October 19, 2015
I imagine that by now, everyone who reads this blog is familiar with Mark Witton’s painting of a giant azhdarchid pterosaur alongside a big giraffe. Here it is, for those who haven’t seen it:
(This is the fifth and most recent version that Mark has created, taken from 9 things you may not know about giant azhdarchid pterosaurs.)
It’s one of those images that really kicks you in the brain the first time you see it. The idea that an animal the size of a giraffe could fly under its own power seems ludicrous — yet that’s what the evidence tells us.
But wait — what do we mean by “an animal the size of a giraffe”? Yes, the pterosaur in this image is the same height as the giraffe, but how does its weight compare?
Mark says “The giraffe is a big bull Masai individual, standing a healthy 5.6 m tall, close to the maximum known Masai giraffe height.” He doesn’t give a mass, but Wikipedia, citing Owen-Smith (1988), says “Fully grown giraffes stand 5–6 m (16–20 ft) tall, with males taller than females. The average weight is 1,192 kg (2,628 lb) for an adult male and 828 kg (1,825 lb) for an adult female with maximum weights of 1,930 kg (4,250 lb) and 1,180 kg (2,600 lb) having been recorded for males and females, respectively.” So it seems reasonable to use a mass intermediate between those of an average and maximum-sized male, (1192+1930)/2 = 1561 kg.
So much for the giraffe. What does the azhdarchid weigh? The literature is studded with figures that vary wildly, from the 544 kg that Henderson (2010) found for Quetzalcoatlus, right down to the widely cited 70 kg that Chatterjee and Templin (2004) found for the same individual — and even the astonishing 50 kg that seems to be favoured by Unwin (2005:192). In the middle is the 259 kg of Witton (2008).
It occurred to me that I could visualise these mass estimates by shrinking the giraffe in Mark’s image down to the various proposed masses, and seeing how credible it looks to imagine these reduced-sized giraffes weighting the same as the azhdarchid. The maths is simple. For each proposed azhdarchid mass, we figure out what it is as a proportion of the giraffe’s 1561 kg; then the cube root of that mass proportion gives us the linear proportion.
- 544 kg = 0.389 giraffe masses = 0.704 giraffe lengths
- 259 kg = 0.166 giraffe masses = 0.549 giraffe lengths
- 70 kg =0.0448 giraffe masses = 0.355 giraffe lengths
Let’s see how that looks.
On the left, we have Mark’s artwork, with the giraffe massing 1561 kg. On the right, we have three smaller (isometrically scaled) giraffes of masses corresponding to giant azhdarchid mass estimates in the literature. If Don Henderson (2010) is right, then the pterosaur weighs the same as the 544 kg giraffe, which to me looks pretty feasible if it’s very pneumatic. If Witton (2008) is right, then it weighs the same as the 259 kg giraffe, which I find hard to swallow. And if Chatterjee and Templin (2004) are right, then the giant pterosaur weighs the same as the teeny tiny 70 kg giraffe, which I find frankly ludicrous. (For that matter, 70 kg is in the same size-class as Georgia, the human scale-bar: the idea that she and the pterosaur weigh the same is just silly.)
What is the value of such eyeball comparisons? I’m not sure, beyond a basic reality check. Running this exercise has certainly made me sceptical about even the 250 kg mass range which now seems to be fairly widely accepted among pterosaur workers. Remember, if that mass is correct then the pterosaur and the 259 kg giraffe in the picture above weight the same. Can you buy that?
Or can we find extant analogues? Are there birds and mammals with the same mass that are in the same size relation as these images show?
- Chatterjee, Sankar, and R. J. Templin. 2004. Posture, locomotion, and paleoecology of pterosaurs. Geological Society of America, Special Paper 376. 68 pages.
- Henderson, Donald M. 2010. Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology 30(3):768-785.
- Witton, Mark P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana 28:143-159.
Copyright: promoting the Progress of Science and useful Arts by preventing access to 105-year-old quarry maps
October 11, 2015
In my recent preprint on the incompleteness and distortion of sauropod neck specimens, I discuss three well-known sauropod specimens in detail, and show that they are not as well known as we think they are. One of them is the Giraffatitan brancai lectotype MB.R.2181 (more widely known by its older designation HMN SII), the specimen that provides the bulk of the mighty mounted skeleton in Berlin.
