Tetrapod Zoology

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If I hadn’t spent so much time yesterday socialising and celebrating Will’s 6th birthday, then this post – the third part in my series on the events of the Wellnhofer pterosaur meeting (part I here, part II here) – might have been finished earlier. Oh well, priorities and all that. Before I start: I assume everyone who visits Tet Zoo knows that scienceblogs is holding a 500,000th comments contest: whoever posts the 500,000th comment will win a 5-day trip to the ‘greatest science city in the world’ (and there is a vote as to exactly which city that might be). So, anyway, as if you didn’t have one already, you now have a really compelling incentive to post comments: arguably as many as possible.

I finished part II by briefly discussing the controversial subject of how extensive the brachiopatagium was in pterosaurs. And on the subject of controversies, another subject that came up a few times was the exact location and orientation of the pteroid. The pteroid is a unique rod-like bone that projected from the pterosaur wrist and helped support the propatagium, a part of the wing that extended from the shoulder to the wrist and probably helped control air-flow over the rest of the wing. While it has generally been assumed (based on articulated, but often flattened, specimens from Solnhofen and elsewhere) that the pteroid projected medially toward the shoulder, a novel orientation was proposed by Frey & Riess (1981). They argued that the pteroid projected forwards, parallel to the animal’s sagittal axis, creating a broader, much bigger propatagium than that traditionally imagined. While this hypothetical configuration was initially criticised quite heavily (e.g., Padian 1984), it has more recently received support both from articulated Chinese specimens (e.g., of the anurognathid Jeholopterus), and from new studies of pterosaur aerodynamics (Wilkinson 2007, Wilkinson et al. 2006).

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In order for this configuration to work, however, the pteroid has to articulate with the lateral carpal bone (aka preaxial carpal or medial carpal) in a manner that allows it to point forwards. Those who favour this orientation have therefore shown the pteroid articulating with the ‘tip’ of the lateral carpal, and fitting into a socket in this area (e.g., Unwin et al. 1996, Wilkinson et al. 2006). In a discussion section held toward the end of the meeting, Chris Bennett presented data showing that the pteroid did not or could not articulate with the lateral carpal in this manner: the socket favoured as the area for the pteroid’s proximal end was occupied instead by a sesamoid, and the pteroid instead articulated on the medial side of the carpal on a small convex eminence. Chris will give two boxes of Canadian beer to anyone who can demonstrate that the pteroid really did articulate with the carpal in the manner favoured by Wilkinson and colleagues. Incidentally, Chris only offers one box of beer for the discovery of nessie or sasquatch, so you know he’s serious [the adjacent reward posters are from Chris' website here].

One recently described, articulated pterosaur wrist – that of the nyctosaurid Muzquizopteryx (ironically, described by Dino Frey and colleagues) – provides strong support for Chris’ contention that the pteroid points medially, not forwards. But what about the Jeholopterus specimens I just mentioned above? Well, the bizarre thing is that, while this taxon shows a forward-pointing pteroid and a large propatagium, the pteroid in this taxon does not appear to be articulating with a carpal at all! I will say no more on this subject for the time being. My preliminary conclusions are that (1) in most pterosaurs, the pteroid did indeed point medially and not forwards, but (2) in at least some taxa, the pteroid did point forwards, but did not fit into the socket on the lateral carpal, but elsewhere.

Chris also gave a talk, mostly on how the pterosaur hand might have become reoriented during evolution. Because the three clawed fingers of pterosaurs flex anteriorly while the wing finger (digit IV) flexes posteriorly, it has often been thought that metacarpal IV must have rotated about its long axis in order to reorient the plane of flexion of digit IV. If that were true, however, we should expect the extensors and flexors of digit IV to loop around metacarpal IV, and instead these muscles seem to have run parallel to the metacarpal in standard fashion. Digit IV was probably not ‘twisted’ after all: instead, it was the orientation of digits I-III that changed as the limb became adapted for flight.

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I mentioned Mike Habib in some of the previous articles. He spoke about Bennettazhia: CT-scanning of the holotype (a complete humerus) revealed internal trabecular bracing consistent with the idea that azhdarchoids launched quadrupedally into flight. As you can see from the adjacent picture, Mike could give Jerry Harris a run for his money when it comes to making small creatures out of restaurant napkins. Pterosaur wing mechanics and flight were also looked at by Laurence Browning and colleagues: a Finite Element structural analysis of the wing bones of Anhanguera piscator gave some idea of how the wing would have deflected under load, and a scale model was constructed to test the same ideas.

