Everything you didn’t think to ask about the pterosaur sternum (and were afraid to ask)

Pterosaurs flew! No big shock there, but obviously flight places major constraints and selective pressures on the skeleton and we see that with the incredibly conservative nature of the pterosaur skeleton as a whole. So one would think that the associate flight apparatus in particular would be especially conservative and say more constrained than the feet or the neck, but it turns out an absolutely critical part of pterosaur anatomy is both basically all but unstudied and wildly variable, yes, it’s the sternum.

To try and correct that, I’ve just published a huge paper cataloguing and describing basically every sternum for every pterosaur out there. I’ve deliberately not covered every known one for a couple of very well-represented taxa like Rhamphorhynchus (where there’s a dozen or so known) but every taxon with a sternum (more than 60 it turns out!), however incomplete, is included and there are technical drawings of all of the well preserved ones. In this regard I need to give a massive, massive, massive shout-out to Skye McDavid who did all the technical illustrations for this paper and is a major reason why it looks so nice and I think helps communicate the anatomy of these bones. See her work and commission her to draw for you here.  Also a quick thank you to Rene and Bruce Lauer of the Lauer Foundation for providing access to, and photos of, a couple of really useful specimens that filled in a gap for me.

There’s been only a handful of descriptions of pterosaur sterna ever described properly. Hunting though the literature I repeatedly came across one line notes about it, even when one was well-preserved and featured in a photograph and only a couple of papers have looked at them in detail (and then not said much to be honest). Phylogenetic analyses of pterosaurs regularly included no sternum traits or only one or two, less than many simple traits like the unguals or pteroid. This is not a well-studied piece of the skeleton, despite it anchoring all the major flight muscles of (checks notes) a clade of flying animals! And ones that also were quadrupedal, so the sternum (and how it fits to the coracoids) and the associated musculature is also critical for terrestrial locomotion as well. This is the sort of thing that pterosaur works should probably not be overlooking!

What astounded me though, as hinted above, is just how incredibly variable they are between and *within* species. For an animal normally so limited in variation this is a key feature which is tremendously varied in overall shape and appearance and with loads of different details in the size, shape, arrangement and thickness of all kinds of bits to it that will affect where and how the coracoids fit, the muscles attach and the shape of the chest as a whole.

However, a major part of this seems to come down to the fact that the sternum is generally really poorly ossified and in fact I suggest it is often primarily cartilaginous in most animals (certainly juveniles) and only becomes bone, and thin bone at that, in near adult animals. That would explain a lot of the variation seen and the often complete absence of the sternum as a whole (or at least the sternal plate) in even some extremely well-preserved pterosaurs that aren’t missing any other features at all. That answers some questions (why the variation) but opens up others. Given how well ossified the flight apparatus is for even embryonic pterosaurs, how the hell have they ended up with a sternal plate of cartilage even in near mature large animals? The forces for flight muscles should be massive and the sort of thing to trigger early ossification not leave it till the last minute. And why is it so varied even in the adults where it’s well-preserved, id there a lot more going on in their muscles and so flight and ability on the ground that we have overlooked? And can we get some useful information out of this on their ecology and evolution, despite the poor preservation? These are questions I’ve left unanswered, but I am looking into them and I’d encourage others to do so as well.

I did, briefly, look at the ontogeny of the sternum and based on a nice (and so far not properly described) sternum seen under UV light it looks like the development is quite close to that hypothesised by Rupert Wild back in the 1970s based on a young Eudimoprhodon specimen. This would nicely align pterosaurs with other derived archosaurs and fits the general idea that they are indeed close to the Dinosauromorpha, but again there much more to do here.

The paper clocks in at 20 000 words and 21 figures (two thirds of which are multi-panel figures) so the MS is already very long and complex and I simply didn’t have the space or energy to get into phylogeny, origins, musculature, mechanics or pterosaur evolution in general even if I’d wanted to. Pointing out some very leading issues and hopefully priming things for future research and discussion is the best I could do after the mammoth description section but I would like to think it leaves the pterosaur sternum in a much better place than we found it and ready to spark renewed interest and research into this critical feature.

This is, to be sure, a pretty niche paper since the discussion in that context is a bit flimsy and I don’t think anyone is going to sit and read through all the descriptions for fun. But any new sternum coming up or any phylogeny or look at flight can now I think use this as a very comprehensive starting point to check what information is out there. Such ‘basic’ papers of anatomical description and illustration are so important (I use Wellnhofer’s 1970s classics and Bennett’s Pteranodon monograph almost every time I write a pterosaur paper) and so I hope this paper will add something useful in that regard. For now though, I’m mostly glad it’s off of my ‘to do’ list.

The paper is fully open access and available online here: Hone, D.W.E. 2023. The anatomy and diversity of the pterosaur sternum. Palaeontologica Electronica, 26.1.A12.

Why I don’t like using modern animal patterns in palaeoart

I remember from some years ago a pub chat with John Conway about what makes ‘good’ palaeoart. We came to the conclusion that it was down to three main things, 1) is it good artistically – is there a nice composition, correct use of perspective, shading and general technique, 2) is it accurate in the sense that the anatomy, environment etc. is right (no Velociraptors vs Diplodocus) and 3) personal taste. In other words, people can produce technically brilliant and scientifically accurate material and you don’t have to like it if it’s not to your taste (though hopefully people would still appreciate it). The others of course remain somewhat subjective too depending on what the artist is actually going for (if you want it to be surrealist or a tribute to 19th Century art then accuracy may not be what you are aiming for – just like John’s own recent History of Painting book.).

This last point about ‘what you like’ is most relevant here because I want to talk about a common theme in palaeoart that I really don’t like and while I’ll try to rationalise and explain it, I do want to be clear that it is a personal preference and so doing this doesn’t really make you wrong and I don’t want to give that impression. So what is this thing I’m now going to moan about for several hundred words? It’s using really clear and obvious patterns and colours from modern animals and applying them to dinosaurs. (And yes, other things too but usually dinosaurs).

I don’t mean really common patterns or general ones like countershading, marine animals being blue or forest ones being dappled or stripes that go through the eyes or anything like that, I mean doing an oviraptorid with the colours of a parrot, or a sauropod with a giraffe pattern or a lammergier pattern on a dromaeosaur or puffin-beaks on pterosaurs or plenty of others. This approach has been around for a long, long time but it appears to be ever more common and increasingly present in high-profile art and projects. I have thought about this a fair bit and what I don’t like boils down to a few key points.

