Is ‘Vjushkovia triplocosta’ a jr synonym for Garjainia prima?

In other words,
are the two erythrosuchid holotypes (Fig. 1) sufficiently alike to be congeneric or conspecific? Garjainia was published first.

Butler et al. 2019 reported
“Two species of Garjainia have been reported from Russia: the type species, Garjainia prima Ochev, 1958, and ‘Vjushkovia triplicostata’ von Huene, 1960, which has been referred to Garjainia as either congeneric (Garjainia triplicostata) or conspecific (G. prima).”

“…little work has been conducted on type or referred material attributed to ‘V. triplicostata’. However, this material includes well-preserved fossils representing all parts of the skeleton and comprises seven individuals. Here, we provide a comprehensive description and review of the cranial anatomy of material attributed to ‘V. triplicostata’, and draw comparisons with G. prima. We conclude that the two Russian taxa are indeed conspecific, and that minor differences between them result from a combination of preservation or intraspecific variation.”

Figure 1. Vjushkova holotype compared to Garjainia. These two nest together in the LRT, but not by much. Several areas, including the antorbital and lateral temporal regions differ greatly. The dorsal view of both are quite distinct, overlooked by Butler et al. 

Combining elements from seven specimens
bears some risk of creating a chimaera. Since Butler et al. felt confident in doing so, and there is no alternative, then I do, too. Given the data presented by Butler et al. I reconstructed the skull from separate elements (Fig. 1), something Butler et al. did not do.

Although the two skulls are extremely similar
and the two taxa nest together in the large reptile tree (LRT, 1602 taxa) a few traits seem to distinguish these two taxa apart from one another, at least at the species level and perhaps at the generic level. Note the larger antorbital fenestra in Vjushkovia. Note the pinched upper portion of the lateral temporal fenestra. Note the concave posterior maxilla. Note the taller, narrower orbit. Note the much more robust quadratojugal and quadrate. Note the greater arch of the posterior postorbital. Note the posterior process of the squamosal. These differences appear to support the separation of these taxa at the generic level, IMHO. The lack of a reconstruction in Butler et al. 2019 may have hampered their decision in this case. The lack of graphic comparison in the paper (no images of the Garjainia holotype are shown side-by-side with those of Vjushkoiva) is also regrettable.

---

References
Butler RJ, Sennikov AG, Dunne EM, Ezcurra MD, Hedrick BP, Maidment SCR, Meade LE, Raven TJ and Gower DJ 2019. Cranial anatomy and taxonomy of the erythrosuchid archosauriform ‘Vjushkovia triplicostata’ Huene, 1960, from the Early Triassic of European Russia. Royal Society Open Science 6: 191289. http://dx.doi.org/10.1098/rsos.191289

Criticisms of other papers by Butler as co-author:

https://pterosaurheresies.wordpress.com/2018/06/25/the-rise-of-the-ruling-reptiles-ezcurra-and-butler-2018-fiasco/

https://pterosaurheresies.wordpress.com/2019/10/21/teyujagua-paradoxa-still-no-paradox-in-the-lrt/

https://pterosaurheresies.wordpress.com/2019/04/05/mythbusting-prorotodactylus/

https://pterosaurheresies.wordpress.com/2019/02/06/what-is-gracilisuchus-add-more-taxa-to-find-out/

https://pterosaurheresies.wordpress.com/2018/12/12/ezcurra-et-al-2018-review-garjainia/

Ezcurra et al. 2018 review Garjainia

Ezcurra et al. 2018
intensively studied the Early Triassic erythrosuchid, Gargainia prima (Fig. 1; Otchev 1958) Early Triassic ~240 mya, 2 m. long) from Russia. The photographic images therein are remarkable for their clarity.

Figure 1. Garjainia at several scales and views.

The authors report,
“We consider ‘Vjushkovia triplicostata’ (Fig. 1) to be a junior synonym of Garjainia prima, (Fig. 1) because of their extremely similar morphology, with the two character states that differ between them being variable intraspecifically in some other diapsids.”  Others have considered Vjushkovia a junior synonym of Youngosuchus.

