Pterosaur Perils!

Posted by Nima On Thursday, July 30, 2009 13 comments

Here we go - drawing pterosaurs the Paleo King way!

I thought I was going to be too busy to finish this for the ArtEvolved gallery, but I have, not one but THREE smokin' hot pterosaur restorations finished (better late than never lol....). I wanted to do more but I figured three high-grade ones are better than ten crappy ones any day.

Now pterosaurs are not my number one area of expertise, but I do know them better than a lot of other creatures (say, for example, Anomalocarids!)

So I had to do a lot of extra research before drawing these guys accurately. And along the way I perfected what you might call "accurate guesswork" - that is, inferring likely proportions of parts of animals based on their close relatives - with a good dose of personal aesthetic appeal thrown in. With some pterosaurs little is known but the skull, and with others good skeletal diagrams are not always available, so educated guesses are more necessary than with stuff I'm more familiar with. I am one of the few people willing to reconstruct a poorly known species in great detail, but I'm not gonna lie, it's anything but easy going.

Soon as I get started on titanosaurs this will become obvious. As for the pterosaurs.... guesswork and interpretation are everywhere.

Wing membranes are the main point of contention - did they attach to the leg, the ankle, or somewhere else? After a lot of debating (which you can see on ArtEvolved) and consulting as many sources as I could find, I settled on the efficient design proposed by Gregory S. Paul - wing membranes attached to the tail, with the legs having their own individual membranes. With Pterodactyliods, this is a good explanation for why the tail was reduced but not lost altogether.


Female Pteranodon "ingens" skeletal by Gregory Paul. The classic large crest was only present in the males.
Note the free legs and how the wing membranes attach to the tail - which wasn't useful for much else.


Of course the ankle-attachment faction will cite this or that fossil, but in the debates I established that none of their evidence is 100% conclusive, and it can in fact be interpreted many different ways (though this provoked some very heated opposition). Membrane stains in slab fossils are often something else entirely. Not every stain is even part of the animal. But many of them do look like squashed skin that was once attached to the tail. Needless to say, this would also make steering easier, whether the tail was used to steer, as in most Rhamphorhynchoids (excluding Anurognathids) or whether steering was done with the legs as rudders (as was likely in pterodactyloids). Ankle attachment works fine for bats, but it would likely be a clumsy, restrictive, and highly maladaptive system for pterosaurs, whose wing anatomy and lifestyle were in fact VERY different from bats.

So with some exotic choices for the creatures and settings, here are the pictures!




Thalassodromeus and other mid-Cretaceous pterosaurs over South America

Though Thalassodromeus was from Brazil, it's likely that it migrated long distances in search of feeding grounds and mates. Here they're flying over Argentina, overshadowing giant ornithocheirids flying below. A few Tapejara fly in the background near the mountain, while the ground is dominated by a herd of massive Argyrosaurus. (I plan to draw the 90-foot long Argyrosaurus as the main subject in a later work, which will definitely be a king-sized challenge).

I was fascinated by Thalassodromeus the moment I saw a picture of it (I think it was the one by Dr. Mark Witton), and I figured it was definitely on my list of pterosaurs for the gallery. This pterosaur has a gigantic head - the beak is deep and there's an obscenely huge crest. Thalassodromeus is a tupuxuarid, and unlike their relatives the tapejarids, they have crests of solid bone rather than a membrane supported by bony struts. The head was light and had low bone density, but still looks disproportionately large. The crest was almost certainly for sexual display, though it may have had some use for steering as well. Like many later pterodactyloids, this guy had no teeth, and was probably a fish eater - though whether it preferred freshwater or saltwater prey is impossible to tell.





Quetzalcoatlus - Sailors of the Sky

Here, some of the last and largest pterosaurs soar over a flooded river in Late Cretaceous New Mexico, passing over three Alamosaurus. I actually began this drawing almost 8 years ago as something to pass the boring empty hours between final exams and summer vacation, and it lay unfinished, hidden in a book... when I rediscovered it I decided to complete it but noticed that the arm proportions on the Quetzalcoatlus were ALL WRONG. So I plunged into several skeletals and papers on giant azdarchids and other large pterosaurs and figured out some more or less accurate proportions for the segments. I went for tail attached rather than ankle attached wings. No complaining, it makes more sense this way! I still think the legs didn't quite come out right, but overall I'm pleased with the look. The toughest part was by far the landscape - after all the time I put into the pterosaurs, the landscape commanded a lot more detail and shading.

