with related taxa. Cutleria is the basalmost therapsid. Stenocybus and the IVPP specimen are also basal anomodonts.

The relatively larger size of the WB 123 specimen skull of Hipposaurus
indicates it was a later, larger variety of the as yet unknown last common ancestor of anomodonts and kynodonts (Fig. 4).

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References
Boonstra LD 1952. Die Gorgonospier-geslag Hipposaurus en die familie Ictidorhinidae: Tydskr. Wet. Kuns 12:142-149.
Broom R 1932. The mammal-like reptiles of South Africa and the origin of mammals. Witherby, London, 376 pp.
Haughton SH 1929. On some new therapsid genera: Annals of the South African Museum 28(1):55-78.
Lewis GE and Vaughn PP 1965. Early Permian Vertebrates from the Cutler Formation of the Placerville Area Colorado. United States Geological Survey Professional Papers 503-C:1-50.

wiki/Hipposaurus

Maybe Anomocephalus had canine fangs, too!

Two dicynodont-mimics,
Tiarajudens (UFRGS PV393P, Cisneros et al. 2011) and Anomocephalus (Modesto et al. 1999) were discovered in the last few two decades. Tiarajudens had sharp teeth and a fang/canine/tusk. Anomocephalus had flat teeth and apparently no tusk (Fig. 1).

Working from the published tracing
I put the scattered teeth of Anomocephalus back into the jaws and discovered that maybe there is a tusk/fang in there, too (Fig. 1). If valid, the fang was broken in half during typhonomy, so it became the same length as the other teeth, all of which had narrow roots, unlike the fang.

Figure 1. Anomocephalus in situ and reconstructed. In situ image from Modesto et al. 199. Apparently a fang/canine/tusk was hiding among the broken teeth.

Tiarajudens and Anomocephalus
are considered middle Permian primitive herbivorous anomodonts by the author(s) of Wikipedia, who also suggest they were ancestral to dicynodonts. By contrast, the large reptile tree (Fig. 2)  nests Tiarajudens and Anomocephalus in a clade close to, but separate from dicynodonts (Fig. 2).

Figure 3. Basal therapsid tree. Note the nesting of the Anomodontia and the dicynodonts here, both derived from smaller dromasaurs.

According to the LRT, the ancestors of dicynodont mimics were 
Venjukovia and Otsheria. The ancestors of dicynodonts include Suminia, a late-survivor of an early radiation. Both were derived from smaller dromasaurs (Fig. 3).

Figure 3. Venjukoviamorphs include the dicynodont mimics, Tiarajudens and Anomcephalus, the latter now with mid-length canines. The Anomocephalus drawing is modified from Modesto et al. 1999 and appears to have certain problems.

References
Cisneros, JC, Abdala F, Rubidge BS, Dentzien-Dias D and Bueno AO 2011. Dental Occlusion in a 260-Million-Year-Old Therapsid with Saber Canines from the Permian of Brazi”. Science 331: 1603–1605.
Modesto S, Rubidge B and Welman J 1999. The most basal anomodont therapsid and the primacy of Gondwana in the evolution of the anomodonts. Proceedings of the Royal Society of London B 266: 331–337. PMC 1689688.

Anomodont tree problems

We still need to add more taxa to our matrices.

Figure 1. Cisneros et al. 2015 cladogram nesting Tiarajudens and Anomolocephalus as basal anomodonts. This is odd because both are quite derived.

 

Figure 2. Cladogram of taxa listed by Cisneros et al. but using the Peters 2015 matrix.

Case in point:
Cisneros et al. 2015, is a recent paper on Tiarajudens (Fig. 4) behavior. Their cladogram (Fig. 1) does not match a larger study (Fig. 2) with regard to the way they ordered basal therapsids.

Two problems right at the start:
Everyone knows Dimetrodon is not basal to therapsids. It is far too derived. No basal therapsid has dorsal spines.

There’s a body of work that demonstrates that Tetraceratops is not a basal therapsid. Again, it is too derived, too bizarre, too different — and it does not nest with synapsids!  In the large reptile tree it nests with Tseajaia. Actual basal therapsids include Cutleria and Biarmosuchus, which Cisneros et al. did use. Even so, they missed several taxa listed here (Fig. 3). Every taxon counts and adds value to the tree.

