Archive for the 'Pterosaurs' Category

Sexual selection in dinosaurs, the story so far…

I have a major new paper coming tomorrow on sexual selection in dinosaurs. This is an area in which I have been extremely heavily involved in the last decade and have published numerous papers on this subject with various colleagues, writing about the underlying theory of sexual selection and how it might appear in the fossil record, providing evidence for it and actively testing hypotheses. This has also led into my working on related issues of ontogeny and social behaviour in dinosaurs which feed back into these areas to try and deal with certain aspects that came up as a result of these analyses.

Suffice to say I’m not going to go back over the whole history of my work in the field, or that of plenty of other researchers which is both relevant and important. But a little bit of context is important with respect to the coming paper because it’s something that I’ve had in my mind to do for about as long as I’ve been working on this subject but I didn’t think I’d be able to do because the dataset didn’t exist.

All of the work I have done really tried to get into answer the questions of which features of which dinosaurs may have been operating under sexual selection and can we tell. (More properly, I should say socio-sexual selection since teasing out social dominance signals from sexually selected signals is probably impossible though mostly the two are more or less synonymous in various ways so it’s not a major issue conceptually). The short answer is that really quite a lot of features probably are under some form of sexual selection. We can see this by the fact that we can rule out functional explanations for things like ceratopsian crests as being anchors for muscles attachments, radiators, or for defence because they are highly variable and / or fundamentally don’t work (Elgin et al., 2008; Hone et al., 2012). They are costly traits to grow and lug around (be they stegosaur plates or hadrosaur crests) and so clearly have a fitness cost, ruling out species recognition as a signal (Knell et al., 2012; Hone & Naish, 2013). Similarly, there is no clear pattern of differentiation among sympatric species as would be critical for a recognition trait (Knapp et al. 2018). They are highly variable both within and between species, another hallmark of sexually selected traits (Hone & Naish, 2013; O’Brien et al., 2018) and finally they grow rapidly as animals reach sexual maturity which is absolutely characteristic of sexual selection (Hone et al., 2016; O’Brien et al., 2018).

The one issue that has remained elusive in all of this is the vexed issue of dimorphism. This has proven very hard to detect for a variety of reasons, but most notably the generally small sample sizes we have for dinosaurs and the tendency for males and females to overlap in size and morphology over much of their lifespan (Hone & Mallon, 2017). To top it off, mutual sexual selection can reduce or even eliminate dimorphism making it harder still to detect and meaning even an apparent absence of it, does not mean sexual selection is not in operation (Hone et al., 2012).

It would be nice to be able to explore the issue of dimorphism in particular in more detail with an extant analogue. Plenty of comparisons have been made to various living taxa in terms of dimorphism (be it body size or major features like a crest or sail) but they run into various issues. Mammals are nice and big and often have things like horns that differ between males and females (either in shape or presence / absence), but they’re phylogenetically very distinct and have the problem of growing quickly to adult size and staying there. Lizards offer something interesting with some dimorphic species with various signal structures (like some chameleons) but then while they are reptiles, most are small and the biggest varanids have no sexually selected structures. Birds are obviously literally dinosaurs but have a mammalian-like growth and are not very big. While there’s plenty of size dimorphism in them, there are few that have obviously dimorphic traits that would show up in the skeleton (like horns).

That leaves the crocodylians, which are off to a good start. Some are very large and take a long time to grown to adult size, all are egg layers, they are sexually mature long before full size meaning they would likely express sexually selected traits while still quite small (like dinosaurs and unlike birds or mammals), and a number are also sexually dimorphic in body size. The only thing missing is some kind of sexually selected bony feature, or at least one with a clear osteological correlate.

And so to the gharials, the wonderfully weird crocodylians of the Indian subcontinent which tick every single one of these boxes right down to the growth on the snout of males, the ghara, that is absent in the females. This has long been obviously the one taxon that ticks pretty much every possible box and would provide an excellent living model to analyse and see how easy (or not) dimorphism is to detect when you have a known dataset to work from. The obvious limit to this plan is that these animals are extremely rare and most museums have few, if any, specimens. The one species that was pretty much perfect for my plans immediately fell out of contention because I couldn’t see how I could get a dataset together that would be sufficient for analysis, so the idea was shelved. Until recently…

Obviously, to be continued.

 

Papers on sexual selection, dimoprhism, socio-sexual signaling, social behaviours and related subjects in fossil reptiles:

O’Brien, D.M., Allen, C.E., Van Kleeck, M.J., Hone, D.W.E., Knell, R.J., Knapp, A., Christiansen, S., & Emlen, D.J. 2018. On the evolution of extreme structures: static scaling and the function of sexually selected signals. Animal Behaviour.

Knapp, A., Knell, R.J., Farke, A.A., Loewen, M.A., & Hone, D.W.E. 2018. Patterns of divergence in the morphology of ceratopsian dinosaurs: sympatry is not a driver of ornament evolution. Proceedings of the Royal Society, Series B.

Hone, D.W.E., & Mallon, J.C. 2017. Protracted growth impedes the detection of sexual dimorphism in non-avian dinosaurs. Palaeontology, 60: 535-545.

Hone, D.W.E., Wood, D., & Knell, R.J. 2016. Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling. Palaeontologia Electronica, 19.1.5A.

Hone, D.W.E. & Faulkes, C.J. 2014. A proposed framework for establishing and evaluating hypotheses about the behaviour of extinct organisms. Journal of Zoology, 292: 260-267.

Hone, D.W.E., & Naish, D. 2013. The ‘species recognition hypothesis’ does not explain the presence and evolution of exaggerated structures in non-avialan dinosaurs. Journal of Zoology, 290: 172-180.

