Posts Tagged 'Pterosaurs'

A post about a tail with no pun in the title

So onto the last major post about Bellubrunnus – the tail. The tails of rhamphorhychines are interesting as they have a somewhat unusual anatomy. Just like the dromaeosaurs (though obviously, convergently acquired) rhamphorhynchines have elongate zygopophyses and chevrons that overlap multiple vertebrae and bind the tail together so that it is a relatively stiffened structure. These extensions are basically rods of bone, and can long enough to overlap the four or five adjacent vertebrae to their origin.

However, Bellubrunnus appears to be unique among rhamphorhynchines in lacking these structures. It still has zygopophyses and chevrons (as can be just about seen in the figure) and compared to some pterosaurs at least these are long, but they are a fraction of the length of other closely related species. This begs the obvious question, of what happened – are these really reduced or is there some other factor at play? Well, there are a number of possible hypotheses to explain this and here I’ll go through them and why we have come to the conclusion that this is a genuine feature. Not all of the chevrons are there for sure, so some have been lost or remain cryptic for whatever reason, but several are quite well preserved and so the below discussions refer to the issue of the size and shape rather than presence / absence of chevrons.

First off, were these simply not properly ossified prior to preservation and were there, just as unpreserved cartilage? This seems really unlikely, even the smallest and youngest specimens of Rhamphorhycnhus (which includes specimens even smaller than Bellubrunnus) have fully ossified chevrons and zygopophyses. These seem to be present at a very early age in the pterosaurs that have them and so it would be odd if they had a different ossification pattern here. Indeed it would be doubly odd since if anything, Bellubrunnus has better ossification of its elements than is usual for small pterosaurs, with well-preserved and ossified tarsals and sternum. So it is far more likely that they are fully ossified, they are just much smaller.

Could these have been lost through decomposition or disassociation from the specimen, or may not have been preserved even if they were ossified? While a few pieces have begun to disarticulate and move (the gastralia and a few dorsal centra and the prepubes) nothing else on the specimen has really begun to move and indeed the caudal vertebrae as a whole is well articulated. It would be odd indeed if the only thing to have rotted or moved was the chevrons or parts of them, while the rest remained intact and complete. Similarly, with even tiny parts like the delicate palate and gastralia being preserved (and indeed at least a couple of chevrons) it also seems unlikely that these somehow resisted preservation when everything else is there. Certainly it’s possible, but even so, some are still there and the loss of many chevrons would not affect the shape of the ones that have survived and wouldn’t affect the zygopophyses.

Were these destroyed or modified through preparation? This is a tricky one to answer, but again, there’s no obvious reason to think so. The preparation job is superb (look at the skull!) and was done with great care and attention to detail. It’s always possible that thin and delicate structures were lost, but while the matrix has been all but scraped clean, at least some have survived (and again lots of other delicate things) and I find it hard to imagine they were modified in such a consistent manner.

Are these genuinely distinct then? That is the obvious conclusion given the problems with the other hypotheses. However, there is more than just negative arguments against these other ideas, but there are reasons to positively support the idea that these are genuinely short. Although greatly reduced in length, the anatomy of both the zygopophyses and chevrons is otherwise well consistent with the anatomy of these features in other rhamphorhychines. The zygopophyses are rather rod-like and then taper abruptly to a point, just as we see in others, only with a much shorter rod. And similarly the chevrons are long and thin and splint-like, terminating in a point at each end, just as we see in others, only again being rather shorter.

While as noted we are rather short of chevrons for whatever reason, those that remain and indeed the zygopophyses seem to have a genuinely distinct morphology to other rhamphorhynchines, including similarly small and young specimens of Rhamphorhycnhus. This then is a major anatomical difference that separates Bellubrunnus from its nearest relatives as well as providing a little more interest and intrigue in the origins of this structure since while it is present on all other rhamphorhycnhines, it’s also present in basal pterosaurs outside the group and so may well have had multiple origins and losses.

