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Were azhdarchid pterosaurs really terrestrial stalkers? The evidence says yes, yes they (probably) were

The views expressed are those of the author and are not necessarily those of Scientific American.


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Life as a tyrannosaurid hatchling might well have been dangerous: GIANT TERRESTRIAL STALKING KAIJU AZHDARCHID OF DOOM!!!!1! Image by Mark Witton.

Regular Tet Zoo readers will be familiar with azhdarchid pterosaurs and the debate that’s surrounded their ecology and behaviour. Within recent decades, these remarkable, often gigantic, long-necked, long-billed but proportionally short-winged toothless Cretaceous pterosaurs have been imagined as ‘mega-skimmers’, as heron-like waders, as obligate scavengers of dinosaur carcasses, and even as sandpiper-like littoral foragers.

All of these ideas are highly flawed if not nonsensical, since they’re inconsistent with the anatomy of these pterosaurs and simply fail to take account of (and even credit) the numerous anatomical features that correlate with those lifestyles in extant animals.

At top, photo of Abyssinian ground hornbill pair engaging in terrestrial stalking behavour (image by Rod Waddington; licensed under Creative Commons Attribution-Share Alike 2.0 Generic license). At bottom, reconstructed skeleton of azhdarchid Zhejiangopterus in quadrupedal walking pose (note that it's exhibiting a pacing gait as well); image by Mark Witton.

Back in 2008, Mark Witton and I argued that azhdarchids possess a suite of anatomical features that make it most likely that they were terrestrial stalkers: that is, that – while they were adept, specialised soarers, great at rapidly covering extraordinary distances – they seemingly foraged on foot in both wooded and open terrestrial environments, walking quadrupedally with an efficient, narrow gait, reaching down with their long necks and bills to grab small animals, bits of carrion and perhaps fruits and other edible bits of plants (Witton & Naish 2008). Azhdarchids don’t have any precise modern analogues, but we suggested that their behaviour and lifestyle most closely resembled that of modern ground hornbills and terrestrial-foraging populations of marabou stork. [Adjacent ground hornbill photo - I really, really love the composition of this image - by Rod Waddington.]

This view of terrestrial stalking azhdarchids receives support from the anatomy and proportions of these animals, from the environments and animal communities in which their remains are preserved, and from trackway evidence (there’s a long, continuous trackway preserved in Upper Cretaceous Korean sediments, seemingly made by a quadrupedally walking azhdarchid*) (Witton & Naish 2008).

* A trackway argued to have been produced by a bipedal giant azhdarchid was recently published. There are some issues with the conclusions of this study. Stay tuned.

If you need a refresher on any of this, check out the articles linked to below – there’s quite a bit on azhdarchids in the Tet Zoo archives, plus the Witton & Naish (2008) paper is open-access and available to all.

Terrestrial stalking azhdarchid, as featured in the Atlantic Productions documentary Flying Monsters 3D.

The terrestrial stalking hypothesis has been reasonably well received within the pterosaur research community and at least a few of our colleagues have said nice things about it. New data on Romanian azhdarchids supports the view that these were animals of continental environments where they were sharing habitats with dinosaurs and other animals uncontroversially associated with inland, terrestrial places (Vremir et al. 2013). New information on the azhdarchid hand is also consistent with the terrestrial stalking hypothesis, since it indicates specialisation for regular terrestrial walking on firm substrates (Carroll 2013, Carroll et al. 2013). Incidentally, terrestrial stalking azhdarchids were featured in the David Attenborough Flying Monsters 3D documentary and (I believe) the hypothesis also gets credited in the new Walking With Dinosaurs 3D movie… which, of course, is now utterly ruined by the fact that the dinosaurs talk. Good work, guys.

The terrestrial stalking model: challenged!

However, if there’s one thing I’ve learnt about human nature, it’s that people will refuse to give up on poorly supported and even nonsense ideas, even when there’s strong or overwhelming evidence to the contrary. So there are still people supporting the idea of water-trawling azhdarchids and wading azhdarchids and so on. In recent months, two challenges to the terrestrial stalking hypothesis have appeared.

The first (I want to spend as little time as possible on this one) comes from the indefatigable David Peters. Peters challenged our hypothesis by posting a comment at PLoS (that’s right, a 2013 comment on an article published in 2008. Weird): he pointed to his own highly suspect phylogenetic results to support the idea that azhdarchids descended from “petite” “micro-azhdarchids” that, in his view, were most likely waders, and he also challenged the idea that azhdarchids look at all like ground hornbills. Mark and I responded (and then responded again, when he responded to our response): you can read the entire chain of correspondence here.

Range of possible neck movement present in Azhdarcho, according to Averianov (2013).

