Posts Tagged 'flight'

Pterosaur wingtips – not on the straight and narrow

Take a look at almost any illustration of a pterosaur, be it in a research piece or a life reconstruction and the wing finger is generally depicted as being some kind of straight spar. Each of the four wing finger bones is a dead straight element and the leading edge is therefore basically just a line drawn with a ruler). However, take a look at the actual specimens of pterosaurs and it’s actually quite clear that for lots of them, the last (distal) element is often curved, if only a little, but sometimes quite a lot.

This is really obvious in something like Pteranodon for example (and indeed it’s been noted before that this genus has curved distal phalanges) and yet illustrations of this animal, even in the technical literature, will give it a straight distal phalanx. I’d noted for a while that actually there were quite a few pterosaurs with curved phalanges in particular having looked at Bellubrunnus and its bizarre forward swept wingtips. I’d realised that even the posterior curve might actually have some major flight implications – the shape and position of the very distal part of the wing can have a big impact on vortex shedding and other issues even in static glides and anything like a twist or elevation to the tip can make a huge difference to how it performs.

Knowing this would be an issue and working out what it would be and why are two very different areas and I know enough mechanics for the first and not enough to even begin to think about the second. Enter, somewhat inevitably, Mike Habib and he started looking at this issue and working towards what such a curve would mean both in Bellubrunnus but also those pterosaurs with posterior curves on the distal phalanges. We still needed a good dataset and some actual numbers though and so while I trawled the literature and my photographic archives for examples, any I found I passed onto Matt Van Rooijen who had volunteered to produce both the figures for the paper but also do the detailed digital measuring of the curvature of the phalanges.

The resultant paper is rather light on in depth analysis and numbers because there are potentially some severe issues of taphonomy that can distort the apparent curvature of these bones (in particular reducing a curved bone to look straight) but given the strong consistency of at least some results, there do appear to be some major and genuine signals in the data. There’s some fair consistency within and between clades therefore (and to a degree within and between species of a single genus) so despite the taphonomic issue, it’s perhaps not too bad (though still very hard to estimate or account for).

A number of specimens of multiple genera show that scaphognathines and tapejarids have relatively strong curvature to the distal phalanges and so to do various pteranodontids. In other words, two groups often considered to be highly terrestrial, and another than is highly pelagic both seem to go more for this curvature and others show lesser or no curvature. This might seem rather odd with the two extremes of flying environment / style coming together in morphology but it actually makes a fair bit of sense.

Curvature in the pteranodontids would potentially correspond to an expanded wingtip which aligns with existing hypotheses of the forward swept wing position of these animals in flight. A curved wingtip can also increase the chord of the wing which would be good for terrestrial-based fliers, and also might help protect the wingtip from damage from impact which could be important for animals flying in cluttered environments.

An additional issue comes in here of compliance, a compliant phalanx could potentially also help reduce injuries from impact with things like twigs or even the ground when taking off. Bat phalanges are highly compliant (i.e. bendy) under loads but eyeballing bat fossils at least, there’s no obvious difference between the bones of the phalanges and other elements of the skeleton that are less compliant, so perhaps at least some pterosaur phalanges were highly compliant. In that case under loading in flight they could be considerably more curved, and those of Bellubrunnus might actually be straight in flight!

Overall then this paper has a bit of something for everyone (hopefully). There is likely to be some kind of taxonomic and systematic signal in the presence of curved wingtips though it would have to be treated with caution as a potential character, but that’s also true of lots of other things too, it should not be overlooked. Second, there really does seem to be an ecological signal there which helps potentially restore the ecological habits and habitats of various taxa. There is very much some aerodynamic ideas in here which can be explore further in terms of wingtip shape, and the implications for thing like chord, stall speeds and how this might relate to wing position in flight. Out hypothesis about compliant bone can potentially be tested with histological sampling and finally this should provide a bit more information for those of the artistic persuasion who like drawing pterosaurs. Enjoy!

Hone, D.W.E., van Rooijen, M.K., & Habib, M.B. 2015. The wingtips of pterosaurs: anatomy, aeronautical function and ecological implications. Palaeogeography, Palaeoclimatology, Palaeoecology, 440: 431-439.

Guest Post: The Jack Sprat Effect

Today it’s the turn of Colin Palmer, an aero engineer turned pterosaur researcher in Bristol who takes us through his new paper on their flight mechanics. And inevitably has some issues with how his work was portrayed in the media. Colin of course comes into this problem from the opposite end as do most pterosaur workers, but as he explains, that’s no bad thing… Continue reading ‘Guest Post: The Jack Sprat Effect’

Pterosaurs flew, who knew?