That photo is from this post, which is why it’s disfigured by red arrows pointing at its epipophyses. But the vertebra in question — the eighth cervical of MB.R.2181 — is a very old friend: in fact, it was the subject of the first ever SV-POW! post, back in 2007.
In the reprint, to help make the point that this specimen was found extremely disarticulated, I reproduce Heinrich (1999:figure 16), which is Wolf-Dieter Heinrich’s redrawing of Janensch’s original sketch map of Quarry S, made in 1909 or 1910. Here it is again:
For the preprint, as for this blog-post (and indeed the previous one), I just went right ahead and included it. But the formal version of the paper (assuming it passes peer-review) will by very explicitly under a CC By licence, so the right thing to do is get formal permission to include it under those terms. So I’ve been trying to get that permission.
What a stupid, stupid waste of time.
Heinrich’s paper appeared in the somewhat cumbersomely titled Mitteilungen aus dem Museum fur Naturkunde in Berlin, Geowissenschaftliche Reihe, published as a subscription journal by Wiley. Happily, that journal is now open access, published by Pensoft as The Fossil Record. So I wrote to the Fossil Record editors to request permission. They wrote back, saying:
We are not the right persons for your question. The Wiley Company holds the copyright and should therefore be asked. Unfortunately, I do not know who is the correct person.
Thank you for your enquiry.
We are currently experiencing a large volume of email traffic and will deal with your request within the next 15 working days.
We are pleased to advise that permission for the majority of our journal content, and for an increasing number of book publications, may be cleared more quickly by using the RightsLink service via Wiley’s websites http://onlinelibrary.wiley.com and www.wiley.com.
Within the next fifteen working days? That is, in the next three weeks? How can it possibly take that long? Are they engraving their response on a corundum block?
So, OK, let’s follow the automated suggestion and try RightsLink. I went to the Wiley Online Library, and searched for journals whose names contain “naturkunde”. Only one comes up, and it’s not the right one. So Wiley doesn’t admit the existence of the journal.
Well, there’s lots to enjoy here, isn’t there? First, and most important, it doesn’t actually work: “Permission to reproduce this content cannot be granted via the RightsLink service.” Then there’s that cute little registered-trademark symbol “®” on the name RightsLink, because it’s important to remind me not to accidentally set up my own rights-management service with the same name. In the same vein, there’s the “Copyright © 2015 Copyright Clearance Center, Inc. All Rights Reserved” notice at the bottom — copyright not on the content that I want to reuse, but on the RightsLink popup itself. (Which I guess means I am in violation for including the screenshot above.) Oh, and there’s the misrendering of “Museum für Naturkunde” as “Museum fÃ¼r Naturkunde”.
All of this gets me precisely nowhere. As far as I can tell, my only recourse now is to wait three weeks for Wiley to get in touch with me, and hope that they turn out to be in favour of science.
It’s Sunday afternoon. I could be watching Ireland play France in the Rugby World Cup. I could be out at Staverton, seeing (and hearing) the world’s last flying Avro Vulcan overfly Gloucester Airport for the last time. I could be watching Return of the Jedi with the boys, in preparation for the forthcoming Episode VII. Instead, here I am, wrestling with copyright.
How absolutely pointless. What a terrible waste of my life.
Is this what we want researchers to be spending their time on?
Update (13 October 2015): a happy outcome (this time)
I was delighted, on logging in this morning, to find I had email from RIGHTS-and-LICENCES@wiley-vch.de with the subject “Permission to reproduce Heinrich (1999:fig. 16) under CC By licence” — a full thirteen working days earlier than expected. They were apologetic and helpful. Here is key part of what they said:
We are of course happy to handle your request directly from our office – please find the requested permission here:We hereby grant permission for the requested use expected that due credit is given to the original source.If material appears within our work with credit to another source, authorisation from that source must be obtained.Credit must include the following components:– Journals: Author(s) Name(s): Title of the Article. Name of the Journal. Publication year. Volume. Page(s). Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission.
So this is excellent. I would of course have included all those elements in the attribution anyway, with the exception that it might not have occurred to me to state who the copyright holder is. But there is no reason to object to that.
So, two cheers for Wiley on this occasion. I had to waste some time, but at least none of it was due to deliberate obstructiveness, and most importantly they are happy for their figure to be reproduced under CC By.
