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 Gargainia. These two nest together in the LRT, but not by much. Both the antorbital and lateral temporal regions differ greatly.

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/

6 thoughts on “Is ‘Vjushkovia triplocosta’ a jr synonym for Garjainia prima?

  1. Several things, Dave:

    You cannot safely say that “V. triplicostata” has a larger antorbital fenestra than Garjainia, considering that the areas bordering the fenestra have damaged margins.

    The shape and sutural patterns of the skull roof are identical between the lectotype of “V. triplicostata” and other Garjania specimens. The triplicostata lectotype is just a bit bigger and slightly more flattened from taphonomic processes.

    The Garjainia holotype also has a concave posterior portion of the maxilla as seen in that specimen’s description last year. So that is not a valid difference.

    You’ve reconstructed the lateral temporal fenestra in “V. triplicostata” incorrectly by misidentifying the braincase as the squamosal. The “posterior process of the squamosal”, as you call it, is clearly the paroccipital process of the braincase, as seen and described in the paper (fig. 6 c). The braincase is clearly labelled and described, it’s baffling how someone could mistake it for a squamosal, which does not resemble it in the slightest. The actual squamosal is seen in figure 9.

    Likewise, the postorbital in the lectotype braincase has a broken off posterior process (fig. 6 c), and your claimed “greater arch of the posterior postorbital” is not apparent in either that or the referred postorbital in fig. 8c.

    Other claims, such as the taller orbit and more robust quadratojugal and quadrate are a symptom of how your reconstruction is scaled based on multiple “V. triplicostata” specimens from different individuals with variable sizes. The structure of the individual bones is more reliable for comparing the specimens referred to triplicostata and Garjainia. And each bone can be shown to be identical to its counterpart in Garjainia.

    In summary, none of your claimed differences can be shown to be valid, and some (such as mistaking the braincase for the squamosal) result from absurd oversights.

    • Thanks for your observations and corrections, Neil. As mentioned in the text, the two nest together in the LRT. The differences (dorsal views of skull, shapes of orbit and AOF, could be individual or generic, IMHO. The assembly of several specimens into a chimaera bring additional risk. The level of an opinion (= IMHO) does not rise to the level of a hypothesis. Your statement, “each bone can be shown to be identical to its counterpart in Garjainia” is not strictly correct IMHO, based on comparisons of the skulls in lateral and dorsal views. So, there is some wiggle room here. It’s splitters vs. lumpers today. I split Rhamphorhynchus specimens, others don’t

      • Let me start over, because you have evidently not understood my point. This discussion is not a matter of taxonomic opinion, this is a matter of legitimate observations versus illegitimate observations. Your “differences” are all illegitimate.

        There is no difference between each skull bone in the “V. triplicostata” specimens and typical Garjainia specimens. I’m not talking about your erroneous skull reconstructions, I’m talking about individual bones. The triplicostata postorbital is identical to that of Garjainia. The triplicostata dentary is identical to that of Garjainia. And so on and so forth; this is the case with every observable bone in the skull. All of the features diagnostic for Garjainia are also seen in triplicostata whenever the bones are preserved.

        The differences you identify simply cannot be proven to exist. Either they are speculative proportions based on multiple specimens without clear scaling, or blatant misinterpretations of bones (such as your absurd interpetation of the braincase as the squamosal, which still persists in your skull reconstruction and text). I’ve described them individually above. A “lumper vs splitter” debate is based on whether differences in specimens amount to either individual variation within a species, or interspecies variation. But even the most diehard splitter would not split based on nothing. And that’s my point, your supposed differences amount to nothing when properly scrutinized.

        Now, the paper actually did discuss some real differences between the specimens, relating to tooth implantation and palatal dentition. The authors argued that these differences can be reasonably interpreted as individual variation, but a splitter may consider it differently. But you have ignored these actual observations in lieu of whatever you observe when comparing your poorly-made skull reconstructions. Please, don’t distract the science discourse with your misinterpretations of the fossils.

  2. I’ve looked over the dorsal views multiple times and see no real anatomical difference. Conversely, the diagnosis for Garjainia prima includes a “prefrontal strongly flared laterally in dorsal view”, “skull roof with a longitudinal fossa on its dorsal surface that harbours a longitudinal median prominence in its posterior half” and a “straight suture between postfrontal and postorbital”, all of which are also visible in PIN 951/60 (the lectotype skull roof of “V. triplicostata”) and PIN 951/60 (the referred skull roof). So in terms of skull roof material “V. triplicostata” fully corresponds to the anatomical characteristics which are used to distinguish Garjainia prima from other erythrosuchids. Perhaps you were unaware that the holotype skull of Garjainia prima was transversely compressed, explaining why it seems narrower.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.