Aside from the unique color patterns, these are pretty much your standard Quetz's. The top view was a bit tricky (grrr... projects that require perfect symmetry...) but I'd easily do it again now that I have more experience. I gave them small crests near the back of the head, which is consistent with the remains. Artists used to draw Quetz's without a crest, until Greg Paul and others corrected this trend in the '80s. (You can check out Greg Paul's Quetz here, fending off a tyrannosaur). Quetzalcoatlus had a small crest (which is mostly broken on the type skull, leading to the initial error), not a huge one like Pteranodon or Nyctosaurus.





Anurognathus ammoni - the Definitive Version

I've seen a few different illustrations of the tiny Jurassic pterosaur Anurognathus - all of them very different, and NONE of them looked like Anurognathus! I've seen this little guy drawn as a prehistoric bat (by Dr. Mark Witton and MANY others), a flying toad (no, I'm not joking), a winged shrew with the face of a seal, a vampire-like creature with bloodshot eyes (thank you Mr. Bogdanov), and an odd chimera of filaments and fanciful outgrowths not found in the fossils (*cough* David Peters *cough cough*).

Long story short, none of these drawings looked anything like the real animal, so I decided to do my own restoration - not to brag but this is probably the first HIGHLY ACCURATE life restoration of this critter anywhere. I consulted Mike Hanson's skeletals as the main reference for proportions, though I added a few of my own touches such as the membrane shape and the skull proportions (which have been interpreted at least 2 or 3 different ways due to the skull being badly squashed in both known specimens as well as close relatives Jeholopterus and Batrachognathus - I tried for a compromise between the skull proportions restored by Hanson and those from other skeletal artists). I also put some fuzz around the ankles which is apparent on Jeholopterus and was likely also present on Anurognathus. Same goes for the whiskers preserved in the same fossil. Anurognathids all had very long whiskers, presumably for sensing air movement and catching insects. This feature is not found on any other group of pterosaurs.

The wings attach to the tail, and interestingly unlike other rhamphorhynchoids, the anurognathids had short stubby tails - a trait converging on the more advanced pterodactyloids. Anurognathus was probably a fast and highly agile flyer which used its leg membranes for steering rather than relying on a long rudder-like tail. This design also made it capable of zig-zagging through tight spaces in dense Jurassic forests. Based on its small size and pointy teeth, it lived mostly on bugs, though it may have also gobbled up the occasional Jurassic fruit here and there. Like many insect-eating birds today, some cryptic coloration was probably present. The wing pattern turned out a bit too much like giraffe spots, but I ended up liking it.

***

I didn't put any progress pics or "making of" stuff because there just wasn't enough time to scan all the stages, and I was working on all three of the projects at once. However, just by looking at them I'm sure at least a FEW of my artistic secrets may reveal themselves to the insightful.


13 comments:

Justin said...

Greetings from Cape Town,
Wow Nima, you are very talented. I really like the art works.
Juz
http://juztick.blogspot.com

Zachary said...

Wonderful pics, Nima. I especially like those azhdarchids!

Zach Armstrong said...

(A different Zach than the one above). When you make the reference to Anurognathus being drawn as a "flying toad", are you talking about that reconstruction of it by "Dewlap" on deviantArt? Because I think in his description he makes reference to that: "It is kind of a cross between a frog and a bat". (Now I know "frog" and "toad" mean different things to us, but there is actually no legit scientific difference between what is a "toad" and a "frod", if I remember my Anuran classification stuff correctly).

On reconstructing Anurognathus I would refrain from copying the Mike Hanson skeletal you used for restoring the skull. Chris Bennett (and others) have shown that the skull is a lot more "rounder" in the front than first reconstructed.

Also, as for Greg Paul's pterosaur wing membrane configuration: I prefer all of Paul's anatomical intuition on restoring the prehistoric when and where it differs from the mainstream view EXCEPT for on this little detail: the attachment of the uropatagium and brachiopatagium with the hindlimb elements. I sympathize with your concerns in your post about extraneous bits of wing membrane in the fossils, but I also think that the brachiopatagium must have been attached to the legs, because of the fossil evidence. Here, I prefer Mike Habib's configuration, with a narrow-chord wing configuration that juts back sharply to attach to the hind limbs. This makes most sense in light of the anatomical evidence you talk about above, and it agrees with the fossil evidence, and it looks neat too. Anyways, that's my two cents worth..

