Monday, May 25, 2009

Questions about Pterosaurs #1

With the next fantastic gallery coming up in just over a month - the Pterosaurs, I am sure there are many artists out there (like me) unsure of the specifics of pterosaur anatomy and current scientific theory. I thought we'd like to start a series of posts that answer questions about pterosaurs, all with the hope of creating a more accurate and wicked reconstruction of these winged beasts!

I will start with a question I've been really curious about. Hopefully some of our members, as well as scientists-in-the-know, might help answer it - either in the comment section or in a new "answer" post.

The question is this: Where does the bottom of a pterosaur's wing attach to it's body?


If this fossil impression at the London Natural History Museum is accurate (and real?), then it looks like the bottom of the wing attaches on the Pteranodon's leg at about the knee. I have also seen many life-restorations of pterosaurs with the base of the wing connecting at the hips and others where it connects at the ankle! Which is correct?

Are these artistic interpretations based on any fossil evidence? Is there a difference between earlier and later pterosaurs, or between different groups?


As someone trying to create an accurate reconstruction of these amazing animals, we need to know how their wing attaches! Thanks and I look forward to hearing from you.

Photos were taken by me in 2002 at the Natural History Museum in London.

22 comments:

Nima said...
This comment has been removed by the author.
Nima said...

The wings attach at the base of the tail near the hips - as per the Paulian model. This is by far the most efficient and well-adapted system.

Restorations with wings attached to the legs are as old (and inaccurate) as Owen's horned Iguanodon. Yet sadly about 90% of artists STILL draw them that way, like mesozoic bats. We're talking about a totally different (and much stronger) wing structure than any bat. And Pterosaurs had neither the need nor the spinal flexibility to catch food in some sort of leg-attached flap and then bend down midair to ear it like bats do. No trace of wings attaching to the legs has ever been found (though guys like David Peters claim that photoshop can somehow magically bring them out).

Pterosaurs were mostly bipedal (though the big Azdarchids got a bit too top-heavy to be constantly bipedal, practically speaking).

Did they shuffle-crawl on their hands? Only by choice OR by gravity, NOT constrained by bat-like skin flaps. Pterosaurs were NOT bats and it's long overdue that people stopped restoring them as bats.

Sean Craven said...

Can you point me to a more detailed discussion of bipedal Pterosaurs? Everything I've read recently says the opposite, although I do have something Kevin Padian wrote a while ago in support of that position.

Manabu "Mambo-Bob" Sakamoto said...

If I am not mistaken (and I don't read all that much on pterosaurs), Kevin Padian seems to be in the minority when it comes to pterosaur terrestrial locomotion, i.e. most pterosaur workers I know consider them to be quadrupeds when on the ground.

Nima said...

Yeah, Padian does support the bipedal theory. I remember reading in 1987 article in Dinosaurs Past and Present (...maybe pterosaurs should also have been in the book's title...) Padian's main candidate for bipedal locomotion was Dimorphodon, which I agree with.

Things got a bit more complicated with much later pterosaurs like Pteranodon, whose legs were much more reduced in proportion to the body - these guys apparently spent a lot more time on the wing than on the ground regardless of their leg posture.

As for bipedal large pterosaurs, Greg Paul included a skeletal diagram of a Pteranodon ingens (most likely a small-crested female) in his article "The Many Myths, some old, some new, of Dinosaurology" of which I am extremely grateful to him for giving me a copy. The Pteranodon was doing a bipedal takeoff, and also the wing membranes were hooked to the short tail, not to the legs.

I don't reject the mere possibility that SOME pterosaurs were quadrupedal at least SOME of the time - but I simply don't buy the model of bat-winged pterosaurs clumsily shuffling along with their leg movements hampered at every turn by overstretched wing membranes.

Indeed, the MOST credible scientists and artists I know of, do not subscribe to the bat-wing model that FORCES pterosaurs to be quadrupeds. If anything, the bigger ones were only quadrupeds due to their forward center of gravity, and some ramphorhynchoids may have been quadrupeds doe to their arboreal or rock-climbing lifestyle. Some of the artists who have illustrated NON-bat like pterosaurs include:

John Conway (probably the most experienced pterosaur artist out there) uses both the Paulian model and Mike Habib's model (which is essentially a more curved-wing butterfly-like version of Paul's) neither of which show wings attaching to legs - the legs actually have their own slim, separate membranes.