Knell, R., Naish, D., Tompkins, J.L. & Hone, D.W.E. 2013. Is sexual selection defined by dimorphism alone? A reply to Padian & Horner. Trends in Ecology & Evolution, 28: 250-251.

Knell, R., Naish, D., Tompkins, J.L. & Hone, D.W.E. 2013. Sexual selection in prehistoric animals: detection and implications. Trends in Ecology and Evolution, 28: 38-47.

Hone, D.W.E., Naish, D. & Cuthill, I.C. 2012. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia, 45: 139-156.

Taylor, M.T., Hone, D.W.E., Wedel, M.J. & Naish, D. 2011. The long necks of sauropods did not evolve primarily through sexual selection. Journal of Zoology, 285: 150-161.

Elgin, R.A., Grau, C., Palmer, C., Hone, D.W.E., Greenwell, D. & Benton, M.J. 2008. Aerodynamic characters of the cranial crest in Pteranodon. Zitteliana B, 28: 169-176.

 

 

Can we make pterosaur planes yet?

Short answer, no, longer answer, maybe one day but there is at least some cool potential here. That’s the basic gist of a new paper I have out today with Liz Martin-Silverstone and Mike Habib on flight in the fossil record and its implications for aircraft design.

Back in the earliest days of human-powered flight there was an inevitable draw to birds for inspiration as heavier than air fliers, and there’s more than enough videos of cranky machines flopping around on their wings failing to get off the ground if you are into that sort of thing. Aerospace technology has moved on though and bird-like flying machines (called ornithopters) do now exist. More and more technology takes inspiration from living organisms (biomemetics, bioinspired tech) and when it comes to flight, so often at the forefront of engineering, this has included all manner of bits of bird and feather-like features. Bats have played a lesser role too and insects are increasingly looked at since now aircraft do not have to have pilots and remote controlled craft, drones, autonomous vehicles (and plenty of other names and acronyms) are increasing in number and diversifying in form.

Amidst all of this, the fossil record goes almost unnoticed. Flying organisms have all manner of adaptations for weight reduction, streamlining, ways of manipulating lift, drag and control and of structural support with unusual forces and combining issues like take-off and landing on usual surfaces with having to actually fly. They provide known working models that can be directly copies and mimicked, or at least used as a starting point to investigate ideas. Given the plethora of flying animals in the fossil record (both gliders and powered fliers) that have no living analogues, these would seem an excellent place to seek out new technological innovations and ideas and the idea of this paper is to try and trigger some interest in this. True, people have looked at pterosaur flight, though mostly to see how pterosaurs might have flown. Only a very limited amount of work has been done looking at these as possible aircraft models and even then it’s been holistic with no real look at the details of wing construction or control. And this is just one clade and ignores things like Yi, with its combination of membranes and feathers, Microraptor with its multiple control surfaces, Sharovipteryx the delta-winged glider and others.

The paper is short though and writing such a piece that is trying to work for engineers with potentially little knowledge of biology, biomechanicists with little knowledge of palaeontology and palaeontologists with little knowledge of either. As a result, it’s rather superficial in terms of its treatment of many ideas and concepts despite a vast amount of cited literature (we had to get dispensation for the editor to include so many and the referees were still unhappy and wanted more) but it does hopefully provide some real information and ideas for these three groups of researchers to come together and make use of the palaeontological resources at their disposal.

So while we might not see any pterosaur-based drones around anytime soon (or indeed ever) we hopefully will see considerably more interest in flying animals in the fossil record on all sides and this certainly has the potential to feed back into new designs. I’d obviously love to see an azhdarchid drone that can walk, run, launch and fly but even seeing something like an anctinofibril-based system of wing warping or pteroid-supported propatagium would be super cool. Stanger bits of the biological world have been looked at for engineering and hopefully various fossils will become a part of this in the near future.

 

Martin-Silverstone, E., Habib, M.B., & Hone, D.W.E. 2020. Volant fossil vertebrates: potential for bioinspired flight technology. Trends in Ecology and Evolution.

Note: this has gone live a week earlier than we were told to expect and the version out there is currently the uncorrected proof, and while we didn’t make any substantive changes, a better version of this should follow.

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.

A little more Luchibang

Life reconstruction of Luchibang by Matt Van Rooijen

After the previous mammoth post on the long and painful history of the publication of the new paper, I still wanted to write a little more about the specimen and what we have learned. As noted in the first post this specimen is preserved alongside a couple of fish and apparently has some soft tissues associated with it.

The istiodactylids are one of those groups where their ecology has been very uncertain with a variety of activities suggested. Based on their affinities with the highly piscivorous ornithocheiroids it’s been suggested they were fish eaters, though their teeth don’t look well suited to catching fish at all, and that little cluster of interdigitating and cutting teeth has been used to put them forwards as scavengers. That doesn’t sit too well either since they appear to generally be quite aquatic in their habits and while we have a great many birds that are specialist scavengers today, none of them are marine soarers.

Luchibang doesn’t actually help resolve this much. While it’s limb proportions and especially long legs point to greater terrestrial competence and might point to an animal that is therefore scavenging more, it’s also preserved with two fish specimens. One of these is down and under the ribs and apparently in the ribcage. In the paper we are cautious over this specimen as small fish are commonly associated with these kinds of Liaoning specimens (indeed, there’s one already here by the head which clearly wasn’t’ eaten) but it is certainly possible that it represented preserved stomach contents.