First off, it seems really unoriginal. If you are making palaeoart that is supposed to be as rigorous and scientifically accurate as possible then there’s a lot of creativity potentially taken out of what you can do, but there’s plenty of options and freedom in colours and patterns (while still being realistic) with the unknown. Taking that away that option from yourself and your audience seems a real waste and one I can’t understand. OK, I can’t draw for toffee, but isn’t making up the colours and designs of the animals one of the most fun and creative bits? Just copying another species seems such an incredible waste of an opportunity.

Next up, it’s very distracting. I’m sure there are all manner of weird and unusual animals out there with odd patterns that can be copied without it being obvious (though I still think it’s better avoided) but it certainly pulls me out of looking at the art in front of me and simply going ‘but that just looks like a weird golden pheasant / king vulture / gemsbok’ rather than considering the art itself. It actively does a disservice to the work by distracting you from it.

Perhaps more importantly, I think duplicating well-known colours and patterns is something that, accidentally or deliberately, conveys things about animal depicted because of our understanding and associations with those patterns. If you put a peacock’s colours on a maniraptoran theropod you are imbuing it with cultural or behavioural traits about how they display and their mating system, their habitats and so on that we generally don’t know at all (or are most unlikely to be similar). It’s making inferences that shouldn’t be there and that’s not a good way to communicate about long lost animals and surely that’s a major aim of most palaeoart? I think it often shows a lack of understanding about signals too – after all, something like an agamid might have a bight head and neck to best show off it’s colours, but transferring that to a ceratopsian doesn’t make a lot of sense when the back of the frill and the neck would not be the most obvious place for bright signal colours to appear when the front of the frill has evolved to be the main signal. It’s ignoring or misunderstanding how the signals likely work in both the living model and the extinct animals and again that’s not conveying good information.

There are for sure common patterns like the general white and grey of seabirds, or eye stripes and bright breasts in birds, or occasional striping on antelope that can be easily transferred to dinosaurs and pterosaurs and the like *because* they are either generic, or ecologically driven, or are non-descript (you can’t point to a bird with an eye stripe as being unique it’s so common in a way that you can a puffin bill or a macaw’s pattern) and so again, this isn’t any kind of ‘never’ instruction to copy living taxa. But I think it’s far, far more often a problem than it is a good thing and I can’t be the only one who thinks this, can I?

Actually I know I’m not, since I’ve had this conversation with a few colleagues (palaeoartists and academics and those who span the two) and I know I’m not alone, though I also don’t know how far this feeling runs. Again, I’m not saying this can’t or shouldn’t be done and there’s always a time and place to break the ‘rules’ for various reasons, but what appears to be an often default opinion of just taking one set of colours and patterns and transferring them to another is way too common. It is, to me, not only dull and unoriginal but actively misleading in a way and imbues ancient animals with symbolism and traits that they shouldn’t have while taking the audience out of the moment. So please do it less and think about why you do it when you do.

Display features in the fossil record

It’s been more than a while coming but here’s an actual normal blogpost for the blog that’s not just PR for one of my own papers or projects (don’t worry, more of that coming sooner or later). This one has been prompted by some repeated comments I’ve seen in recent months about the hypothesis of various features being used for display by academics discussing dinosaurs in particular, but other extinct animals too.

The argument basically runs ‘you say it’s for display only because you don’t know what it is’ and usually followed with ‘like when archaeologists say it’s for ceremonial purposes when they don’t know what it’s for’. I can’t speak for my fellow professionals studying human culture, but I can very much speak for the assessment of display features having written perhaps more on this than anyone else when it comes to dinosaurs and pterosaurs at least.

First off, yeah, some researchers are very much guilty of this. One recent paper did argue something was for ‘display’ and that was the last word on the subject. That is, there was no actual evidence or discussion of the implications and how it might function or have evolved or what it was a good signal etc. and that’s clearly suboptimal at best. And it’s hardly new, it’s a classic old argument for lots of things on dinosaurs that’s been about for a century at this point and so people arguing for display without data isn’t some recent phenomenon. However, for plenty of cases we either do have decent scientific evidence or it’s fairly trivial to make a reasonable argument and that comes from our understanding of sexual selection in particular and signaling structures in general. So here’s a breakdown of the kind of lines of evidence and reasoning that can support display as a function.

1. It has no clear mechanical function. Not every bit of anatomy is functional in presenting a positive advantage to an animal, and some can be optimised for multiple things, or are used only very occasionally, or, yes, can be cryptic and we don’t know what they are for. But in general, selection is very good at getting rid of things that are costly and not useful (see how quickly flightless birds reduce their wings for example) and things argued to be for display are often large and heavy and are unlikely to survive many round of selection.

2. Diversity of form between species. There’s a reason the claws, fingers, ulna, humeri, spine and even ribs of moles, golden moles, marsupial moles, pangolins, aardvarks, armadillos and anteaters look very similar and that’s convergent evolution based on strong selection for a clear mechanical function. Animals, especially closely related ones, doing the same things in the same ways will almost inevitably end up with very similar anatomy. There’s a reason the wings of birds all look similar (flight), but the variety seen in their tails or head wattles etc. (display) are so varied. There’s probably only one or two optimum mechanical shapes and repeatedly deviating from that, especially in close relatives is a display hallmark. There’s also a general suggestion (though I think untested) that these tend to evolve rapidly as well compared to more classic functional traits.

3. Diversity of form within species. Moose all look alike but their antlers can be very different to one another and there’s usually far more variability of display features between individuals than other anatomical features, and that’s before the possibility of things like dimorphism (though an absence of dimorphism is not an argument against a signalling function for various reasons).

4. Rapid growth late in ontogeny. Sexually selected and display structures grow when the animal is at, or close to, sexual maturity and are very small or non-existent before then. So if there’s any indications of the growth rate from having multiple animals at different ages or sizes this can really help.

5. Structures are costly. A related point to 1, but the idea of ‘honest’ signals means that these features should be expensive to grow or maintain and have some kind of disadvantage for bearing them. And that also means they tend to be big and obvious (though with various trade-offs often at play limiting size – things can’t grow forever).