The second challenge was made by Alexander Averianov in a paper mostly devoted to a discussion of neck mobility in the Central Asian azhdarchid Azhdarcho lancicollis (Averianov 2013). Much of the paper is very interesting, since Averianov postulated the range of motion possible in Azhdarcho’s neck, concluding that – while motion was limited – the neck was probably less stiff and straight than usually thought, there being enough flexibility to allow easy contact of the jaw tips with the ground. There are some issues with his conclusions on neck flexibility, but that’s an argument for another time.

Anyway, in the rest of his paper, Averianov (2013) presented three main arguments against the terrestrial stalking hypothesis. He claimed that: (1) azhdarchid fossils might come from continental places, but they’re always associated with sediments deposited in aquatic habitats, and, hence, azhdarchids most likely were aquatic foragers of some sort; (2) claims of strong terrestriality in azhdarchids would require them to inhabit places where big, terrestrial theropods occurred, and this is surely untenable due to the danger these big predators would have presented to a grounded pterosaur; and (3) azhdarchids possess mandibular characters better consistent with the idea that they pulled the lower jaw through the water while in flight, catching prey in a mandibular pouch. In short, Averianov (2013) argued that azhdarchids should be interpreted as water-trawling ‘skimming pelicans’, not as terrestrial stalkers. This is a… novel way of imagining azhdarchids, and (in my and Mark’s opinion) a very odd one.

There's a theme to my azhdarchoid publications -- can you guess what it is?

When your own work is challenged, I consider it good practice to respond in print… unless, that is, that your argument or data really has been trounced. So Mark and I set about producing a response: we didn’t submit it to the same venue as Averianov’s (2013) original paper (Paleontological Journal) because (when possible) we use open access journals. Rather, it was submitted to Acta Palaeontologica Polonica where it’s currently – technically – ‘In press’, and will be regarded as so for several more months yet (Witton & Naish 2013). It actually appeared online back in October but I haven’t had time to write about it until now.

So, what do we say? I don’t want to go into the whole argument in enormous depth, partly because Mark already covered it at his blog back in October and also because, again, you can read the full article yourself… it’s fully open-access. So let’s keep this short (Err.. that didn’t work out so well, sorry).

On the claim that azhdarchid fossils are always associated with sediments deposited in aquatic settings… note to start with that fossils are, across the board and across all taxa, most typically preserved in aquatic sediments. As we say in the paper, this is true of “fossil cattle, giraffes, primates, and perching birds” (Witton & Naish 2013, p. 4): it tells you little to nothing about lifestyle. In any case, Averianov’s generalisation is misleading, since there are azhdarchid fossils from volcanic rocks and even from sediments deposited in deserts. Do these support strong ecological ties to an aquatic lifestyle? No. We think it significant that azhdarchid fossils often come from arid places; in fact, some of the geological locations that yield the highest number and greatest diversity of azhdarchids represent dry, terrestrially exposed environments (Witton & Naish 2013).

Shock horror: you can probably walk around in the Mesozoic without being eaten!!

Averianov’s second point is that azhdarchids would be too vulnerable to terrestrial predation to permit a lifestyle dedicated to terrestrial foraging. Our response to this argument is perhaps the most novel part of our manuscript, since it allowed us to say a lot about Mesozoic ecology and animal behaviour that people don’t say often enough.

Despite what you may have heard, the Mesozoic was not like this, all the time. Image by Mark Witton.

For starters, the idea being promoted here is that the Mesozoic was so over-run with rapacious uber-predators that vulnerable animals would surely be snatched up and devoured instantaneously. While environments frequented by big animals are, to a degree, potentially dangerous, the fact is that animals of all sorts – hypothetical time-travelling humans included – could certainly wander about the habitats of the Cretaceous world without being instantly grabbed, disemboweled, consumed, torn limb from limb, or swallowed whole. Predators, even big ones, aren’t on the prowl constantly, they don’t live everywhere, and they might even ignore or avoid unfamiliar, formidable or awkward animals that might otherwise look like potential prey. This goes for the modern world as well as the Cretaceous one.

Another point: most time we see Mesozoic predation events discussed or illustrated, it’s allosauroids taking on giant sauropods, tyrannosaurids fighting adult ceratopsians, and so on. People don’t make the point enough that predatory theropods – even the giant tyrannosaurids that Averianov had in mind – likely preferred cute little baby animals (Hone & Rauhut 2010) to big, gnarly, difficult-to-kill adult ones. So, not only were giant theropods not a constant, ubiquitous menace, we should also keep in mind the fact that they would have gone for easy, lazy meals whenever possible.