Nima said...

Dewlap's illustration was actually not bad, actually it wasn't much like a frog or toad... more like a cute, fuzzy Dr. Seuss monster... though this IS the "frog jaw" pterosaur so it's understandable... No, despite his reference I was not referring to his drawing - by "flying toad" I mean that some artists put a crazy amount of webbing all over the feet and everywhere else, make the head far too fleshy, and overall make this creature look like something that couldn't realistically exist.

Mike Hanson ("Archosaurian") drew it this way, which is strange considering how top-notch his other illustrations are. Dmitri Bogdanov also used a toad look for Anuro, though his version is more like a creepy red-eyed piranha with wings.

As for the skull - I didn't rely solely on Hanson's skeletals. In fact Hansen himself has a second "rounder" version of the reconstructed skull similar to what you described. I used Qilong's and other people's skeletals for background reference. So my Anuro's head is basically a well-rounded mean of all the credible versions I could find (obviously David Peters didn't even come close to making the list - though I wish he hadn't trashed his credibility like that).

With Greg Paul's wings (KFC should make that a menu item LOL!) I tend to favor them because of their elegant simplicity. I don't doubt that Mike Habib's configuration is also likely. In fact I floated that idea in the great pterosaur battle at ArtEvolved (the link is above...) and Mike himself actually showed up in the debate to throw in his two cents.

In the end I want with Paul's version because upon closer inspection I saw a trend towards independent individual leg membranes and tail-attached wings in the fossils and this fit with the recurring pattern of short (but not absent) tails in BOTH anurognathids and pterodactyloids... Habib could be just as valid in some instances, so I'm not rejecting or bashing his results in any way. I just favor Paul's for physiological reasons - and the evidence could pretty much get smushed to look the same way in either scenario.

Zach Armstrong said...

Gotcha about Dewlap's illustration.

About the webbing on the feet, hasn't Jeholopterus shown that the feet were generously endowed with webs?

The thing that bothers me about the tail-attachment scenario is that with a short tail like that, it doesn't seem like a very strong place to anchor the wings. The hips, legs and ankles give a far greater amount of space to attach the wings and distribute stress and pressure.

Also, footprint evidence indicates a quadrapedal mode of movement--which would be a lot less likely if the wings were not attached to the legs and to the tail instead.

I think the idea has also fallen out of favor with Greg Paul. If you notice in his Dinosaurs of the Air, none of his pterosaur skeletals indicate membrane attachment. And in figure 1 of appendix 2 (p. 333), you will notice that the Quetzalcoatlus and Pteranodon support knee-attached wing membranes. The Quetz outline even leaves attachement to the tail out all together. He also suggest in DA that pterosaurs could not lose flight because they were "four-limbed" in the air, like bats, and not "two-limbed" like birds; in other words, the hindlimbs were incorporated into the brachiopatagium.

Nima said...

Wow that's interesting... I never knew Greg Paul was on DeviantArt. What's his nickname on there? I'd like to see his new stuff...

When you say that Paul's pterosaur skeletals leave out membrane attachment, does that mean he just omits the membranes altogether like Mike Hanson? WAIT a minute... Mike Hanson actually did include some VERY narrow-chord wing membranes for Jeholopterus (and no webs) in a skeletal - in fact he didn't even extend them as far back as the tail! Here's the link:

http://en.wikipedia.org/wiki/File:Jeholopterus_ningchengensis.png

BTW, while we're on the same topic, Jeholopterus does not show any conclusive proof of webbed feet. In fact if you look closely at the feet, the "webs" are only immediately around the toes, and have empty space between them. This isn't a true web, but rather just squashed skin like in hadrosaur mummies. There's a similar dark patch jutting out of its shin, but anatomically there's no reason for a web to be there at all. It's also just a trace of squashed skin due to the fossil being crushed. There are no webs but there ARE definite traces of furry plumes at the rear of the ankles, and the wing and leg membranes appear to be separate structures.