So we can provide some tentative evidence to support both scavenging and piscivory in this animal (and of course these are not mutually exclusive positions) and so while what we have here is interesting it doesn’t resolve much. This uncertainty is reflected in the very nice life reconstruction that Matt Van Rooijen kindly did for the paper (quite a few years ago now, he’s been sat on it a while!). In the foreground Luchibang is wading in the shallow waters and grabbing a fish while nearby is the carcass of an iguanodontian which is available as an alternate source of sustenance.

One last thing to comment on is the preservation of soft material on the specimen that we interpret as soft tissues. It is really rather poorly preserved and is little more than some stains on the rock but with some regular patterning and shape that appears to be organic. There are several spots and they all look similar and are associated with the skull, the neck and the ulnae. They don’t appear to be parts of the wings suggesting these are skin traces. There’s no indications of any pycnofibers but then, assuming these are soft tissues, they are rather decayed.

That’s quite enough on Luchibang for now, the paper is fully open access so you can read the full description and discussion there. This only leaves me to thank Matt for his artwork, my coauthors and the referees and editors on this paper.

 

 

Ten years in the making of Luchibang

Some research papers can take a long time to finish and delays for all kinds of reasons can put projects on hold indefinitely or even kill them eventually. Luchibang has a particularly long lead up time but the history of this description and naming take in a whole bunch of issues over publication which are informative and important.

To begin at the beginning, way back sometime around 2010 (or possibly even 2009) while I was doing my postdoc at the IVPP, Xu Xing came to my office and asked me to look at a pterosaur specimen. A colleague of his was looking to acquire it for a museum and had been assured it was a new taxon but wanted confirmation. It was, of course, what has become the holotype of Luchibang, and it was immediately obvious that this was unusual and new with the large legs and somewhat odd tooth arrangement and so after a few minutes of checking various details and cross referencing with a few papers, the curator left happy.

A few months later the specimen was back as I’d been invited to describe it. I really hadn’t expected the opportunity and was delighted to do so and so set about the task of doing a full description. I didn’t include a phylogenetic analysis for a number of reasons, but notably as the specimen was so clearly an istiodactylid and their own relationships were rather unresolved, adding what was obviously a juvenile into the mix would have been a fair bit of work to not actually add any real information.

Looking through my files this was submitted sometime in late 2010 or early 2011. The paper came back from review after a time when I had left China and was now in Ireland, with one referee liking it a lot, but with the other review came a bombshell. They through the specimen might be a composite.

This was obviously a huge problem because first, I was worried it genuinely was and I’d somehow missed this and second because now I was back in Europe the specimen was hardly easy to access, and proving it was genuine was going to be tough. The referee pointed to the unusual hindlimbs and what they thought were unusually long cervical vertebrae and suggested this was an azhdarchid body on an istiodactylid head. My lack of phylogeny had also come back to haunt me as they suggested an analysis where the head and body were coded separately should reveal what respective animals they might come from. It then took me about three years to be able to begin to resolve this issue. Eventually I did get back to see the specimen and was able to do the most important thing to show it was genuine – to reprepare bits of it myself by hand.

The matrix and even the bone vary quite a lot in the specimen and that’s quite common in various specimens from Liaoning so this itself was no concern. It was suggested UV photographs might reveal any shenanigans, but work Helmut Tischlinger and I had done on several specimens at the IVPP showed that even those collected and prepared by the museum could show dramatically variable reflectance on single slabs and this would be unreliable in this situation (not that Helmut was around at the time either!). So instead I set to the specimen with some picks and carefully chipped away at the matrix at various points on the specimen where the head met the body. There was no glue, no cracks, no joins, no restoration, only natural and original sediments. Checking the margins of the slab also showed no cracks or joins where a piece could have been incised into the rest of the specimen and again, no traces of glue or other tampering at the margins. The very tip of the snout also is broken off at the margin of the specimen which helps trace the bones to the very edges. Critically, if you look closely it’s also clear that every part of the main skeleton is in direct contact to another part. The bones of the skull actually touch those of the neck, which contact those of the wings and chest, which contact the legs. If the head had been added to the specimen, it has been done to make the bones touch each other and even merge with each other (this happens on flattened specimens) and with no joins between them under preparation. In short, this must be genuine.

I have seen plenty of faked, and otherwise ‘improved’ specimens at various times and they are never even close to looking convincing once you study them in detail (and most are not convincing at all) and there’s some other circumstantial evidence to support his being genuine. Despite the odd loss of the back of the head, we’d expect in such a juvenile animal that the skull bones would not be fused together and so the ontogenetic status of the head does match the body and the proportions are about right too. It seems unlikely that not only were people able to insert a skull perfectly onto a postcranium but did so with an animal of the right size and growth stage (and why would they not put in a complete skull at that?). Minor points compared to the lack of evidence for any tampering, but all suggesting a genuine specimen.

Despite the lack of a phylogeny, I now wrote to the editor of the journal and pointed out that I was now able to confirm that the specimen was genuine. I’d been able to show that some of the alleged azhdarchid traits were actually shared with some ornithocherids too reducing that side of the equation, and I had even had a PhD student who was in China at the time do some prep themselves and confirm my observations and was able to have them send a supporting letter to support this. To my dismay, despite having previously agreed this would be sufficient, the editor now said they didn’t think it was enough to support publication of the specimen and they wanted to see some systematics.

I no longer had access to my systematics programs and while a couple of times I approached potential coauthors to help me run some phylogenetics, no one with the expertise I needed had the time. With my career now changing and my having less and less time for such work and the frustration of the delays the whole project fell to one side. I couldn’t convince the editor and didn’t have the time to do the new analyses and couldn’t get help with it. I didn’t abandon it, but nor did I think it was ever going to get done. I also had doubts about being about to convince any other referees or journals about the specimen so didn’t want to invest time and just have the paper bounce from journal to journal.