- Heinrich, Wolf-Dieter. 1999. The taphonomy of dinosaurs from the Upper Jurassic of Tendaguru, Tanzania (East Africa), based on field sketches of the German Tendaguru expedition (1909-1913). Mitteilungen aus dem Museum fur Naturkunde in Berlin, Geowissenschaftliche Reihe 2:25-61.
September 22, 2015
The process of reassembling my cat skull continues. I now have the sphenoid and both nasals now back in place, and the time has come for the now-traditional multiview. (Previous examples: pig skull, wallaby skull, sheep skull.
Click through for seriously high resolution (9602 × 7642).
And here it is on a black background:
As though you need to be told: the top row shows the dorsal view, the middle row (from left to right) shows posterior, right lateral and anterior views, and the bottom row shows the ventral view.
September 17, 2015
Regular readers will remember that I recently fished my cat skull out of the tub where invertebrates had been hard at work defleshing it, and put it to soak — first in soapy water, then in clean water, and finally in dilute hydrogen peroxide. It was in a pretty terrible state, having either been smashed by a car, or damaged by my rather unsophisticated process of removing the head from the torso. Here’s a reminder:
After bleaching in H2O2, the skull parts looked much better, but were still very delicate. Here is the main portion of the cranium, missing the braincase and the right upper jaw, upside down, in right posteroventral view.
Putting it back together was difficult. I am using regular water-soluble wood glue, largely so that if I make a mistake I can just soak the wrongly-joined bits apart and try again.
I started by gluing the braincase (at the top of the plate in the first picture) onto the back of the main cranium piece. Unfortunately, as you’ll see below, I wasn’t able to get a very clean join — I can only assume that one or other part was slightly distorted by whatever force broke the skull apart. Still, having done that, I had a better platform to reattach the right upper jaw (lower left of the plate). I was then able to reattach the broken-off part of the right zygomatic arch (at about 4 o’clock on the plate, just to the right of the lower of the two dentaries, and below a vertebra). It didn’t fit quite right, but what can you do? FInally, I was able to reattach another small piece — at 6:30 pm on the plate — which I think is part of the left auditory bulla.
That gave me a workable cranium (though I have some bits left over — see below.) It was time to repair the right dentary. Its articular cylinder (not really a condyle, despite its name) had somehow got blasted off, as had its retroarticular process: it was quite satisfying to figure out how those Shards Of Mediocrity fitted onto the main part of the dentary.
With that done, I had to glue together the two dentaries. That’s hard to do: it’s awkward to brace them in position for the glue to set, and difficult to get the angle between the two bones correct so that the two articular cylinders both sit neatle in their receptacles in the cranium. Here’s the solution I came up with:
I rested the cranium upside down, covered the jaw with some thin, pliant plastic (actually a sandwich bag) and used the cranium itself as a perfectly proportioned brace to hold the dentaries in place. Then I was able to glue them more or less correctly, and to reinforce the joint with more glue once the first lot had set.
I’ve still not got it quite right — the mandibular symphysis is wonky — but I think it will do. And if I change my mind, I can always soak the mandible apart and try again.
(As a matter of fact, I’d already done that once, having initially glued the dentaries together at the wrong angle, so that the assembled mandible was too narrow, and wouldn’t articulate properly with the cranium.)
So now I have a pretty good mandible and cranium, as well as the first five cervical vertebrae (all but one of the postzygs of C5, which was lost in the head-removal process.) Here is the whole thing, put together, in dorsal view:
(You can see where the left zygomatic arch is damaged: the bones are not articulating correctly, as they do on the right.)
And here is the same assembly in left dorsolateral view:
And finally, the skull in anterodorsal view:
Note that the left canine is truncated. I am completely certain that this, at least, is not my doing, and must be damage that was done in life. Note, too, how the mandible is visibly wonky from this angle. Hmm. Maybe I will reset it again.
At the end of this process, I have a pretty nice cat skull. Unfortunately, I have seven shards left over, none of them more than about fifteen millimeters long. Here they are:
I’d welcome any help in figuring out what these bits are, and where on the skull they should be reattached. I don’t want to just throw them away. Click through for much higher resolution to get a better idea of what’s what. The top right piece is such a weird shape that someone must know what it is. The two peices at bottom right seem to be pairs, but I don’t know what they are a pair of. The rest? No idea.
I leave you with the dorsal view again, but this time in glorious 3D for those of you who have been wise enough to get some red-cyan 3D glasses. (Seriously folks, they’re like fifty cents a pair. Just get some. You won’t regret it.)