Greg Paul himself (look at any of his beautiful Quetzalcoatlus paintings)

Julius Csotonyi (he did this with Dimorphodon, but oddly used bat-like form with Ornithocheirus! Perhaps reflecting a diversity of opinion.)

John Bindon (his pterosaurs have the wing attached ator near the knee, not the ankle - not quite the same as Paul's model but not quite bat-like either)

Mike Hanson (a.k.a "archosaurian" on DeviantArt) - all his pterosaur skeletals and life restorations show wings attached to the body but not the legs.

The best "proof" for leg-attached wing membranes comes from the type specimen of the anurognathid Jeholopterus which preserves the wing membranes. But whether it attaches to the legs at all is questionable due to the played-out nature of the legs in the crushed fossil. There is still a lot of debate over where the wings on this guy attached.

A good place to start would be Conway's blog, and also Mike Habib - he's apparently done a lot of good research on this stuff. A bad place would be - well, Peters and his Photoshop theory.

Of course it's possible what different families of pterosaurs had different wing arrangements suited to their lifestyles. What may have worked for a tiny bug-eater like Sordes probably didn't work so well for a giant maritime flyer like Pteranodon or Ornithocheirus. That said, I still think a bat-like shuffle-forcing wing structure would be maladaptive and work against pterosaurs rather than for them.

Nima said...

lol, correction: "played out" should have been "splayed out".

Gina said...

Trackway evidence for rhamphorhynchoids is not currently available (at least, it's not known). Pterodactyloids walked on all fours. Fingers pointing diagonally forward and laterally, sprawling forelimbs, plantigrade feet. In rhamphorhynchoids, the hindlimbs were connected at the ankle by a large cruropatagium, so bipedality is out of the question.

In pterodactyloids, the cruropatagium became reduced so that they went from each ankle to the end of the short tail, not across to each other. The cheiropatagium's leg attachment may have varied between groups. Ankles or knees, but never above.

Nima said...

Lol I guess this is what you get when people get a little too passionate about pterosaur mechanics! *slaps head* Shoulda' seen it coming!

Gina, with all due respect can you cite any names or papers to back up these conclusions? Or a single undisputed fossil with wing impressions attaching to the tail? (Hint: don't say "Jeholopterus").

For the life of me, I have NEVER seen any solid fossil proof of ramphorhynchoids having a huge flap of skin from one ankle to the other (my goodness, forget mesozoic bats - that sounds more like mesozoic flying squirrels!) - nor have I seen any proof of pterosaurs in general having wings connected to the "ankles or knees but NEVER above". Such proof has failed to materialize.

That's why there is still a DEBATE over the wing morphology, hence the assumption "bipedality is out of the question" carries a HUGE burden-of-proof with it. (BTW, a few quadrupedal pterodactyloid trackways - assuming they exist - don't DISPROVE bipedality - especially with creatures as light as pterosaurs. That's a logical fallacy. They ONLY prove that QUADRUPEDALITY was not impossible.)

I named some top artists and pterosaur experts who reject or at least question the bat-winged/flying-squirrel model of Burian and Zallinger's long-outdated restorations. Can you please also cite some as well to back up your claims?

I'm honestly curious. Are they facts or personal opinions?

Weapon of Mass Imagination said...

Wow loving the discussion here.

Nima- Since your asking Gina for sources, how many of yours have PHD's and have actually published papers on this topic. I would love to read literature on this subject, as opposed to take their restorations word for it.

Not that their bad sources, for example I LOVE Conway's stuff, but I'm noticing a lot of them are palaeo artists and/or researchers who study other things mostly (Gregory Paul for example).

One of my fav Pterosaur artists is Mark Witton and he has a PHD studying Pterosaurs. He draws all of them as quadrupedal, and I know for a matter of fact he knows what he is talking about (he works with Conway a lot from what I've gathered). Witton's stuff can be found here http://www.flickr.com/photos/markwitton/sets/72057594082038974/

Gina- I've seen a set of those footprints (mind you of a Cretaceous Asian Pterosaur, so probably not a rhamphorhynchoid ;p the subject of much debate here), and to me that these are smoking gun of quadrupeds.

