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. 

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.

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

8 thoughts on “Youngosuchus – at the base of the Rauisuchia and near the Archosauria

  1. You’ve mistakenly created a chimeric taxon here.

    All the Vjushkovia triplicostata images found in Von Huene (1960) reconstruct a robust, Garjainia-like animal completely unlike the sinewy creature in your skeletal. However, I noticed that your “Vjushkovia” has a skull identical to that of Youngosuchus sinensis, a putative rauisuchid which was originally named as a species of Vjushkovia in 1973 before receiving its own genus and being reclassified in 1985.

    No wonder you consider Vjushkovia as a link between erythrosuchids and rauisuchids, you’re combining data from the description of Von Huene (which represents an erythrosuchid likely synonymous with Garjainia) and pictures of Youngosuchus (which was a completely unrelated rauisuchid).

    You should probably have closely inspected Ezcurra (2016), which included Youngosuchus sinensis (your “Vjushkovia”) and found it sister to Batrachotomus while being completely unrelated to any erythrosuchid. There is substantial evidence that the original Vjushkovia triplicostata is synonymous with Garjainia, based on both Von Huene’s original description and personal inspection. Sources supporting this interpretation with good evidence include Kalandadze & Sennikov (1985), Ochev & Shishkin (1988) two 1995 papers by Sennikov, Gower & Sennikov (2000), Gower et al. (2014), Ezcurra (2016), and Ezcurra et al. (2018). You probably would have noticed these points if you actually read the last of these papers, rather than ranting about taxon exclusion during your post about it.

    I hope you’re happy that your blunder is responsible for the most prominent view of Vjushkovia on the internet. It’s hard to find a reconstruction that does not retain the Batrachotomus-like proportions of Youngosuchus, rather than the clearly Garjainia-like erythrosuchid described by Von Huene (1960). Be more careful, Dave.

    • Neil, thank you for the insight. I see that currently V. triplicostata has become a junior synonym… that photos of the identical specimen bear different names… and that my blunder is responsible for exactly one image of Vjushkovia on the Internet, the one from ReptileEvolution.com. The backstory for this image is simple: I copied it from a Greg Paul illustration. Generally he’s known for accuracy. Evidently, not this time. I did not pursue further data in the meantime. I will review the situation and will likely drop this taxon from the LRT, given what I’ve learned about it at present. For future reference, bringing emotion into a scientific discussion (“I hope you’re happy…”) and speculation (“You probably would have noticed these points if you actually read”) is unprofessional.

      • I was not aware that your skeletal was copied from Greg Paul, since an image search made it seem like you had the only skeletal, and that many life reconstructions were based off of yours. With context, I regret placing the blame solely on you.

        Positing Vjushkovia and Youngosuchus as synonyms (using the slash) is a misunderstanding of taxonomic nomenclature. The genus Vjushkovia refers to Von Huene’s “Vjushkovia triplicostata”, a set of russian erythrosuchid fossils which are very likely part of the hypodigm of Garjainia mandiba. Therefore Vjushkovia is a nomen dubium and junior synonym of Garjainia mandiba. Youngosuchus is not a nomen novum for Vjushkovia triplicostata, it is a new genus for “Vjushkovia” sinensis, a completely different species of reptile which never should have been placed under the Vjushkovia banner in the first place.

        To anyone knowledgeable about the rules of taxonomic nomenclature, implying that “Vjushkovia” and Youngosuchus are interchangeable names implies that “Vjushkovia triplicostata” and Youngosuchus sinensis are interchangeable, which is far from the truth. You even list them as synonyms on reptileeveolution.com. You’re basically saying that Garjainia mandiba (=Vjushkovia triplicostata) is equivalent to a separate species of Batrochotomus-like rauisuchid (=Youngosuchus sinensis), which is just not true.

        You have already made some revisions to your posts mentioning this taxon, but you still have a lot of work to do.

      • Thank you, Neil. Your phrase “very likely part of the hypodigm of Garjainia mandible” sounds like the issue remains at least partly unsettled. I need something more substantial. Captions describing the photo of the pertinent specimen (museum number unknown) label it Vjushkovia in one instance, Youngosuchus in another. Let’s consider the present situation a band-aid (bandage) until more data flows in. Please send pertinent PDFs to info@reptileevolution.com and I will review them.

  2. Photos I can find (such as this one: https://upload.wikimedia.org/wikipedia/commons/2/27/Youngosuchus-Paleozoological_Museum_of_China.jpg) label the specimen (IVPP V3239) as Vjushkovia sinensis (Young, 1973), which is an invalid name since the specimen represents an animal which is generally considered a different genus than Von Huene (1960)’s original Vjushkovia, Vjushkovia triplicostata. The replacement name for V. sinensis (NOT V. triplicostata) is Youngosuchus sinensis, which was named by Kalandadze and Sennikov, 1985. Some authors, like Parrish (1992), and evidently Greg Paul, still placed sinensis within Vjushkovia. Even then, they never synonymized sinensis with triplicostata, as you have done. Many others, like Ochev, Gower, Sennikov, and Butler, have not upheld the retention of Youngosuchus as a second species of Vjushkovia.