Azhdarchids: quite capable in a fight, thank you very much

Fact: big storks can walk around without getting eaten by big predators. They're actually very good at looking after themselves. Marabou, by Nino Barbieri; licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

And it’s important to note that azhdarchids were far from flimsy and helpless, as Averianov (2013) implied in his argument. The big ones really were big (shoulder heights of 2.5 m or so, head height of 4 m), had robust skulls and huge, pointed rostra more than 1 m long, and would have superficially recalled giant storks – a group of animals that are more than capable of defending themselves against big animals (witness the cases of Jabiru vs tapir, Jabiru vs human zookeeper, Marabou vs human child) (Witton & Naish 2013). [Adjacent photo by Nino Barbieri.]

Mark produced this excellent illustration (from Witton & Naish 2013) to show how a giant azhdarchid would compare to a giant theropod. Hopefully you get the point that we’re trying to make: even the biggest, badassest, hungriest Tyrannosaurus is (we not unreasonably assume) going to thing twice about tackling that azhdarchid, and it might well decide not to do so at all. Furthermore, some azhdarchids were the biggest predators in their ecosystems anyway – the biggest theropod living alongside Hatzegopteryx from Romania is Balaur, and it somehow seems doubtful that this 2-m-long maniraptoran was any kind of danger to the azhdarchid.

A giant azhdarchid is a formidable beast. This illustration - from Witton & Naish (2013) - shows (A) Tyrannosaurus, (B) Romanian maniraptoran Balaur, (C) the long-necked giant azhdarchid Arambourgiania, and (D) a human, all to scale. Image by Mark Witton, from Witton & Naish (2013).

In short, Averianov’s (2013) contention that azhdarchids would have been too vulnerable to terrestrial predators to permit a terrestrial stalking lifestyle is highly arguable, and probably flat out wrong. Averianov (2013) also said that an azhdarchid would be unable to get quickly into flight when rapid escape was needed. Obviously, this ignores recent work on quadrupedal launching (Habib 2008, 2013, Witton and Habib 2010), all of which shows that azhdarchids could actually launch immediately into flight from a quadrupedal standing start.

Azhdarchids: water-trawling pelican-skimmer hybrids? Err, no

A pelican can use its mandible as a scoop-net because its mandible is highly specialised for this function. Can an azhdarchid do likewise? As this diagram shows (see Witton & Naish (2013) for the details).. no, it cannot.

Finally, Averianov (2013) also contested the terrestrial stalking hypothesis by proposing that azhdarchids used their lower jaws as ‘scoop nets’: he specifically suggested that the form of azhdarchid jaw joints allowed these animals to expand the halves of the lower jaw outwards and then use the whole lower jaw (plus a throat sac) as a fish-catching scoop, employed in flight. In other words, he proposed that azhdarchids combined both a pelican-like use of the lower jaw with a Rynchops-like skimming habit. Hm.

We see quite a few problems with this proposal. Put simply, the form of the azhdarchid lower jaw is absolutely inconsistent with the idea of notable outward movement of the halves of the lower jaw, the very long mandibular (inflexible) symphysis would have incurred enormous drag if the lower jaw was trawled through the water, there’s no good reason to think that a throat sac was present (Witton & Naish 2013), and the whole idea of skim-feeding in pterosaurs is essentially untenable for functional and energetic reasons (Zusi 1962, Humphries et al. 2007, Witton & Naish 2008). For the full, detailed argument (we worked out the mandible and throat volume of both large and small azhdarchids and did other fancy calculations), do see the paper… did I mention that it’s open access?

Captive White pelicans (Pelecanus onocrotalus) display the remarkable mandibular bowing and 'scoop-netting' that pelican mandibles are specialised for. Photo by Darren Naish, from Witton & Naish (2013). Image CC BY.

Terrestrial stalking: support from multiple lines of evidence

The whole idea of terrestrial stalking azhdarchids can be considered multi-layered: Mark and I developed the hypothesis as we first saw a consistent pattern emerging from the form of azhdarchid skulls, proximal forelimb bones, wing-fingers, proximal hindlimb bones and feet, and from their overall, ‘pseudo-ungulate’ proportions (Witton & Naish 2008, 2013).

The terrestrial stalking hypothesis is based on multiple lines of evidence: it does not (like so many other hypotheses about pterosaur behaviour and ecology) rely on cherry-picking one or two anatomical or palaeoenvironmental features. This image - from Witton & Naish (2013) - shows how several independent pieces of data all provide support for our hypothesis.

The sedimentological, geographical and environmental context of the azhdarchid fossil record adds strong additional support to our model, and trackway evidence adds soft tissue and postural data as further support (Witton & Naish 2008, 2013). Furthermore, azhdarchids lack the anatomical features you expect for the various other lifestyles that have been proposed for the group – they lack any and all features associated with skim-feeding, with sediment-probing, and with wading, for example. So, if somebody seriously wants to overturn the terrestrial stalking model, they have to come up with a model that better explains the several lines of evidence that we marshalled together. Thus far, that hasn’t happened.

