Intraspecific variation and taxonomy

One aspect of vertebrate palaeontology that often gets overlooked is how much individuals can vary from the ‘type’. Most people focus on interspecific variation – that is, difference between species, but just as important is intraspecific variation – the differences seen within species. In a great many cases (and most especially when it comes to dinosaurs) the fossil record of an animal can be limited to one good specimen with various other bits of others that may be badly distorted, incomplete, broken, or with elements that do not overlap with others. As such you can end up with a rather fixed view of what a taxon looks like if you only take one specimen into consideration (or can only use one).

However, biology deals with a continuum, not absolutes – species are not the same as elements or atoms in their definition or reliability of diagnosis. Individuals vary – you look like your parents and siblings, but not *exactly* like them (even identical twins usually have some distinguishing features). If you look at humans across the earth (admittedly a big sample size and with more variation than many species) you can find individuals of all manner of sizes and body proportions, with no clavicles, extra or fewer fingers and toes, all manner of skin, eye and hair colours (or no hair at all) and more. Some of these are the result of odd occasional defects (like the extra fingers) but can still be hereditary and in large numbers (like missing clavicles) and in both of these cases at least, would of course show up in the fossil record. This is therefore a pretty important consideration when trying to define species and separate out differences between closely related groups.

Obviously we typically lack the sample sizes needed to try and establish this kind of variation in dinosaurs (for example) but we *can* look at patterns we see in extant creatures to see what we might expect in fossils. Does size vary a lot among living populations? Oh yeah! Right, don’t include absolute size as a criterion for defining taxa unless the differences are consistent and very big. Do the number of digits (unless obviously duplicated by a generic error) usually vary? No – so this is a viable indicator of a taxonomic difference. Does the number of teeth vary? In mammals, generally not, but in reptiles, yes (at least a little). So best not use the gain or loss of a single tooth as a factor, but the loss or gain of several is better evidence. And so on, pretty much ad infinitum, though of course just a couple of concepts (relative sizes for example) can cover an awful lot of ground and most of these are pretty obvious.

Sadly, despite the general simplicity of the concept and its application this is not always so vigorously applied. There are plenty of species (and dinosaurs especially) out there that are characterised by being a bit bigger than an otherwise identical taxon, or because they have one more tooth, or one fewer tail vertebrae. A great deal of taxonomic research is, frustratingly and time consuming-ly, a clean-up of old (and even new) bad taxonomic identifications, assignments and descriptions (aside from the normal disagreements). Obviously the field has moved on over the decades (and yes, centuries) but it is amazing how much poor stuff still comes out regularly and how much stuff has never been revised. As I have noted elsewhere, taxonomy is absolutely crucial for basic biology and we are running out of taxonomists and behind on taxonomic progress. I don’t want to be too pessimistic, but the situation is far from bright and the more good taxonomy and less bad that is produced the better off near every field in biology will be.

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Flamingo in repose

Another quick picture post before we dive into taxonomy next week. I shot this flamingo in the zoo in Seoul just on Friday and rather like the resting posture seen here on the massively elongate metatarsals (though these are mostly in the air thanks to the solid ground and the bulbous ankles). You often see ratites in this kind of posture but I’ve not seen too many other birds adopt this position and it’s neat to see it in a bird with such exaggerated legs. It is also something you occasionally see in theropod tracks such as the resting trace I covered a few months back.

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Archaeoceratops

Well I’m back from a very busy week in Seoul and while I’m clearing out e-mails and so fourth, you’ll have to make do with a couple of quick picture posts to satisfy any archosaur related cravings you may have. Here we have the interesting little basal ceratopsian Archaeoceratops from Liaoning. Proper posts coming soon, promise – I have big series lined up on the problems facing vertebrate palaeontologists with the taxonomy of archosaurs. Won’t that be fun? (Probably not, but it might be educational, which is kinda the point).

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Knowledge and the application of knowledge

In some of my recent posts I was, it is fair to say, highly critical of people who leave comments on forums, online articles and the rest many of whom seem to think that they know far more than they actually do about science. There are two aspects of this misestimation of knowledge that are worth commenting on that are important, and for once do not overlap with each other to any great extent.