Some time soon: those first five cervicals in more detail.
September 11, 2015
Just under a year ago, the children across the road, who know I’m interested in comparative anatomy, told me that they’d found a dead cat by the side of the road, and asked whether I wanted it. Silly question, of course I did!
I’ve learned from bitter experience that prepping the whole skeleton out of an animal is a very time-consuming process — so time-consuming that I usually just don’t get around to it. This time, I thought I’d just do the skull. So I removed the head (not a pleasant process) and discarded the body.
I did the usual sequence of simmerings with the head, peeling off the skin and fur, then removing muscle, till I was down to just bone, gristle, and the hard-to-remove bits of soft tissue that always adhere in one place or another. At that point, I left the bones in a plastic tub in the woodshed, with a couple of holes in the lid so that invertebrates could get in and deal with the remaining gloop.
Yesterday I had a look (and a smell), and it seems all the soft-tissue is gone, thanks to the hard work of the tiny collaborators who never make it into the acknowledgements. So I soaked the skull pieces in soapy water for a day. Then today, I rinsed them off and left them to soak in pure water for a few hours. Finally, I changed the water, and added some H2O2 to degrease the bones. They are now foaming away merrily. Tomorrow I’ll take them out, rinse them off one more time, dry them, and see what state they’re in.
Here’s how they look today, after rinsing:
And here is a closeup of a mandible (slightly foreshortened):
“But Mike”, you ask, “Why is it in so many pieces?”
I actually don’t know. As I was taking the head apart, it seemed to be whole, but as it got down to the raw bone, it was apparent that the skull was very badly damaged. In the picture above, the main part of the cranium is upside down, half way down the left hand side. Below it is the rest of the cranium, the left side of the upper jaw. Above that is the back of the cranium, most of the braincase. The whole thing just came apart into three pieces — and not along sutures. This is breakage.
I’m not sure how it happened. At first, I thought it must be how the cat died — maybe struck a glancing blow by a car. But I increasingly wonder whether I stupidly did this myself in the process of removing the head from the torso. (I did not use a scalpel.)
Anyway, we’ll see how well the pieces can be reassembled once they have dried out. I’m optimised that I can still wind up with a pretty good cat skull.
September 7, 2015
My last post (Unhappy thoughts on student projects at SVPCA 2015) was stupid and ill-judged. As a result of very helpful conversations with a senior palaeontologist (who was much more courteous about it that he or she needed to be), I have decided to retract that article rather than editing it further to clarify. I deeply wish I’d never posted it, and I offer my apologies to everyone I insulted.
First, and most importantly, to people presenting projects under the influence of nerves, which I misinterpreted as a lack of interest in their own projects. Nervousness particularly affects people giving their first talks — an effect I should have allowed for. It’s awful to think that what I wrote may have been discouraging to people taking first steps into palaeo.
Second, to supervisors who felt that the “roll four dice” section in the middle of the post was aimed at them. All I can say is that it wasn’t. I had no-one in mind when I wrote that: I was just so seduced by the comical imagery of generating a project by rolling dice that I wrote it down without thinking through how it would be interpreted.
Did I have good intentions? I honestly did. Did I have legitimate concerns about the ubiquitous application of techniques that are not always appropriate, and whose results are not always interpreted with a suitable degree of scepticism? I think so. But clearly I should have discussed those concerns privately with more involved people, rather than spilling my brains all over the blog. I welcome the increasing availability of techniques that allow us to bring numerical rigour to our palaeobiological speculations. (I could discuss in more detail when and how I think those techniques should be used, but that’s for another day. My purpose here is to apologise, not to justify myself.)
In short, I had a very bad day at the office on Friday, and I hate the idea that in my carelessness I could have hurt anyone other than myself. To those in that category, I can only ask your forgiveness; and promise to think more before blogging in future.
September 4, 2015
THIS POST IS RETRACTED. The reasons are explained in the next post. I wish I had never posted this, but you can’t undo what is done, especially on the Internet, so I am not deleting it but marking it as retracted. I suggest you don’t bother reading on, but it’s here if you want to.
There were some surprises in the the contents of the SVPCA programme this year. Sauropods were woefully under-represented with only two talks (mine on apatosaur neck combat and Daniel Vidal’s on the range of movement of the tail of Spinophorosaurus). In fact non-avian dinosaurs as a whole got short shrift, with two theropod talks, three ornithischian talks and one on dinosaur diversity. This is partly, of course, because so many dinosaur workers among the SVPCA mainstays were absent for one reason or another: Matt Wedel, Paul Upchurch, Paul Barrett, Richard Butler, Roger Benson, Steve Brusatte, David Norman, the list goes on.