As we approach the end of December, I begin to look back at all the stuff that happened during the year. 2013 wasn’t bad as goes my output on azhdarchids and their relatives, the azhdarchoids. Together with colleagues, I described the new Romanian azhdarchid Eurazhdarcho (Vremir et al. 2013), the small, Isle of Wight tapejarid-like Vectidraco (Naish et al. 2013), and of course published the paper on azhdarchid lifestyle and ecology that you’ve just been reading about. But, alas, there are several other projects that both Mark and I (with co-authors) presented at meetings, and which we simply weren’t able to get finished and published. They will appear eventually. If only we weren’t so lazy. Oh yeah: Mark also published a giant BOOK on pterosaurs. Ah yeah, about that…

For previous Tet Zoo articles on azhdarchids on other azhdarchoid pterosaurs, see…

Refs – -

Averianov, A. O. 2013. Reconstruction of the neck of Azhdarcho lancicollis and lifestyle of azhdarchids (Pterosauria, Azhdarchidae). Paleontological Journal 47, 203-209.

Carroll, N. 2013. Functional morphology of the azhdarchid manus. Journal of Vertebrate Paleontology 33, Supplement to Issue 3, 102A.

Carroll, N. R., Poust, A. W. and Varricchio, D. J. 2013. A third azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana. In: Sayão, J. M., Costa, F. R., Bantim, R. A. M. & Kellner, A. W. A. International Symposium on Pterosaurs, Rio Ptero 2013, Short Communications. Universidad Federal do Rio de Janeiro: pp 40-42.

Habib, M. B. 2008.Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana B28, 161-168.

- . 2013. Constraining the air giants: limits on size in flying animals as an example of constraint-based biomechanical theories of form. Biological Theory. doi: 10.1007/s13752-013-0118-y

Hone, D. W. & Rauhut, O. W. 2010. Feeding behaviour and bone utilization by theropod dinosaurs. Lethaia 43, 232-244.

Humphries, S., Bonser, R. H., Witton, M. P. & Martill, D. M. 2007. Did pterosaurs feed by skimming? Physical modelling and anatomical evaluation of an unusual feeding method. PLoS Biology 5: e204.

Naish, D., Simpson, M. I. & Dyke, G. J. 2013. A new small-bodied azhdarchoid pterosaur from the Lower Cretaceous of England and its implications for pterosaur anatomy, diversity and phylogeny. PLoS ONE 8: e58451.

Vremir, M., Kellner, A. W. A., Naish, D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8: e54268.

Witton, M. P. & Habib, M. B. 2010. On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PLoS ONE 5: e13982.

- . & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3: e2271.

- . & Naish, D. 2013. Azhdarchid pterosaurs: water-trawling pelican mimics or “terrestrial stalkers”? Acta Palaeontologica Polonica doi: http://dx.doi.org/10.4202/app.00005.2013

Zusi, R. L. 1962. Structural adaptations of the head and neck in the black skimmer. Publications of the Nuttall Ornithological Club 3, 1-101.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Gigantala 6:59 pm 12/15/2013

    Averianov’s paper and it’s utter lack of professionalism infuriates me to no end. At least David Peters bothers to read other papers, even if his conclusions are nonsensical.

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  2. 2. Shuhray 9:17 pm 12/15/2013

    They had wings with holes (like a net) and fished, I had a dream.

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  3. 3. Finback 9:22 pm 12/15/2013

    I want, nay, *demand* we get a new genus named Killstorkodoom. And is Benedict Cucumbersandwich the new standard of scale? I thought it was girls in bikinis, or is that just for proboscideans? :)

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  4. 4. Yodelling Cyclist 9:39 pm 12/15/2013

    Is there any information as to how rapidly the giant azhdarcids grew/matured?

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  5. 5. David Marjanović 10:39 pm 12/15/2013

    For lack of money, papers from the West are still poorly accessible in Russia.

    And I’ve heard a gruesome story about what peer review in Russian journals looks like. Short version: there basically isn’t any.

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  6. 6. David Marjanović 10:41 pm 12/15/2013

    Oops. My previous comment was a response to comment 1.

    I thought it was girls in bikinis, or is that just for proboscideans?

    It’s very, very tiny girls in bikinis. ;-) They’re never to scale.

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  7. 7. Dino Hunter 11:36 pm 12/15/2013

    Azhdarchids have been found in a variety of environments which include Marine. How does that fit in with terrestrial feeding? Couldn’t they have had different feeding styles? It turns out though, not all are huge animals, but many are smaller ones with a wing span of 2 to 3 meters, how do they fit in with terrestrial feeding?