Brunn – not the Solnhofen

At the end of my last post I raised a most significant point – Bellubrunnus isn’t a Solnhofen pterosaur. While it’s easy to think that those Jurassic lithographic beds from Bavaria are the Solnhofen, it’s not the case. Like all rock records, different divisions are known and are grouped in various hierarchical clusters. The Solnhofen is home to a lot of important species (Archaeopteryx for starters, not to mention all the pterosaurs and insects and plants and fishes) and a good deal of work has gone into working out the stratigraphy of all these different fossil-bearing beads, but not all lithographic limestones lie in the Solnhofen.

Obviously this doesn’t mean that an animal from one layer right above or below the Solnhofen didn’t overlap in time with other strata – the rocks don’t delineate when and where species lived. However, Brunn is rather older than even the oldest Solnhofen beds and from the Kimmeridgian rather than the Tithonian. While the rocks are of a similar kind and were put down in a similar manner in similar ecosystems, the two are different.

Work on the Brunn beds are still very new and I must confess I’ve not looked into it in any great detail (not least as all the literature seems to be in German) and have had to rely heavily on my colleagues here. Still, the two do seem to contain different taxa as a whole and while to date the higher vertebrates at Brunn have been few and far between, given the quality of the preservation, I don’t think there’s any reason to expect that we won’t get a lot more in the future. Moreover this does suggest that Brunn is different to the Solnhofen and so we might expect a different (if closely related) fauna to be present. In short, the fact that we now have literally hundreds of pterosaurs from the Solnhofen and no record of Bellubrunnus there, supports the idea that this is a different genus, and also the idea that there might be many more new pterosaur species in there to be found. At the very least, there is a lot more to learn from the Brunn biota.

One last point to address here lies in the temporal distribution of rhamphorhycnhines. The recently described Qinlongopterus is also known from a single, small, and young specimen, though it heralds from the Middle Jurassic of China. As described this taxon is really rather similar to Rhamphorhynchus and it was suggested that as such, the rhamphorhycnhines might be really rather stable as a group and went long periods of time with little morphological change. Obviously Bellubrunnus interrupts this apparent trend, as compared to the Middle Jurassic of China, it’s much closer in time and space to Rhamphoprhynchus, yet does have quite a few differences. This is probably due to that fact that unlike Bellubrunnus, Qinlongopterus is really badly preserved, and morphological information is rather limited. What can be seen in Qinlongopterus is very Rhamphorhynchus-like, but that’s not saying much since the condition of it means that not all the many details can be seen. Plus of course the young of species tend to be much harder to tell apart than the adults, since, well they don’t have all their adult features yet and typically the younger they are the harder that will be. So in fact this ‘stability’ is illusory based on the age and condition of Qinlongopterus and in any case is interrupted by the emergence of Bellubrunnus and its differing anatomy.

And on that subject, next up, that interesting tail…

Bellubrunnus – definition, diagnosis, and why it’s not Rhamphorhynchus

Right, lets crack straight on with dealing with the details of this lovely little thing. First off, if you have read this post on pterosaur ontogeny, you should be able to recognise that while Bellubrunnus is small (in fact it’s tiny, with a wingspan under 30 cm and a skull just a fraction over 2 cm), it’s also very young. The head is proportionally huge, and the eyes (represented by the sclerotic rings) are massive too, lots of neurocentral sutures are open (as can be seen by displaced centra in the dorsal series) and the wrists, pelvis and scapulocoracoids are unfused, and even the skull is coming apart. Unusually for such a small pterosaur though, the tarsals are well ossified, though they are rather amorphous in shape, which is a classic feature of young pterosaurs.

This then is a very young animal. That does of course complicate issues a little as obviously some things change during growth and we don’t want to misdiagnose this by thinking it has some unique features which are in fact simply a result of its age. On the other hand though, following mostly from the work by Chris Bennett, we have a good idea of the ontogenetic changes undergone by Rhamphorhynchus as it grew so we do know what kinds of things change as they grow (and so can be avoided, or used carefully) and which don’t (and can be used pretty freely).

Lets start with the most obvious thing – Bellubrunnus is a rhamphorhynchoid pterosaur. It has a proportionally small head (compared to the size of the animal as a whole, and the body specifically), short neck, short wrist and pteroid, short metacarpal IV, long tail, long 5th toe and other characteristics. Moreover, it’s also a rhamphorhynchine – a derived member of this basal assemblage and close to things like Rhamphorhynchus and the recently described Qinlongopterus. Bellubrunnus exhibits a number of characters associated with this clade such as the shape of the deltopectoral crest and the proportional length of the wing finger.