A unique view of pterosaur wing morphology and evolution was presented by Dietrich Schaller: Schaller contends that pterosaurs had a remarkably narrow brachiopatagium, divided into several distinct segments, and his views on how the wings must have evolved led him to propose a new classification with new taxonomic names (including such gems as Brachiokaiskelopterida and Rhamphorhynchomorpha). It is difficult to be confident that he’s right, given that his views on wing anatomy are based on the apparent compartmentalisation of the Zittel wing as deduced from a blown-up photo (Schaller 1985, 2007).

On a personal level, it was interesting and pleasing to see Mark Witton – one of my closest allies (he knows too much) – give his first presentation at an academic conference, and it both looked excellent (in terms of graphics and artwork), and was academically sound. It concerned pterosaur mass estimates: the entrenched dogma within pterosaurology is – to quote Greg Paul – that pterosaurs were ultralight airbeings (Paul 1991, p. 88). Indeed, I particularly enjoyed the following exchange during Mark’s talk…

Mark: “Greg Paul has been saying this for a while but he’s been…”
Someone in audience laughs loudly
Mark: “Well, laughed at”

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As most interested people will now know, by employing various methods, Mark found that pterosaurs were not sky-beasts composed of 90% air as most people seem to have been saying; instead they were animals about comparable in mass to what you might guess from similar-sized birds and other tetrapods. A good, detailed discussion of Mark’s work can be found here at his flickr site. Despite concerns that he might need to do the talk from within a cage or behind some fencing (much like that scene in The Blues Brothers) in order to avoid the beer bottles and vegetables lobbed in his direction, Mark’s talk was well received and he made a very strong case. A giant pterosaur like Quetzalcoatlus – “It could look a giraffe in the eyes”, said Mark – couldn’t really have weighed 50 or 60 kg or so, but was actually more like 250 kg (that’s still very, very light for its size of course: the giraffe in the picture might weigh 2000 kg). In another desperate effort to emphasise my importance within our field (joke), I will note that I’ve been stating this for ages. In best, intuitive fashion, I have never been able to take seriously the idea that, say, a tetrapod with a 5 m wingspan really weighed 6 kg, let alone 50 kg in the case of the 10-11 m Quetzalcoatlus.

At the risk of seeming like a taxonomic stamp-collector, I am always very much excited by announcements of new species; consequently one of the most jaw-dropping of presentations at the meeting was Rico Stecher’s on a new and totally unique Triassic pterosaur from Switzerland. This animal has to be seen to be believed (sorry, I don’t have any pictures), and I’m pleased to say that a paper is in the process of being published. Without giving all the details away, this animal – while very clearly a true pterosaur – looks like no other pterosaur yet described, particularly in its superficially theropod-like skull. It is heterodont, with campylognathoidid-like multicusped posterior teeth, interlocking anterior teeth (a diastema separates these two regions of the dentition), a rostral dentary crest, and a great big nasal horn! Its fully inturned femoral head indicates parasagittal hindlimbs. Its humerus is notably long and slender. As Dave Hone pointed out, the fact that multicusped teeth of this sort occur in this taxon might mean that we will have to re-evaluate all the other multicusped pterosaur teeth that have been referred to Eudimorphodon. Expect to hear a lot more about this taxon on Tet Zoo in the future: I will definitely blog about it. I was, incidentally, going to publish an article on Caviramus schesaplanensis that had the title ‘The strangest pterosaur ever’. Caviramus is still a very, very strange pterosaur (albeit one known only from a lower jaw), but Rico’s new animal takes the biscuit (or whatever the phrase is).

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As I’ve stated a few times, there was loads more stuff than what I’ve covered here: these three articles are just the edited highlights. The conference ended with Peter Wellnhofer giving a talk on the history of pterosaur research: earlier in the meeting he had been given a new painting by Luis Rey, produced specially for the meeting. It depicts both Archaeopteryx and a fleet of ornithocheiroids; the adjacent photo shows Peter with the painting, and comes courtsey of Marcus Moser.

As I’ve mentioned before, the conference was also outstanding in that we got to see multiple really, really significant and/or interesting pterosaur fossils, including a number of new, as-yet-unpublished specimens and taxa. I was particularly taken with the new, tiny anurognathid (soon to be published by Chris Bennett), and by the fantastic ‘Painten pelican’ (a new taxon from the Solnhofen limestone). We also got out of the BSPG and visited the Bürgermeister-Müller-Museum and Jura Museum, both the repositories of more outstanding specimens; Martill, Witton and I had to dash off at midday however, so we didn’t get to go to the Jura Museum (we’ve all been there before however).