Then came the most recent Flugsaurier conference in LA and this coincided with my having a bit of free time. I decided this would be a great opportunity for a test case – I could present the specimen to a whole raft of researchers and lay out everything as I’ve done here and see what people said. After all, various experts on istiodactylids, ornithocheirds and azhdarchids would be there and the collective knowledge in the room would be greater than mine and a couple of coauthors and referees. In creating the talk, I was also able to delve back into the pterosaurian literature and with many years of new papers and in particular phylogenies meaning there were lots of new traits described and defined that could be used to support various taxonomic affinities. This really helped as I could now also find more traits in both the vertebrae and even the long legs that were clearly ornothocheiroid in nature and not azhdarchoid.

To my delight the audience was very receptive to the idea and only one person flagged a single trait that they thought might compromise my diagnosis as it should be present but didn’t appear to be. Talking to them more about it afterward and going through some photos we were able to establish that this was there as well and the apparent last of the questions over the possibility of any fakery were removed. Still though, a phylogeny would be nice and at this meeting I met Adam Fitch who was playing with pterosaur phylogenetics and had the time to get involved. We ran analyses to show that both the head and postcranium independently clustered with other ornithocheirids and I wrote a section to provide the evidence that the specimen was genuine. So the paper was dragged out into the light, got updated and revised and had a new phylogeny added that Adam and I produced. And so, submission and plain sailing to publication.

If only.

The first journal we sent it to rejected it with a long review pointing out that we really shouldn’t have included a lot of information showing the specimen was genuine. If there was any question about it, it shouldn’t be published at all, so we should take that information out. So the paper was revised, the material relegated to the supplementary information and onto the next journal.

This time it got rejected with the referee noting that the specimen either was actually a weird toothed azhdarchid or might not be genuine and we should include a clear explanation as to why we thought it was. They clearly hadn’t read the supplementary info with several pages of material on this exact subject or considered that maybe the long list of traits that we showed were homologies of ornithocheirids and istiodactylids. To make it worse, that same person then phoned me a couple of months later to say they’d seen a very similar specimen in another lab in China. So not only is there allegedly another one out there (making this seem more likely to be genuine) but now after all this time we might get eaten to the punch by another lab while we were being rejected for publication based on the review of a person now telling me they thought it was genuine.

So, we submitted to Palaeontological Electronica. It meant we could include lots of colour images and come out with an OA publication and importantly they require a four week turn around for reviews. Of course the paper then sat with the journal for nearly four months and several e-mails went ignored by an editor which only added to the frustration. During this time a new istiodactylid was published from China and then a near-complete specimen of the very closely related Mimodactylus meaning the paper managed to get out of date more in 3 months in review than it had in a 10-year hiatus. Eventually the reviews came back and the only substantive comments from the referees were that we should include the taxa which had just come out while our paper was in review. That meant redoing the phylogenetic analysis which wasn’t trivial (and it yielded effectively identical results), but we were able to return the paper fairly swiftly and now it’s finally out.

Hopefully this goes a very long way to explaining the various dips and delays in taking this specimen from first penning a description a decade ago to coming out now. Self-imposed breaks, unavoidable delays in accessing the specimen while on the wrong side of the world, other commitments, and recalcitrant referees and editors have all played a part. Establishing that the specimen is genuine was obviously important once the spectre had been raised, and it clearly improved the paper by forcing me to refine my arguments and make more detailed comparisons with various other taxa and by delving deeper into their anatomies. That said, it was a huge issue I could have done without and the timing could not have been worse as I’d just left China. This is though, the end of the tale now that the specimen is published, but there’s still more blog to come on the wonderful (and rather late) Luchibang.

A long overdue welcome to Luchibang

 

Luchibang has arrived

Today sees the publication of a new pterosaur that has been a very long time in coming. There’s a hell of a lot to unpack here with both the animal itself and the history of the research so this is going to take quite some time to get through. So, here’s the start of a lot of information on this really rather unusual animal.

First off, this is an istiodactylid. These are a branch of the pretty familiar ornithocheiroids which include things like Anhanguera and Ornithocheirus and (according to most researchers) aare close to Pteranodon too. In short, a group of medium to large sized, ocean-going fish eaters, many of which have lots of large grabby teeth to go with big wings and small legs. The istiodactylids are really rather unusual in that they have only a few small teeth at the front of the jaws and they also have giant fenestrae in the skulls which makes them very recognisable. Apart from the eponymous British Istiodactylus, they are all known from China which has really quite a diversity of them though in varying degrees of completeness. This is another specimen attributed to the Yixian Formation and its diverse pterosaur biota.

Luchibang immediately becomes important as it’s by far the most complete known istiodactylid. It is, unfortunately, crushed nearly flat, but apart from the back of the skull, the tail and few tiny bits, everything is there. There’s even rare elements like the gastralia and sternum in good condition and there’s not too much overlap of bones meaning everything is visible (though often at odd angles). The loss of the back of the head is especially annoying but otherwise this is an exceptional specimen. This alone would make it important but it also has some patches of what may be soft tissues in places and it’s also apparently got a fish preserved in the chest cavity (more on this later). One top of that, it’s also really big, or at least would have got bigger. The specimen is about 2 m or so in wingspan but it is also a very young animal. One of the major fusions of various elements that we see even in some relatively young pterosaurs, let along subadults or adults, are present and so this animal would have been considerably larger at adult, perhaps being one of the largest istiodactylids.

