How to grow your dragon – pterosaur ontogeny

Life reconstructions of Rhamphorhynchus on display in Munich.

The giant pelagic pterosaur Pteranodon is probably the most famous, and is certainly the most iconic, of pterosaurs and specimens and casts of this show up in museums around the world. There’s something like 1100 specimens in public collection and plenty more in private hands. Unfortunately though, almost all of them a squashed very flat and they are often rather distorted and worse, the overwhelming majority are very incomplete and often composed of only a few elements. They are also almost all of a good size (‘subadult’ and up) with only one specimen recognised as being something close to juvenile in age. That means that while this is an amazing number of specimens, it’s also really quite hard to work with as the data is limited in lots of ways.

However, if we turn to Rhamphorhynchus we have only a fraction of the number of specimens but pretty much all the other issues are absent. Most specimens are complete or at least have a very healthy amount of the specimen present, they are often flat but show nothing like the distortion of Pteranodon and there are even fully 3D specimens. They also cover a near order of magnitude in size with everything for animals of c 30 cm wingspan up to nearly 2 metres and include everything from putative hatchling-sized animals to a couple of genuine outliers that are much bigger than other known individuals. Thus despite the relatively low numbers they represent and absolutely fantastic resource for studying various aspects of pterosaur biology.

The numbers of course are not tiny, well over 100 good specimens, and that alone would make them an exceptional sample of most terrestrial Mesozoic archosaurs. The legendary Solnhofen researcher Peter Wellnhofer catalogued over 100 of these in his amazing 1975 monograph on them and this dataset has become an industry standard for pterosaur research ever since. However, we are still discovering more and there are plenty sitting in various collections around the world that nave never entered the literature because, well, there’s already 100 of them out there. But even big samples are improved with the addition of more material and so for the last decade I’ve been scouring collections and databases and hunting down every specimen I can to add it to Peter’s data. That takes us from his total of 108 to 129. The ‘real’ total is actually a little lower since several of his were in private hands and two of mine are casts, though of unique specimens, and not all of these are complete. Even so, it represents a hefty increase in the available data and marks the first major increase in the catalogue in 45 years.

Obviously I’m not going to make a dataset like that and sit on it, so this post inevitably marks the publication of an analysis of growth in Rhamphorhyunchus. In a lot of ways, this mirrors Chris Bennett’s fantastic 1995 paper on this genus where he convincingly demonstrated that all specimens belonged to a single species and not multiple ones as previously thought, and part of his arguments for doing this looked at the relationships between various elements based on Wellhofer’s dataset. Chris’ point was that while there were some discreet clusters of specimens (which he attributed to year classes) most of the alleged differences between the putative species vanished when you put them on a graph and the rest were classic ontogenetic traits like the fusion of the pelvis in large individuals of big eyes in small ones. So while he didn’t really deal with growth as such, he was already showing similar patterns to what I and my coauthors confirm now – Rhamphorhynchus was weirdly isometric in growth.

In other words, in the case of the vast majority of their anatomy, young animals are basically just scaled down adults. This is a weird proposition for a terrestrial vertebrate as most undergo some quite notable and even extreme allometry with some parts proportionally growing and others shrinking as they grow. Think of young animals with big eyes, in big heads and large hands and feet, or antelope with especially spindly legs and so on. But in the pterosaurs even the smallest animals are, aside from the eyes, basically carbon copies of the adults.

One of the less well preserved Rhamphorhynchus out there, it nevertheless has most elements intact

To put this in context we looked at another group of quadrupedal, powered flying vertebrates with bony spars supporting membraneous wings, the bats. Yes, obviously they are not ideal in terms of their ancestry but functionally they are about the best analogue you could get for a pterosaur. Looking at their development we see that juveniles have proportionally very small wings and right around the time they start to fly and become independent, their wings grow rapidly. This is the pattern we would expect, young animals have only so much they can invest in their development and growing wings that are not being used is what we would expect, exactly as things like sheep (and indeed dinosaurs) don’t grow their horns until they reach sexual maturity, they are not being used before then. We do though, see the bats developing their legs early as they need to grip into cave roofs and their mothers so it’s not a case of overall reduced development of limbs, but clearly selective growth.