Bellubrunnus is also really rather like Rhamphorhynchus which might be no surprise given the rocks it heralds from (though more on this later) – the area is kinda famous for producing specimens this genus in serious numbers. The two share a number of characters previously used to diagnose the latter alone such as edentulous jaw tips, a femur shorter than the humuers, and an H-shaped prepubis. However, the two also have some rather notable differences that clearly mark them as different taxa. Among other things, Bellubrunnus has only 22 teeth (or perhaps even fewer) compared to some 34 in Rhamphorhynchus, it has a rather different tail anatomy (more on this to follow as well) a different humeral shape, and several major proportions of the limbs are quite different.

The point about proportions is quite a significant one. Proportional ratios between various elements are common characters for pterosaur taxonomy and systematics, but unhelpfully, we also know that some of these change during ontogeny in at least some groups. So we do need to be careful and this is no exception. The best example here is the ratio of the humerus to the femur – in Rhamphorhynchus this seems to get larger as the animal gets bigger. Small (and so young) specimens tend to have a lower ratio and adults a high one. Bellubrunnus is among the smallest pterosaurs known and comparable in size to the smallest (and youngest) specimens of Rhamphorhynchus, but it’s ratio is the higher than any specimen of the other genus.

While I’ve not mentioned it here, in the paper we do compare this to other members of the rhamphorhynchine clade and provide similar numbers of difference in things like tooth count, anatomical features, skeletal proportions and the like. A number of these taxa are rather fragmentary and hard to say too much about, but do always differ from Bellubrunnus.

So in short while we can be sure this is a very young animal, we can also be confident with our assignment to the rhamphorhycnhoids and rhamphorhynchines, and while this would appear to be a close relative of Rhamphorhynchus, it’s also clearly quite different in a number of characters, marking it out as a new and distinct taxon. One last point needs to be raised here too as a launch-pad for the next post, Bellubrunnus is from Brunn, and Brunn, well it’s not actually part of the traditional Solnhofen that is home to Rhamphorhynchus. It’s older and the two were not contemporaneous.

Introducing Bellubrunnus

Visitors to the Solnhofen Museum in Germany in recent years might well have seen a delightful specimen of a small Rhamphorhynchus on display. While clearly a nice little find, it was hard to see too much detail under the glass given how a) small it was and b) just how close in colour the bones were to the matrix it was preserved in. Certainly I didn’t give it much more than a glance when I first saw it as part of the Flugsaurier fieldtrip way back in 2007, and I’m not sure that many of my colleagues did either (though to be fair we had only an hour or two to try and do the whole museum, and well, if you work on pterosaurs you generally have seen a lot of Rhamphorhynchus material).

However, while I was in Dublin, a PhD student working on Solnhofen jellyfish pointed me back to this as something worthy of more special interest. Once I had some decent photos of it, it was clear that it was indeed something rather more special than just a young and complete specimen of Rhamphorhynchus. Indeed, while clearly having a lot in common with this very well known genus, there were some obvious and pretty significant differences. Talking to the curator at the Solnhofen, Martin Roeper, I discovered that (perhaps inevitably) Helmut Tischlinger had already taken a number of UV images of the material and he and Dino Frey had planned to work on it, but things had fallen behind. A few more exchanges and I was generously offered the chance to lead the formal description of the material and write up this interesting find.

That paper has now been completed and indeed published, and as such the inconveniently labelled specimen BSP–1993–XVIII–2 should now be known as Bellubrunnus rothgaengeri. The species name honours Monica Rothgaenger who led the team that uncovered the material and donated it to the museum (note that while this has a BSPG number, it is on permanent loan to the Solnhofen). The generic name comes from the locality of the matieral, Brunn, and the Latin ‘bellus’ meaning beautiful. This is the beautiful one from Brunn, and well, as you can hopefully see, it really is a superb specimen. It’s effectively complete and articulated and preserved in ventral view. While it is indeed hard to make out too much detail under normal lighting conditions, under UV, the difference between bone and matrix is obvious in the extreme and the details quite apparent and with tiny and fragile parts like the sclerotic rings, the palate, the tarsals and prepubes being preserved. Sadly though, there’s no sign of a single jot of soft tissues anywhere, despite the superb (indeed, unusually good) preservation of the bones. The matrix around the bones has been prepared right down to help expose them and you can see the scrape marks of preparation tools around the specimen.