The skull and upper body of Luchibang xinghe

If you take more than a quick glance, it quickly becomes clear that while Luchibang has the incredibly typical head and tooth arrangement of istiodactylids, it’s also got a few very odd features. Most obviously, the hindlegs are really long and the feet are very big. Although rather incomplete, there is no evidence for anything like these proportions in other istiodactylids or the ornithocheiroids as a whole and marks it out as being quite unusual. In fact, when we plot out the proportions of the fore and hindlimbs, Luchibang plots over with the azhdarchoids rather than other ornithocheirids and otherwise the two groups are quite distinct in their anatomical arrangements.

This rather strongly suggests that Luchibang is doing something rather unusual and was much more terrestrially capable than its relatives and also then led to its name. Luchibang translates from Chinese as the ‘heron wing’ to convey the apparent heron-like attributed of long legs and catching fish, with the species name xingzhe meaning ‘walker’ also relating to this. Although this name was first created many years ago, while this manuscript was making its way through development hell, the pterosaur community lost palaeontologist Lü Junchang. JC, as he was generally known, was a friend and collaborator on various pterosaur projects and so this new taxon then became a great opportunity to honour his work and his memory and so the etymology formally recognises him too.

So, welcome JC’s walking heron wing, and in the next post I’ll talk some more about the long and tortured history of this publication which dates back a full decade.

 

Hone, D.W.E., Fitch, A.J., Ma, F., & Xu, X. 2020. An unusual new genus of istiodactylid pterosaur from China based on a near complete specimen. Palaeontologica Electronica.*

 

*Yes, there’s an error in the abstract with their weird hanging ‘postcranial’ in the last line. We asked the journal to remove it at the proofs stage but they refused because it had already gone for translation, so we can’t fix it. Feel free to mentally delete it yourself. And the ‘original’ planned species name of ‘wuke’ has managed to sneak through the proofing process and appears in Fig 8. Annoying and stupid but doesn’t affect the taxonomy, though it means I’ve effectievbly accidentally created a nomen nudum.

Late 2019 roundup

I do try to do a roundup of each year and even with the Musings being more and more infrequently updated, I wanted to keep this up. The year has been very slow so not too much has happened in terms of publications or other news and the major even (the naming of Cryodrakon) I did manage to give some good coverage. My only other publication was a response paper written with Tom Holtz that argued (again) that some of the evidence suggested for highly aquatic lifestyles of various spinosaurs are overstated or at least much more complex than sometimes stated. Once again (see also adult dinosaurs, social behaviour etc.) this is at least in part an issue of definitions and the turn of phrase ‘semi aquatic’ which covers a vast range of behaviours and selective pressures and degrees of adaptation being used without anything like enough specificity.

I do now have a whole bunch of papers in review and a couple that are (provisionally at least) accepted and should be out this year, and so while the Musings is likely to carry on being generally quiet there will be some research to talk about with any luck. Most of that will be pterosaurian in nature but there’s some dinosaur stuff in the works as well.

Also coming at some indeterminate point are some new books. I’ve all but finished a first draft for my next popular science book that should be out sometime this year (probably late autumn) and I’m also involved in a couple of others so stay tuned.

In the meantime I am still posting photographs and micro-updates on projects on my Facebook page and this is the best place to keep up day to day, but I’ve no intention of shutting down the blog even if the posts will be sporadic.

Happy New Year.

 

 

Hone, D.W., Habib, M.B. and Therrien, F., 2019. Cryodrakon boreas, gen. et sp. nov., a Late Cretaceous Canadian Azhdarchid Pterosaur. Journal of Vertebrate Paleontology, 39(3), p.e1649681.
Hone, D.W.E. and Holtz T.R., 2019. Comment on: Aquatic adaptation in the skull of carnivorous dinosaurs (Theropoda: Spinosauridae) and the evolution of aquatic habits in spinosaurids. 93: 275-284. Cretaceous Research.

Many more Cryodrakon images

Scavening on a dead Cryodrakon by Mark Witton

Chatting to Mark Witton the other day it transpired that artwork of Cryodrakon has already existed for some year. Large azhdarchids would have been a decent meal for small scavengers and we know of at least two incidences of dromaeosaurs eating them, one of which being the holotype of Cryodrakon (the other was Velociraptor I described with a pterosaur bone in it). The above piece was done in reference to this but Mark told me his point was to specifically reference the Canadian specimen which only now has a name.

I’m sure there’s other artworks out there that similarly were based on this northern ‘Quetzalcoatlus’ and would now refer to Cryodrakon, but almost inevitably once the paper came out there was a rush on to produce new images that rapidly appeared online alongside the ‘official’ artwork of David Maas. Here are a few of those.

Cryodrakon attacks a dromaeosaur by Gabriel Uguerto

First off is that by Gabriel Uguerto and this one is a bit of a cheat perhaps because he drew it for me as a commission but I’m delighted to have the original and it’s nice to see an azhdarchid giving something back to the theropods and not just being eaten by them or only following what is now a meme and eating baby sauropods.

Cryodrakon skeletal (full sized) by Dean Schnabel

There are already skeletal outlines appearing for Cryodrakon too. Dean Schnabel (who goes under the pseudonym of Sassy Palaeo Nerd on Deviant Art and Twitter) has produced two. One of all the known material scaled to the incomplete giant cervical (above) and a second that is just the holotype material at the correct size for that specimen (below).