Figure 2. Erythrosuchids (white background) to scale. Note the differences between Vjushkovia and Garjainia. Click to enlarge.

That’s unfortunate.
Even without firsthand study, the large reptile tree (LRT, 1353 taxa) was able to clearly and cleanly split Garjainia from Vjushkovia (Fig. 3). As recovered here, Vjushkovia is not an erythrosuchid, but a basal rauisuchid, a clade derived from basal euarchosauriformes (Fig. 3) and separated from Erythrosuchidae by the clade Ornithosuchidae.

Figure 3. Subset of the LRT focusing on the Euarchosauriformes, where Garjainia is a basal erythrosuchid and Vjushkovia is a basal rauisuchid. Proterosuchus nests outside of this clade.

The authors also report,
“A new phylogenetic analysis recovered a monophyletic Garjainia as sister to Middle Triassic erythrosuchids and recovered Fugusuchus hejiapanensis as sister to all other erythrosuchids.” 

Figure 4. Ezcurra et al. 2018 cladogram needs more taxa to clarify relationships. Compare to subset of the LRT in figure 3.

Unfortunately
Ezcurra et al. 2018 omit so many pertinent taxa that their results (Fig. 4) do not match the more inclusive results of the LRT (Fig. 3). Pertinent taxa are listed online. Interested workers should insert pertinent taxa using their own character lists. As it stands, the Ezcurra et al. taxon list is far from complete and recovers an odd topology as a result.

Eucrocopoda
Ezcurra 2016 recovered a clade Eucrocopoda that reappears for the first and only time again in Ezcurra et al. 2018. With more taxa, the LRT recovers a different topology and refutes the monophyly of the clade Eucrocopoda.

Once again
the primacy of the second-hand paleontologist hypothesis has been validated: It continues to be more important to have a wide gamut phylogenetic analysis of hundreds to thousands of specimens than to have first-hand access to a specimen in order to figure out (or recover) what an individual taxon is in the context of valid sister taxa. The bigger picture is misinterpreted when a wide gamut of taxa are omitted.

References
Ezcurra MD, Gower DJ, Sennikov AG and Butler RJ 2018. The osteology of the holotype of the early erythrosuchid Garjainia prima (Diapsida: Archosauromorpha) from the upper Lower Triassic of European Russia. Zoological Journal of the Linnean Society, 2018, XX, 1–67.
Otchev VG 1958. Novye dannye po pseudozukhiyam SSSR: Doklady Akademii Nauk SSR, 123(4):749-751.

What is Tasmaniosaurus?

Updated September 20, 2014 with a new reconstruction and nesting for this taxon.

Revised skull reconstruction of Tasmaniosaurus nesting at the base of the Erythrosuchia.

Ezcurra 2014 considered the tiny Early Triassic archosauriform Tasmaniosaurus traissicus (Camp and Banks 1978) a tiny proterosuchid, following the original assessment.

Previous authors thought the maxilla was exposed in lateral view. If so, it has a maxillary fossa. Ezcurra thought the maxilla was exposed in medial view. Proterosuchids do not have a maxillary fossa. If the premaxilla was not downturned, Tasmaniosaurus is anything but a proterosuchid. If the maxilla is exposed in lateral view, Tasmaniosaurus is anything but a proterosuchid.

The caudal vertebrae are very long, longer than 3x their width, very un-proterosuchid like. Seven in a row have no neutrals spines.

The interclavicle of Tasmaniosaurus is T-shaped with a very long and slender posterior process. Among archosauriforms, only Euparkeria has a T-shaped interclavicle. Many are I-shaped.

The femur and tibia/fibula are short and robust, so no possible biped here and the Early Triassic is a little too early for bipeds.

Tasmaniosaurus is tiny. About the size of Youngina and Euparkeria, much smaller than any known proterosuchid or erythrosuchid.