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  8. 8. vdinets 1:00 am 12/16/2013

    A combination of long-distance soaring with quadripedal foraging and very small body suggests adaptation to some ephemeral, rare, but easy to digest food. Egg clutches at communal nesting grounds? Carrion from regular die-offs? Fish in drying-out ponds? Mass fruiting of something? Is there any way to tell from the bill wear?

    I’m trying to imagine skim-feeding with a pelican-like bill. Wouldn’t any flier that tries it be instantly stalled by water resistance? Why not simply skim-feeding with a skimmer-like bill?

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  9. 9. Andreas Johansson 1:25 am 12/16/2013

    Did Arambourgiania really stand that erect? The other azhdarchids illustrated seem to hold their bodies at much lower angles.

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  10. 10. Dartian 3:24 am 12/16/2013

    Darren:
    terrestrial-foraging populations of marabou stork

    They are separate populations?

    There’s a theme to my azhdarchoid publications — can you guess what it is?

    The obvious answer would be that you prefer to publish in open access journals, but that would be too obvious. So I’m going to go with the guess that you like to start your paper titles with the indefinite article ‘a’. ;)

    Oh, and the the human scale in your figure is indeed obviously based on Benedict Cumberbatch. Is that a subtle hint of a forthcoming Tet Zoo article on the biomechanics and the ecology of Smaug? ;)

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  11. 11. jtdwyer 3:41 am 12/16/2013

    What did they eat? I seem to have difficulty envisioning pterosaurs running around after a mouse or squirrel. Maybe I could see it eating a clam or bugs, maybe even a crab – something within its reach. BTW, storks don’t have to awkwardly walk on their wings…

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  12. 12. naishd 3:50 am 12/16/2013

    Thanks for comments, lot to reply to. I’ll start with Dino Hunter’s comment # 7…

    Azhdarchids have been found in a variety of environments which include Marine. How does that fit in with terrestrial feeding?

    As discussed in Witton & Naish (2008), the majority of specimens come from terrestrial environments, and the specimens from marine strata mostly come from units where taxa have been derived from terrestrial environments. See Fig. 2 in the paper (a graph). Since dead animals (and bits of dead animals) frequently get transported down rivers and into the sea, preservation in the marine environment does not = life in the marine environment. Having said all that, of course it’s not impossible that some azhdarchids did live close to, or forage in, coastal places. But do they have any adaptations that look specifically linked to life in the marine environment?

    Couldn’t they have had different feeding styles?

    Sure. But do we have evidence for this?

    It turns out though, not all are huge animals, but many are smaller ones with a wing span of 2 to 3 meters, how do they fit in with terrestrial feeding?

    Yes, the fact that azhdarchids belong to several size classes has been mentioned throughout the body of work we’re referring to here (have you seen Vremir et al. (2013)? It specifically discusses the issue of different size classes. And Dyke et al. (2010) reported an azhdarchid cervical centrum that would have been about 10 cm long when complete). There is no claim that terrestrial stalking only works when gigantic taxa are being considered: the model applies to small azhdarchids as well given that they exhibit the same morphological features discussed throughout this work.

    Refs – -

    Dyke, G., Benton, M., Posmosanu, E., & Naish, D. 2010. Early Cretaceous (Berriasian) birds and pterosaurs from the Cornet bauxite mine, Romania. Palaeontology 54, 79-95.

    Vremir, M., Kellner, A. W. A., Naish, D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8: e54268.

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  13. 13. naishd 4:00 am 12/16/2013

    Response to vdinet’s comment # 8…

    A combination of long-distance soaring with quadripedal foraging and very small body suggests adaptation to some ephemeral, rare, but easy to digest food. Egg clutches at communal nesting grounds? Carrion from regular die-offs? Fish in drying-out ponds? Mass fruiting of something? Is there any way to tell from the bill wear?

    I’d say that a combination of long-distance soaring with a stork-like rostrum suggests a stork-like ability to eat just about anything. The azhdarchid rostrum does not look specialised for anything in particular, other than for picking things up. We have no data on bill wear (remember that we only have bones, not the keratinous beak tissue itself). Fingers crossed we, one day, get stomach contents from one of these animals.

    I’m trying to imagine skim-feeding with a pelican-like bill. Wouldn’t any flier that tries it be instantly stalled by water resistance?

    As Mark and I show in the paper (Witton & Naish 2013) – and see Humphries et al. (2007) as well, you simply can’t skim-feed with an azhdarchid mandible, it’s not possible to move the mandible through the water at speeds consistent with flight. In fact, the aerial ‘scoop-netting’ model suggested by Averianov would require neck-snapping forces something like 300 times the normal bending stress of the vertebrae.

    Why not simply skim-feeding with a skimmer-like bill?