Well, almost everyone of course, but that hasn’t stopped some people claiming that they couldn’t. Or at least that some of the Cretaceous giants like Pteranodon and Quetzalcoatlus couldn’t. The main ‘offender’ of late was a paper I took to task for commenting on pterosaur flight while clearly written by people who didn’t know much about them and was not refereed by pterosaur workers either. If you are going to go out on a limb and talk about pterosaurs in a paper, it might be an idea to learn a bit about them first. If not, you run the risk of making some big errors and wasting other people’s time correcting something that shouldn’t need correcting.

In this case, Mark Witton and Mike Habib have gone out there and made the case for big pterosaurs being flight capable. They also talk about the problems of scaling the giant pterosaurs from rather fragmentary remains and of comparing birds to pterosaurs. So, if you want proof (if it really were needed) that pterosaurs were flying animals, then hop over to the blog where posts are coming, or PLoS One where the paper is freely available. Enjoy.

Oh, and the media have been all over this already, though primarily focusing on the ‘pterosaurs could vault?’ bit, which of course was published in 2008 and got plenty of coverage in 2009 thanks to this. Still, if you want the media side of things then you can see here, here, and here among others (warning: this may include pterosaurs being called dinosaurs. Again).

On a wing and an ankle attachment

Proof, if it were needed, that the team do actually work on pterosaurs and not just blab endlessly about them comes from todays new paper featureing Ross Elgin, myself and Dino Frey. Once more, this is an odd time to talk about it since what has actually turned up are the uncorrected proofs, but it is out there and being read, so now is the time to talk about it. (You can download and read it here, and a very old post of mine here might be a good primer if you don’t know your pterosaur wings too well).

Continue reading ‘On a wing and an ankle attachment’

Guest Post: Fragile feathers cause problems for flight?

My longtime friend and colleague Gareth Dyke has a new paper out this week on the feathers of early birds and the implications for flight. In short ths shaft (rachis) of soem of the flight feathers are a bit weak. He’s kindly (or foolishly) agreed to provide this little post on the origins of the paper:

Continue reading ‘Guest Post: Fragile feathers cause problems for flight?’

Pterosaur tail vanes – presence and structure

Time for some more pterosaurs since we’ve been rather short of them on the Musings for a while. It seems pretty well know than the rhamphorhynchoids are blessed with a long tail, but also a vane of soft tissue at the end of this. However, beyond this, things get a bit murky and quite a lot is often illustrated with little reference to the actual fossils. This is a bit of a surprise as there is really very little known about them since so few are preserved so it shouldn’t be too hard to check up.

First off, what does have a tail vane? Quite a number are known for Rhamphorhynchus itself, and one specimen of Sordes has one as does Pterorhynchus, and, errr, that’s about it. Aside from the taxa listed above, it’s probably fairly safe to assume that most, if not all rhamphorhycnhoids had a tail vane. Pterosaurs are generally fairly conservative in their anatomy, and of course when it comes to soft tissues, these are rarely preserved and so have to be inferred from the few that do have them. Anuroganthids near certainly don’t have one however – not only does the short tail of this clade argue against this mechanically (since the vane is thought to have  role in steering or steadying during flight) but we do have several specimens of anurognathids that preserve soft tissues in excellent condition with no sign of a vane.

Secondly, what lacks a vane? Anuroganthids aside, it’s generally considered that no pterodactyloids have one. Again the mechanics argument comes into play, but also again we do have a number (while admittedly very few) of pterodactyloid specimens with good soft tissues preserved and no trace of a tail vane. Given the huge change in character evolution from the rhamphorhynchoid to the pterodactyloid bodyplan (change in wing proportions, shape of the fifth toes and foot, tail length, skull elongation, neck elongation etc. etc.), this is pretty reasonable.

Tail vanes do turn up quite often in Rhamphorhynchus at least, and appear in cases where the wings are not preserved or not so well preserved which rather implies that they were fairly tough structures. Certainly they are more common and by inference, more robust than wing membranes or foot webbing at any rate (this also feeds back to the point about their absence in pterodactyloids – these should preserve if present). Structurally, all vanes have transverse banding across them which is presumably some form of reinforcement, though where the vanes are composed entirely of skin and interstitial tissues or have perhaps cartilage or anything else involved in their composition is not known.

But what shape were these vanes? If I had more time, that information would be appearing here, but I don’t so it won’t – more tomorrow.

Guest post: Birds in a flap thanks to dinosaur wrists

My latest paper is out today on the subject of theropod wrists. However, first credit must go to project leader Corwin Sullivan who has also penned this post for the Musings on our research. I’ll be adding a bit more tomorrow with my take on the paper, but for now, take it away Corwin….