6. Analogy. While few features are clearly analogous to those seen in living clades (though of course some like fossil deer have lots of living and well-studied relatives) it is possible to draw analogies for some. The elongate tail streamers of microraptorines and various Cretaceous birds are obviously similar to those of numerous extant birds which have been shown to be signaling structures, so it’s reasonable to infer that similarly shaped ones in related animals with similar ecologies and behaviours and doing similar things.

Not everything fits these moulds perfectly. Features can be multi-functional like elephant tusks where they are under sexual selection but also are used to fight off predators, strip bark from trees and other things and probably are under selection to optimise multiple activities. And of course functions can change over evolutionary history with, for example, horns potentially shifting from an initial display feature to an anti-predator function or combining the two. Thus what the original function of a feature may have been and what selection pressures drove it to its current condition are not necessarily the same thing (though I suspect often are).

Take something like pterosaur head crests which have repeatedly been suggested to have some kind of steering function. We’d expect there to be only one or two optimised versions of this given the complexities of flight and the extreme similarity of pterosaur wings to each other, but instead we see enormous varieties of crests, they vary between and within species and both grow in size and change shape during ontogeny and are apparently small or absent in young juveniles. Despite the suggestion that this has a mechanical advantage, it’s not clear how it would work and one might expect if head crests were so useful they would have appeared in birds and bats too at some point, and it’s not like pterosaurs are short of flight control surfaces. Plus of course, for such light and flying animals, these would have been heavy features and therefore presumably costly.

So it’s fairly easy to make a case for these as display features even if we can’t do a detailed analysis of their flight mechanics or look at the detailed ontogeny and variation of many (any?) species to the degree we would like. In short, yes, palaeontologists need to be much better at explaining how and why they are arguing for display as a feature and simply saying ‘it’s big and odd’ while kinda hinting at a couple of these points, really isn’t good enough. But on the other hand, a lot of the things argued to be display features (ankylosaur armour, ceratopsian frills, hadrosaur crests, tyrannosaur hornlets, spinosaur sails etc.) fit most or all of these categories and even if in-depth analyses aren’t possible, it’s certainly a reasonable starting hypothesis that they are there for display.

So the often knee-jerk response of ‘ugh, you just say it’s display without evidence’ belies a real lack of understanding of the ways we can make reasonable inferences about these features and the simple fact that big and weird structures almost by default will match these lines of evidence (when say a big tooth or long leg or extra toe will not) should not argue against these as a starting point for discussion. Display features are rampant in large tetrapods at least and it should be no surprise that highly vision-oriented animals like dinosaurs and pterosaurs would have gone down various display routes. Yes, we need better arguments and testing, but I’m more than confident that many of these features will ultimately be shown to have had display as a major part of their functionality.

Anurognathid pterosaurs ate insects at night

Yes, it’s very early in the year but before 2023 had even hit, this paper managed to squeeze out actually appearing online on New Year’s Eve when I, and indeed most of the world, were not keeping tabs on journals so it rather passed everyone by and I’m now rushing to catch up! The good news is that it’s more anurognathid pterosaurs (arguably the best pterosaurs and certainly the cutest). These odd little animals have had a lot of attention in recent years with a bunch of new finds (some of which include new taxa like Cascocauda) and are just generally an increasingly well-studied clade given how many seem to preserve soft tissues which is rather nice.

For as long as I think anyone remembers, the anurognathids have been considered to be aerial insectivores, flying around at night and trying to catch insects on the wing. I don’t think there are any papers that have seriously challenged this hypothesis, and it’s been the default for decades given that their basic body plan and head shape means they have a massive gape, huge eyes, small teeth and wings well suited to this kind of flight. But it’s also an idea that hasn’t really been tested in any real way, relying on some basic (but perfectly reasonably) comparisons to things like whip-poor-wills and other similar birds.

So the central point of this paper was to try and do some more formal comparisons and see just how the anurognathids fare in comparison. I must confess I didn’t contribute massively to this paper, the lead author Alex Clark, who is based in Cincinnati, contacted me last year with the idea for the paper and really needed help with the pterosaur bit. He’s wrapping up his Masters on bird ecology and thought that it would be a good idea to do some formal comparisons on head shape in various insect-catching birds and those that operate in low light to the anurognathids to see how they overlapped. We also put in some comparisons to some insectivorous bats in terms of their canine shape and the similarly shaped teeth in the pterosaurs.

The details are of course in the paper but the really short version is this. Anurognathid heads shapes in terms of their gape is really similar to that of other birds that catch insects on the wing (like swallows and nightjars) and not like that of other pterosaurs. Their eyes are huge and again are like those of nocturnal, or low-light operating birds (in fact they are generally proportionally even larger). In short, this really strongly supports the conventional interpretations of anurognathid ecology. The tooth comparisons to bats were rather less helpful and the data is very scattered, and it’s at least not contradictory to the general idea.

No, on the one hand, no real surprises here. Our fundamental ideas were solid and the previous comparisons were reasonable, meaningful and turned out to be well-supported. Still, it’s really nice that this does back things up and that our basic inferences about anurognathids were correct and it means that those almost infinite drawings of the spiraling around after insects in the dark are not out of date. On that note, the paper does include some lovely new art of that very action with a new piece by Rudolf Himawan shown here.

I’d like to add a final quick thanks to Chris Bennett for generously letting us reuse some of his drawings to make our own figures clearer and to Manabu Sakamoto who gave us some useful pointers on some of the analyses. Mostly though, I need to thank Alex for inviting me to work with him on this project in the first place and seeing this paper through to the end.

Clark, A.D., and Hone, D.W.E. 2023. Evolutionary pressures of aerial insectivory reflected in anurognathid pterosaurs. Journal of Anatomy.

Microraptor ate mammals!

Ok, if we are being totally reductionist, one Microraptor ate part of one mammal once. But that’s certainly indicative of a pattern and that’s quite exciting. As you might guess, I have a new paper out today describing a Chinese specimen that shows this, though those with excellent memories and niche dinosaur knowledge might already know about this because it’s been announced before and way back in 2010!