That and their leg sprawl combined with such large arms leads me to think bipedalness would be more work and awkward then letting the arms help in moving around on the ground. However I'm speaking strictly from common sense, and no hard research at all for the record!

EVERYONE- So back to Peter's first question, which was about where the wing membranes actually connect on a Pterosaur body. I'm taking it the jury is right out on this one then. As in no paper or specimen that definatively shows it one way or the other.

I ask as my 3d Model is done and I'm about to start mucking with it to pose it. If I have the wings wrong (not quick bat like for you Nima ;p but the wings do attach to the legs) nows the time to fix them.

Zach said...

Hey, guys. For whatever reason, I'm logged in as "Gina," who is my wife, which means she was signed into Gmail at the time.

Gina is me in this instance.

Nima, lots of citations and books, and a talk at SVP last year. Don't have the energy to find the exact sources. :-(

Nima said...

Oooooops! Didn't know it was you Zach. Hope the real Gina's not upset over this :)

As for the PhDs..... Kevin Padian is one, and he hasn't retracted his views. The other major Pterosaur PhDs I remember are Mark Witton and David Unwin... both of whom disagree with Padian. However, Mike Habib (who's a master, not a PhD) has a similar view to Padian, Paul, etc. which is essentially that there WERE small leg membranes separate from the wings, and a tiny sliver of outer membrane that connected to the wing at a VERY sharp angle (this would explain much of the folding that is responsible for the *apparent* wing-knee attachment)

The fact is there are far fewer people researching Pterosaurs in depth than Dinosaurs... Dinosaurs are just more common and get more attention (and funding).

And Craig, as for Greg Paul and the other guys that also study other things... I think that is not always a negative. It actually enhances one's analytical mind and deductive reasoning. Imagine someone who's spent their whole professional career in museums and researching fossils - their results are prone to be more distanced from reality than those of a researcher who also has studied other disciplines - anatomy and modern animals for instance.

Larry Witmer is a first-class anatomist, though he concentrates mostly on dinosaurs with some impressive 3D sinus models (can't say I agree with his theory on sauropod nostrils - but that's a different matter altogether).

Nearly every PhD paleontologist has backgrounds in other topics - they have to, to even get that far (whether it's in geology or biology or anatomy). How often I have lamented the fact that Paleontology is not a stand-alone field in its own right!

Another point is that despite all their knowledge and research, even PhD's somtimes make serious anatomical mistakes or invent unsupported theories. Dale Russell made quite a few, as did Edwin Colbert, the veritable king of dino-PhDs of his time. Dong Zhiming has probably contributed more to our knowledge of Asian sauropods more than anyone else alive, yet his papers contain skeletons with dragging tails and other anatomical errors. Some of the best PhD's in the history of the field only specialized in bone morphology, and have been anything but good artists and anatomists (even Alan Feduccia, with all his flawed conclusions, is nevertheless a PhD!)

I DO like Mark Witton's art, it's very dynamic and colorful... BUT, I doubt his bat-winged Azdarchids could ever realistically get off the ground with their limbs to restricted like that. Anything that big would have needed a running bipedal takeoff with legs FREE of all restraint, EVEN if it was normally quadrupedal on the ground (which I don't really dispute in any case - big Pterosaurs were probably too top-heavy to be full-time bipeds.)

So when it comes to physical restorations... as long as you have access to the research, or better yet, the source material (as Greg Paul has had) having a PhD isn't necessarily the deciding factor in the accuracy of your art. The simple logic of anatomy (and often physics) is.

And logically, barring any misinterpretation of crumpled fossil wing impressions, ankle-length wings and flying squirrel membranes connecting the legs, are simply awkward and very poorly adapted to any sort of walking - and bad for any sort of takeoff except jumping off a cliff.

THEORETICALLY either side has an equal possibility of being correct. But LOGICALLY, having the wings attach to the base of the tail is far more efficient and results in far more agile (and less vulnerable) Pterosaurs, than the bat or flying squirrel model. And evolution always favors the design that best enables your survival.

