Weigeltisaurid wing morphology in first gliding reptiles from Permian (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Free pdf:

Valentin Buffa, Jordan Gônet, Thomas van de Kamp, Marcus Zuber, Marc Girondot, Eberhard Frey, J.-Sébastien Steyer, Michel Laurin
Morphology and osteo-histology of the weigeltisaurid wing: Implications for aerial locomotion in the world's first gliding reptiles
Journal of Anatomy (advance online publication)
doi: https://doi.org/10.1111/joa.70058
https://onlinelibrary.wiley.com/doi/10.1111/joa.70058

Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1111/joa.70058


The Late Permian Weigeltisauridae are the world's first gliding reptiles, but much remains unknown regarding the anatomy of their patagium (or wing), which, in turn, confounds our understanding of their gliding mechanism and paleobiology. Here, we examine the morphology and osteo-histology of the patagial skeleton of weigeltisaurids using an array of imaging techniques and several thin sections through the wing skeleton of a specimen of Weigeltisaurus from the Late Permian of Germany. We demonstrate that patagials and gastralia share a one-to-one articulation, permitted by the uniquely specialized anatomy of the lateral gastralia. We also show, based on skeletal anatomy, histology, and inferred musculoskeletal relationships, that patagials are likely neomorphic ossifications and are thus not strictly homologous to the gastralia. We provide the first reconstruction of the musculoskeletal anatomy of the weigeltisaurid wing, suggesting that the base of the patagials was likely embedded in the M. obliquus externus group. Similar to the condition in the extant flying lizard Draco, these muscles may have contributed to the unfolding of the patagium, which was likely supported by hooking the manual claws onto the leading edge of the patagium. This would have provided weigeltisaurids with a means to maintain the patagium expanded and under tension while gliding, as well as some measure of control of the dihedral angle of the wing, thereby offering a means to control stability and maneuverability in flight. Wing folding may have been permitted by muscular and tendinous connections between the elements of the patagial skeleton, generating elastic tension toward a folded state, as in Draco. Lastly, the cross sections of the patagials show a bimodal cortical distribution with much thicker cortices along their cross-sectional long axis than short axis. This made the patagials rigid, which likely helped prevent patagial collapse during gliding. This work represents a critical step toward understanding the wing structure and gliding mechanism in weigeltisaurids, paving the way for future morphofunctional or biomechanical studies on the locomotion of the world's first flying vertebrates.

[Gregory Paul]

As per the mighty battleship HMS Hood, the Pride of the Royal Navy, suddenly blowing up at the Battle of the Denmark Straits in May 1942, leaving hardly any survivors and to the dismay of Britain. 

There had been warnings, the ship was two decades old, the armor was not what it should have been (but not as bad as often thought), and worst the Brits were using dangerously unstable cordite charges (no German battleship or battlecruiser blew up in a gunnery duel, including the Bismark that sunk the Hood in its final battle when it had the hell beat out of it). 

So time to face the music. You know, like the Womack song covered by The Rolling Stones (and performed superbly by Jagger and Arcade Fire a while back on SNL) -- 

It's All Over Now.  

For the ETRH. 

This is apparent in https://www.livescience.com/animals/dinosaurs/i-was-wrong-dinosaur-scientists-agree-that-small-tyrannosaur-nanotyrannus-was-real-pivotal-new-study-finds. Looks like support for the ETRH (that automatically requires that every TT-zone tyrannosaur fossil be rex) has at long last been abandoned to one degree or another by apparently all. With the discussion now being what specimens belong to which taxa. Including the new suggestion of Tyrannosaurus lancensis.  

Another analogy to illustrate what has happened. In the 1920s the Pride of Germany was built, the great Mohne Dam (analog for the special status of T. rex via the ETRH). And reinforced dams were seen as nearly impregnable. In WW2 the RAF wanted to take it out. But how? Barnes Wallis figured it out, leading to the renowned Dam Busters raid of May 1943 (analog for the MTTH:). 

Ina night attack a Lancaster bomber skipped a giant 4 tonne, back spinning bomb into the back of the dam. That oughta work (analog MTTH papers coming out in the 2000s and 2010s led by Larson). 

Yet the dam did not breach (continued wide support for the ETRH) to startled disconcertment of Wallis et al. awaiting the code message in England. 

Skipped in another bomb (L&S and the two megapapers I was involved in). 

Darn still stood (continued and even more passive-aggressive support for the ERH) to yet more eye rolling exasperation by Wallis etc.