Yes, this paper has been on the cards for a very long while. Back in 2010 Hans Larsson was over in the IVPP with his then PhD student Alex Dececchi and looking at various theropods. I was based there at the time working alongside my fellow Postdoc Corwin Sullivan under Professor Xu Xing. While looking over some flattened Yixian specimens, Hans spotted something that really people should have seen before (including me!). Clear as day in the holotype of Microraptor zhaoianus was the foot of a small mammal. Under the ribs.  Yeah, one of the most important and studied early feathered theropod finds had an obvious and very interesting set of stomach contents that had been completely missed.

Hans rather generously asked us all to collaborate on this find and we put in an abstract to SVP that year and so if you have the right knowledge you may have spotted this (or even seen his talk in Pittsburgh). In that regard this isn’t exactly news, and so it might come as a surprise that we ever got this out and so much later. Well, I’ll blame the others for that, (OK, mostly Hans!) but the fact remains it is now out and properly described, documented and put into some context and it’s the first, to my knowledge, example of a dinosaur eating a mammal, so that alone is nice and novel.

We don’t, annoyingly, know what the mammal actually is, despite having a much of things to compare it to, but we do know it’s small (mouse sizes) and doesn’t appear to have much in the way of climbing adaptations so would have been pretty terrestrial. That contrasts with interpretations of Microraptor as some kind of arboreal adapted flier that’s spending a lot of time in the trees. Still, we can’t say if this was predation or scavenging – though either way, it was likely this was picked up on the ground so it’s an interesting nugget of info on Microraptor diet.

On that note, this is now the fourth reported set of stomach contents for this genus with fish, lizards and birds also on the menu. Rather oddly, both fish and birds have been suggested to be something that Microraptor was specialised for, despite showing a) a diverse diet and b) no particularly obvious anatomical specialisations for either of these. Indeed, there’s a greater diversity of things eaten known for this animal now than any other dinosaur and that rather points to a generalist diet of any small thing going down the hatch. This of course comes with a few caveats here, there’s multiple specimens of Microraptor at play from more than one putative species and it’s at least possible that 1 species preferred things like lizards and mammals say, while another took birds etc. or these varied over time and space. Still, if there was any kind of specialistion we would expect to see multiple examples of single clades being taken, and I think that a generalist diet is likely.

That also fits with what we see in other small theropods as there are several with stomach contents or pellets featuring multiple taxa (e.g., Scipionyx) and suggesting they tended to eat a variety of things and specifically those that were rather smaller than them. This is in fact a bit of a pattern in general and while mammals aren’t always the best analogies, there is lots of data for them, and this is a trend seen there so it might well be that small theropod (be they small taxa or juveniles of big ones) tended to be more generalist. We do need to be careful here of course as we also then have preservation biases – Microraptor might, for example, have predated primarily on things like invertebrates and we know there were loads of beetles, spiders and the like around in the Jehol. But those don’t tend to fossilise well (especially not if crunched up and partially digested) compared to small bones, so perhaps these are just missing.

So one other thing we worked in here was to look at the jaw shape of dromaeosaurs in general and how this might fit with biting mechanics and so diet. While generally having incomplete skulls, Microraptor has a rather short head and lies in contrast to animals like Velociraptor with a longer and more slender skull, pointing to a proportionally harder but lest quick bite in the former (for its size) b. That also points to them not being especially adapted for things like insects where a hard bite wouldn’t be too necessary to kill or process them, but a quick bite would be an advantage. So while Micrioraptor might well have taken invertebrates as part of its diet, it doesn’t appear to be especially well suited to the task and biting small vertebrates looks like it was something more normal.

So there we have it, dinosaurs – perhaps unsurprisingly – ate mammals (and at least got their own back for Rapenomammus) at least on occasion. And more than that, Microraptor was (probably) a generalist predator of small vertebrate prey, though we can’t rule out scavenging or indeed other things like insects or even fruit as occasional parts of the diet. This might well be something common to many small theropods, though the general lack of data inhibits us from saying too much, the overall pattern of what information we have would tend to confirm this. It has taken us far too long to get this information out into the world but it’s finally made it and adds a nice note on theropod ecology and behaviour.

Finally, a quick thanks to my coauthors for sticking through all of this but also especially Ralph Attanasia III who kindly provided the illustration that went out with the press release and is shown above.

Hone, D.W.E., Dececchi, T.A., Sullivan, C., Xu, X., and Larsson, H.C.E. 2023. Generalist diet of Microraptor zhaoianus included mammals. Journal of Vertebrate Paleontology.

Larsson, H.C.E., Hone, D.W.E., Dececchi, T.A., Sullivan, C. & Xu, X. 2010. The winged non-avian dinosaur Microraptor fed on mammals: implications for the Jehol Biota ecosystems. Society of Vertebrate Paleontology (SVP), Pittsburgh, U.S.A.

Fifteen years of Musings

The Musings has been very quiet the last few years. I’ve obviously been busy at work and a lot of my outreach has shifted with the podcast (now more than 50 episodes done), various books (2 out, another nearly ready to got to the publisher), having the Guardian column for a few years, and being based in the UK again, I’m able to go and do more things in person, and then there’s Twitter of course which is so much better for dropping in a photo and comment than WordPress ever was.

Inevitably therefore, my output here has dropped and while it has typically been only a few posts a year and usually based around new papers. It still works very well for this, I can go into far more detail than on Twitter or similar platforms, cover all the ground I want to, link back to things, show photos or figures, and have control over it all (unlike media coverage). In short, I still like the format of blogs and I think they still have a place and I’m loathe to give up this one even if it has moved to being much more infrequent and most of the time is now only really about my research. So, it is likely to trundle on for now and fans and readers (assuming they still exist) can expect a few more posts to come and I’ve no immediate plans to wind this up.

That said, while it might be on a long and slow decline, I can take some solace in that it’s still going for now and by my count it’s now some 15 years of blogging (the vast majority on here and then a brief forerunner in a previous and now I think lost website). Compared to the palaeo-centric blogs out there (for example my hopelessly out of date and not at all curated list in the sidebar) I think this means that I’m one of the very longest out there and certainly one of fairly few survivors of the great burst of new palaeo blogs from the 2005-2010 era. I’d like to think that’s in part because this has remained a useful resource and while the posts and comments are less frequent than they used to be, plenty of old posts are still getting plenty of hits daily with some occasional big spikes when new stories break (the Fighting Dinosaurs post is going to be racking up hits forever).