Zach said...

I think this is a good example of different models can be tested to figure out which one works best. I don't know if any studies have been done using computer models (or physical models) to simulate differences in flight performance based on different patagia attachments.

As for the cruropatagium, a well-preserved Sordes (don't know the specimen number--I'm looking at a photo) shows the ankles attached by a patagium. The question is whether the cruropatagium attached to the TAIL (thus making it split into two halves) or the tail was free, but the patagium ran up to just below the tail.

As to pterosaurs taking off, they apparently used a leapfrog motion, but I have a lot of trouble visualizing it. Supposedly there's going to be a presentation as SVP this year that demonstrates it with a nice big computer model.

Weapon of Mass Imagination said...

Nima- You have misunderstoodd my point.

I know many of these guys do great work, and I definately know multi disiplinary studies are a great thing... I applogize for asking for a PHD speficially, I wrote that in a hurry without proof reading (aka second thinking) it properly. I am well aware that non professors can write papers, and that PHD's make mistakes...

This comes back to my inital point though, you only addressed my first part of two. The second was the key one.

I asked if any of these workers have "published papers on this topic" I wanted to know if these guys your telling us about have actually had their ideas peer reviewed... as that way I know their ideas have gone through proper scientific scrutiny.

More to the point I want to read it for myself. So I can varify what your stating as fact...

Which I will admit I have taken issue with in your first comment. I am not saying any of this in an angry tone mind you, but simply a call for consideration...

If you are going to tell us about anything "scientific" in nature on ART Evolved please phrase it in its context. If it is a fact, then yes state it as such. However if some point or "fact" has not been proven conclusively or is contensious among workers in the field, then please tell us it is one possibility.

Weapon of Mass Imagination said...

What tiggered me to ask you for these papers Nima is your statements

"Restorations with wings attached to the legs are as old (and inaccurate) as Owen's horned Iguanodon." and "Pterosaurs were mostly bipedal"...

These are written as matter of fact, and something we should all know, and thus change our Pterosaur paradigms to incorporate.

However the impression I am getting from other people's following comments (and my readings) is this just one opinion, and not a certainty among Pterosaur studies.

This to me is a crucial distinction, and one that MUST be made from now on please (EVERYBODY!, not just you Nima... as again I'm not mean to target you. Just clarify conduct in the comments section).

This site is about increasing people's knowledge about palaeontology not bottlenecking it. To state a single opinion as fact, when in fact it is one of many possibilites, defeats any educational purpose we are aiming for.

Especially on a question like the one Peter started off with.

I have been prompted to read more on Pterosaurs today (a good thing) due to this, and so far I'm finding where the wing membranes attached is really not overly certain (but I only did a brief search)...

If it were the case that there was a definate answer known, I'd welcome it. However I'm going to ask everyone from now on to cite papers and sources for such definate facts.

Also if you know it is only one opinion or theory in the research please state that too ;)

So for example, Nima, your reply to my comment was perfect, as you state the possibilities and conflicts in Pterosaur researchers, and state your conclusions as your opinion. So I send you a virtual high five!

Nima this was not meant as a personal attack, but a means of ensuring we ALL keep ART Evolved's quality high.

Though I did take a little offense to your stating the obvious

"The fact is there are far fewer people researching Pterosaurs in depth than Dinosaurs... Dinosaurs are just more common and get more attention (and funding)."

Personally I feel you were talking down to me a little bit like I don't know this (please read my bio post and you'll see I worked at the Royal Tyrrell Museum for 4 years... I'm well aware of the realities in Palaeontology research). Could we please keep talking down comments like this out of the dialouge.

As everyone who'll be leaving comments on this site will likely be a palaeo-enthusiast, such statements of the obvious shouldn't be nessecary.

I'm hoping I just misinterupted your intent and inflection, but it come across as a little confrontational (and condescending... but that again is with my "online reading of" filter, and as we know that tends to be towards the more negative).

However I'm cool if your cool, and don't want to make a thing of it.

I do want to make a thing of just making sure we're presenting the science and art of palaeontology as accurately as we can.

So we ALL need to mak sure we state what is fact and what is theory from here on in!

Nima said...