The first is that there seems to be a misunderstanding that science is purely about knowledge. Science (or the scientist) either knows something or does not. If they do not know it, they simply have to find it out and then it is known, or so the logic seems to run. However this itself misses two key points. First is that of course a great deal of scientific information is not in a state of known vs unknown (even if we know we know things, or know we don’t know things) but is the subject of debate. To pick an obvious candidate we do not know exactly what oviraptorosaurs were eating and this is not simply a case of not knowing, it’s pretty hard to find out and the subject is up for debate. We can discuss all manner of issues (shape of the beak, the claws on the hands, gastroliths, ancestry etc.) without really settling on an answer so while much is *known* the answer is *not* known with any great certainty even if we have lots of evidence and good clues.

In addition there is the idea that scientists simply acquire knowledge by just reading books or if something is new just somehow ‘finding out’. Science is not just about knowledge but also the application of knowledge. You could read every paper ever on tyrannosaurs next week and learn a colossal amount about them, but without an understanding of evolutionary theory, how bone strength metrics are calculated, stratigraphy, anatomy, population ecology and animal behaviour you might struggle to put any of it in context. Even if you could dot hat, if you wanted to find out more about them through actual research you would have to know how to get a grant / perform a palaeontological dig / collect the right data / analyses the data correctly / put this in context / write a paper etc. (and that hardly touches on which stats you should use etc.). In short, just *knowing* something is hardly the sum total of science. So to return to those kinds of ‘but I already kinda knew that’ comments – great. Who cares? Did you know what it *means* and what that can *tell* you as well and what you can *do* with it? If not, don’t bother.

The second major issue here is one I have touched on before but can be put forward more explicitly thanks to one of the most awesomely title papers of all time. Basically people who don’t know much don’t realise they don’t know much and don’t realise that people who do know a lot do know a lot. To put it another way, the less expert you are in a field or skill, the more you overestimate your ability *and* the worse a judge you are of the skills of others. This has actually been demonstrated in the fantastically titled paper “Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments” (by Kruger & Dunning, 1999 if you are interested). Also very much worthy of note here is the fact that those who are *most* skilled actually tend to *underestimate* their abilities as well.

You can therefore have the situation that I largely hint at in my annoyance of these comments where the ignorant think they know it all and the expert is useless AND the expert thinks he is not quite as good as he actually is. It’s an understandable recipe for disaster (or at least conflict) and even when mediated (such as when ‘both sides’ are covered by a journalist or a chair in a debate) unless that mediator is an expert too, the situation is unlikely to improve as they will then miss what is and is not valid / right / good as well. One can see how in an especially technical field like science which is then watered down (and I don’t necessarily mean in a bad way) for a media report that a non-expert reading it thinks the expert has got it wrong and he knows better.

From a science communication perspective, sadly the solution to this problem would appear to be that either we have to train everyone in the world to our standards for any given subject for them to appreciate it effectively, or to patronise them horribly by pointing out that actually they are wrong and know nothing and they should just believe. There is a third (and less sarcastic) solution too of course: to carry on doing what we are doing – presenting the evidence as best to can to as wide an audience as possible and know that for every commenting idiot, there are people who understand and appreciate what is being done and respect the work and the commitment it takes to produce that work, and if they don’t understand will seek out further knowledge.

However, this is not to say that this idle slating of people is not valuable (apart from it providing further catharsis for me). The better knowledge and understanding you can have of the lack of understanding of others, the better it can be dealt with. Here I think are two critical issues to understanding science that are missed by a large part of the public – knowledge is not understanding and *your* knowledge and understanding is not *all* knowledge and understanding.

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The other side of the Marginocephalia

Since I covered pachycephalosaurs the other day, it seem pertinent to put up a picture of a ceratopsian – the other group of dinosaurs that comprise the Marginocephalia. These are likely more familiar to many of you as in addition to ‘classics’ like Triceratops, I have also covered Protoceratops and Psittacosaurus on here at various times. Here however is the large ceratopsian Chasmosaurus, again taken from the Fukui Prefectural Dinosaur Museum. I’m off to Korea at rather short notice tomorrow, then off with a National Geographic film crew to Liaoning again and then off to the UK for SVP. As such the Musings may be a bit sparse over the next month, but I do have a fair few posts in waiting and I’ll have sufficient internet access to keep them coming, but my usual rate of one a day may go down a fair bit.