So, Happy Anniversary to the Musings (even if that’s coming from its author) and I do hope there will be at least a few more years of posts to come.

The Future of Dinosaurs

After numerous substantial delays, my next popular science book is out now with Hodder. Called by the slightly cryptic title of ‘The Future of Dinosaurs’ the subtitle rather better explains what it’s really about ‘What we don’t know, what we can, and what we’ll never know’. Yes, this is all about the gaps in our knowledge and trying to spot some things that we probably can solve in the future with further application of our new techniques and new finds, but also look for areas which might essentially be unsolvable.

So this is a bit of futurism and crystal ball gazing, but hopefully something that’s interesting and based on a real understanding of current palaeontology. It’s not all just guesswork and gaps though, clearly to set the scene of what we *don’t* know, I have to start with what we do. What’s the state of play for various different aspects of dinosaur biology (there’s chapters on origins, physiology, appearance, behaviour, extinction and more) and what is certain or uncertain.

From there, it’s other what we don’t know. To give an example, we have recently started to piece together the colours and patterns of some dinosaurs which is something that I think many researchers thought would be effectively impossible. Its potential is enormous for understanding dinosaur biology, but it’s also something that we’ve clearly not yet exploited. Working out the (rough) colour of one black, white and orange Anchiornis is great, but we don’t know if that individual was an exceptional animal – maybe it was leucistic or melanistic and others were less black or less white in places, maybe it was a male in breeding plumage and the females were a different colour, maybe they went white in winter, maybe they were different colours in different regions or this changed over time? All of these are possible, perhaps even likely, and with the huge numbers of well-preserved specimens that have been discovered already and the likelihood of even more being found in the future, then this is something that I think we will inevitably begin to tackle in the coming years (OK, maybe decades). It really should be possible and while it would take a ton of time and research effort, there’s no obvious barrier to eventually being able to work this out and is something we will build on and understand better soon.

On the other hand, there are things we’ll perhaps never know about their feathers and colours. We can only work out some aspects of colour and patterns and things that rely on e.g. the orientation of the melanosomes that we use to work out colour are almost always going to be disrupted and other pigments for whatever reason don’t leave any kind of trace in the fossil record and can never be detected. It is also going to be nearly impossible to work out what displays they might have done, how they might have paired up or had different mating systems and so on, and so the colours will only get us so far.

While lots of people have talked at various times about where various branches of science are going next and what discoveries remain to be made, I don’t think there’s ever been a book like this trying to tackle lots of different aspects of our understanding (or lack thereof) and what shape our knowledge of dinosaurs might look like in the future. How successful I am, either in predicting what’s going to happen, or in suggesting why it might be the case, or for that matter in interesting my audience of course remains to be seen, but the book is out there now so let’s see.

If you do want to buy it, it’s available now as a physical book and ebook in the UK at least, and there is an audiobook version coming soon. This is also going to be released in North America soon through Princeton University Press under a different title (and different cover) as ‘How Fast did T. rex Run?’ but the content is identical.

Cascocauda – a new anurognathid pterosaur

Back when I was working on my big review of all anurognathid pterosaur specimens and their taxonomy, I realised that at least a couple of then unnamed specimens were probably distinctive and warranted naming.

One of them was a rather small, and not especially well preserved skeleton, that despite being nearly complete and with rather poor conditions to the bones, had extensive soft tissues. The preservation of these (both wings and filaments) had been the basis of some work on the specimen and not knowing what else might be going on, I dropped some of the authors a line to ask if they had any interest in the taxonomy of the thing and what they might be planning to do about it.

Cascocauda. Taken from Yang et al., 2022

As it happened, Zixiao Yang was indeed looking further into this as part of his PhD and was putting together a dataset on anurognathids to look at their growth. Having also been looking at this area in pterosaurs too they were kind enough to invite me to join them, and this work is now out.

The first thing to note is that we find that the specimen in question is indeed a new taxon and is named Cascocauda rong roughly translating as the fluffy ancient tail. For an anurognathid at least it has a rather long tail and hence that was chosen to be a key part of its new name. In terms of its relationships, we find it to be with the recently named Sinomacrops and Batrachognathus with all the other anurognathids forming a clade as the sister taxon to this group. We actually got this result using two different versions of the phylogenetic codings of which more in a second.

In addition to this more ‘basic’ work, the main part of the paper looks at the ontogeny of anuroganthids as a whole. While work that I’ve done (and plenty of others) have noted that a lot of pterosaur traits seems to be isometric and basically unchanging with growth, a) we don’t know how true that is of all taxa and b) if it’s not that’s potentially a big problem given how many taxonomic and phylogenetic traits we use for pterosaurs based on things like the ratios of the wing and leg bones.

So this is something we looked at here with the anurognathids, though with the rather odd caveat that we basically took the group as a whole rather than looking at the ontogeny of a single species (since that’s basically impossible). But if the anurognathids are as conservative morphologically as we think that they are then this is a reasonable approach to take and is certainly worth a look.

We do find that various bits of anuroganthids vary with size in some interesting ways though perhaps the most interesting is the length, and especially width, of the skull. They are called frog-mouths for a reason and that big gape is a key feature yet larger anuroganthids have a proportionally smaller skull. That points to both adults and juveniles having surprisingly similar head sizes and suggests that they are feeding on relatively similar sized prey even as they themselves get rather bigger.

Some other traits also appear to change during growth and could well be throwing off analyses that have used these characters when trying to piece together their phylogeny so these were removed or recoded in the analysis. As it happens this didn’t actually make a real difference to our results, but it’s nice to know that this isn’t apparel screwing up the relationships of the anurognathids at least, though it’s going to be something to keep an eye on in future when looking at pterosaur phylogenies given the number of taxa represented by only juvenile animals.

I’ll leave things there and won’t go into more detail since the paper is easily accessible and that will be the place to go for more details.

Yang, Z., Benton, M.J., Hone, D.W.E., Xu, X., McNamara, M.E., and Jiang, B. 2022. Allometric analysis sheds light on the systematics and ontogeny of the anurognathid pterosaurs. Journal of Vertebrate Paleontology.