Hey Craig, I didn't mean to "talk down" to you or anyone else for that matter... so sorry if it came across that way... It's true, the internet isn't the best communicator of voice tone and emotion. Maybe it's just a habit but I tend to include general facts like the situation of pterosaur and dinosaur research for the benefit of anyone reading. (the same caveat applies to this post)... I know you've been working at Royal Tyrell (which, IMO, is one of the best dinosaur museums in the world, I'd love to take a visit someday). I've read a lot of your Traumador blog and I really like it. Indeed, I wish I had your level of storytelling skill. Alas, other passions and interests entrap me...

But I did not assume that everyone reading this blog would know about the present state of pterosaur research - I don't want to give the false impression that my view is any less valid than the opposing one, just because Padian is the only PhD I can find who shares it. So I just wanted to point out for everyone's benefit that there's a paucity of PhD's on EITHER side of the debate, because PhDs who concentrate mainly on Pterosaur research are few and far between. Please don't take it personally. As for papers... I've read Padian's but I don't have a copy, and it's a real pain finding his (or Unwin's or anyone else's) pterosaur papers online.

It's true that bipedal pterosaurs are not "fact" - it has NOT been proven beyond any reasonable doubt. Nor is it likely that it can ever be proven (or disproven) any time soon with full certainty, due to the anatomy of pterosaurs, and now the footprints make it less likely for some groups. I'm not really a big fan of habitual bipedalism in big pterosaurs anyway (though in small ones like Dimorphodon I think it's more likely).

As for free-legged pterosaurs, this also is not "fact" in a scientific sense, any more than the opposing bat-winged model can be "fact". There are wing membranes in pterosaur fossils, but even the best specimens (like Jeholopterus) are notoriously difficult to interpret. With the legs all folded up and the wings not fully outstretched, the exact distal attachment point of the membrane is very hard to pinpoint.

As artists we can illustrate them either way. But I don't think recycling old concepts is necessarily the best way to produce accurate art. And I have an uneasy feeling that the gallery will soon be full of bat-winged pterosaurs... but, each to their own view. I'm not imposing anything.

What I was going for was to point out how clumsy and inefficient the bat winged model is compared to the free-legged model. In terms of scientific evidence, the jury's still out. But in terms to the anatomy and probable lifestyle of these creatures... I don't see how having wings attached to the ankles could be a good adaptation for flight, walking, or much of anything other than a bat-like lifestyle, hanging from cliffs/caves and never landing on the ground further inland.

I too have a hard time fathoming how a big pterosaur could take off from the ground, but it's a lot easier to imagine if the pterosaur is a free-legged one. A combination of flapping and a short bipedal run makes takeoff easier than it would be with legs hampered by a wing membrane.

Mainly I feel that the bat-winged model is a legacy of the flawed "orthodox" view of ornithodires as maladaptive failures, that was so common in the pre-Bakker era, i.e. a very negative and catastrophist view of these creatures. Interestingly though, Bakker actually drew them with wings attached to the legs, but Paul, Conway, Habib and others question this view.

Nima said...

As for scientific papers... I wish I could find Padian's papers online but a google search turned up nothing.

Here's a paper which takes the free-legged view with a model similar to Conway's:

http://pterosaur.stanford.edu/Proposals/ProjectDescription.pdf

Here's a paper which supports a bat-winged model for rhamphorhynchoids based on limb proportions (but makes no such conclusion about pterodactyloids):

http://www3.interscience.wiley.com/cgi-bin/fulltext/118631882/PDFSTART

Here's another article that uses the bat-winged model (but doesn't seem to give a substantive reason for it) and admits that scientific knowledge of Azdarchid flight and wing anatomy is still poorly understood.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002271

here, Witton and Naish point out:

"...controversy over the shape of the pterosaur brachiopatagium has resulted in multiple interpretations of azhdarchid flight style. Langston [17], Wellnhofer [24] and Chatterjee and Templin [16] reconstructed azhdarchids with narrow brachiopatagia extending to the top of the hindlimbs, whereas Frey et al. [74] suggested that the membrane extended to the ankle, forming a much broader wing. No fossilised azhdarchid wing membranes are known..."

So there are at least four other professors mentioned in this paper who favored a free-legged model.