Birds are functionally poor analogues of pterosaurs but are much closer phylogenetically and are the only other powered flying tetrapod so we also looked at some existing datasets for them too. Most birds, unsurprisingly have allometric growth of various elements, but like bats the legs develop before the wings with one notable exception, those that are hyperprecocial. Some birds like mallee fowl are capable of flying within days, or even hours of having hatched from the egg. These birds have isometric growth and this immediately then suggests that Rhamphorhynchus at least (as has been suggested before) was precocial and flying while young.

This may sound correct since if you are flying when young and flying when adult you probably want to be the same but that’s not the case. As a flying animal in particular, relying on wings to hold you up you have a problem. If you grow isometrically you wings will get longer and wider but your weight will increase much faster since you as a whole will get longer and wider and deeper. So mass will increase much faster than wing area and that can only have a profound impact on how you fly. There are two things that might offset this, first of all different animals can use different flying gaits at different sizes which might mean that performance is not quite as different as might be predicted from this (though we’d still expect juveniles to be more agile) and secondly, changes in pneumaticity. Birds increase penumaticity as they grow and there’s evidence this is the case in other pneumatic clades too and if so for pterosaurs, then the mass increase in adults would also be offset somewhat by a proportionally lower mass in adults for a given volume than juveniles.

Precociousness has been suggested in pterosaurs before based on the evidence for them flying while young, but it has also been challenged. It suggested that to be flying at that size would require a huge amount of effort and this would leave little energy for growth. That’s largely true, but overlooks that there could be post hatching parental parental care. That is normal for archosaurs (including dinosaurs) and we would expect it for pterosaurs. Being precocial in terms of the ability to move does not mean they have to be independent, things like horses have babies that are capable of running within hours of birth but are still suckled for months, and various ducks take their ducklings out to sea soon after hatching. That’s obviously not the quite same thing as the energetics of flight, but it does show that being a good locomotor is not mutually exclusive with parents protecting and feeding their offspring.

So in short, Rhamphorhynchus is perhaps the best pterosaur for large studies about populations and growth and this genius at least grew isometrically, and this may or may not be the same for other pterosaurs. This then may or may not have some big implications for pterosaur taxonomy which is often based on the ratios of various wing elements. But it does imply that young pterosaur could fly, and fly well and that adults and juveniles were probably flying in different ways to each other and that could then have implications for where and how they foraged and what they ate. This is an incremental step in our understanding of this group (and again, much of what we say has been said before but this firms things up nicely) and hopefully opens up the options for further research on them as living animals.

 

The paper is open access and available here:

Hone, D.W.E., Ratcliffe, J.M., Riskin, D.K., Hermanson, J.W. & Reisz, R.R. 2020. Unique near isometric ontogeny in the pterosaur Rhamphorhynchus suggests hatchlings could fly. Lethaia.

Big wings in the Solnhofen

The Solnhofen limestones of Bavaria are famous for their well-preserved fossils and for a pterosaurs researcher, the plethora of specimens and taxa that are represented. Finds continue to this day and we now have more species known from more specimens than ever before, including from a variety of a branches of the pterosaurian tree. The Late Jurassic was an interesting time with the pterodactyloids diversifying, the non-pterodactyloids soon to fade (though doing pretty well) and a few intermediates (wukongopterids, or if you prefer, darwinopterids) are still about. One thing that is true of all of them though is that they are not very big.

While later pterosaurs are famous for producing numerous lineages with wingspans well in excess of 4 and 5 meters and all the way up to 10, before the Cretaceous, there’s basically nothing that even gets up to 2 m in wingspan, and even those tend to be relative giants and quite rare. This is especially true of the Jurassic pterodactyloids which really don’t seem to have got going yet in the size stakes. However, there are some tanatalising hints of bigger individuals or even big species with various bits of limb elements (and slightly bizarrely, some isolated but articulated feet). Not much has been done with these in part because they tend to be very incomplete.