Welcome Dearc, a giant rhamphorhynchine

Today sees the publication of a new and very cool British pterosaur – Dearc sgiathanach and as I got to see the paper a while back as a referee I thought I’d used that privileged advanced knowledge to write a post about it as it’s a really neat animal and British (and specifically Scottish) pterosaurs do not come around every day.

Photo of the skull and part of the body of Dearc, taken from Natalia Jagielska’s Twitter feed

First off, the basics on the name. It’s full name basically means ‘wing reptile from Skye’ and following s recent trend of using local languages for scientific names rather than Latin or ancient Greek, this is actually based on Gaelic. That’s really rather neat and I can’t think of any other Mesozoic animal so named in the UK and I hope it is not the last. Oh, and the authors (Natalia Jagielska and company) were also good enough to include a phonetic pronunciation in the paper (link below) as ‘jark ski-an-ach’ so hopefully people will be using that properly.

For a Middle Jurassic pterosaur, it has got a lot of good material and not only is it preserved in 3D (and there’s some great CT scan data of it) with most of the skull and wings, and a good amount of the vertebrae column etc. as well. You’d always want more of course, but it’s really a lot and in good condition too. The paper covers a lot of the anatomy in depth but I’m also sure there will be more to come on this in the future.

It’s clearly a non-monofenestratan pterosaur and actually one that is very close to Rhamphorhynchus, enough in fact to be found to be a member of the Rhamphorhynchinae in the phylogenetic analysis that they did. It actually comes out with the odd Chinese pterosaur Angustinaripterus which is known from a single large skull with exceptionally long teeth. In short, you’d expect this animal to be one of the larger and later version of these non-monofenestratans and a shoreline or even oceangoing predator of fish.

What’s really interesting about this animal is its size. The largest good specimen of any non-pterodactyloid pterosaur that we have is a really large Rhamphorhynchus that is held in the Natural History Museum in London and is right around 1.8 m in wingspan or perhaps is a touch more. That is already much larger than any other specimen (the next biggest is about 1.4 m) and while there are some odd large bones out there (like the Angustinaripterus skull) that has long been thought to be about as big as they get. On top of that, Rhamphorhynchus is from near the end of the Late Jurassic and so (anurognathids aside) is among the very last of the non-pterodactyloid pterosaurs. 

Although incomplete and impossible to measure or estimate perfectly accurately, Dearc is complete and robust enough to give it an estimate of over 2.5 m in wingspan. So that’s massively bigger than we have for even the largest Rhamphorhynchus (out of 150 specimens!) and being Middle Jurassic, it’s much older too. Add to that, it probably had more growing to do too.

So that pretty much blows out of the water two classic ideas about the size of non-pterodactyloids. They could get above 2 m in wingspan and indeed much bigger, and it didn’t take them till the very end of the Jurassic to even get up to 2 m in wingspan. That’s really quite an interesting shift in our perceptions of their evolution and in particular means they were getting into some biomechanical realms that we didn’t think they could achieve without a pterodactyloid bauplan. In short, this is a really cool find and it promises much more in the future for our understanding of the evolution and flight of these pterosaurs.

Jagielska, N., et al., 2022. An exquisite skeleton from the Middle Jurassic of Scotland illuminates an earlier origin of large pterosaurs. Current Biology.

Ceratosuchops and Riparovenator: two new British Baryonychines

Today sees the publication of my most recent paper and it’s inevitably exciting as it describes two (yes two, count them) new, large theropods from the UK. Both join the burgeoning ranks of the spinosaurs, which have been increasing in lumber a lot of late and more specifically these are baryonychines.

While Spinosaurus tends to get all the attention, it and its kin, the especially large and sail-backed spinosaurines are known from extremely fragmentary remains and the smaller and less spiny baryonychines include Suchomimus and Baryonyx that are known from much more material.

In the case of the latter, this has been absolutely central to work on the spinosaurs as a whole as being the most complete and by far the best described specimen out there. The foundational monograph by Alan Charig and Angela Milner (who sadly passed away recently) being a cornerstone of spinosaur research. It’s also inevitably rather central to our work here since with two new baryonychines then we going to have to compare them to Baryonyx.

As usual, I don’t want to get into the minutia here since if you really want to look through the details of the diagnoses and traits and stratigraphy that’s all covered in the paper and this post is better placed to give some context to what we have done and why. The first thing of course is the names and their meanings. First off we have Ceratosuchops inferodios or the horned crocodile face hell-heron, the generic name referring to its appearance and species referring to the putative ecology of spinosaurs as a whole. After that is Riparovenator milnerae or Milner’s riverside hunter, in tribute to Angela’s work on these animals and again the ecology of these animals.

The second obvious thing to look at is what actually is there for the remains. Sadly, (if rather predictably) not that much though we do have nice snouts and parts of the skull roof and braincase for both, and in the case of Riparovenator, there’s also a nice section of tail. While pretty incomplete therefore, we do have more than some other spinosaurids and crucially we have the same parts of the skulls of both of these as we do for Baryonyx and Suchomimus. That’s obviously a huge bonus when it comes to the taxonomy work of sorting these animals out and we can make direct comparisons to these parts of the skulls that hold a lot of important traits.

Still, an obvious question about these British animals would be the vexed issue of ontogeny and if one (or both) were juveniles of each other. Happily, all three of the British ones are all extremely similar in size (within about 105 of each other) so it would be pretty hard to argue that they were very different ages and so the differences in anatomy are going to be ‘real’ and not part of their growth patterns. (And if they were very different ages but still the same size that would also suggest they have very different growth patterns and are therefore likely different taxa anyway). While we’re on the subject of the quality of the data here, it’s also worth noting that the specimens are generally really well preserved and not distorted so again, it’s a pretty safe bet to take the available features at face value as being genuine.

A major part of this paper is a new phylogenetic analysis done at the specimen level, with loads of odd bits and scraps of spinosaur material included for the first time in a comprehensive study (though some more things have appeared since we finished so it’s not 100% coverage). There’s not too many real surprises in there, but it should be a great start for resolving some other taxonomic issues for spinosaurs going forwards. One key thing though is the very clear signal that all of the earliest spinosaur material is European in origin and it looks to be a very strong case that this is a European group that then migrated out from here on multiple occasions.