    It’s surprising that some pterosaur workers still don’t get just how remarkable, unusual and specialised skim-feeding is. Rynchops has more than 30 obvious cranial, mandibular and vertebral specialisations for its skimming lifestyle, all of which are obvious in the skeleton, not one of which is seen in the pterosaurs that keep getting mentioned as possible skim-feeders.

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  14. 14. MarkWitton 4:50 am 12/16/2013

    Andreas: Azhdarchid forelimbs (excluding the wing finger) are about 30% longer than the hindlimbs. This combines with a very short torso (about 70 cm long in the biggest forms) to give azhdarchids a fairly erect stance when walking. I suspect the low stances of other illustrations reflect the fact that pterosaur torsos are almost always illustrated longer than they should be.

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  15. 15. Jerzy v. 3.0. 8:51 am 12/16/2013

    Well, storks, ground hornbills and marabous have no trouble avoiding predators in African savanna. I think height was important to spot predators from the distance. In any case, feet of azhdarchids show (I take your word here) that they had to cope with terrestial predators, because they couldn’t climb trees nor swim.

    I am quite interested how these things grew. Were they fed and quickly grew to near the adult size like birds, or lived independently and grew slowly over the years?

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  16. 16. David Marjanović 10:18 am 12/16/2013

    BTW, storks don’t have to awkwardly walk on their wings…

    Why “awkwardly”? The simulations of walking pterosaurs I’ve seen look very elegant indeed.

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  17. 17. Yodelling Cyclist 10:23 am 12/16/2013

    Has anyone ever calculated the top running speeds of these animals?

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  18. 18. VelocitySquared 2:19 pm 12/16/2013

    A lot of focus seems for and against methods of locomotion are based on the bones themselves and not the signs of connective tissues, cartilage and muscles attached to the bones. The size and shape of the joints just by eyeballing the bones really looks a bit like it could support a knuckle walking. The joints are the critical part of the equation in my opinion: Those joints are going to be very telling from impact stresses over time. If you had a specimen that you knew died of old age you could really tell how it moved over its lifespan.
    Of course I haven’t read the research yet so I’ll just shut my mouth now. :)

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  19. 19. Stripey_cat 3:30 pm 12/16/2013

    What had me really ranting was the ridiculous assumptions A. made, that break his own argument. Even if his assertions are right, and they were from lacustrine/riverine environments, and they needed a running take-off, they still could have been terrestrial foragers because *not all wetland environments are really soft*. Analogy to extant animals: I will get mired if I try to run or walk in soft sediments or moss, but I can still cross a floodplain or even peat bogs because I learn what vegetation is associated with substrates that won’t bear my weight. Does he assume that azhdarchids are too stupid to distinguish safe footing from dangerous? Also, wouldn’t large terrestrial predators have exactly the same problem anyway? T. rex pes does not look adapted to running in quicksands or sphagnum bog. Were there lots of crocodiles that miraculously escaped fossilisation in all the pterosaur-bearing assemblages?

    Also, how the heck does he jump from “not terrestrial feeders” to “skim-scoop hybrid method”? Does he even consider an actual pelican-like float and grab/scoop technique? Or would that require take-off abilities he’s already rules out by fiat? (Never mind that the jaws aren’t appropriate for this, as he claims that they are.)

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  20. 20. Boesse 5:37 pm 12/16/2013

    I’m a bit confused regarding the hybrid Pelican/skimmer hypothesis… from a mandibular function perspective, they are totally mutually exclusive adaptations. Skimming as in Rhynchops requires a transversely compressed and narrow symphyseal region, generally going hand in hand with a fused mandibular symphysis… whereas a pelican/balaenopterid feeding style requires an unfused mandibular symphysis with mandibles that rotate about their longitudinal axes. The two are morphological extremes and don’t exactly have much overlap where both behaviors can be optimized…

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  21. 21. JAHeadden 6:56 pm 12/16/2013

    Response to Boesse @ 20: Pelican mandibular symphyses are fused (Class IV). Where the bending occurs is proximal to the symphysis itself: bending cocurs at then regions in the mandibular rami, and at several points along it, allowing it to bend outward. To accommodate this, the mandibular symphysis is very short, which increases gular dimensions rostrocaudally. However, the criticism of a Rhynchops-like symphysis with Pelecanus-like bending zones is apt: the mandible of Rhynchops has to resist very high oral-gular compressive forces, and bending zones at and around the symphysis would increase potential distortion and cause the jaw to warp and twist or turn to the side.

    Jaws in azhdarchids, depending on the species, still seem extremely inapt for resisting very high oral-gular compression, but there are biomechanical elements of the jaws, especially of the symphyses, that haven’t been modeled to permit any conclusions other than the general on how they were used. Gross shape similarities — like comparing to maribou — is one thing, but hasn’t been demonstrated to be more consistent with the hypothesis than other, less maribou-like behaviors. (I am not saying Witton/Naish hypothesis is in correct, mind.)