Cryodrakon skeletal (holotype only) by Dean Schnabel

Finally, Joschua Knüppe put out this black one on an especially snowy background. While on the subject of snow, it’s popping up a lot I artworks already. The name Cryodrakon was intended to invoke Alberta as it is now rather than when the animal was alive when it was semi-tropical. That doesn’t though mean that snow is wrong (indeed David Maas sneaked a bit into one of his images) as even the warmest places will get snowfall on occasion and azhdarchids generally could fly long distance and the newly forming Rocky Mountains were not far away. I’m sure on occasion Cryodrakon ended up striding through snow and flying over white landscapes even if it wasn’t the norm.

Cryodrakon in the snow by Joschua Knüppe

These are not the only ones out there, a quick google will reveal a wealth of alternate takes on Instagram, Deviant Art and elsewhere (alongside a load of older rebadged art that various media organisations stumbled to produce and plenty of versions of David’s work, often inappropriately rebadged with someone else’s watermark). More I’m sure are coming but it’s nice to see your own scientific work reach out into people’s imaginations and artistic efforts.

 

Coda: I spoke to all the artists about linking to their work before putting them up here.

Welcome Cryodrakon – a giant Canadian azhdarchid pterosaur

Life reconstruction of Cryodrakon boreas. Artwork by David Maas, used with permission.

A few years ago Mike Habib invited me to collaborate on a paper looking at the anatomy of the exceptionally well preserved humerus of an azhdarchid pterosaur from Dinosaur Provincial Park in Alberta. This specimen is well known as it is a partial skeleton and includes a tibia with bite marks and even a shed tooth from a small theropod. It, and a number of other pterosaur bits from the park were described in the famous Dinosaur Park book from the early 2000s and were tentatively refereed to Quetzalcoatlus. Intending to use both this and soem Quetz material for his study, Mike asked me to look at the material and add something on the taxonomy to make sure this really was the same thing and if not, see if we could say anything meaningful about it’s identity. I got about 6000 words into a draft before I realised that this was in now way a subsection of a paper on mechanics and anatomy and this was going to have to be it’s own entity. Fast forward a couple of years and here is the newly named and distinct Cryodrakon boreas.

Mid cervical vertebra of Cryodrakon boreas, nicknamed the teddybear for obvious reasons.

The name means the ‘frozen dragon of the north wind’ is clearly an azhdarchid pterosaur. We’ve recently found that not all of these animals had super long necks and some were rather short and robust-necked animals. Cryodrakon is certainly one of the longer-necked ones, but it’s vertebrae do seem to be shorter and wider than comparable Quetz vertebrae suggesting that it had a more robust neck than it’s more famous cousin. It’s humerus is also a little less robust than the Texan so presumably it’s ecology was a little different too given how important this element is for walking, take-off and flight.

There’s a fair bit of material known too. The holotype has a humerus, midcervical, pteroid, tibia, rib and wing metacrapl all well preserved (amazing for an azhdarchid) and represent a juvenile of about 5 m wingspan. There’s a lot of bits including lots of isolated cervicals of animals of various sizes right down to things of perhaps 1.5 m wingspan and one huge and fragmentary vertebra that we estimate would represent an anuld in the 10 m wingspan realm. So at adult this would be an aniaml approaching or comparable to the other biggest azhdarchids known. The fact we have so much material is a real bonus as we’re able to show that essentailly all the vertebrae have a unifying set of features so we can infer that even young animals have the same features as adults and we can unify them as a single species. There could be more here of course (it’s hard to say too much about things like an isolated partial scapulocoracoid of soem of the very crushed vertebae) but for now the best interepretation is that there’s one species represented by lots of specimens.

Life reconstruction of Cryodrakon boreas. Artwrok by David Maas, used with permission.

My thanks also to David Maas for his beautiful artwork which he did at short notice to help show off the animal (he retains the copyright, these are used with permission). The colours are supposed to be a bit of fun and obviously echo the Canadian flag but are also not implausible given how little we know about pterosaur colours and the bright patterns we have for at least some very large modern birds. Equally the environment it primarily lived in was subtropical but it’s also likely it would have seen snow on occasion and certainly would have seen the northern lights, but the name primarily refers to the Albertan winter.

Hone, David; Habib, Michael; Therrien, Francois.  2019. Cryodrakon boreas gen. et sp. nov. a Late Cretaceous Canadian azhdarchid pterosaur’. Journal of Vertebrate Paleontology.  DOI: 10.1080/02724634.2019.1649681

The problem with floating pterosaurs

A few years ago I published a neat little paper with Don Henderson on the possible posture pterosaur might adopt in water. This was done to try and see if they might have issues if they became stranded on the surface and especially if the head was left at or even under the surface (you can read about this in some more detail here). However, what I want to talk about in this post is how badly and how often this simple paper seems to have been misinterpreted. I’ve been thinking about this for a while but Heinrich Mallison has just linked to an old post on his blog making the same general point about accuracy of citations. Like him, I’m sure I’m not blameless and we all make mistakes occasionally and cite the wrong paper or misattribute a source or get some details wrong. It happens and while obviously not ideal, such is life. However, some papers more than others seem to suffer from this and the floating pterosaur paper is one of them.

It is only a short paper, under 10 pages long and there’s lots of figures and references in that too and the subject itself is fairly simple so one would hope to minimise confusion. Unfortunately, this seems not to be the case and it’s already acquired a number of citations and comments that at best miss the point and at worst say the direct opposite of a point we made. Below are some direct quotes from papers and then points or quotes from the original paper to show how these are quite incorrect. I won’t directly name and shame the perpetrators as the point here is intended to be illustrative of the problem rather than go after colleagues when I can’t rule out having made the same mistake myself somewhere.