Finally, there is the issue of the ecology of these animals. We don’t actually know if the two were contemporaneous with each either and either or both could be with Baryonyx and so while I’m sure some people will read this as ‘there were three together?!!’ we don’t actually say that. It’s perfectly possible from the data we have that all were somewhat separate in time and in space and of course niche partitioning is absolutely a thing too. I wrote this post on these issues a while back with this paper in mind to make the point about these kinds of situations and how it is easy to misinterpret them or assume that multiple species of large carnivores being together is somehow unusual or wrong. In the case of spinosaurs in particular, I’ve suggested that they are rather off in that they are except when they are common when they are suddenly very common (https://archosaurmusings.wordpress.com/2010/01/25/a-late-cretaceous-asian-baryonychine-probably/

) and this perhaps another example of that and hence the plethora of finds in the South of the UK.

I’ll finish up here, but obviously I want to thank Chris Barker and Neil Gostling for inviting me into this project and all my co-authors for their contributions to this publication. The paper is fully open access and available here: Barker, C.T., Hone, D.W.E., Naish, D., Cau, A., Lockwood, J.A.F., Foster, B., Clarkin, C.E., Schneider, P., and Gostling, N.J. 2021. New spinosaurids from the Wessex Formation (Early Cretaceous, UK) and the European Origins of Spinosauridae. Scientific reports.

There’s lots more about these finds online with a Terrible Lizards podcast here with Chris Barker and Darren Naish, and both Darren and Andrea Cau have blogposts out on this too.

Niche separation in the fossil record

There is a slow but steady publication papers that describe new fossil taxa that state or imply that the presence of some new species is evidence for niche partitioning in the animal’s ecosystem. This is basically redundant and is akin to the classic ‘this new species adds to the known diversity’ as if it could do anything else. One of the fundamental ideas of niche theory is that two species will not occupy the exact same niche. If they do, one will go extinct (or be forced out) or will adapt. In other words, for two species to live alongside each other there will be, by definition, niche separation, so pointing it out as some revelation or important insight or gained knowledge from two species being present is really not the case.

Worse, it might be wrong. Most of the time with new finds we don’t have very much to go on, so we don’t actually know that it truly did occupy a unique niche. Perhaps it was a transient species and so could survive briefly in full competition with another species as it passed through or had only just invaded and in the fullness of time would outcompete (or be outcompeted) by another species. So a statement about two (or more) species with similar biology (perhaps they are close relatives) being evidence for niche partitioning is most likely either redundant or wrong. Either way, as currently reported, it’s really not needed as commentary on a lot of papers about palaeoecology.

As a related point, there is an idea floating around (online and in discussions rather than I think in the scientific literature) that large predators can’t coexist normally, especially if they are closely related. There’s an expectation that ecosystems with say three large theropods in (or even three large tyrannosaurs) would be really weird and somehow not normal or possible. I’m not sure why this idea is out there but I think it’s a misunderstanding of the above point about niche separation and is somehow a conflation of the idea that species somehow doing the same thing or eating the same prey means one will inevitably come out on top, but again this isn’t really correct.

First off, species can be catching prey in very different ways, but still competing with each other. You only need to see videos of a baitball and any combination of sharks, dolphins, whales, sealions, large fish, diving birds and others all going after the same small fish. Each has its own technique and feeds and processes food very differently, but they are in direct competition for that same resource. So just because birds are flying and have no teeth, doesn’t mean they don’t compete with the dolphins and there is at least some niche overlap between them. Even very similar and near identical species can still partition successfully depending on quite what they are eating and when. They may be separated by seasonal or daylight cycles, or be targeting different prey species even if they are hunting it in the same manner, they will be likely shifting their niches as they grow, and there could be all kinds of local differences in habitat that are hard enough to spot in living species let alone in the fossil record.

Back in my paper describing Zhuchengtyrannus I made this point and the idea that multiple similar species in ecosystems is not actually that strange. However, some ongoing work on a related issue with theropods has made me look again at this and pull out a couple of relevant examples from modern / recent ecosystems. A quick look at the distribution maps on Wikipedia (hardly the last word in science I know, but sufficient to make the point) shows that the estuarine crocodile C. prorosus overlaps with C. johnstoni in part of Australia, C. mindorensis in the Philippines and C. novaeguinea in New Guinea. C. siamensis and Tomistoma both overlap with it and each other in parts of Indonesia, and there is a similar 3-way overlap with both C. palustris and Gavialis in India. Similarly, in South America, Caiman crocodilus, Melanosuchus and two species of Paleosuchus all overlap with each other. Now, at a very local level in a given pond or a short stretch of river there might be only one or perhaps two species present, and in some cases there are some dramatic differences in skull shape and gross feeding ecology, but these overlaps and the inevitable occasional migrations or transport of individuals means they must be truly sympatric at times and probably under some competition.

For a more terrestrial example, the 2019 paper by Schnitzler and Hermann looking at fairly recent (historical) overlaps of large mammals in Asia (especially lions and tigers) has this wonderful quote [that I have modified a little for clarity] about carnivores in part of Western Asia. “The Western Asian area of the Palearctic Biogeographic Realm includes part of the continental interior of the Near East (the northeastern part of Anatolia in Turkey, and Transcaucasia – Georgia, Armenia, Azerbaijan), part of the Caspian lowlands and western part of Pakistan. [It] had an impressive assemblage of large mammalian carnivores (Asiatic lion, Caspian tiger, Asiatic cheetah, Anatolian leopard, lynx, brown bear, grey wolf, jackal, and striped hyena).”

That’s really quite a set of animals and while jackals were probably not much competing with lions for food, there’s a huge amount of overlap here. Even modern India has striped hyena, jackal, dhole, wolves, leopard, lion, tiger and sloth bears in various parts and until recently cheetah too (plus, of course, three large crocodylians) and while their ranges are now much restricted there would have been much greater overlap in the past. In short, while obviously dinosaurs are very different to mammals and crocs, the idea that a Mesozoic ecosystem couldn’t support two or three large theropod genera looks like a poor hypothesis against the kind of overlaps we see even in modern depauperate and stressed ecosystems. Multiple large carnivores, even including closely very related species from the game genus, that are known to hunt similar prey in similar ways, are commonly sympatric and there’s no clear reason to assume ancient systems were that different.

Schnitzler, A. and Hermann, L., 2019. Chronological distribution of the tiger Panthera tigris and the Asiatic lion Panthera leo persica in their common range in Asia. Mammal Review, 49(4), pp.340-353.