Happily for all fans of sci comms and outreachy things, the paper is in PLoS ONE (the latest in quite a series for pterosaur work this year it must be said) and so freely available. There is, inevitably, a lot to be said about this animal and while the paper IS freely available, I think that there is a good mine of interesting things here that help reveal ideas about pterosaur evolution and anatomy. And let’s face it, even with the best will in the world, it can be hard to fight through a long paper, and it’s rather easier to read a few blog posts. That said, obviously with the paper being freely available, if you do want more details and specifics and citations etc. then the paper should be the first place you look.

This post then is perhaps not so much more than a holding pattern while obviously showing off the material itself, and this superb life reconstruction by Matt van Rooijen (which is also in the paper and so available) whom I must thank for his superb efforts. I’m not going to try and spin this out too much, but there are some nice areas of interest about Bellubrunnus that can be easily separated from the rest and make nice short and self-contained posts, so I’ll try and do just that. We’ll start almost immediately with the most obvious question – what exactly is it?

Hone, David W. E., Helmut Tischlinger, Dino Frey & Martin Röper. 2012. A new non-pterodactyloid pterosaur from the Late Jurassic of southern Germany. Public Library of Science ONE.

Horniman pterosaurs

Yesterday I put up some photos of the gloriously anachronistic dinosaurs at the Horniman museum. As you’ll have already deduced from the title that they also had a couple of pterosaur models. While presumably hailing from the same era (and perhaps even that same artist) they are not quite as inaccurate, though this is, I suspect, more to do with the fact that our ideas of pterosaurs have changed less over time (or in some cases returned to an earlier idea), rather than any greater level of detail being paid to the pterosaurs.

While there are (inevitably) some mistakes, the only really standout one is the neck of the Pteranodon. It’s absolutely tiny and makes it look like the head has just been welded onto the body. Given that one of the defining characteristics of the pterodactyloids is the long neck, and that in Pteranodon it should be about half to two-thirds of the length of the skull, this is far from a good representation of a pretty basic bit of anatomy.

Academics on Archosaurs: Mike Habib

Michael Habib, University of Southern California
I primarily study the biomechanics of flying vertebrates, especially early birds and pterosaurs.

1. What first got you interested or involved in your research field?

I’m a classic – I declared loudly that I wanted to be a paleontologist at about the age of four.  The most important catalyst was probably the trips I took with my family to the National Museum of Natural History, in Washington, DC (I grew up in that region).

Perhaps a more interesting story is how I ended up in my particular speciality.  While I am really a rather general biomechanist, I think most Musings readers will know me as a pterosaur worker.  I’m quite pleased by that label, but it came as something of a lucky break – I really got rolling on pterosaurs after attending the 2007 Flugsaurier Conference in Munich, which I originally attended on something of a whim because I’d been playing with a few pterosaur bits at the USNM collections in between bird work. That was a real full circle moment because I’d loved pterosaurs as a kid.  Of course, as Musings folks will no doubt recall, Dave organized that conference!  Thanks Dave, it rocked.

2. What is your favourite piece of research?
Okay, no surprise here – I’m most pleased by the quadrupedal launch model for pterosaurs I proposed in 2008.  I think that has actually had a measurable impact on how we reconstruct pterosaurs, and it also seems to have affected how other scientists think about animal takeoff and flight evolution.  So that’s pretty darn cool.

To be fair, though, a paper I’m currently writing may end up being one of my all time favorites (it’s the much discussed anurognathid study with Mark Witton.  I know, I’ve been talking about it forever, but we keep adding stuff – this is going to be a wicked paper).

3. What do you think is the most interesting or important discovery in your field in recent years?
This is a much more difficult question for me.  For one thing, I’m not sure what my “field” really is.  If we assume it’s animal flight evolution, then I would have to list the discovery that functional wings existed in theropods outside Aves (which either means theropod flight should up more than once, or that theropod flight came before birds).  If we assume I’m a “pterosaur guy” then I suppose it would be the range of new soft tissue discoveries that have rapidly accrued, in part because of the outstanding UV imaging studies of individuals like Helmut Tischlinger.