In phylogenetic analysis (not updated online yet), Tasmaniosaurus nests at the base of the Erythrosuchidae, as a sister taxon to Fugusuchus + Revueltosaurus. So, another miniaturized taxon nests basal to a large clade.

References
Camp CL, Banks MR 1978. A proterosuchian reptile from the Early Triassic of Tasmania. Alcheringa 2: 143–158.
Ezcurra MD. 2014. The Osteology of the Basal Archosauromorph Tasmaniosaurus triassicus from the Lower Triassic of Tasmania, Australia. PLoS ONE 9(1):e86864. doi:10.1371/journal.pone.0086864

Revueltosaurus: closer to Aetosaurus? or to Fugusuchus?

This post was updated December 8, 2014 with a new nesting of Revueltosaurus with Fugusuchus as a basal erythrosuchid. 

Yesterday we saw a higher resolution Revueltosaurus skull in lateral view and we noted a disagreement in the phylogenetic nesting of this Late Triassic oddball.

According to Nesbitt (2011)…
Nesbitt (2011) nested the odd herbivorous Triassic archosauriform, Revueltosaurus, at the base of the aetosaurs, including Aetosaurus and Stagonolepis. Outgroups include an unresolved clade including Gracilisuchus, Turfanosuchus and Ticinosuchus. Outgroups to this clade include Riojasuchus and Ornithosuchus (= Ornithosuchidae) at the base of the “Pseudosuchia“. Wiki follows Nesbitt (2011).

According to Parker (2014?)…
William Parker, the discoverer of the twelve-specimen nest of Revueltosaurus skeletons, will soon publish a large monograph on this genus. His analysis will also nest Revueltosaurus with aetosaurs. He’s very sure of that.

Figure 1. Revueltosaurus compared to its big sister, Fugusuchus, a basal erythrosuchid.

According to the large reptile tree…
On the other hand, the large reptile tree does not recover the Nesbitt tree topology, but finds Revueltosaurus nests with Fugusuchus (Fig. 1) at the base of the Erythrosuchidae. To move Revueltosaurus to the Aetosauridae requires an additional 35 steps. t.

Like Aetosaurs:
Revueltosaurus is a heavily armored quadruped and a plant eater (judging by its teeth). I’m told by Parker the following traits are identical in Revueltosaurus and aetosaurs: scapula/coracoid, humerus, squamosal and armor design. You can see (Fig. 1) that despite being twice the size, Revueltosaurus has more gracile girdles and limbs and larger hands and feet than Aetosaurus. And the skull has a distinctly different shape in nearly all regards, including the squamosal. Even so…

An herbivorous rauisuchid, with several aetosaur and turtle-like traits.
On Revueltosaurus, the naris is rather unique. The lateral processes of the premaxilla have become more robust, reducing the size of the naris and moving them to an anterior position.  Revueltosaurus shares these traits with Fugusuchus.

Figure 2. Revueltosaurus pelves compared to Aetosaurus and Postosuchus. Red arrows point to limit of femoral head. Blue arrows point to acetabular shelf that roofs over the femur in rauisuchids. Revueltosaurus is a small slow quadrupedal plant eater, so it doesn’t have the long booted pelvis of Postosuchus. But note the similarity of the broad ischium to Aetosaurus!  Wm. Parker tells me, “It’s the plesiomorphic archosauriform condition with the very short anterior process. Lacks the deep supracetabular buttress found in rauisuchids. It actually looks like a juvenile aetosaur and it is difficult to tell them apart.” Schoch reports the aetosaur oblique posterior ridge is unlike the supraacetabular ‘boss’ of rauisuchids.

The pelvis should settle the argument
But it doesn’t. The pelvis of Revueltosaurus appears to bear a acetabular boss beneath which the femur articulates and supports. In aetosaurs the pelvis has a simpler shape without the boss. In aetosaurs the pelvis is wider at the top, which provides a broad platform for the armor, and angles inward ventrally. We don’t have a pelvis and hind limb for Fugusuchus, but Euparkeria is not far off. So is Gargainia. Both have similar elements.Here again, the different nesting sites appear to be based on employing macro-traits or micro-traits. This is a problem I have no solution for at present.