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  22. 22. Heteromeles 7:59 pm 12/16/2013

    Personally, I think of azhdarchid beaks as forceps from hell, possibly evolved for forcibly extracting small animals from what passed for savanna in their time.

    The one thing that hasn’t been brought up is that there were no grass-dominated savannas in the mesozoic. The ground cover neither looked like nor acted like grasses, and the closest modern analog we have are fern-fields (although the wet end of American tall-grass prairies is pretty impenetrable too). That seemingly awkward long beak might be very well adapted for penetrating such a ground cover to extract delicious morsels hiding therein. Conversely, a theropod would have to beat its way in or wait for prey to come into the open.

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  23. 23. Dino Hunter 11:27 pm 12/16/2013

    Thanks Darren, I’ll check those out again. And don’t the morphology of the wings work against a gliding/skim feeding foraging? I’ve thought that a terrestrial Azhadarchid would look very thin on the ground, and may be hard to see by a predator. But when the predator came to close it’d stand on its hind limbs and quickly spread its wings and scare off the predator…ok, it wouldn’t happen…

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  24. 24. Chelydra 11:34 pm 12/16/2013

    I want, nay, *demand* we get a new genus named Killstorkodoom

    Fatorciconia? My Latin is very rusty. Fātum needs to be plural in order to mean doom. Ciconia was apparently also a rude hand gesture, presumably reminiscent of a stork.

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  25. 25. Chelydra 11:36 pm 12/16/2013

    That should have been a blockquote from Finback, comment #3.

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  26. 26. Tayo Bethel 11:39 pm 12/16/2013

    When we say “small” prey, how small do we mean? A pterosaur weighing up to 250 kg would need some substantial meals to keep its metabolic fires burning. … Or be constantly active.
    Slightly off-topic–do we have any evidence at all to show that allosaurs actually attacked adult sauropods? While many allosaurs are quite large predators they dont seem designed to topple the living monoliths that adult sauropods living in the area would have been. In fact, they seem to be built to take down prey of their own size or smaller.

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  27. 27. ChasCPeterson 12:10 am 12/17/2013

    Totally off-topic, but I thought Darren would want to see Kevin Padian’s abstract for the upcoming SICB meeting:
    http://www.sicb.org/meetings/2014/schedule/abstractdetails.php?id=550

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  28. 28. John Harshman 10:17 am 12/17/2013

    Totally off-topic, but I thought Darren would want to see Kevin Padian’s abstract for the upcoming SICB meeting:
    http://www.sicb.org/meetings/2014/schedule/abstractdetails.php?id=550

    Oh dear.

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  29. 29. John Harshman 10:18 am 12/17/2013

    Hey, Darren. Blockquoting isn’t working.

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  30. 30. David Marjanović 12:55 pm 12/17/2013

    It has never worked here. Scientific American is too stupid to expect a discussion in blog comments, apparently believing that comments are only for saying “keep up the good work” over and over.

    I resort to italics…

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  31. 31. David Marjanović 2:19 pm 12/17/2013

    Fatorciconia?

    I recommend you use “killstork” as the genus name and “of doom” (fatorum?) as the species name. Then, further species can be called “of death” and so on. :-)

    While many allosaurs are quite large predators they dont seem designed to topple the living monoliths that adult sauropods living in the area would have been.

    Why topple? Just bite. Not even strictly biting, actually, as using the upper jaw as a hacksaw. Killing is an inevitable byproduct, it’s not the goal; eating is.

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  32. 32. naishd 3:29 pm 12/17/2013

    Thanks for comments. Some quick responses…

    Dino Hunter (comment # 23): wing loading and planform indicates that azdharchids were soarers, perhaps similar in flight style to storks and vultures. Furthermore, they have wing form characteristics suggesting adaptation to takeoff and movement in cluttered habitats. The data against skim-feeding is pretty damning.

    Tayo Bethel (comment # 26): on the size of prey items, the giant taxa had a space of about 50 cm between the jaw joints. Thus they could likely consume animals up to size of… humans. We have no direct evidence as to their diet, but check out Mark’s article here. I think we can take seriously the idea that they used accurate, rapid strikes to grab lizards, mammals and small dinosaurs, at least.

    More in a moment…

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  33. 33. naishd 4:10 pm 12/17/2013

    More responses…

    Yup, as David says, blockquote never works here. Mark off quoted sections with carriage returns and put them in italics: seems to be obvious enough.