Continue reading ‘Guest post: Birds in a flap thanks to dinosaur wrists’

The furcula

For many years one of the arguments against birds being dinosaurs was that birds have a furcula and dinosaurs do not. Now clearly the avian furcula (or wishbone) is a highly specialised bone and it is formed by the fusion of the clavicles (the collar bones) but the absence of a furcual in theropods hardly rules out theropod ancestry. After all, basal theropods don’t have feathers, or beaks, or could fly. One rather key concept of evolution is that things change over time, so an absence of a furcula hardly rules them out of contention – nothing else had a furcula either so unless birds somehow sprang out of the ground fully formed, then the furcula had to have a genesis in one lineage or another.

However, despite this obvious flaw in the argument, there is a rather better argument – the presence of a furcula in numerous theropods. A recent survey of the literature and specimens shows that they are now known in coelophysoids, spinosauroids, allosauroids, tyrannosauroids, compsognathids, oviraptorosaurs, torrdontids and dromaeosaurs. Outside of the theropods, there’s clavicles known in a prosauropod and several in some ornithischians. Dinosaurs have clavicles and furculae.

And just to show off what they look like, here is the furcula of Sinornithosaurus. It’s the boomerang-shaped element in the centre of the picture and is quite typical in morphology, though many of them also have a short spar coming out of the middle.

Dragons of the Air

IMGP2431My PhD student Ross Elgin has made an appearance on the Musings from time to time, most notably with his guest post on pterosaur head crests (from his paper that was part of the Wellnhofer volume – still available people!). Now however Ross has launched is own blog too in order to help put his work and that of the ‘Pterosaur Flight Dynamics Group’ based in Karlsruhe into the spotlight.

For those who love their pterosaurs therefore, I suggest you head on over to Dragons of the Air where the first posts are already up, with more to follow, plus of course a number of pages on the research group too. Shamefully this means that I can’t get him to write any more guest posts for me, but on the upside, there’ll be more pterosaur goodness for everyone.  In order to kick things off in as an appropriate manner as possible, have a nice picture of a Tapejara in all its magnificence as can be found hanging from the ceiling in the main hall of the Museum of Natural History in Karlsruhe.


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Pterosaur wing folding

Yes, it’s another picture from Stuttgart (hey, they have some fantastic models) but with a specific purpose this time out, to talk about the way the wings of pterosaurs fold. We have already covered on here the shape and structure of the pterosaurian wing, and the bony structure, and also the mechanism by which the wing finger might extend and retract but here I want to talk about what this might mean in practical terms for a living animal, or at least how things might look.
Continue reading ‘Pterosaur wing folding’

Pterosaur trabeculae

Time for another obscure word in the annals of vertebrate palaeontology and here is one that ties together birds and pterosaurs, if only in a nomenclatural sense. For those that do not know, both pterosaurs and birds have hollowed out, pneumatic bones which in life were filled with air sacs that were extensions of the lungs. However, this obviously could potentially weaken the bones and make them vulnerable to being broken and given the kinds of high forces that many of them would have to deal with (like the bones of the wing or legs for flight and landing respectively) you want to keep them strong.

IMGP2213Evolution has evolved an elegant way around the conflict here – keeping things hollow (and thus light) but strong with some biological scaffolding. The trabeculae are therefore the various small and often intricate little webs and buttresses and spars of bones that populate the insides of various bird and pterosaur bones, providing strength and support to the bone with the minimum of extra mass. These naturally tend to be denser in number and more complex in the ends of bones such as the one pictured here or those with higher stresses and strains, but they can be quite sparse in others.

Inevitably they are little discussed in the literature since in a well preserved bone you can’t see them and even in those that are broken open they are not always visible. Even if they are visible are themselves broken, or as shown here, so complex as to be beyond description. As a result they receive little attention though they are potentially very important as they may help show which bones are taking which stresses where and even in what orientation. As such there may be much functional anatomy hidden in the trabeculae and we have yet to investigate them properly, though with modern scanning methods and further interest beginning this may not be the case for too many more years.

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What on Earth are pycnofibers?
Viewing6You wait month to publish a paper and then two come along in as many days. So with the baby killing theropods now dealt with, we can turn to pycnofibers.

Yes, finally that term all pterosaur workers have been waiting for has been established. Pterosaur ‘hair’, ‘body fibers’, ‘fur’ and the rest can be consigned to the bin to be replaced by the term pycnofiber. A new paper in Proceedings of the Royal Society B led by Alex Kellner (pictured), however redescribes some of the soft tissues from the wonderfully preserved anurognathid pterosaur Jeholopterus from the Yixian and sets this problem to rights by coining the term pycnofiber. It really is more of a housekeeping issue than anything else, but a useful one. Of course that’s hardly the main thrust of the paper in which we discuss the structure of the main wing as well as the pycnofibers themselves with both new observations and some more UV work from Helmut Tischlinger.

Continue reading ‘What on Earth are pycnofibers?’

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