Third bomb deployed (Z&N)

Dam suddenly bursts and reservoir rapidly emptied of water (vanishing support for the ETRH) and Wallis and friends are felling pretty, pretty good (you know who we are). (The need to repair the Mohne dam disrupted the building of beach defense at Nornandy, aiding the success of D-day a year later.) (The 1950s movie The Dam Busters is a great watch -- the scenes of the big bombers flying in formation skimming over the lake exchanging tracer fire with the dam AA batteries, while dropping the bombs with care, was the inspiration for the space battle scenes in Star Wars, including Luke plugging the Death Star).

A point of the above is that the final ETRH killing Z&N paper was not really ground breaking, it was the most recent in a long long of MTTH papers starting with Gilmore in 1946, with the advantage of having the best gracile specimen to work with. But it was the one that tipped things just enough to burst the ETRH dam. 

And it is not just the above article. Please note that in their discussion Z&N, who participated in the Carr et al. 2022 that failed to refute Paul et al (2022, and of course you have all read my detailed Mesozoic journal discussion on why Carr et al. 2022 is errant in so many ways, right?), are now admitting that there may be multiple species of the mighty Tyrannosaurus after all:) Well glory be. They say there is a need for further research beyond Paul et al. (2022). Well I just did that this year, showing the marvelous large variations in postorbital bosses that correlate with stratigraphy, not seen in any other tyrannosaurid genus and exceeding that in all tyrannosaurids combined. And more spiffy robust/gracile differences in the skulls that correlates with the stratigraphy and the bosses (leaving only poor old AMNH 5027 as a major specimen taxonomiuc species level floater, dear thing). Not that Paul 2025 is the last word. A basic idea behind my paper has been to get folks off their butts and actually study the species situation in the tyrant lizard rather than lean on the ETRH which effectively barred testing the issue. Think about it, was there ever a paper that actually took a holistic look at the situation in support of the ETRH? Carr et al. (2022) did not do that because it merely criticized Paul et al. 2022, and came up with little  new data. 

So you all get out there and get to work, like I did for the last 15 years. I doubt my research will be altered all that much. Low in the TT-zone it is robust T. imperator with its way cool spindle bosses not seen high up in the formations, and up there also robust T. rex with its even cooler disc bosses and generally fewer incisors, and then there is T. regina which is unusually gracile femured relative to all tyrannosaurids and lacks either the spindles of the Mickey Mouse discs. And of course two giant tyrannosaurids one robust and the other less so in the same formation is seen elsewhere.  And the Nanxiong Formation contains a giant with a couple of small tyrannosaurs, it is probably that intraformation tyrannosaur diversity is often higher than realized. Throw in the migration of Appalachia eutyrannosaurs into the TT-zone that I proposed in my new paper and Z&N picked up. Thus disappears the ETRH. 

So let's see what future work turns up.

I will also note that Z&N really go hard hitting critical about the Carr hypothesis, more than did L&N, and at least as much as I did this summer. 

Tyrannosaurus lancensis. Yes, not everything that is not Tyrannosaurus as per the norms in the TT-zone is Nanotyrannus. And it is not certain if Nano and Jane have the long hands (but as far as I know the latter has a long humerus that indicates it does, if anyone knows otherwise please say so). But even if we define the genus as including Tarbosaurus which is viable and I have done (depending on whether I think they are very close relatives that shared a common Asian ancestor, or not if Tyrannosaurus evolved on its own in N Amer) and does Carr, and even put Daspletosaurus in Tyrannosaurus as I did back in PDW ah the good old days, Nano and Jane fall well outside of that, and are not even tyrannosaurids on numerous grounds. 

It is vexing and quite wrong that in the coverage of the Z&N paper I have not seen any example of proponents of the MTTH being asked to comment (there may be some behind paywalls). It appears to be the "establishment" critics. This group-think coverage has been part of the problem all along this story going way back. Branch out in who you talk to journalists. Surprised Science Friday did not cover this big dinosaur story, maybe because they did not have their usual headlines intro section. 

I see Wikipedia has their brand new Nanotyrannus entry:) Good for them. The Tyrannosaurus entry needs a lot of reworking, including putting T. imperator and regina in the official columns along with rex and mcraeensis (which if anything is less well founded than imp. and reg.)

So the preferred paradigm has undergone the tectonic shift it needed since the 2000s. It is now understood what has been true since 1946 -- it is not whether there are multiple tyranno taxa in the TT-zone, it is how many species and genera there are. 

I don't think anyone is going to disagree with that now. 

GSPaul

[Thomas Carr]

Greg,

I disagree that your gloating, public missives are necessary. No matter how right we think we are, we can't realistically expect our favorite hypotheses to exceed the momentary.

-TDC.

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