First off our study was apparently carried out in order to ‘imitate the swimming strokes of pterosaurs’. In the title and throughout the paper we refer to the floating posture and talk about static posture in water, not swimming per se. While in the discussion we did refer to the posture some pterosaurs took in water and pointed to how it matches putative swimming tracks, this was clearly not the aim of the paper. That makes this point a bit wide of the mark, but not bad and a rejig of the phrasing would clear this up.

Next up, we apparently show that ‘pterosaurs would not have been able to float without tipping over’. That’s clearly not correct as can be seen from the figures (see below). We do discuss the issue of tipping forwards in pterodactyloids in some postures, and the heads are indeed low, but that’s not the same as saying that all pterosaurs did this all the time and indeed the pterosaurs were generally stable.

Hypothesised floating postures fo various pterosaurs

Moving onto some greater issues, we apparently state that the ‘hairlike pycno-fibers covering their body would likely not trap a layer of air, as feathers of birds, and could become water-logged’. That’s very clearly not what we say at all as we make the very clear statement that ‘the effect of such a coat may have been positive (trapped air increasing buoyancy) or negative (waterlogged).’. Yes it may have been an issue, but we don’t know and are equally open to the possibility it could assist buoyancy and we point to the fur on aquatic mammals as a possible analogy, so this quote clearly is not in line with our position on what effect pycnofibers might have had.

We also are cited for the point that pterosaurs were ‘unable to take off from the surface’. This is not a point we really address (since it’s not directly related to floating posture’ but even in the abstract we say that pterosaurs ‘if immersed would need to take off again rapidly’ which clearly implies we are happy with the idea of water launched and later on we cite Habib and Cunningham and saying ‘A recent study suggests that even the biggest pterosaurs might be capable of taking off from the surface of the water’. In short we’re clearly happy with the idea they could take off from water and while we discuss the possibility that some pterosaurs might not have been able to, at no point do we say that they could not.

Then we have this very problematic statement that ‘simulations of the buoyancy of pterosaurs made using computers indicate that these reptiles had no ability to float well in water’. We clearly do not say this and point multiple times to the high pneumaticity of ptersoaurs any say things including ‘it is not surprising that the pterosaur model floats on water’ and ‘We show that in general pterosaurs adopted a position that was high on the waterline’ which make it very clear they floated and floated well.

These five statements are varying degrees of problematic, but given that this paper has only less than 20 citations from peer-reviewed papers (and several of them are by me which I don’t think I’ve miss-cited) that points to a pretty high percentage of erroneous citations on this one piece of work. When several of them are clearly flat wrong, and even information in the abstract points to them being in error it suggests that it’s really not been taken on board. Hopefully this paper is simply unlucky in keeping getting such erroneous takes but it’s a shame that a paper that I’m really quite proud of seems to be repeatedly cited for things it doesn’t say or imply. It’s probably only a matter of time before it is used to contend that pterosaurs could not swim (something the paper also clearly does not say) and I’ve seen our paper referenced in this context in popular writing so it may yet go that way in the literature.

In short, read papers properly and check what you are saying. It’s important.

 

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(Somewhat late) roundup of 2018

Lots of people are doing little end of the year reviews and with my general decrease in blogging in recent months this seemed a good motivation for me to do something similar if a bit later than everyone else.

It has been a fairly productive year for me research wise though there are lots more things that are nearing completion or are already out for review so hopefully the next couple of years will show a better return. Even the list below is inevitably a bit warped as some of these papers are effectively in press so will likely end up with a 2019 date on them, while others were out in 2017 but only now have a year appended.

First off are a few on the subject of trophic interactiosn between species. Most recently has been my paper on a Pteranodon with a shark tooth stuck in it, though this year also brough some theropod bite marks on juvenile dinosaurs. There was a rather broken peice of centrosaur frill that not nipped by something small itself, but more interestingly was a rather savaged juvenile diplodocid femur from Dinosaur National Monument. This one had bites very reminiscent of those made by derived tyrannosaurs at a time when they were not around suggesting simialr feeding mechanisms might have been present more extensively in big theropods and the paper also included some work on the issues of identifing ‘biters’ too.

My work on sexual selection and signaling also continued with two papers on this subject. First came one which is the first piece of work by my PhD student Andy Knapp looking at the evolution and changes in the horns and frills of various ceratopsians. This specifically targeted the idea that these things might have evolved as recognition signals but there was no evidence that these eveolved in response to sympatry (being in the same place so where you might want to be different to avoid confusion) and thus supporting the idea that they were more likely under sociosexual selection. Second in this area was work led by Devin O’Brien on the way things like ceratopsian frills grow which can be an indicator of sexual selection. This has been used in one form or another for years but this papers made things more rigorous in the use of reference traits for comparisons to sexually selected traits and marking out other things that also grow fast but are naturally selected.

Finally there’s a couple of papers that don’t really fit into either category. First there’s some work I was involved in looking at the exceptional preservation of dinosaur ‘dandruff’ and the implications that this brings about their biology. Second was a revision of the pterosaur genus Noripterus which has a complex taxonomic history and has suffered through most of the key material being lost. That turning up again allowed proper clarification over the definition of the taxon and a number of other genera that has been referred (os should have been to it).

So all in all a fairly productive time with a couple of my main research themes keeping pace while continuing to work on some other important areas. On the outreach front I continue to do lots of talks and school visits as well as podcasts and some consulting for various TV shows and the odd appearance. The Guardian cancelled their science blog network which ended the Lost Worlds, though it means I am doing more blogging here again as a result. Finally, an early 2019 addition was the creation of a Facebook page for my work and outreach which does a different job to both these pages and Twitter so do please follow me there too.