Adding taxa is a chore.
So, is that why paleontologists don’t like to add any more than they have to? It seems they often ask a grad student to do the work, and they’re new at it! They’re not experts until after they’ve done their studies. Workers can always reference the large reptile tree (Fig. 3). It works in whole or in part.

Figure 3. Where Tiarajudens and Anomocephalus nest as a subset of the large reptile tree. Here they nest as derived taxa, not basal taxa. They did not produce descendants.

Anomocephalus and Tiarajudens
are giant, terrestrial dromasaurs, a clade of otherwise small, long-tailed, arboreal anomodonts. Giant dromasaurs converge with dicynodonts in several regards (short toes, tusks, size). Perhaps that leads to confusion generally.

Figure 4. Dromasaurs to scale. Tiarajudens and Anomocephalus are giant terrestrial dromasaurs. The pmx/ms suture IMHO probably includes four teeth, like Suminia.

BTW
Biseridens has nothing to do with basal anomondonts. It’s a derived dinocephalian (Fig. 3) when more taxa are added. Let’s get that straight, too.

References
Cisneros JC, Abdala F, Jashashvili T, de Oliveira Bueno A and Dentzien-Dias P 2015. Tiarajudens eccentricus and Anomocephalus africanus, two bizarre anomodonts (Synapsida, Therapsida) with dental occlusion from the Permian of Gondwana.

The origin and evolution of the Dicynodontia

Figure 1. The origin of the Dicynodontia from basal therapsids. Here Cutleria, Stenocybus, two unnamed taxa, Otsheria, Venjukovia, Eodicynodo and Dicynodon are shown in order along with the major trait that each portrays. Click to enlarge. Most basal synapsids are known from skulls. During the evolution of the dicynodonts, the tail became very short and the toes were shorter as well.

Earlier we looked at the origin of dicynodonts and dromasaurs separate from all other synapsids. Here (Fig. 1) are a selection of skulls that demonstrate the evolutionary origin of the very odd skull of Dicynodon, only one of many dicynodonts.

Wikipedia reports
“Dicynodontia is a taxon of anomodont therapsids or synapsids with beginnings in the mid-Permian, which were dominant in the Late Permian and continued throughout the Triassic, with a few possibly surviving into the Early Cretaceous. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means ‘two dog tooth’. They are also the most successful and diverse of the non-mammalian therapsids, with over 70 genera known, varying from rat- to ox-sized.”

Wikipedia also reports
that dicynodonts nested between dinocephalians and gorgonopsians. That is not supported in the large reptile tree as both are quite derived and don’t take into account basal pre-dicynodont taxa.

You can see a number of therapsid skulls in evolutionary order here.

 

Ever wonder about Galepus?

As opposed to the wildly popular bird-like dromaesaurs, the squirrel-like dromasaurs (lacking the “e” in the middle), like Galepus (Fig. 1, Broom 1910) are rarely studied. Brinkman (1981) made an important contribution. These less popular anomodonts are cousins to the hippo-like dicynodonts (Fig. 2). Both were herbivores of the Late Permian, nesting within the Therapsida and Synapsida.

I’ve seen a century-old reconstruction of the skull of Galepus, but I’ve never seen the whole body reconstructed (Fig. 10. That seems a shame as it is represented by a nicely curled nearly complete skeleton at the American Museum of Natural History (hirez color images kindly provided by their staff). And it’s been known for some time now. Much of the skull and skeleton is represented by impressions of missing bone in coarse sandstone.

Figure 1. Galepus, the dromasaur, anomodont, therapsid, synapsid reconstructed from the complete skeleton #5541 at the AMNH. Wrist and ankle are reconstructed according to patterns seen in Galechirus and Suminia (Fig. 2, wrist and ankle inserts copied above). Note the oversized clavicle here. I’m wondering if I made a misidentification here, or is this taxon just odd that way? The hands are indeed robust with great symmetry, like a mammalian burrower, the mole, also known for its strong forelimbs.

The skull is only a cast of the internal surface of the roofing bones. Well marked, but odd.

Galepus has been nested (ref) with Galechirus close to Galeops at the transition to Eodicynodon (Fig. 3) between dromasaurs + kin and dicynodonts + kin.

Figure 2. Two other dromasaurs, Suminia and Galechirus. Galepus was close in size. Note the small clavicles here. Those go along with smaller forelimbs and a more asymmetric manus.