The tail on short-tailed pterosaurs might look fragile but I would expect that if it didn't anchor SOMETHING it would have disappeared in later pterosaurs... but even the late-surviving Nyctosaurus and Quetzalcoatlus retained the tail. In fact the tail was quite stiff and not all that pneumatic. Also keep in mind that with Paul's classic model, the majority of the membrane was attached to the sides of the body - only a small fraction at the end attached to the tail. So the tail did not have to support the full stress on the wing during flight.

There's also a possibility that the tail was wrapped in tendons for strength, to brace the wings. But not a surety.

It's true that leg attachment leads to more surface area for the wing - however if you read my comments on ArtEvolved, you will see that I explained in detail the faulty assumptions behind the "surface area uber alles" argument.

However I think Mike Habib's model also has some valid points, in the end it was down to which one made slightly more sense given the skeletal structure AND the real nature of the fossils (i.e. taking into account that not every stain is a trace of skin or tissue, and NOT every trace of skin/tissue is a web or a wing membrane). So you can of course disagree but it does not make either model totally valid or totally invalid. The evidence just isn't good enough for a final conclusion, except in maybe one or two pterosaur specimens.

Zach Armstrong said...

Haha, yes Greg Paul is on deviantART....Not! "DA" is short here for "Dinosaurs of the Air"....but I get the joke :D

I don't know if you have that book, but you are right in concluding that he leaves out the membranes all together in his skeletals...however, in the appendix he has a body outline that does indicate membrane attachment (p. 333). In the Pteranodon the wing membranes attach to the knees and there is a uropatagium attached to the legs and tail. In the Quetzalcoatlus he indicates knee attachment for the brachiopatagium, but leaves out a uropatagium attached to the tail and legs completely. The only reason I pointed this out was to let you know that Paul's ideas apparently have changed (not that I necessarily agree with them or provide proof of a certain membrane attachment configuration).

And you're right, Jeholopterus doesn't give definitive evidence of webbed feet. But nothing in science gives definitive evidence. So that really is a non-argument. The preponderance of evidence suggests that pterosaurs had webbed feet (including footprint evidence, mind you). Also, the reason hadrosaurs were thought to have a web is because the foot pad was misinterpreted; are you suggesting pterosaurs had a foot pad, too? Obviously not, so my question is, where would the "extra" flesh come from? The "extra" flesh in hadrosaurs was a fleshly structure, not a web, albeit, but a foot pad, which makes sense for a four-limbed terrestrial animal. What is the corresponding source of extra flesh in Jeholopterus, then? It appears more parsimonious to me to accept the "extra" flesh was actually membranes, "webs" between the toes here, and membrane attached to the legs for the brachiopatagium there.

Also, my point was not that the tail was fragile, but that it would not be a suitable place for the wings to attach too. The wings exacted a lot of force in flight, and the tail would not have proved to be a suitable anchor to anchor the ever shape-shifting flight membrane. It should be noticed, too, that all membranous flying/gliding creatures today incorporate all four limbs ALWAYS, and usually, the tail. There are exceptions for the tail (i.e., free-tailed bats), but NONE, that I am aware of, for exceptions to four-limbed membrane attachement (this of course excludes animals like gliding lizards and snakes which do not attach ANY of the membranes to a limb, and instead use vertebral or extra bone-like rods for support). It would thus seem most parsimonious and in agreement with the scientific evidence to have the brachiopatagium attach to the legs.

I agree that you should not take every stain or trace to be tissue, or wing or membrane, but when several pterosaur experts have personally examined the fossil and say that the membrane attachments in question are indeed membranous attachments, it seems reasonable to accept that as the case, unless further evidence demonstrates otherwise. In the cases of the Chinese feathered dinosaurs, it was somtimes proven that some of the dark spots sometimes interpreted as liver or what-have-you were experimentally proved to be extra globs of preparation material. No such evidence has come to light in the case of the Jeholopterus, and it seems most reasonable to take the obvious interpretation at face value: that the brachiopatagium did indeed attach to the hindlimbs in pterosaurs to various extents. I rest my case. Thanks for discussing this with me BTW, no matter how annoying I am ;) .

Zachary said...

Nima, I'd like to see you do a David Peters style pterosaur just for the hell of it. But here's the challenge: you have to make it look convincing.

Nima said...

Haha good show :D If Paul was on Deviant Art, that would be quite the reunion.

Now to be fair, I also rest my case...
As for the "webs" - look at Jeholopterus closely, you'll see there are sections missing from the "webs" between the toes. The "webs" are nothing more than the skin on the toes, which got distended and squashed.