However, quite a few years ago now, Dino Frey at the Karlshue museum in Germany acquired a complete and articulated wing of a large Solnhofen pterodactyloid. It was much bigger than any other known complete wing and it eventually feel to Ross Elgin (then a PhD student under Dino and myself) to work on. We started on this and worked up a manuscript and then sometime later I happened to be in Berlin and spotted on the wall of the collections, another, equally large (though rather less complete and less well preserved) Solnhofen wing. This has apparently sat all but ignored for many years and as far as we can tell, it’s never featured in any paper or been referred to before. So now we had two wings to describe, each of which would have been from an animal with a wingspan of just over 2 m and they turned out to be pretty similar to each other, but what were they?

Working out what they were took some work. After all, it’s perfectly possible that these represent known taxa, but are merely unusually large individuals. And with only the wings to go from, a lot of the anatomical data you would normally want from the skull or some gross proportions of the neck, legs and so on are missing. To make it more awkward, we don’t have a great understanding of the growth patterns of many pterosaurs so it’s not obviously what the trajectories might be of the rarer species where we have only a few specimens.

Looking in detail at our two wings and various other larger Solnhofen pterodactyloids and other isolated large wings showed that these two new ones are different to each other and there are likely two different ‘big wing’ morphs present. A number of major pterodactyloid clades are either around or at least suspected to be present in the Jurassic, and so there was a wide range of possible candidates. However, the anatomy present ruled out most of them (ornithocheiroids, istiodactyloids, azhdarchoids) though it did leave the identity uncertain and they could be ctenochasmatids or very early dsungaripterids.

So while we don’t know exactly what we have here (and we suspect there’s a new taxon in this material based on some unusual features of the Karlsruhe specimen) it is still interesting stuff. We now have a good record of all the largest Jurassic pterodactyloids and clear evidence of animals of over 2 m wingspan. We also have much more detailed information on their anatomy and while the exact identities are uncertain, it looks like there is more diversity here than previously realised and that there are more taxa to be discovered. New specimens are still being uncovered in the Solnhofen so hopefully it is only a matter of time until we have complete, large, pterodactyloids before the Cretaceous.

The paper is open access and fully available here.

Elgin, R.A. & Hone, D.W.E. 2020. A review of two large Jurassic pterodactyloid specimens from the Solnhofen of southern Germany. Palaeontologica Electronica.

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.

A new German ‘Darwinopterid’ pterosaur

Regular readers of the Pterosaur.net blog will have already seen this post and might well have put two and two together and realised that this is ‘Darwinopterus’-like pterosaur from the Solnhofen. We are still waiting some kind of proper description on this (and it’ll need a name too) but it has had a mention in the literature and been on show a number a times. It’s incomplete and disarticulated, but it’s far from a bad specimen and very obviously has the classic features one would expect – a combined nasoantorbital fenestra, a big head, and yet some rather more basal features in the wings and feet.

Darwinopterus is the key taxon that helps us join up the basal pterosaurs and pterodactyloids, and there’s been a series of taxa named from the Chinese Daohugou beds that lived alongside this genus (a number of which are probably synonyms to be honest) as had made China the centre for this. Still, a couple of specimens from the UK have been found (or rather, rediscovered) that suggest these forms might have been more widely distributed and once they appeared in China, the Solnhofen and surrounding beds then became an anomaly – they were full of both pterodactyloids and basal forms, so surely the intermediates might have also hung around and been present given the numbers seen in China.

Now though a second one has turned up in Germany and it’s a lovely specimen of what is a small, and juvenile animal. The preservation is superb, and as Helmut Tischlinger has been working on it, there’s obviously some exceptional images, but there’s also some interesting features.

The short paper covering this animal is in German, so I might well be repeating things already said in the manuscript, but I’m going from only the English abstract and figure captions and my own thoughts, so this might be badly mangling or even completely replicating things already written. If so, my apologies to the authors or anyone else who has read the paper.

For me the more obviously interesting features all lie in the back end of the animal. First off as you can see below the distal phalanx of one wing had had a nasty break and then healed with a mass of bone that least the end at a rather major angle compared to the proximal part. There are a few pterosaur pathological wings out there, but this is quite a big one.