However,
The large reptile tree found a different relationship, with dromasaurs + dicynodonts splitting from the other therapsids at the base of that clade. Earlier we looked at differences and similarities between Galeops and Eodicynodon (Fig. 3). While they share many traits, phylogenetic analysis finds more parsimonious relationships when more taxa are introduced. Earlier we also looked at the base of the Anomodontia and the new taxa now nesting there.

Figure 3. Click to enlarge. Eodicynodon the basal dicynodont and Galeops the derived dromasaur. Did dicynodonts arise from dromasaurs? Despite several convergent traits, not likely according to the large reptile tree which nests Stenocybus as their last common ancestor and recovers other taxa closer to both.

Earlier we looked at Stenocybus nesting at the base of the Anomodontia. Here’s the new synapsid tree (Fig. 4).

Figure 4. Therapsid family tree. Note anomodonts are separate from the other therapsids. And dromasaurs are distinct from dicynodonts. Stenocybus is their common ancestor. Here sister taxa are more parsimoniously nested. IOW they look more like each other and share more traits.

References
Brinkman D 1981. The Structure and Relationships of the Dromasaurs (Reptilia: Therapsida). Brevioria, 465: 1-34.
Broom R 1910. A comparison of the Permian reptiles of North America with those of South Africa. Bulletin of the American Museum of Natural History 28: 197-234.

Another look at Anomocephalus

Figure 1. Anomocephalus skull with teeth replaced, no longer loose. It is apparent that the teeth ground against one another and that no tusks or enlarge canines were present. Maybe less tilt to the qj and qu which would push the posterior mandible elements forward. Original tracing from Modesto and Rubidge 2000. Are some teeth upside down? Maybe. 

Earlier I made several mistakes on the skull of Anomocephalus, BP/1/5582, (since repaired). I made those mistakes because I had crappy data (small retracings of the original). And I didn’t wrap my mind around the concept of flat-topped teeth. These were novel structures, not seen in sister taxa.

Figure 2. The original reconstruction by Modesto et al. 1999.

You know,
it didn’t take much to reconstruct this skull from the in situ tracing by Modesto and Rubidge (2000) that I ran across recently. I just had to replace the teeth in their sockets reasonably. Here there are no canines and no sharp teeth whatsoever. The teeth are still strikingly odd, but now (Fig. 1) everything seems to ‘fit’ just fine. Perhaps  a wee bit different from the original reconstruction (Fig. 2) by Modesto et al. 1999, assuming all the scattered teeth come from the same side of the skull, the exposed side.

This, too, is an example of DGS
It is easy to see that the original reconstruction by Modesto et al. 1999 (Fig. 2) is a free hand sketch, streamlined to removed odd bumps and such. Such sketches tend to be conservative, following in patterns established by other taxa, because that’s the way the artists’ mind works. Mine does, too. However, if you just take Photoshop and cut out the teeth (Fig. 1), then put them back into the skull (DGS, digital graphic segregation) and test their occlusion by rotating the entire tooth-filled mandible within the software program, then you’ve got something that minimizes preconceptions — so you can go with what you’ve got — not what you preconceive.

Looks more “real” too, doesn’t it? There are fewer degrees of separation in figure 1 compared to figure 2.

References
Modesto S, Rubidge B and Welman J 1999. The most basal anomodont therapsid and the primacy of Gondwana in the evolution of the anomodonts: Proceedings of the Royal Society of London, series B, 266: 331-337.
Modesto S and Rubidge B 2000. A basal anomodont therapsid from the lower Beaufort Group, Upper Permian of South Africa. Journal of Vertebrate Paleontology 20(3):515-521.

Eodicynodon – at the base of the dicynodonts

One final note on the Eodicynodon / Galeops sisterhood issue.
As reported earlier here and here, everyone else nested the dromasaur Galeops (Fig. 1) as the outgroup to the Dicynodontia with Eodicynodon (Barry 1974) at its base. However, by adding taxa, the large reptile tree nested Microurania at the base of the Dicynodontia + Venjukovioidea. Elsewhere Galeops nested as a derived dromasaur, having arisen from their common ancestor a sister to Stenocybus..

It would be great
to see Eodicynodon and Galeops to scale side-by-side for ready comparison, since they nest together in all traditional trees. Like Clark Kent and Superman, they have never been pictured together. So here they are (Fig. 1) for the first time.