    I’ll send you PDFs of pertinent sources if I can find them, but I’ll report relevant info on them here:

    Von Huene (1960), “Ein grosser Pseudosuchier aus der Orenburger Trias” (A large pseudosuchian from the Orenburger Trias) : Names and describes Vjushkovia triplocostata based on a set of Russian erythrosuchid fossils. Garjainia, which was named two years prior, was not mentioned.

    Young (1973), “On the occurrence of Vjushkovia in Sinkiang” : IVPP V 3239 is given a name as the second species of Vjushkovia, Vjushkovia sinensis.

    Kalandadze & Sennikov (1985), “New reptiles from the Middle Triassic of the southern Cis-Urals” : Proposed that Vjushkovia triplicostata was synonymous with Garjainia prima and gave Vjushkovia sinensis its own genus, Youngosuchus. They suggest that Youngosuchus is not an erythrosuchid, but rather a “rauisuchian”.

    Ochev & Shishkin (1988), “On the principles of global correlation of the continental Triassic on the basis of tetrapods.” : Implied synonymy between Garjainia and Vjushkovia.

    Parrish (1992), “Phylogeny of the Erythrosuchidae” : Retained Vjushkovia triplicostata as a species seperate from Garjainia prima. Agrees with Young (1973) by retaining Youngosuchus sinensis as a species of Vjushkovia (but not synonymizing it with the original species).

    Gower & Sennikov (2000), “Early archosaurs from Russia” : They find issues in Parrish’s study and return to the conclusions of Kalandadze & Sennikov (1985).

    Ezcurra (2016), “The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms” : After inspecting all specimens of Garjainia, Vjushkovia, and Youngosuchus first-hand, he concludes that the first two are synonyms and the last is a distinct genus as argued in 1985. Youngosuchus is also given a new diagnosis. Youngosuchus sinensis is found far away from Garjainia prima, closer to Batrachotomus instead.

    Ezcurra, Gower, Sennikov, & Butler (2018), “The osteology of the holotype of the early erythrosuchid Garjainia prima (Diapsida: Archosauromorpha) from the upper Lower Triassic of European Russia” : Mainly focuses on the holotype of Garjainia, but also notes that Vjushkovia triplicostata retains many autapomorphies of Garjainia prima while having only a few differences which can be explained (with evidence) as examples of intraspecific variation. This is the best source I can find for discussing the differences and similarities between the Garjainia prima and Vjushkovia triplicostata specimens.

    They also list the hypodygm of Vjushkovia triplicostata: “The hypodigm of ‘Vjushkovia
    triplicostata’, which includes the lectotype (a skull roof, PIN 951/59) and isolated skull and postcranial bones (PIN 951/1–40, 46, 54–64, 69, 70, 78–105; Gamian Gorizont).”

    • Fantastic backstory here. Thank you 3x! Neil, I hope you’ll appreciate that I need to see and compare the Russian specimen(s) with the Chinese specimen before I change text. Without a reconstruction of the Russian material (= science) I know from experience not to trust authorities (= faith), especially when they disagree with one another. Specimen numbers update the current text. This clarifies things. Thank you, again.

      • I fully appreciate your desire for pictures, though I do not share your pessimistic view of the scientific integrity of the authors I have cited. But we can discuss that some other time.

        You have already found one photo of IVPP V 3239, and I linked another one right above. Richard Butler has also posted a photo on his twitter account (https://twitter.com/butlerlabbham/status/923891039450083328).

        Line drawings of the skull and a rib of Youngosuchus have appeared in Parrish (1992), figures 8 and 9. Oddly enough, they are labelled as IVPP 4067, which is a specimen of “Chasmatosuchus” yuani, a dubious species of sympatric proterosuchid. This is probably a mislabel, since the text uses the correct specimen designation.

        Skeletal reconstructions and apparently photographic plates of Vjushkovia triplicostata appear in Von Huene (1960), though the translated version I emailed you unfortunately did not include the plates. I have yet to find a copy of the original version, maybe you can ask for a copy from Gower, Sennikov, Butler or Ezcurra, who seem to be the scientists currently most familiar with Russian erythrosuchids. Better photographs appear in Gower & Sennikov (2000), from which I sent you some screenshots. These photos include the lectotype skull roof (PIN 951/59, figure 8.4C), a premaxilla (PIN 951/63, figure 8.4B), a shoulder girdle (PIN 951/2, 8.5A), humerus (PIN 951/36, 8.5B), and femur (PIN 951/27, 8.5C).

        The braincase was heavily discussed and photographed in various publications by Gower, although they probably wouldn’t be very helpful for you considering that braincase characters are basically worthless to the LRT. Butler and Ezcurra will eventually have a full description of the triplicostata specimens, probably pictured to the same extent as the Garjainia holotype in their recent description of that. Speaking of that recent description, you can use that paper to evaluate which postcranial bones in Garjainia skeletals are sourced from either the holotype or the triplicostata specimens. It seems like the holotype of Garjainia prima is composed of the skull, jaw, a few vertebrae, ribs, a pectoral girdle, and a single metatarsal. The rest of the skeleton is triplicostata stuff.

        One last useful source of pictures is a 2013 paper by Ezcurra, Butler, and Gower (link: https://www.researchgate.net/publication/260632796_'Proterosuchia'_the_origin_and_early_history_of_Archosauriformes), which includes an illustration of the skull of Youngosuchus (figure 5b) and many postcranial elements of “Garjainia triplicostata” (figure 5 e-q).

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