So, all in all, it was awesome. I learnt a lot, and saw a lot, and met lots of new people. Again I must say how awestruck I am that Dave Hone and colleagues put together such a successful meeting; I also owe Dave personal thanks for the accommodation and for access to his flat-mate’s alcohol supply. The next pterosaur meeting is scheduled for 2010 and will be held in China – I doubt if I’ll be going, but you never know.

Refs – –

Frey, E. & Riess, J. 1981. A new reconstruction of the pterosaur wing. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 161, 1-27.

Padian, K. 1984. A large pterodactyloid pterosaur from the Two Medicine Formation (Campanian) of Montana. Journal of Vertebrate Paleontology 4, 516-524.

Paul. G. S. 1991. The many myths, some old, some new, of dinosaurology. Modern Geology 16, 69-99.

Schaller, D. 1985. Wing evolution. In Hecht, M. K., Ostrom, J. H., Viohl, G. & Wellnhofer, P. (eds) The Beginnings of Birds – Proceedings of the International Archaeopteryx Conference, Eichstätt 1984, pp. 333-348.

– . 2007. The superordinate pterosaur evolution as deduced from the evolution of their wings. Verlag Dr. Friedrich Pfeil, München.

Unwin, D. M., Frey, E., Martill, D. M., Clarke, J. B. & Riess, J. 1996. On the nature of the pteroid in pterosaurs. Proceedings of the Royal Society of London B 263, 45-52.

Wilkinson, M. T. 2007. Sailing the skies: the improbable aeronautical success of the pterosaurs. Journal of Experimental Biology 210,1663-71.

– ., Unwin, D. M. & Ellington, C. P. 2006. High lift function of the pteroid bone and forewing of pterosaurs. Biological Society Proceedings 273, 119-26.

Comments

  1. #1 Richard Hing
    September 21, 2007

    Finally, after all this talk singing the praises of these obsolete monsters, Luis Rey has drawn a picture of the noble bird banishing the evil pterosaur overlords, sending these horrific visions back to the Hell from whence they came. Too long had these grotesque, creaking, antiquated leviathans ruled the primordial skies, in the days when the Earth was young, indeed, it’s a miracle that these cold-blooded scaly gliders were able to stay dominant for as long as they did. Thankfully, birds were able to conquer the air to usher in a new era of peace and glorious diversification.

    Ave Aves!

  2. #2 Darren Naish
    September 21, 2007

    Uh-oh, Richard’s medication has run out again.

  3. #3 Richard Hing
    September 21, 2007

    Go fish!

  4. #4 Darren Naish
    September 21, 2007

    Go San Dimus High!

    [reference]

  5. #5 Andreas Johansson
    September 21, 2007

    I can’t resist pointing out that when the first pterosaur reared it’s ugly head against the bird-free skies, the Earth was already something like 95% of it’s present age.

  6. #6 David Marjanovi?
    September 21, 2007

    Uh-oh, Richard’s medication has run out again.

    And how he’s unhinged…?

    <duck & cover>

  7. #7 Dave Hone
    September 21, 2007

    Well Darren I am glad you finally got your quote in. Thanks for an amazing write-up on the meeting – it makes me look good!

    Glad you coulkd make it and I *WILL* see you in Beijing 2010!

  8. #8 Scott
    September 21, 2007

    Argh, another Archaeopteryx with mythical tertials illustrated!

  9. #9 Mike Keesey
    September 21, 2007

    (San Dimas — I’ve driven through many times but never stopped.)

    A Triassic pterosaur with a theropod-like skull and parasagittal hindlimbs. Wow. Sounds like a good candidate for being outside the clade of all other known pterosaurs.

    Which brings up an interesting issue to the nomenclaturally-minded: what is the cutoff point for Pterosauria? To my knowledge, the only definition published to date is a node-based one specified by about a dozen internal genera. Using that, if this new guy is outside the clade of all other known pterosaurs — well, then it’s just not a pterosaur.

    To my thinking, this nicely illustrates that a node-based Pterosauria is a crappy idea. It should be apomorphy-based, something like, “the first ancestor of [i]Pterodactylus antiquus[/i] to possess forelimb wings constructed of skin membranes supported by digit IV homologous with the wings of [i]P. antiquus[/i], and all descendants of that ancestor” (preferably accompanied by a more detailed description of the apomorphy). Then the new guy could join the club.

  10. #10 Mike Keesey
    September 21, 2007

    Actually, on second thought, it sounds more like a derived theropod-mimicking pterosaur than a very basal one. (Which is still extremely cool, of course.) But, given how little we know about pterosaurs, who knows? (And the nomenclatural dilemma still holds, although it becomes less immediately important.)