Enjoy.

Dan Varner said...

I suggest viewing this excellent website that will answer a lot of questions (or at least those that can be answered): http://www.pterosaur.net/

Nima said...

Great website Dan!

This is what John Conway says in "Restoring Pterosaurs". (though he does not illustrate with the ankle-attachment model!)

"Historically, the extent and shape of pterosaur membranes has been controversial, and remains so to this day. Many wing-membrane impressions are known, but they are often frustratingly ambiguous as to the attachemnt to the body and hind leg. Most scientists prefer the ankle attachment scenario, which is clearly seen in some pterosaur fossils. Others maintain that there might have been a variety of attachments, and that having the hindlimb free of the main wing would have aerodynamic advantages for the large dynamic soarers (such as Anhanguera and Pteranodon)."

- John Conway

I also agree it would have had advantages... the main one being that takeoff and landing would be a lot easier.

I'm a bit surprised there haven't been more posts on this topic recently :(

Weapon of Mass Imagination said...

Nima- Thanks dude, and again we're cool.

Again I offer a virtual high five! (please don't leave me virtually hanging ;p)

I'm taking the plunge and modifying my 3D stem Pterosaur (I'm aiming for a generic early Jurassic pterosaur for use in a upcoming Traumador project... it is supposed to be non specific unless someone can point out a southern hemisphere 190ish mya pterosaur) to have less wing to leg attachement on your advice. So standby for the new version shortly.

Dan- Thanks for the website! I'll be sure to ubber plug it in the upcoming Pterosaurs in art summary post.

Sadly I haven't had a chance to delve too far into it, and only just scanned it in 5 minutes. It looks like a wealth of knowledge though, and can't wait to focus on it when I have time.

Dinorider d'Andoandor said...

oh, seems like many things I had thought were "facts" may not be that certain.

Nima said...

I just realized something - there are a lot of pterosaur restorations out there (in exponentially varying degrees of accuracy) but one thing I don't see very much is depictions of likely pterosaur BEHAVIOR - There are always paintings of a lone pterosaur flying, maybe even occasionally a group of them.

But they don't really explore anything near the full range of possibilities. I think there should be a bit more interaction between species that likely ate the same foods (various fish-eating Rhamphorhynchoids, for example) or competed for the same space (a bit like Ornithocheirus and Tapejara in Walking with Dinosaurs)

I wouldn't be surprised if some large pteorsaurs killed and ate smaller ones, or even clashed with mesozoic birds in the forests - deadly hot-blooded pterosaur dogfights, the sort of stuff that Bakker loves to draw.

Another thing I don't see too often is pterosaurs as symbionts or scavengers. Yet it's likely that there there were species to fill both roles. Anhanguera, a fish-eater, was almost certainly open to scavenging whenever some huge dead mosasaur washed up on the beach. One use for the large maxillary "knobs" on some large pterosaur skulls could be to push rotten flesh out of the way as the pterosaur poked its snout deeper to eat nutritious organs like the liver.

As for symbiosis - that's nearly impossible to prove, though anurognathids and other tiny insect-eaters like Sordes, seem likely candidates for ridding sauropods of pesky blood-sucking ticks and mosquitoes. Also I'd say look at John Conway's site, which has skeletals of even smaller, possibly arboreal, pterosaurs that might make good symbionts for very tall dinosaurs.

And of course, most interesting of all - baby pterosaurs and nests. Baby pterosaurs are practically unheard of, and rarely illustrated.

SOMEBODY here's got to do a pterosaur nesting scene (and I'll say it up front, I already have a different pterosaur-related piece in the works, so it's probably NOT gonna be me)

I hope these ideas inspire you all.

Peter Bond said...

A huge thank you to Nima, Zach, Craig, Sean and Manabu for this amazing discussion on pterosaur locomotion. It has lead me to search the net and learn and realize that there really isn't a difinitive answer to "where do the wings attach." And that's OK.

Another big thank you to Dan for suggesting the pterosaur website (www.pterosaur.net), where I learned tons!

This discussion has inspired me to attempt to reconstruct pteosaur babies and nests. Not quite sure the subject of the painting, but with the deadline in a month, it's time to choose the genus...