Secondly the tail is rather short. In my paper on pterosaur tails with Lu Junchang we suggested that Darwinopterus might have a tail of rather intermediate length between the classic ‘long’ and ‘short’ tails and this specimen might be going the same way. Not only that, but the tail also seems to have relatively short zygopophyses that are barely as long as the abutting centrum, whereas Darwinopterus at least has very Rhamphorhynchus-like ones that are very long.

The fifth toe also seems to be something of an intermediate – it is not a small nub like the pterodactyloids, but nor is the second phalanx that long and it’s not curved either as in other basal forms. Finally, the wing metacarpal looks to my eye to be rather longer than in other non-pterodactyloids. In other words, at least some of these features look to me not just to lie between the non-pterodactyloids and pterodactyloids, but actually somewhere between what we see in Darwinopterus-like animals and the pterodactyloids.

In short, this is not just a lovely-looking and intriguing specimen, but it certainly helps to fill in the ‘missing’ part of the Solnhofen and surrounding beds (this one is from Painten). Moreover, at first glance at least, it offers some tantalising prospects for looking at the evolution of characters towards the origin of the pterodactyloids and the changes especially to the wing metacarpals, tail and feet (all key characters for wings / control surfaces) and what this may have meant for their biology. More on this and other specimens is coming, so there’s some interesting work to be done and much to find out.

Tischlinger & Frey. 2014. A new pterosaur with mosaic characters of basal and pterodactyloid pterosauria from the Upper Kimmeridgian of Painten (Upper Palatinate, Germany). Archaeopteryx, 31: 1-13.

 

Edit: Helmut has asked me to clarify that in the paper he and Dino do not say this is an animal likely to be specifically part of the Wukonogpteridae (i.e. Darwinopetus and kin) but suggest it is closer to the pterodactyloids.

Parapsicephalus

A last left-over AMNH pterosaur and again I’m most grateful to Steve Cohen for the photos. This is all there is of this little taxon (assuming you think it’s valid – Dave Unwin sank it into Dorygnathus, but Kevin Padian kept it separate in his more recent review of Dorygnathus). I don’t know where the original specimen is, but as it was from the UK I assume it’s here and that this is a cast, but if so it’s rather a good one.

The view here is dorsal, looking down on the skull (well, most of the skull) with the posterior part at the top of the picture and the snout pointing down as seen. As you can hopefully make out, this is essentially an incomplete skull which as I recall has no teeth in it. Just another incomplete pterosaur, but nicely preserved and in 3D which is always a bonus for such a basal animal.

Camplognathoides

Bit of a late one today! I’m slipping.

Anyway, this is the horrible-to-spell Campylognathoides, a basal non-pterodasctyloid pterosaur known from Lower Jurassic beds. This is an especially nice specimen that’s on display in the Carnegie (how did you guess) and shows off things like the sternum which is all too rare for pterosaurs.

One thing Campylognathoides does give me the opportunity to talk about is pterosaur systemtics. Those in the know will be aware that for about a decade now there have basically been two competing pterosaur phylognies that have fundamental differences and never seem to meet in the middle (though there have been suggestions that Darwinopterus might just fix this issue). However, as Dave Uniwn is fond of saying (and quite rightly) for all that people highlight the disagreements between these phylogenies, there is really quite a lot of fundamental agreement, and the two trees are in a lot of ways really pretty congruent. One thing that is certainly common in both is the sister-taxon relationship of Campylognathoides with Eudimorphodon and that at least is one thing it appears pretty much everyone agrees on.

Quetzalcoatlus

There are various mounts of this giant pterosaur around the world. I’ve seen versions in Germany and Mexico and I know of a couple of others that are out there. I have even managed to get one photo on the Musings before, but usually the things are so big and so close to the ground that there’s no way of fitting much into a photo. This one is nice and high up however and it’s possible to show off the whole thing (though ironically, once you do, it’s so huge that many of the bones look tiny). At the Carnegie, not only is this so elevated you can get a real appreciation of it, but thanks to the presence of a balcony, you can see it in something approaching a lateral view which is a novelty for me, and certainly changes your perspective.