But that’s OK. I’ve often found, to my surprise, that the dinosaur talks aren’t always my favourites anyway. (Oddly enough, fish talks can quite often catch my imagination; and pterosaurs are always good for a laugh.)
A more surprising development was the complete absence of any finite element analysis this year — a technique that was crazy trendy a couple of years ago, but seems to have to the end of its fashion cycle.
Instead, I felt that the talks were strongly dominated by one technique: principal component analysis (PCA). As a technique, I have mixed feelings about it: I don’t go as far as John Conway, who as far as I can tell thinks it’s almost literally meaningless. But I have strong reservations about the plug-and-play way it seems to get used for pretty much everything at the moment, and how very tenuous some of the inferences are that people derive from their morphospace plots. It’s difficult to be specific without criticising individuals, which I’d like to avoid doing. But I do think think that when we draw sweeping and heterodox conclusions about an animal’s lifestyle from a PCA of a single facet of a single bone, the validity of that conclusion is, to put it politely, open to question.
In fact an awful lot of the projects presented in this year’s talks seemed to follow the same template. In an idle (and, yes, unnecessarily snide) moment, I sketched an Automatic Masters Project Generator for lazy supervisors. You just throw four dice, then pick your technique name, body-part, period and taxon from these tables:
Table 1: roll 1d6 for a technique
- 2d landmark analysis
- principal component analysis
- geometric morphometrics
- morphospace analysis
- finite element analysis
- ecomorphological diversity analysis
Table 2: roll 1d6 for a body part
Table 3: roll 1d6 for a period
- Late Cretaceous
Table 4: roll 1d6 for a taxon
- lamnid sharks
- golden moles
Try it yourself! Morphospace analysis of the ulna in Miocene mustelids! Ready, steady, go! Your Masters degree will be ready as soon as you can talk reasonably coherently about this combination for fifteen minutes and leap to an obvious but weakly supported conclusion based on vague shapes drawn on a PC1-vs.-PC2 plot that captures only 32.6% of the variation!
(To be clear: I am not saying that PCA is intrinsically worthless. As I found myself repeatedly arguing in pubs with John and others, it’s evidently a very powerful tool for discovering correlations. For me, it goes wrong when very weak results pop out, but are given a veneer of respectability and objectivity because a computer was involved in the process.)
As the week went on, I found myself worrying increasingly about these projects. It’s not just that they are (with a few creditable exceptions) samey to listen to and uninteresting in their results. I worry more that these projects kill the interest of the people who take them on. I may be reading my own biases back into my observations here, but it seemed to me that I detected a distinct lack of enthusiasm in several of the speakers, and my hunch is that for a lot of them this will be their first and last SVPCA. They presumably went into palaeo because they loved some specific extinct taxon; instead, they found themselves spending a year staring at a hundred almost identical photographs of moodily lit tubes of toothpaste. And really, if anything is going to kill the passion of a pterosaur lover stone dead, it’s taking measurements of the distal articular facets of the ulnae of a 154 Miocene mustelids.
So I found myself longing for more talks about taxa, and about ideas, rather than techniques. Most obviously, there was very little pure descriptive palaeontology to be seen this year. But also, our own talk aside, very little of what I would think of as exploratory work — thinking about structures, chewing through their implications, considering alternatives. In short: the fun stuff. I would hate palaeontology to be reduced to a process of harvesting data from specimens (looking only at the aspects needed to fill in the matrix), pouring that data into a sausage machine, and turning the handle until something statistically significant comes out.
We have to be able to offer grad-students more than that. We are, and I say this with all due objectivity, in the most exciting science in the world. People go into palaeo because they love it. I wouldn’t like to think they go straight back out of it, as soon as they have their higher degree, hating it. We need to get students looking at and thinking about and discussing actual specimens — proposing ideas, arguing about them, running into reasons why they might be wrong, figuring out why they might be right after all, putting together an argument. Not sitting in front of computers full time running T-tests.
Of course there is a role, and an important one, for numerical methods. But they have to be the means, not the end. We have to have a more interesting goal than finding a statistically significant correlation. Otherwise we’re going to lose people.