  11. #11 Zach Miller
    September 21, 2007

    Darren, promise me…PROMISE ME…that you’ll PDF me a copy of that new Triassic pterosaur! IT IS TOO AWESOME FOR WORDS! PARASAGGITAL LIMB POSTURE? THEROPODIAN SKULL?!? CRESTS AND HORNS????

    *brain implodes*

    It’s…it’s all too much. And really, what better time to describe a “missing link” pterosaur than right after I blog about who the damn ancestors are? *squeals with glee*

  12. #12 Dave Hone
    September 22, 2007

    Having been editing Rico’s paper on this little baby I can confirm that both the humerus and femur are really, really odd. This little critter has a whole bunch of very strange features and although I have yet to run it through a cladisitc analysis, my hunch is that it is from a new family. It *may* nest at the base of Eudimorphodontidae, but I doubt it.

    Either way it is obviously very basal, though clearly holds some highly specialised and derived characterisitics (not least the crest *and* the expanded mandible). Rico tells me the paper is due out early next year and he has already collected more material which is in preparation.

  13. #13 David Marjanovi?
    September 22, 2007

    Darren, promise me…PROMISE ME…that you’ll PDF me a copy of that new Triassic pterosaur! IT IS TOO AWESOME FOR WORDS! PARASAGGITAL LIMB POSTURE? THEROPODIAN SKULL?!? CRESTS AND HORNS????

    *brain implodes*

    It’s…it’s all too much. And really, what better time to describe a “missing link” pterosaur than right after I blog about who the damn ancestors are? *squeals with glee*

    Sit down.

    Close your eyes.

    Empty your mind.

    And then fill it with:

    … WAIT … FOR … THE … PAPER … … WAIT … FOR … THE … PAPER … … WAIT … FOR … THE … PAPER … … WAIT … FOR … THE … PAPER …

    :-)

  14. #14 Tengu
    September 22, 2007

    Richard, whats this new fangled thing about dinos learning to fly?
    It will never catch on.
    (back from a head scratching session with a African Grey Dino.)

  15. #15 Brad McFeeters
    September 22, 2007

    Regarding the new Triassic pterosaur, wouldn’t its phylogenetic position depend on which outgroup is used? If pterosaurs are the sister group of dinosaurs, it could be the most basal one. If pterosaurs aren’t archosaurs, it could be a derived dinosaur-mimic. The description reminds me of Dimorphodon, which has a kinda theropod-like head and was one reconstructed as a runner…

  16. #16 Mike
    September 22, 2007

    Darren is too self-effacing to do this, so I’ll point out that TheScientist.com has asked people what their favourite science blogs are. Three of us have mentioned Tet Zoo so far. Folk can go to The Scientist if they want to give Darren props in the hope that with more traffic donations will keep him from having to sit by the road with a sign saying ‘Will Identify Roadkill for Food’ and maybe even get him part way to China.

    Darren: if you’re not sure you want more traffic, feel free not to let this post not appear. I don’t aim to cause you problems.

    [from Darren: traffic? I like traffic; traffic is good. Many thanks for the support - let the flow of cash commence]

  17. #17 arachnophile_grrl
    September 22, 2007

    I am LOVING all the information from Wellnhofer but FOR THE LOVE OF GOD, MAN, what is that pelt you posted before you left!

    *achem*

    Sorry for that outburst. I’ll be much more mature in future posts, I promise. ;)

    First time poster – LOVE the site B.T.W.

    [from Darren: thanks for the comment/outburst... news on the frustrating pelt to come soon, I promise. Really :)]

  18. #18 Dave Hone
    September 23, 2007

    Brad, I can assure you that this thing is no derived theropod. It is absolutely and unquestionably a theropod. As to the phylogenetric position, there are of course issues with outgroups when analysisng pterosaurs and while I will do my own informal analysis, whoever does this properly for the new genus will have to be careful.

    Nevertheless, there should be no significant problems for typing and assessing its likely relationships. Plus as I mention above, Rico has some more material that should add to our knowledge and help fill in some blanks.

  19. #19 Nick
    January 21, 2008

    Luis’s painting is great (as always), but does it look to anyone else a little like the Archaeopteryx is conducting a chorus of ornithocheiroids?

  20. #20 Darren Naish
    January 21, 2008

    I should note that – despite what I said in the article – those pterosaurs might be ctenochasmatoids rather than ornithocheiroids (and yes I know that this would be more appropriate: I’d assumed initially that Luis was using artistic license). I suppose I should ask Luis.

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