Figure 2. Revueltosaurus

 

References
Hunt AP 1989. A new ornithischian dinosaur from the Bull Canyon Formation (Upper Triassic) of east-central New Mexico. In Lucas, S. G. and A. P. Hunt (Eds.), Dawn of the age of dinosaurs in the American Southwest 355–358.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Parker WG., et al. 2005. The Pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. In Proceedings of the Royal Society London B 272(1566):963–969.

wiki/Revueltosaurus

Revueltosaurus in higher resolution

An online photo of Revueltosaurus (Fig. 1) adds details and clarifies problems. There is also a Vimeo video here featuring paleontologist, William Parker, who authors the Chinleana blogsite. He also discovered 11 skeletons of Revueltosaurus from one site with two that are nearly complete or complete. From that data the complete skeleton (Fig. 1) has been recreated.

Figure 1. Revueltosaurus skull from online source (link above) color coded to bone. Above, the aetosaur, Stagonolepis, to which Nesbitt and Parker nest Revueltosaurus. In contrast, the large reptile tree nests Fugusuchus with Revueltosaurus as a derived herbivorous erythrosuchid.

With this data, Nesbitt (2011) nested Revueltosaurus at the base of the Aetosauria with Aetosaurus and Stagonolepis.

In counterpoint,
The large reptile tree, employing a different character list, nested Revueltosaurus with Postosuchus, as a derived, smaller, somewhat turtle-ized rauisuchid.

We’ll look at the pros and cons of both analyses tomorrow.

References
Hunt AP 1989. A new ornithischian dinosaur from the Bull Canyon Formation (Upper Triassic) of east-central New Mexico. In Lucas, S. G. and A. P. Hunt (Eds.), Dawn of the age of dinosaurs in the American Southwest 355–358.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Parker WG., et al. 2005. The Pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. In Proceedings of the Royal Society London B 272(1566):963–969.

wiki/Revueltosaurus

Luperosuchus: an erythrosuchid, not a rauisuchian

Luperosuchus fractus (Romer 1972, PULR 04) was considered a indistinct pseudosuchian originally and later a rauisuchian by Desojo and Arcucci (2009). The large reptile tree recovers it as an erythrosuchid and a sister to Shansisuchus, which had an even larger subnarial fenestra. Earlier we looked at the two Shansisuchus specimens, noting that the referred specimen was much larger than the holotype with a distinct morphology, more like Luperosuchus.

Figure 1. Luperosuchus restored based on Romer 1971. Above: original drawing by Romer. Below tracing based on photo in Romer 1971, specimen PULR 04. Extension of the qj and a deeper max gives it more of a erythrosuchid look. At right is referred specimen PULR 057. Although related, the referred specimen strikes me as generically different with the low placement of the naris and large postorbital. Analysis on PULR 057 has not been done.

The reconstruction by Desojo and Arcucci (2009, Fig. 1, above) assumes a short quadratojugal, but a longer qj (Fig. 1, below) matches sister taxa.

This one is probably a rauisuchid
Another much smaller specimen (PULR 057, Fig. 1) was referred to Luperosuchus. That seems doubtful based on the lower placement of the naris, the straighter rostral profile, the larger antorbital fenestra, the deeper pmx/mx notch and the more robust postorbital. These traits appear to lead to Ticinosuchus and the aetosaurs as other archosauriformes retain a high naris. A second possibility leads toward the euparkeriid Osmolskina. A phylogenetic analysis was not attempted due to the small number of traits shown.

References
Desojo JB and Arcucci AB 2009. New material of Luperosuchus fractus (Archosauria: Crurotarsi) from the Middle Triassic of Argentina: the earliest known South American ‘Rauisuchian’. Journal of Vertebrate Paleontology 29(4): 1311-1315. 
Romer AS 1971. The Chañares (Argentina) Triassic reptile fauna. VIII. A fragmentary skull of a large thecodont, Luperosuchus fractus. Breviora 373:1-8.