Figure 1. Click to enlarge. Eodicynodon the basal dicynodont and Galeops the derived dromasaur. One was terrestrial and one was arboreal. Did dicynodonts arise from dromasaurs? Not likely according to the large reptile tree which nests Stenocybus as their last common ancestor. Eodicynodon was small for a dicynodont. Later forms grew to great size while retaining this basic morphology. 

Similar, yes,
but those details were by convergence and common ancestry with Stenocybus. And this origin appears to be distinct from all other therapsids (see below). Overall, a suite of traits nests Eodicynodon and Galeops apart. Likely they did not share the same niche. The large reptile tree found them to be “strange bedfellows” nesting together by default because better nesting partners were not included in analyses.

Tree topology changes
Synapsida, according to Wiki, includes Casesauria, which the large reptile tree nests with Millerettids. So that’s an ongoing problem.

Therapsida, according to Wiki, includes Tetraceratops, which the large reptile tree nests with diadectomorphs and limnoscelids. That’s another ongoing problem.

Anomodontia (dromasaurs + dicynodonts), according to Wiki, are derived from Dinocephalia. which also (according to Wiki) give rise to Theriodonts, which leads to mammals. That puts two plant-eating clades in the middle of a string of carnivores. Not good. Red flag.

On the other hand,
the large reptile tree nested anomodonts with Stenocybus, arising from Ophiacodon/Haptodus. The large reptile tree nested the rest of the therapsids with Nikkasaurus and Biarmosuchus arising out of Archaeothyris/Ophiacodon. Then both Dinocephalians and Theriodonts arise from Phthinosuchus and Eotitanosuchus, which really makes more sense, keeping the carnivorous line carnivorous and the herbivore line distinct.

The trouble is
Stenocybus, Microurania and Nikkasaurus are only known from skulls and, to my knowledge, have not been added to therapsid family trees. They need to be.

References
Barry TH 1974. A new dicynodont ancestor from the Upper Ecca. Annals of the South African Museum 64: 117-136.
Rubidge BS, King GM and Hancox PJ 1994. The postcranial skeleton of the earliest dicynodont synapsid, Eodicynodon from the Upper Permian of South Africa. Palaeontology 37(2):397-408.

Galeops – a toothless(?) dromasaur NOT at the base of the Dicynodontia

Earlier we looked at the Ruta et al. (2013) family tree of the Anomodontia and noted their placement of Galeops (Fig. 1, AMNH 5536) as the transitional taxon linking more basal dromasaurs to more derived dicynodonts. Liu et al (2009) had the same results.

Indeed, the short high face and toothless grin of Galeops does remind one of dicynodonts. But was that by convergence?

Figure 1. Galeops, a dromasaur found without teeth, but the jaws have tooth sockets. Apparently not related to dicynodonts, contra Ruta et al. 2013. Above and below, in situ from Brinkman 1981. Middle, reconstructed.

Figure 2. Basal therapsid family tree. Galeops nests with other dromasaurs, not at the base of the dicynodonts.

Dromasaurs and Dicynodonts.
According to the results of the large reptile tree (Fig. 2), the Anomodontia (dicynodonts + dromasaurs) have ancestors going back to a primitive short-faced therapsid, Stenocybus, a taxon ignored by Ruta et al. (2013).

According to the results of the large reptile tree (Fig. 2) Galeops finds its closest sister in Galechirus, another small dromasaur with tiny teeth, a long tail and was a likely tree-dweller. Their purported sisters, according to Ruta et al. (2013), were dicynodonts like Eodicynodon. Arguing against this, dicynodonts were not tree-dwellers, but had short toes, a short tail and a large body. According to the large reptile tree, dromasaurs were closer to the smaller less tubby ancestors of dicynodonts, not the derived forms, like Eodicynodon.

Yesterday we looked at Microurania, a rarely studied ancestor of dicynodonts and their phylogenetic predecessors. That’s the taxon missing from the Ruta et al. (2013) tree that would probably upset their topology, as it does here (Fig. 2).

No teeth?
No teeth were found with Galeops (Fig. 1), but small root impressions remain in the both jaws, all the same size.

Galeops had a shorter, taller face than other dromasaurs. The jaw “joint” permitted the jaws to slide back and forth relative to each other, a trait dromasaurs shared with dicynodonts.