Solnhofen wall

One thing I was not aware of before my first visit to the Carnegie is that they have a superb collection of Solnhofen material. Better yet, there is a major display of this alongside the Jurassic dinosaurs in the form of a massive case that is literally crammed full of fossils. Naturally this is dominated by fish of various sizes, but there are other things like turtles, plants, insects and the like. Obviously for me, I was pleased to see several pterosaurs including this rather nice and near complete Pterodactylus below.

Darwinopterus + egg = awesome

Many of you may have seen this already, but a new paper is out with what can only be described as a female pterosaur. This is big news, while there have been suggestions in the literature (most notably about Pteranodon) about some specimens representing males or females, this is one rather more convincing than many for the simple reason that there is an egg associated with it. That it is another Darwinopterus and a great specimen too, only adds to the interest.

The egg, sadly, lacks any trace of an embryo (though this is perhaps not surprising as obviously the egg was only about to be laid, not about to hatch) but has all the characteristics of pterosaur eggs and is the right size and shape. It also lies between the legs of the female and just behind the pelvis. That it is not in the body is not a major issue – a similar situation is commonly seen with icthyosaurs for example where decomposition leads to bloating of the body and forces out anything large and solid like a late term embryo or as in this case, and egg that’s ready to be laid.

Oddly enough the real interest in the paper lies in the head of the animal. The egg clearly points to this being a female but the head has no trace of a crest, despite other specimens of Darwinopterus having one (as you can see here for example). The strong suggestion therefore is that Darwinopterus is sexually dimorphic with males having crests and females none. The authors make a pretty good case, though a hatful of other specimens with other consistent differences in something approaching a 50:50 split would be better still.

One note of warning I would add though, is not to take this too far. Such extrapolation is fine for Darwinopterus, but I’d be very wary of taking the same basic criterion and applying it to other pterosaurs. Just as a quick example, many antelope and bovids have horns in males and females, and some can be nearly identical between the two, and in reindeer the females have antlers for parts of the year when males have none, while in most deer of course only males present antlers. I suspect it’s a matter of days before we see the first crested pterosaur specimen = male (or no crest = female) blog posts or media reports but this would be, for me, a very big assumption too far. A great start yes, but not even the end of the beginning for pterosaur dimoprhism.

Special thanks to Lu Jungchang for these special photos.

Guest post: Gwawinapterus – a new Canadian pterosaur

Those with an ear to the ground might well have heard already about Gwawinapterus a new istiodacylid pterosaur from Canada. This is quite a find as it represents the first istiodactylid from outside Eurasia and is by far the most recent extending both the geographic and temporal range of the group. Describer Victoria Arbour, (who also writes the rather entertaining Pseudplocephalus blog about her dinosaur travels) takes us through the history of the find and the difficult identification of the jaws.

Those damned ropens again

This thing has sat around for the best part of a year, and I never got through the images that I had indeed so it’s had a bit of a rewrite and is being shoved out into the harsh light of day. It might not work to well therefore, but should be OK.
……………………………………

I am big football fan and being stuck in China I often have to rely on reports for details of games rather than watching the game or even the highlights. Recently (err, last season now) I read two different reports of the same goal as scored by my team Tottenham. In one, the final pass was delivered by Luca Modric, in the second the pass was by Tom Huddlestone. Why is this interesting? Well the reporters were professional football journalists, who I assume have a lot of practice at following the on field drama and then writing it up. For football at least, the journalists sit together in the press box, so if someone does miss an event they have colleagues (and of course TV replays) to help them get it right. Frankly I am scared that someone could confuse Tom with Luca. For a start the names of the shirts should be a clue, as are the different numbers (6 for the former and 14 for the latter could hardly be confused). If you look up their stats you will see Huddlestone is a massive 6’3” (that’s 1.9m) and 94kg, whereas little Luca Modric is just 5’6” (1.73m) and only 65kg. It might be forgivable if Smith in the 18 shirt played with Smythe in 10, but this seems a stretch. Those who watch much English football will have already seen the kicker coming, for those who don’t, this is what they look like: