So you may have become aware of some research into Quetzalcoatlus lately. I am going to ignore it. What a nice topic to start on.
Quetzalcoatlus Northropi is my namesake, the largest pterosaur, and by extension volant creature, ever. Quetzalcoatlus Lawsoni was just named. See, we've long had two Quetzalcoatlus specimens, a largely complete little thing and several elements of a left wing from a clearly much larger one. Little one had been placed provisionally in Q. Sp, but a monograph recently gave it a proper name. And analysis. And holy fuck.
Look, I opened this site on the pretense that I'm no professional, and I'm going to be talking down on the work of people who are. But to be fair, I'm not alone. Big man himself Mark Witton and others have expressed skepticism at many of this paper's findings of the biomechanics of the animal in question. Fuck, in some cases, the other two authors OF THE PAPER are disagreeing with what Padian is saying. Let's go over this.
The first, most superficially noticeable, and most easily opposed thing is the wing planform. In summary the paper analyzes three proposed wing planforms for pterosaurs in Figure 20. Figure 20A and 20B are debunked, outdated models that are biomechanically hard to reconcile, demanding wing shapes and flexibility that are implausible. 20C is the one I've gone off of, it's the one everyone goes off of, it's the one authors of the monograph John Conway and James R. Cunningham prefer iN THE SAME PAPER, and it's the one that Padian drops in favor of 20D, which is a bird, it's just a bird and i hate i HAT E I AHDFTYUA
Ok look I'm invested in the current look of pterosaurs. I like it. Yes. Bias. But also, consider, it sucks. Simply appealing to authority, it's pretty strongly against Kevin Padian. I'm pretty sure even David Peters's hellfuck model of pterosaur planforms is a variant of 20C but Padian's going against the grain. This seems to go back to... 2017? 2018? When he did a study that was good for Microraptor and bad for everything else.
Essentially, Padian went and had the thought, the reasonable thought not unique to him, that soft tissue would restrict skeletal motion. You know, it can only stretch, or compress, so far- so looking at the very birdlike hips of the gliding dromaeosaur Microraptor versus a quail, it became apparent that it couldn't splay its hindwings out so far- everyone depicting it as "four-winged" had to drop it, because fitting muscles onto it would have caused either overcompression of dorsal muscles or overtension of ventral muscles I forget but BASICALLY between that and the shape of the hip the hindwings could not have been wings, but instead more of a vertical stabilizer. Maybe just enough splay to contribute a little lift, but clearly not a tandem wing. This has now become the norm, and has been lauded.
And in the same breath Padian said this also applied to pterosaurs.
Pterosaurs are not birds. They're not even dinosaurs. They're their own thing. The closest dinosaur relatives that aren't themselves dinosaurs. You might be thinking "isn't that birds?" No, birds are dinosaurs. So it seems really a stretch to call for the application of quail biomechanics to pterosaurs. As always, the media lit up about it. Padian talked about his ideas as though 20B was the norm at that point even though everyone was using 20C, which lended credence to his idea, many news sites talking about how wrong and dated this "bat like" depiction was while skipping all the work done with 20C, showing literally the first reconstructions of Pterodactylus after it left its paddle phase as examples of this wrong and backwards science.
Look, look, look, Padian's probably a great guy, and I'm trying not to lean too much into the insane crotchety people-eating anime girl persona here- try to find THAT sentence on any other paleontology blog- but frankly reading the monograph it's pretty clear who was writing the final draft (and who skipped the actual "Reconstruction of the Wing Planform" section to rush the conclusion, Ben). The idea that this idea could be unambiguously applied to all ornithodirans was not really taken very seriously and people have continued reconstructing them normally. Padian, however, basically wants to give them the legs that we've long considered the wrong cartoon scifi legs- not bound in the wing, tucked up below the body.
The 20C style of leg-inclusive wing essentially turns the legs into a useful aerodynamic tail for control- which, critically, I think the 20D planform is woefully insufficient in replacing. I know there's some birds lacking in the tail department, but an aerodynamic tail is crucial to flight- unless there's some weird shit with the wings themselves I'm not appreciating, they could not achieve pitch or yaw otherwise, especially at large sizes- I'm gonna go out on a limb and guess, in fact, that the tiny overall size of proto-birds let them get away with little to no big aerodynamic caudal feathers, as tail and head deflections would provide proportionally significant turning forces without them at that size, like how many smaller animals can swim fine without dedicated fins. Not so for a 250kg mega-pterosaur. Motions of the legs and feet in the 20C model would provide pitch and yaw moments. The feet, with their planes positioned vertically, would be like rudders, the uropatagium an elevator. There are useful criticisms of some previous stances here- for instance, the idea that the feet themselves splayed from the metacarpals to provide additional area for their "rudders" seems unlikely, but even if we eliminate the foot-rudder idea, the torso could presumably be twisted at least slightly to allow the uropatagium to act as the rudder, as birds do with their caudal feathers- something that would be especially crucial for pterosaurs, which are now believed to have held their wings in a forwards sweep that would have induced yaw instability, which would have necessitated a dedicated fucking rudder. Even with the implication that it could control pitch with wing sweep- which would have a lot of other aerodynamic implications- I don't understand how a yawing movement, or more importantly correction, could be achieved.
Moreover, the legs don't have to be fully horizontal for them to be part of the wing. The paper acknowledges this, but I'd go further- a significant anhedral to the femurs would be acceptable, inducing a "washed in" wing camber as seen on many birds and even aircraft. This area of the wing would likely stall first, which is admittedly bad because it's the most rearwards section, and induce extra drag, but would also generate more lift. Frankly I can splay my legs to a degree that I think wouldn't be an issue in any case. I think that makes me a slut. Padian et al. called me a slut.
For these reasons I am hesitant (read: very much angry) about accepting the "20D" flight model in any future reconstructions I make for the time being. But that's not the only thing.
Second, also important, is launch. Remember how the two other authors were against Padian doing weird things with the legs? Yeah, that again. Quadrupedal launch has been supported by most authors as instrumental to giant pterosaurs achieving flight, as it allows a more efficient allocation of weight than birds- birds need to launch with their legs before they can open the wings and start flapping, and the legs become useless in flight. Pterosaurs launch with their wings, vaulting over them as they compress and then spring out, only needing one big muscle set. This gives them the ground clearance and forwards speed needed to initiate flight for free. This has been thoroughly modeled, albeit with pterosaurs that are a bit different from Quetz- but, hey, most birds launch pretty much the same way, why would pterosaurs vary much?
Oh Padian says the legs were jacked and it just lept up like a person would. Vertically. Only vertically.
Now, a high jump might sound good for flight, but unless it has a TWR in excess of one, um, no. It's going to start falling immediately and unless it's able to hover it won't be able to get its forwards speed up in time to stop that. Just ask all the Harrier pilots that had engine failures, or the X-50 CRW- high up means jack shit without forwards speed. The quad-launch gives it this speed.
This is in addition to the glaring fact that the amount of muscle needed for the legs under a high jump model would be both a ton of weight to add on an animal that's already pushing it and, well... Look, the paper talks about how the arms- the huge fucking muscular arms- might have had difficulty taking all the structural stress of a quad launch. But a vertical launch powered by equally huge muscles on the legs alone? The teeny tiny toothpick legbones? Yeah, like, don't know if they're less pneumaticized than the arms and thus stronger for their diameter, but, eh. It's also a little funny to me that issue is taken with how far the legs have to fold in quad launch but thinks they can fold entirely for flight, if I'm being honest.
Also the fact that it says bats can't be a good model organism because Quetz would be getting thrust from its legs too sounds like a reason to go with the quad launch. Which I am going to continue to do for now (and be very butthurt if I'm ever proven wrong).
Finally we get to the last big thing, that being gait. I don't mind this so much I guess. The idea that the hindlegs were powering most of the stride is weird given how much muscle is up front, especially if we're not on board with Padian pumping the hindlimbs up, but I guess the biggest forelimb muscles would have been for adduction, not forwards/backwards motion. The arms, in this model, would be trying mostly to just stay out of the way of the legs. They'd move in a sort of camel-ish side-at-a-time gait, which makes sense for the ungulate-like anatomy and would prevent stretching of the brachiopatagium if it did have the arm-leg connection, which it did, which it did.
This would be a "nerf" to the terrestrial speed of Azhdarchids, potentially giving them trouble chasing quick prey. Given the current prevailing theory- largely supported in the paper- that they just marauded about on land snatching things up, this does beg the question of exactly how fast they are. The paper does propose they went after fish opportunistically, but doesn't seem to mean to insinuate they were total piscivores or anything, just heron stuff.
There's a lot of other stuff, rearrangements of postures and things that seem to be agreed upon among the authors and, to me, agreeable, but are also being questioned from the buzz I saw on paleotwt around the paper. I don't know, it's a lot.
Well there's my first post. Check the bibliography for the paper itself and hopefully I did all that right so I don't get C&D'd day one- that's why I used images from the article itself instead of google or my own art, idk I'm just paranoid about that.
Bibliography:
Kevin Padian, James R. Cunningham, Wann Langston JR. & John Conway (2021) Functional morphology of Quetzalcoatlus Lawson 1975 (Pterodactyloidea: Azhdarchoidea), Journal of Vertebrate Paleontology, 41:sup1, 218-251, DOI: 10.1080/02724634.2020.1780247
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