It's not a "foot pad", and in fact hadrosaur hands didn't have a "pad" either, they had a mitten of skin that wrapped the digits together. In both cases, squashed skin gives the appearance of webbing.

You may have a point with the leg attachment, but there are plenty of fossils that do not show ANYTHING attaching to the legs - look at Pterodactylus kochi for example:

http://upload.wikimedia.org/wikipedia/commons/4/41/Pterodactylus_kochi.jpg

There you see what appear to be traces of fuzz, but NO leg attached membranes.

And here:
http://www.pterosaur.net/assets/pterodactylus_kochi_skel_260.jpg

The legs appear pristine and free of membranes. You COULD argue there's hip or thigh attachment, but NOTHING on the shins or ankles whatsoever.

I'll have to buy DoA to see the details though. I though that book dealt mostly with birds and coelurosaurs, I never knew Paul included pterosaurs in it.

Zach Armstrong said...

The only thing with the Pterodactylus kochi images is that they show no membranes at all...what is this, a flightless pterosaurs? ;) JK

On a more serious note, the "fuzz" I assume you are talking about are the dark colored streak-ish looking stuff. If you notice though, there are these long streaks on the snout, too. Now, I suppose this Peters-esque integument is possible, but not likely in my opinion. It'd make more sense to me that these are mineral or preparator traces...to me they even have a pattern characteristic of crystal-like minerals.

On the second image, again there is no trace at all of wing membranes, only a throat pouch. Now the lack of membranous material I chalk up to poor preservation, like sometimes seen in the record of Chinese feathered dinosaurs: sometimes we have the different specimens of the same species preserving fluffy feathery goodness, and sometimes it's just the bones.

Show me an image of P. kochi with lots of clearly preserved soft tissue, and then we'll start talking.

BTW, the reason pterosaurs retained a short tail may have to do with neutral selection, i.e., it is neither advantageous or disadvantageous, so it just stayed there. It is also possible it had some other role, like being used for fine adjustment of the uropatagium.

As for the hadrosaur mitt/pad thing. The point wasn't the English term, but what purpose it served. On page 159 of the Dinosaur Heresies (a copy of which I own, BTW), Bob Bakker shows how the mitt was worn (pun intended): the drawing shows a little "cushion" on the underside of the phalanges, and is labeled with an arrow as "cushion", so maybe I should have used that term. Whatever the case may be, this likely helped provide traction. It is unlikely that pterosaurs needed a "cushion", so that is why I think this is an unlikely explanation for extra skin being squished on preservation.

As for the "spaces" between the soft tissue and the bone, this simply could be part of the decomposition process: as the membrane rotted or dissolved in its environment, this may have caused it to detach from the skeleton. At any rate, I don't find it a very convincing argument to deal away with "webbed" pterosaur feet. And there is another reason why the "webs" are reasonable to me (which is different in the case of a hadrosaur; if anybody had been honest in their comparative anatomy back at the time, tehy would have realized that hadrosaurs are not built for an aquatic lifestyle): they have a likely, and suitable purpose. Like all membranous flying/gliding animals, having webs between the feet helps the animal stay in the air. If you look at colugos, they have webbing between their toes. See here. So do flying frogs, and some gliding geckos. An interesting thing is that geckos don't really have "webs" per se, but elongated , pad-like scales. So maybe pterosaur feet weren't "webbed" but had elongated gliding "pads" like geckos that stuck out from the sides of the toes, but did not connect all together; that could explain the "spacing" in between the tissue. (Also, some flying geckos even have full-fledged webbing.) At any rate, it appears that pterosaurs did have some extra web-like things on the feet.

SVidovic said...

"not to brag but this is probably the first HIGHLY ACCURATE life restoration of this critter anywhere"
What are you on about?! I think bragging is all that you do well. It's probably the first HIGHLY WRONG life restoration anywhere! The membrains are all wrong. They should pass below the tail and finish at the fifth toe. Where's its fur? and why's its eye so small? Its neck seems too long, and if any of the old reconstructions you slagged off were wrong anywhere it was by using rictal bristles which have no support from the specimens, although they show some very forward thinking in comparative functional anatomy. So you have succeeded in making a less accurate drawing despite new research and information. If you claim to have done something, back it up! And listen to the people who spend their working life studying these specimens and papers. Show some respect!

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