Diplovertebron vs. Gephyrostegus

Updated June 13, 2017 with the realization that Watson’s 1926 Diplovertebron is the same specimen as Gephyrostegus watsoni (bohemicus). 

This blog had its genesis in a reader comment
that considered the taxon, Diplovertebron congeneric with the coeval Gephyrostegus bohemicus and G. watsoni (Fig. 1), echoing earlier authors. Although there may be some confusion here (see below), and several specimens have been attributed to Gephyrostegus by various authors, the specimen illustrated and labeled by Watson 1926 (Fig. 1) is not one of them, unless it was drawn very poorly. If anyone has in situ skeletal material, please send it along for an update.

Gleaning data from several papers, provided that update. 

Part of my confusion
lies in the Wikipedia article on Diplovertebron, which states it was 60 cm in length, at least 5x larger than the one illustrated by Watson and far larger than any of its sister taxa. There may be a paper I am unfamiliar with at present that clarifies the matter.

So far, I have not found it. 60 cm may be an error.

The Westphalian (310 mya) tetrapods
include some reptile-like amphibians and some amphibian-like reptiles. This strata is 30 million years younger than the Viséan, where members from the first great radiation of reptiles can be found. Several late-survivors of earlier radiations can still be found in Westphalian strata.

Earlier G. watsoni nested among basal archosauromorpha, apart from G. bohemicus at the base of the Reptilia and separated by Eldeceeon. So the three taxa in figure 1 are separated from each other by intervening genera and therefore cannot be congeneric.

With present data, flawed though it may be
Diplovertebron nests in the large reptile tree (LRT) with Utegenia, at the base of the Lepospondyli, the clade that ultimately gives us frogs, like Rana, salamanders, like Andrias, and caecilians, like Dermophis.

Figure 1. Diplovertebron, Gephyrostegus bohemicus and Gephyrostegus watsoni. None of these are congeneric.

Figure 1. Diplovertebron, Gephyrostegus bohemicus and Gephyrostegus watsoni. to scale  None of these are congeneric. That’s because Watson’s drawing (upper left) was poorly drafted. 

Revised backstory:
Diplovertebron punctatum (Fritsch 1879, Waton 1926; DMSW B.65, UMZC T.1222a; Moscovian, Westphalian, Late Carboniferous, 300 mya) aka:  Gephyrostegus watsoniBrough and Brough 1967) and  Gephyrostegus bohemicus (Carroll 1970; Klembara et al. 2014) after several name changes perhaps this specimen should revert back to its original name as it nests a few nodes away from Gephyrostegus.

Derived from a sister to EldeceeonDiplovertebron was basal to the larger Solenodonsaurusand the smaller BrouffiaCasineria and WestlothianaDiplovertebron was a contemporary ofGephyrostegus bohemicus, Upper Carboniferous (~310 mya), so it, too, was a late survivor.

Overall smaller and distinct from Eldeceeon, the skull of Diplovertebron had a shorter rostrum, larger orbit and greater quadrate lean. The dorsal vertebrae formed a hump and had elongate spines. The hind limbs were much longer than the forelimbs. The tail is incomplete, but appears to have been short and deep.

Seven sphere shapes were preserved alongside this specimen. They may be the most primitive amniote eggs known.

Watson 1926 attempted a freehand reconstruction (see below) that was so different from this specimen that for a time it nested as a separate taxon, now deleted.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL 1970. 
The Ancestry of Reptiles. Philosophical Transactions of the Royal Society London B 257:267–308. online pdf
Fritsch A 1879. Fauna der Gaskohle und der Kalksteine der Permformation “B¨ ohmens. Band 1, Heft 1. Selbstverlag, Prague: 1–92.
Jaeckel O 1902. Über Gephyrostegus bohemicus n.g. n.sp. Zeitschrift der Deutschen Geologischen Gesellschaft 54:127–132.
Klembara J, Clack J, Milner AR and Ruta M 2014. Cranial anatomy, ontogeny, and relationships of the Late Carboniferous tetrapod Gephyrostegus bohemicus Jaekel, 1902. Journal of Vertebrate Paleontology 34:774–792.
Ruta M, Jeffery JE and Coates MI 2003. A supertree of early tetrapods. Proceedings of teh Royal Society, London B (2003) 270, 2507–2516 DOI 10.1098/rspb.2003.2524 online pdf
Watson DMS 1926. VI. Croonian lecture. The evolution and origin of the Amphibia. Proceedings of the Zoological Society, London 214:189–257.

wiki/Gephyrostegus
wiki/Diplovertebron

 

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3 thoughts on “Diplovertebron vs. Gephyrostegus

  1. Although there may be some confusion here (see below), and several specimens have been attributed to Gephyrostegus by various authors, the specimen illustrated and labeled by Watson 1926 (Fig. 1) is not one of them, unless it was drawn very poorly.

    It was drawn very poorly. It is a quick-and-dirty attempt to show how Watson imagined the whole animal; it is not a specimen drawing.

    In short, as I’ve already said, you’ve based your whole Diplovertebron OTU on paleofantasy.

    Part of my confusion
    lies in the Wikipedia article on Diplovertebron

    See, that’s what you get for trusting Wikipedia on vertebrate paleontology.

    any of its sister taxa

    For at least 12 years I’ve been telling you what the term “sister-group” means. You have never reacted at all. Why is that?

    This strata is

    First, one stratum is, two strata are. Second, the Westphalian isn’t a single stratum = layer, it’s a regional stage, lasting several million years and overlapping the Bashkirian and Moscovian of international chronostratigraphy.

    (Also, the term “stratum” is so poorly defined that the geologists have practically abandoned it. Most Google hits for “strata” are on creationist websites.)

    So the three taxa in figure 1 are separated from each other by intervening genera and therefore cannot be congeneric.

    That’s because your Diplovertebron OTU is Watson’s paleofantasy – as I already said last time.

    The pubis did not ossify</blockquote<

    Juvenile.

    I’m particularly curious about the lumbar region, which includes ribs all the way back to the pelvis, a situation that does not occur in sister taxa.

    The loss of lumbar ribs is an autapomorphy of Eldeceeon. New specimens of Eldeceeon have been found, and the whole taxon is being redescribed.

    (That may take another ten years. One of the promised coauthors is Jenny Clack, who’s also working on a large number of other redescriptions. One of the most recently published ones is the one of the skull of Gephyrostegus by Klembara et al. [2014], which you should really get your hands on to see just how off Watson and, to a lesser but still considerable extent, Carroll were. …as I already told you last time.)

  2. The comment in question is here. I just noticed I never presented the complete citation of Klembara et al. (2014); it’s in issue 34(4) of the JVP, you should find it easily. If you don’t have access, tell me.

  3. I have the JVP article on the skull of Gephyrostegus and the discussion of Diplovertebron. What I don’t see there and I don’t have is a specimen photo or drawing of what Watson considered Diplovertebron. Changes will happen when the data comes in.

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