4. What do you think is the biggest unanswered question in your field right now?

Within animal flight overall, the largest questions relate to the origin of flight in pterosaurs and bats.  While debate will range on about the details of the origin of avian flight, we have the base layer pretty well worked out now.  However, the early stages of flight in pterosaurs and bats are darn near completely unknown at this stage.  I’m waiting for some really excellent stem-pterosaurs to be discovered.

5. What advice would you give to students about research?
Remember that you are a professional writer.  You have to do good science to have things worthy of writing about, but at the end of the day, every academic scientist (and that’s practically every professional paleontologist) is basically a professional writer.  Own that fact, and live up to it.  Work hard to write well, and think carefully about your readership and how to reach the people you want to read your work.

Pterosaur ontogeny

 Not too long ago, Matt Wedel had an SV-POW! post that talked about ways of diagnosing an adult vs non-adult sauropod. Inspired by this and the fact that I have recently been playing around with issues of ontogeny in pterosaurs, I decided to write something similar for the non-avian Mesozoic fliers. If you have a pterosaur specimen in front of you, just how do you know if it’s an adult or not?

Obviously there are some general indicators that are pretty good for vertebrates as a whole that will get you quite a long way (even if this is a new species). Size is obviously rarely a great indicator, but if you have a pterodactyloid with a 20 cm wingspan then it’s going to be a juvenile, and likewise if you have a rhamphorhynchoid coming in close to the 2 m mark it’s very unlikely to be anything but a big adult. Young animals (and especially very young animals) tend to have big heads compared to their body and especially very big eyes compared to the size of the head. A bunch of fusions are absent in young pterosaurs that are present in adults too, just as you’d expect for most animals. The sutures between the centrum and neural arch of the vertebrae will be open in juveniles and closed in adults, and similarly the elements of the pelvis and sacrum, and the scapula and coracoid will be separate in young animals and fused together in adults.

Pterosaurs also have some characters of ontogenetic change that are rather more peculiar to them than vertebrates in general. Very young pterosaurs also tend to have a very grainy texture to the surfaces of their longbones, despite the fact that even embryonic pterosaurs have a pretty ossified set of bones (unlike many young animals). Smaller pterosaurs also tend to have various parts of the skeleton being less ossified and rather amorphous compared to those of adults. The tarsals are often not well ossified and can be missing (well don’t preserve) and if present may be very simple shapes. The carpals tend to look more ‘blobby’ and lack the detailed morphology seen in adults and will be separated into multiple elements whereas in adults the wrist will primarily be formed of just two massive elements (plus the pteroid). Finally, while obviously you would expect skulls to fuse up during ontogeny, pterosaurs do tend to take it one step further than most. Rather like birds, in adult pterosaurs the sutures all but disappear, or even go entirely, such that the skull looks like a single smooth piece of bone. Also as in some birds, bigger pterodactyloids have a notarium and this only fuses up and fully develops in adults. Similar to the point above about absolute size, the presence and development of some form of head crest is indicative, but not a great indicator of age. Yes a massive and elaborate crest in an animal is indicative that it’s an adult, but there could be a fairly well developed crest in an animal that is close to becoming and adult and of course there are taxa without crests and in at least once case it appears that females don’t have crests.

As in mammals, but unlike dinosaurs and birds, pterosaur also have epiphyses. The growing plates at the ends of the long bones physically separate the main shaft of the bone from the proximal and distal ends, so things like the femur can appear to be in three pieces. Obviously as growth slows towards maturity these epiphyses slowly disappear as they fuse into the single element that you would expect to see.

So in short, something that is small, with grainy textured bones, a big head, with big eyes, unossified tarsals, amorphous carpals, no crest, clear sutures in the skull, no notarium, and separated scapulocoracids, pelvis, epiphyses and neurocentral sutures is going to be a young juvenile. And the close these various features get to the opposite condition the closer the animal is likely to be to adulthood.