    As for the new Padian & Horner paper… needless to say, neither I nor the colleagues I’ve spoken to can see eye-to-eye with the argument here. I, personally, continue to be troubled by the fact that P&H think that they alone can redefine terms used widely in biology and claim the high horse on “what Darwin actually said”. Beyond that, the article is snipey and personal (quotes from Humpty Dumpty… seriously?), it is shot full of holes in logic, and it’s a re-hash of previous papers. I wonder why it ended up in CR Palevol?

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  34. 34. Andreas Johansson 4:17 pm 12/17/2013

    Darren wrote:
    the giant taxa had a space of about 50 cm between the jaw joints. Thus they could likely consume animals up to size of… humans.

    Wouldn’t the dinky torsos and therefore presumably stomachs be more of a limit here? Or are we to imagine deep sea fish style stomach distension?

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  35. 35. naishd 4:32 pm 12/17/2013

    Andreas: that’s a fair enough point; but, no, we don’t need to posit black swallower-like stomach distention, merely that they have the jaws and gullets required to grab and swallow small and even mid-sized animals and other objects. An animal similar in size to a domestic cat, say, is going to be an easy swallow for a giant azhdarchid. For the smaller, stork-sized ones.. well, you can imagine them swallowing prey similar to those swallowed by the storks.

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  36. 36. Stripey_cat 4:36 pm 12/17/2013

    There’s a fossil pterosaur of some sort with a partially-digested fish preserved that takes up most of its torso. Sorry I can’t remember more usefully. Mark Witton did the calculations on weight capacity and reckoned that a large Azhdarchid could fly carrying a small adult human, internally or externally (there was a brilliant pair of posts a while back on pterasaur.net discussing hypothetical human-azhdarchid interactions, and predation was considered).

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  37. 37. Hydrarchos 2:25 pm 12/18/2013

    I’ve always found the huge heads and tiny torsos of pterosaurs in general really bizarre and hard to believe that such an animal could really “work”. Where did they fit their lungs, livers, etc? And wouldn’t such a huge head, unbalanced by a significant tail, have given them huge problems (whether walking or flying) with balance due to their centre of gravity being so far forward?

    Something with a 3m-long skull and a torso smaller than mine just seems ridiculous to me – am I missing something?

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  38. 38. Tayo Bethel 10:26 pm 12/18/2013

    Sorry … wrong wording. I personally don’t hold with the hacksaw theory. Yes, eating is the goal .. but in most cases large prey has to be immobilized in some way before the eating can commence.

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  39. 39. Heteromeles 10:07 am 12/19/2013

    @Hydrarchos: A couple of things: One is that pterosaur bones are quite thin, and the bones more air sacs even than birds. The other thing is something I learned from planes: what matters is the center of gravity. As long as the center of lift from the wings goes through the center of gravity, it’s not a problem. We’re kind of fooled by birds, because feathers are really light structures, and we’re used to those very long, but very light, bird tails. It’s somewhat more useful to look at bat skeletons instead.

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  40. 40. Yodelling Cyclist 12:46 pm 12/19/2013

    Tyo Bethel: Yes, eating is the goal .. but in most cases large prey has to be immobilized in some way before the eating can commence.

    True, though modern African hunting dogs have been claimed to eat their prey on the hoof. Death by blood loss just happens along the way. If the predator is small enough and agile enough compared to the prey, darting in for a chunk of flesh becomes a reasonable solution. Particularly with pack mates to distract attention.

    Also, because I have to share this, apparently at least one human has made a habit of eating cats. Alive.

    http://en.wikipedia.org/wiki/Charles_Domery

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  41. 41. David Marjanović 2:36 pm 12/19/2013

    Azhdarchid skulls consist mainly of foam… and lungs with an air sac system can afford to be much smaller than those of a mammal of the same body size.

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  42. 42. Tayo Bethel 10:56 am 12/20/2013

    @Yodelling Cyclist
    … Gruesome.
    Since we have no evidence for allosaur hunting behavior, this topic will likely remain open–probably indefinitely. I personally imagine allosaurs as solitary predators adapted to taking down prey of up to three times their body size, using their flexible hands to grasp the prey. A paper by Anton (2009) might be of interest–he makes a strong case against the hacksaw theory.

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  43. 43. ProgradeBurn 2:45 pm 12/24/2013

    I now really wonder how T. rex and Q. northropi interacted with each other. While I cannot really see the azhdarchid as a credible threat to a fully grown tyrannosaurine (and vice versa, the pterosaur would simply fly away), they could easily predate on young tyrannosaurs. If the growth figures of Erickson are indeed correct, I would assume that adult Tyrannosauruses almost certainly lived together with their young. On the same note, Quetzalcoatlus did probably sit in about the same ecological niche as juvenile Tyrannosaurs and Nanotyrannus, if this genus is valid.

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