Dinosaur tails redux

Getting on for ten years ago, I published a paper looking at the lengths of the tails of dinosaurs. The short version of that is that total length of tails in dinosaurs varies massively both between clades and even within groups (or within species!) which mean that a lot of the ‘total length X’ estimates for various dinosaurs are probably way out. Still, it wasn’t the biggest dataset and there’s not a lot of nuance to looking at total length vs body length, plus being restricted to only complete tails really cuts down on the number of specimens you can use.

Still, not too long after the paper was published, I set about trying to get a better dataset together as more dinosaur tails were coming out of the woodwork. That led to this appeal on here which helped reel in a few more specimens. Still, I wanted to do something more detailed and that led me to roping in my friend and colleague Steve LeComber.

At the Cheltenham Science Festival (L-R, Me, Steve Le Comber, Chris Faulkes, Jane Hallam)

Steve will be all but unknown to readers on the Musings as he never worked on dinosaurs before, though as a great science communicator he helped me out at a number of my events, especially when we went to the Cheltenham Science Festival together a few years ago.  Sadly, this will also be one of his last papers as he passed away at the end of 2019. Steve was one of my closest friends and colleagues, and was one of the most popular and friendly people I have ever met. He had an entire career as a journalist and writer before switching to science and was a superb statistician as well as a great biologist and a wonderful educator.It’s a testament to his work that papers are still coming out of his lab and his work on geographic profiling will have an important and lasting legacy in biology. He will be forever missed. (A scientific obituary was published for Steve here in the Journal of Zoology, where he was an editor for many years).

I had turned to Steve because he was tremendously creative with analyses and I had no idea how to approach the next problem I wanted to tackle – what was happening with individual vertebrae in the tails of dinosaurs? Very little has ever been written about this, and what there is implies or even states that as you go down the tail, each vertebra is shorter than the last. But you only have to look at a couple of specimens to see that this really isn’t the case. It’s true for big chunks of the tail, but the part closest to the hips often has short vertebrae but after that they tend to get longer, and in very long tails like those of sauropods you can find multiple sets of vertebrae that are lengthening. But how to capture this information? If groups of vertebrae are letting longer or shorter, and if this changes slowly or dramatically, or is just an oddity, can we capture it? Happily, he had some ideas.

As I was by now established at Queen Mary, I really lacked the time and opportunities to revisit collections and measure individual vertebrae so we then roped in Scott Persons, who has his own interest in dinosaur tails and had measurements we could use, or was able to get into some of the Canadian collections to procure more data. Various issues delayed the paper on numerous occasions but it is now out so here’s some quick take-home results (the full paper is in PeerJ and open access so you can see all the figs and data there).

First off, with more and better data, we did revisit the issue of overall dinosaur tail length and it is still very variable and unpredictable. Total length estimates without most of the tail present could easily be very wrong, and even some tails that you might think are pretty complete could easily truncate suddenly or go on much longer than you might think. There’s still a place for these of course (especially for engaging the public) but the standard ‘my theropod is longer than yours’ battles really need to stop. Total length isn’t a great indicator of size (mass is) and tail lengths, and by extension total lengths, are very hard to estimate without a near complete tail.

Obviously we do now have a much better Spinosaurus tail, but this old image by Scott Hartman demonstrates just how wildly different tail lengths (and so total lengths) of an animal could be for the same body size.

On to patterns within tails. First off we do find that individual vertebrae within tails simply don’t tend to get shorter as you go along them. There’s some interesting and cool patterns going on and I don’t want to cover all of them here (for example Coeplohysis is all over the place, and Juravenator seems really weird) but here’s a few of the more interesting ones. We use broken-stick regressions where we can have multiple different trajectories of sections of the tail lengthening, staying the same length or shortening. It’s a great tool to see what is happening and is visually nice and easy to follow, without getting mired down in the odd vertebra that’s rather out of place with the others.

First off, that means that it’s good for spotting changes in patterns of vertebrae lengths and also deal with (bits of) missing data quite well. This is also really useful for predicting the lengths of missing vertebrae and this is likely to be useful for things like working out total lengths of animals and the sizes of individual verts when reconstructing fossils. It’s also absolutely ideal for putting together skeletals and even mounted skeletons in the future.

Second, many dinosaurs have a pattern of a set of short vertebrae, then longer ones, and then the rest of the tail does indeed taper off. The second switch (were the long ones stop and it starts to taper) coincides with the ‘transition point’ in the tail, where the main leg muscles terminate, suggesting an important link between the two and from this we hypothesis that this short-longer- tapering pattern is a functional one linked to tail flexibility and muscle power. This clearly needs more work, but it’s a very interesting starting point.

Next, some exceptions. Plenty of dinosaurs don’t fit this pattern for various reasons (some it’s probably just missing data or it’s a subtlety like the tapering happens in two different phases), including some that do just generally taper. There’s some huge intraspecific variation in some but others are very consistent. All three specimens of Archaeopteryx we included show a weird humped distribution which is also very similar to Microraptor, and also different to other dromaeosaurs. That rather implies that this is flight related and that this is an important convergence, though again quite what and how is well beyond what we cover in the paper, it’s an area that hopefully others will pick up on. And aside from Microraptor, the dromaeosaurs appear to be highly variable which we attribute to their ‘sheath’ of elongated supporting rods for most of the tail length which would dominate any other functional issues and might leave the lengths of individual vertebrae to be fairly free of constraints.

I’ll leave it there since the paper is freely accessible and there’s lots that can be extracted from it, but I think this covers some of the more interesting points. The methods in particular should work well for any repeating units and while we have focused on dinosaur tails here, they should apply equally to any vertebral series or things like ribs, arthropod segments, and so on. I’d really hope that people will immediately see the use of this for describing things like sauropod or plesiosaur necks, pterosaur tails, or the lengths of neural spines or size teeth in a series. Of course I also need to say thanks to Scott and Steve and various referees and editors for helping get this published, and especially thanks to all those who contributed data to get this moving.

Hone, D.W.E., Persons, W.S.C. & LeComber, S.C. 2021. New data on tail lengths and variation along the caudal series in non-avialan dinosaurs. PeerJ. 9:e10721.