  • Hone, D.W.E., Witton, M. P., & Habib, M.B. 2018. Evidence for the Cretaceous shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation. Peer J.
  • Hone, D.W.E., Tanke, D.H., & Brown, C.M. 2018. Bite marks on the frill of a juvenile Centrosaurus from the Late Cretaceous Dinosaur Provincial Park Formation, Alberta, Canada. Peer J.
  • O’Brien, D.M., Allen, C.E., Van Kleeck, M.J., Hone, D.W.E., Knell, R.J., Knapp, A., Christiansen, S., & Emlen, D.J. 2018. On the evolution of extreme structures: static scaling and the function of sexually selected signals. Animal Behaviour.
  • McNamara, M.E., Zhang, F., Kearns, S.L., Orr, P.J., Toulouse, A., Foley, T., Hone, D.W.E., Rogers, C.S., Benton, M.J., Johnson, D., Xu, X., & Zhou, Z. 2018. Exceptionally preserved skin structure reveals the coevolution of skin, feathers and metabolism in feathered dinosaurs and early birds. Nature communications.
  • Knapp, A., Knell, R.J., Farke, A.A., Loewen, M.A., & Hone, D.W.E. 2018. Patterns of divergence in the morphology of ceratopsian dinosaurs: sympatry is not a driver of ornament evolution. Proceedings of the Royal Society, Series B,
  • Hone, D.W.E., & Chure, D.J. 2018. Difficulties in assigning trace makers from theropodan bite marks: an example from a young diplodocoid sauropod. Lethaia.
  • Hone, D.W.E., Jiang, S., & Xu, X. 2018. A taxonomic revision of Noripterus complicidens (Young, 1973) and Asian members of Dsungaripteridae. Geological Society of London, Special Volume, 149-157

Pteranodon vs Cretoxyrhina

Shark vs Pterosaur. By Mark Witton.

Over the last 10 years I have published quite a few papers on various feeding traces, shed teeth and stomach contents that help demonstrate and refine some understandings about who ate who in the Mesozoic. These are often very interesting but also frustratingly incomplete and it can be hard to identify one, let alone both, of the protagonists and in any case these are often isolated examples that may or may not represent wider trends. Still, at least sometimes there can be a good set of marks with repeated patterns and enough data to be quite confident about a relationship.

One such is that between the classic giant pelagic pterosaur Pteranodon and various sharks from the Cretaceous, most notably Squalicorax. This is no big surprise, these pterosaurs were spending a large amount of time out over the water and could probably dive and swim after prey, even if they didn’t likely sit for long on the surface when they did so. Even aside from the possibility of being caught, at least some pterosaurs must have died while out over the water or been stranded and ill or injured on the surface and that would inevitably attract large predators to come for a meal. Given the huge numbers of Pteranodon bones we have, it should not then be a surprise that there are a good number of them described with various bite marks that can be confidently attributed to large sharks. Pterosaurs were generally lightweight for their size but that doesn’t mean there was not some decent muscle on them and modern seabirds are not infrequently eaten by sharks providing a nice analogy too.

‘Complete’ Pteranodon at the LACM.

Such data though is limited to marks on bones and it’s always nice to have something more detailed than this. Although mentioned before in several previous papers, one outstanding Pteranodon specimen in LA has never been described or illustrated properly and so when I got my hands on it while visiting Mike Habib a few years ago, it was rather inevitable that something would happen, and the paper on that, with the healthy addition of Mark Witton as a collaborator, is now out.

The indivdual in question is mounted as a lovely complete (and sort of 3-D) pterosaur on display in the Los Angeles County Museum but it is a composite of somewhat indeterminate origin and it’s not entirely clear how many individuals were used to make it or how complete any of them were. What is clear though is that there is a short series of articulated cervical vertebrae and that these have the tooth of a decently sized shark with them. It’s trapped under a prezygopophysis so it’s hard to think it just drifted in there by chance onto a skeleton at the very bottom of the sea, and while the tooth doesn’t look like it penetrates the bone it is a reasonable interpretation that this is a shed tooth from a bite.

The tooth is diagnostic of the large pelagic shark Cretoxyrhina and we have a good enough idea of where in the mouth it sat which means we can get decent estimates of the sizes of each of the two animals here. The Pteranodon clocks in at around 5 m in wingspan with the shark being 2.5 m in length, but despite this apparent discrepancy, the shark would have been by far the heavier animal and in the water it would swim rings round the pterosaur. In short, while we don’t know quite what happened here (was it predation or scavenging) it looks like a decent sized shark took a chunk out of a pterosaur and lost a tooth in the process.

This is the first record of sucha trophic relationship between these two genera, though of course various unattributed bites that are already known might also have been made by Cretoxyrhina. However, despite the large numbers of Pteranodon specimens known, apparent bites on them turn up in only about 1% of cases. In some ways this may sound like a lot but there’s perhaps a 6% rate of carnivore-consumed interactions known for Rhamphorhynchus, so the open ocean (perhaps unsurprisingly) might have had fewer incidences of large predators getting to grips with large pterosaurs than near shore ones with much smaller animals.

All in all though, this adds a nice new point to the dataset on pterosaurs and their position in various food chains. We have a healthy record of them eating things, and being eaten, and each new bit of data like this helps us get a better and better handle on how pterosaurs fitted into ecosystems and how they might have lived, and died, in the Mesozoic.

 

The paper is fully OA and available here.

 


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