Short note: ReptileEvolution.com has just passed a million hits for this year. Between 4.2 and 5.7 thousand unique visitors access the site every month.

Isochirotherium = Erythrosuchid tracks

Haubold 1983 described Isochirotherium tracks (Fig. 1) from the Early Triassic Bundsandstein Formation as “thecodonts with partial affinities to dinosaurs or crocodiles.”

Figure 1. Isochirotherium tracks matched to erythrosuchid pedes based on the longest digits from the heel are 2 and 3, unique to this clade.

Isochirotherium tracks have sub equal digits 2 and 3. The only reptiles with such a pes are derived erythrosuchids. If digit 3 is longer than 2 (X’d out in figure 1), then the track is more likely a rauisuchid or a more derived taxon. Shansisuchus and Erythrosuchus have a pes matching Isochirotherium. Primitive Garjainia does not. It has a longer pedal digit 4, like Proterosuchus and, to a less extent, Ornithosuchus.

References
Haubold H 1983. Archosaur evidence in the Buntsandstein (Lower Triassic). Second Symposium on Mesozoic Terrestrial Ecosystems, Jadwisin 1981. Acta Palaeontologica Polonica 28 (1-2):123-132.

New big Shansisuchus – close to Garjainia

Shansisuchus is a small erythrosuchid (Fig. 1) immediately identified by its very large subnarial fenestra between the naris and the antorbital fenestra. It looks like it has two antorbital fenestra, one before the other. The holotype (IVPP V2503,Young 1964) is a little less than 2 m in length.

Figure 1. Erythrosuchids. Click to enlarge. Long-legged Vjushkovia was basal to rauischids and the line that led to archosaurs.

A new specimen (Wang et al. 2013) from the Late Middle Triassic is quite a bit larger and more like Garjainia, it’s sister taxon.

Figure 2. The holotype Shansisuchus (below) and the new one (above) both to scale. The 9 cervicals are green. The estimated 19 dorsals are red. The big intercentra are yellow. Those are pretty big cervical ribs. This reptile was big overall, seemingly a new genus nesting close to Shansisuchus.

Wang et al. (2013) note the premaxilla bears 6 teeth, unique among erythrosuchids. The naris is close to the midline and rather small. The skull is very narrow, as in other erythrosuchids.

In my opinion, the two specimens are not conspecific and perhaps not congeneric.

Wang’s phylogenetic analysis includes several taxa that just don’t belong including, Mesosuchus and Dimorphodon (lepidosaurs), Vancleavea (thalattosaur) and Chanaresuchus (pararchosauriform). Otherwise the tree echoes the the large reptile tree (and most every other study) in nesting Shansisuchus with erythrosuchids (Garjainia not included and close to Fugusuchus, Osmolskina and Euparkeria.

These erythrosuchids appear to have been like hippos of the Triassic, but carnivorous. It would be interesting to know if the new specimen bore large running legs or short wading ones. Recently we looked at the resemblance of the basal erythrosuchid Garjainia to Youngina, the phylogenetic ancestor. Youngina belongs at the base of archosauriform analyses, not Mesosuchus.

References
Wang R-F, Xu S-C, Wu X-C, Li C and Wang S-Z 2013. A New Specimen of Shansisuchus shansisuchus Young, 1964 (Diapsida: Archosauriformes) from the Triassic of Shanxi, China. Acta Geologica Sinica (English Ed.) 87(5):1185-1197.
Young C-C 1964. The pseudosuchians in China: Palaeontologia Sinica 151, new series C., 9:1-205.

wiki/Shansisuchus

Youngosuchus – at the base of the Rauisuchia and near the Archosauria

Updated July 25, 2019 by renaming the taxon and deleting the post-crania previously copied from another artist. The resulting phylogenetic nesting did not change.