As ever with such things these are not absolutes, but merely guides. Good guides, certainly – you simply won’t see a notarium in a very young pterosaur, or open neurocentral arches in a big, old adult. However, in terms of determining more subtle difference in age it will be tricky – one animal may have fused up the notarium, but may have incompletely ossified tarsals and another could have the reverse. Although at least some characters do seem to have a bit of a pattern (the scapulocoracoid seems to fuse pretty early in most things) a general lack of numerous specimens of different ages makes it hard to do any more detailed analysis. Still, in terms of gross age (hatchling – young – adolescent – adult) even for a specimen of a previously unknown species with no obvious close relatives, it should be relatively easy to determine the approximate age of the animal.

AMNH pterosaurs 3 – Azhdarchoids

OK so the last two for now. Above is a cast of the famous Quetzalcoatlus wing. This is something I’ve never seen before so is rather cool. There are casts of the humerus floating around in various places, but this is the first time I’ve seen the rest, including that lovely long metacarpal block and pretty thin phalanx 1 of the wing. As with yesterday’s Pteranodon, fingers 1-3 do seem to be backwards though.

Below is a cast of Tupuxuara and again, I’ve seen copies of the head but not the rest. This is an animal that has a proper grounding in the concepts of massive head crests, and indeed a big skull in general and a mount like this really does show off the extreme proportions of this group – the heads are huge, the legs pretty long, but the body? Well the pelvis and sternum almost completely cover it and if you were feeling jaunty, you might be able to cram the torso *thought* the nasoanorbital fenestra. Cool.

Pterosaurs of the AMNH pt 2 – Pteranodon

Following on from yesterday’s coverage of the Solnhofen material, today we move into the Cretaceous and to Pteranodon. There’s a rather incomplete post-cranial specimen, a rather incomplete skull and then a nicely mounted cast / model. Pteranodon is known from a lot of material (over 1 200 specimens have been identified to date) but a huge amount of this stuff in very incomplete and badly broken. So while it is well represented in general, both of the specimens shown here are actually really pretty nice.

Pterosaurs of the AMNH pt 1 – Solnhofen

Recently I talked about the slow diffusion of Solnhofen specimens that have made their way to institutions around the world. I’ve had a few good leads and comments already which is nice, and reader Steve Cohen was kind enough to send in some photos of the various specimens and mounts at the legendary AMNH. While this material is well known, most of the images I’ve seen date back to the 70’s and photocopies of scanned black and white photos are quite simply pretty low resolution.

My thanks to Steve for these and there’s more, non-Solnhofen stuff coming tomorrow. For the non-pterosaur taxonomists reading this, that’s a rather nice Rhamphrhynchus at the top. Below we have small Ctenochasma and then a really nice and complete Pterodactylus with a near-perfect counterplate.

Guest post: Rhamphorhynchus…again: Superprecocial “flaplings” or defenseless hatchlings?

Today a guest post by Edina Prondvai. Edina and her work group have a new paper out looking at the growth rates of specimens of the ubiquitous Solnhofen pterosaur Rhamphorhynchus which has important implications for the ecology of young animals. Here she takes us through the work (which is in PloS ONE and so available to all right here):

Continue reading ‘Guest post: Rhamphorhynchus…again: Superprecocial “flaplings” or defenseless hatchlings?’

Make your own Quetzalcoatlus!

Back in my stint at the Carnegie, I had a great chat to Mark Klingler about his palaeoart. Mark mentioned that years ago he had created a little ‘build your own pterosaur’ kit where you could print out a Quetzalcoatlus he had designed and stick it together. He was extremely generous in offering this to the Musings to go up for people to do themselves, but he needed to check the copyright issues and find the necessary files.

Mark got back to me the other day to tell me that unbeknown to him, the files were already online and available on the Carnegie’s own website. So problem solved, you can get them whenever you want and make your own (small) giant pterosaur. Just go here and follow the instructions. Mark was cunning enough to make it so that it’s a skeletal view on one side and a life reconstruction on the other!

So get building and enjoy. my great thanks to mark for his original generous offer and for tracking down his files. Sure it’s easy enough to get them where they are, but even he didn’t know, so I’m delighted to bring this to a wider audience and well done to the Carnegie too for making this freely available for kids (and palaeontologists).

@Dave_Hone on Twitter

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 504 other followers