The clavicles were larger in Galeops than in other dromasaurs studied.

Different than other therapsids?
The current basal therapsid family tree (Fig. 2) indicates the Anomodontia had a different origin than the rest of the Therapsida, including mammals. Add in a few taxa like Stenocybus and Microurania and the traditional topology changes to the heretical one.

So is the Therapsida diphyletic? Perhaps so… another heretical result produced by expanding the taxon list.

Addendum: Giving credit where credit is due, Olson 1962 remarked that therapsids might have had a dual origin, with anomodonts arising from the edaphosaur pelycosaurs. 

Is Galeops the sister to the dicynodonts? Apparently no, for the same reason.

References
Brinkman D 1981. The Structure and Relationships of the Dromasaurs (Reptilia: Therapsida) Breviora 465:34 pp. online here.
Broom, R. 1912. On some New Fossil Reptiles from the Permian and Triassic Beds of South Africa, Proc. zool. Soc. London 1912:859—876. online here.
Liu J, Rubidge B and Li J 2009. A new specimen of Biseridens qilianicus indicates its phylogenetic position as the most basal anomodont. Proceedings of the Royal Society B 277 (1679): 285–292.
Olson EC 1962. Late Permian terrestrial vertebrates, USA and USSR. Transactions of the American Philatelci Society N.S> 25: 1-225.
Ruta M, Angielczyk KD, Fröbisch J and Benton MJ 2013. Decoupling of morphological disparity and taxic diversity during the adaptive radiation of anomodont therapsids. Proceedings of the Royal Society B (Biological Sciences) online here. Supp material here.]

Microurania – A rarely studied taxon at the base of the Dicynodonts

Earlier we looked at basal anomodonts, noting that Biseridens should not be part of this inclusion set because it is a basal dinocephalian. Instead Microurania (Fig. 1) and Stenocybus should be included as they nest in that basal position in the large reptile tree.

There are few references for the rarely studied Russian therapsid Microurania (Ivakhnenko 1995, 2003, Middle Permian, Lower Tatarian), and only one illustration that I know of. Yet it is an important transitional taxon leading to the base of the Dicynodontia.

Figure 1. All that is known of Microurania, a basal therapsid, basal anomodont and dicynodont precursor. Image from Ivakhnenko 2003.

Close to Stenocybus and Nikkasaurus at the base of the Therapsida, the proto-dicynodont Microurania (Fig. 1) retained upper and lower single canines. It was considered a biarmosuchian but nests in the therapsid subset of the large reptile tree closer to Otsheria and Venjukovia {now Ulemica] (Fig.1) at the base of the Anomodontia.

The holotype (PIN 4337/1) is a partial skull with leaf-like postcanine teeth similar to those in Phthinosuchus.

Microurania has a shorter snout than Biarmosuchus, closer to Stenocybus with which it shares procumbent teeth. Microurania retained canines, unlike Nikkasaurus.

Figure 2. Basal therapsids and sisters to their ancestors. The short skull of Stenocybus is retained by anomodonts like Microurania, dromasaurs and dicynodonts. This also demonstrates the present diphyletic therapsids with two lineages arising from basal ophiacodonts.

Figure 4. Basal therapsid family tree. Biseridens nests far from the anomodonts and Microurania.

Plain Jane/Brown Sparrow
Microurania is one of those plain Jane / brown sparrow unspectacular sorts of reptiles. Frankly, it looks kind of boring. The ironic reality is, such “generic” taxa are exactly where evolution is making key transitions. They are blends, hybrids,  part this and part that.

Microurania does not have the elevated suborbital/cheek region found in Otsheria, Venjukovia [now UIlemica] and Eodicynodon. The large canines found in dicynodonts may be new traits. Immediate predecessors do not have such large canine teeth.

The Therapsida may turn out to be essentially diphyletic. Stenocybus and the Anomodontia form one branch. Nikkasaurus and the rest of the Therapsida (including mammals) form the other branch. Ophiacodon is currently the most completely known common ancestor, but two scrappy double-canine taxa may be transitional forms.

References
Ivakhnenko MF 1995. New primitive therapsids from the Permian of Eastern Europe, Paleontol. Zh. 1995(4):110–119.
Ivakhnenko MF 2003. Eotherapsids from the East European Placket (Late Permian). Paleontological Journal, 37, Suppl. 4: S339-S464.