Vjushkovia = Youngosuchus is considered an Early-Middle Triassic erythrosuchid and indeed it could be considered as such since it is a descendant of the erythrosuchids. In the large reptile tree Youngosuchus was more derived than erythrosuchids and Euparkeria, Riojasuchus and Ornithosuchus. It nested at the base of the Rauisuchia and this clade nested at the base of the Archosauria  (crocs + dinos) and all intervening taxa.

Figure 1. Vjushkovia = Youngosuchus. This largely overlooked taxon is an erythrosuchid descendant that was ancestral to the Rauisuchia, the Aetosauria and the Archosauria.

Other than here,
Youngosuchus/Vjushkovia has not gotten a lot of press. And that’s too bad considering its importance at the “crossroads” of the Archosauria and Rauisuchia. Wiki reports, “The ankle does not have the large calcaneal “heel” that characterizes those two clades [ornithosuchids and rauisuchids) and marks the origin of the Archosauria.” Not sure why they said this about the archosaur ankle, because the basal archosaur ankle is not enlarged. It does become enlarged by convergence in poposaur dinosaurs and in derived crocs, like Protosuchus.

Figure 2. Skull and neck of Vjushkovia/ Youngosuchus.

All descendants of Youngosuchus/Vjushkovia
have a longer pubis and ischium, (check out Decuriasuchus, for instance) so there is a likely transitional taxon that looks like Vjushkovia, but with a deeper pelvis that we haven’t found yet. This morphology also indicates a more erect set of hind limbs (again, like all of its descendant taxa). So at this point we’re taking the first tentative steps in the gradual accumulation of bipedal traits in derived taxa like basal crocs and basal dinosaurs.

I’d like to know more about Vjushkovia if any more data is available.

References
Huene F von 1960. Ein grosser Pseudosuchier aus der Orenurger Trias. Palaeontographica Abteilung A 114:105-111

wiki/Vjushkovia — this link now redirects elsewhere

Sometimes the larger sister has the more juvenile traits.

A few posts ago we noted the interesting fact that the larger Garjainia  (Otchev 1958, Early Triassic ~240 mya, 2 m. long) had the relatively larger skull compared to its sister, Euparkeria  (Broom 1913 Early Triassic, ~240 mya, 60 cm). Generally a larger head is considered a juvenile trait. Garjainia also had a shorter tail and a shorter torso.

Figure 1. In the background is Garjainia, a basal erythrosuchid. Euparkeria is at its ankles, both to scale. Euparkeria is the more derived taxon. Below the tail of Euparkeria is a greatly reduced Garjainia as if a juvenile of Euparkeria. No fossils exist of Garjainia at this size.

On the other hand
Euparkeria did have the slightly larger orbit, a trait generally considered juvenile. The skull of Euparkeria also had smoother contours (no pmx/mx notch, less of a jugal descent).

Evolution Uses Premature Maturation
The greatly reduced size of Euparkeria is yet another example of a new clade arising from shrimps arising from old clades. Others have complained that size is not pertinent to phylogenetic matrices, but this example shows otherwise. Deciding where to draw “the line” will continue to be argued, no doubt.

Figure 2. Here Euparkeria nests between Garjainia, a basal erythrosuchid, and Ornithosuchus, an ornithosuchid, following the nestings recovered by the large reptile tree. Note the relative size of the skull in Garjainia, much larger than the much smaller Euparkeria.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Broom R 1913. On the South-African Pseudosuchian Euparkeria and Allied Genera. Proceedings of the Zoological Society of London 83: 619–633.
Ewer RF 1965. The Anatomy of the Thecodont Reptile Euparkeria capensis Broom Philosophical Transactions of the Royal Society London B 248 379-435.
Otchev VG 1958. Novye dannye po pseudozukhiyam SSSR: Doklady Akademii Nauk SSR, 123(4):749-751.
Parrish JM 1992. Phylogeny of the Erythrosuchidae. Journal of Vertebrate Paleontology 12:93–102.

wiki/Euparkeria
wiki/Garjainia