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Is this the worst media coverage of pterosaurs ever?

No, that’s not hyperbole. We really have a stinker here. Allow me to elaborate: as some of you may be aware, a paper came out this week covering a pterosaur trace fossil of an animal landing – in other words, it came into land after a flight and then walked off. I don’t often cover new papers on here, and don’t always cover even my own so no marks are lost for having missed it. Anyway, this got some coverage in the media and I was quoted in several stories about the paper. Here is one of the originals and it’s worth reading so that you can get some context for later.

Then I found this online. Oh dear. For all my recent complaints about the media, hopefully at least some of you will have noted that I did have some nice things to say about the stories in general and emphasised that while many are woefully bad, some stories are very good. This is genuinely one of the worst excesses I have seen of media screw-ups. I can only conclude that they read one of the original stories and then tried to change it so that it looked a bit different (since I wasn’t quoted on the press release they must have taken my quotes from a piece by Charles Choi, the only person I spoke to about this).

In doing so they fell for every classic error I complain about. They copy stuff indiscriminately, they get things wrong, they misattribute things and add errors and here, even contradictions. It really is horrendous, and, to cap it all, it was written by the sites science editor! Their only possible defence is that they are a software website, but for me this would be pitiful – if you report enough on science to require a titled editor you should get it right. Hell, if you are doing *anything* like this you should get it right (or very nearly right, everyone makes mistakes and you can’t always go into the detail you want). This is another level though, and allow me to elaborate more.

Let’s start with the title which includes ‘preferred’. Occasional anthropomorphism aside, this implies a choice was made – pterosaurs went for their runways as a matter of choice. Not true and not stated anywhere by anyone. Underneath it says “The conclusion belongs to a new scientific study” which to me is just poor English as well as being generally incorrect since the study doesn’t say this. In any case, how would you know? – this is the first example and you cannot extrapolate for a data point of one. Incidentally the English is dodgy throughout and I suspect the author is a non-native speaker and while this may not be his fault as such, if you are writing for an English-language website then I have little sympathy.

Next there is the top left with the image, one of Mark Witton’s that they have used without permission (so I understand) and certainly without credit (though I’ll admit I’m not sure why it was on Wikicommons). If you click on it there is a bit of text that says that pterosaurs only flew when they had to, though who knows where they got that from and that it is eating a lizard which is of course a sauropod.

The first word of the article is “Archaeologists”. This one AGAIN. Palaeontologists are not archaeologists. Not are they “Anthropologists” which also turns up later on. The word palaeontologist never turns up at all! Still in the same sentence we are told that pterosaurs are the ancestors of birds. No, no, no, no and no. And no. They then say that the track is very rare which should be obvious given that it is the first one ever discovered, good investigative journalism there. Still in the opening paragraph we get ‘proto-birds’ and then a horribly mangled sentence of “did not leave a massive imprint on the ground, such as the largest dinosaurs that ever roamed the Earth, the 50-tonne sauropods, did, LiveScience reports” horribly mangling my own quote while entertainingly revealing where they cribbed all this stuff from.

Moving on we are told that they have “two-foot-long feet” which will be a big surprise as the wingspan was probably only around 3 feet. Were they wearing skis? I think they mean the *track* is two feet long, but this is not what they say.

Now we get a stunning line where they seem to manage to think that the term pterosaur refers to a species (or think they are all the same size) while calling them flying lizards. So birds are pterosaurs which are lizards. Awesome! In the following ‘anthropologist’ sentence we are told that this track shows a take off and landing trace which is wrong, they only land. The original report they quote from even says that scientists now want to find a take-off trace as well which they clearly missed.

The next bit is fine, presumably because they copied it nearly wholesale and thus failed to screw anything up including lifting quotes directly. However, not to worry as in the last paragraph they manage to say that pterosaurs had great flight control and flight capabilities which rather contradicts their opening gambit that they only flew when necessary.

So there you have it, an absolute litany of crass basic errors that have been introduced for no apparent reason despite the whole thing being an obvious cut-and-paste hatchet job of an article which they even cite as the source. Quotes mangled, image appropriated, contradictions introduced and basic misunderstandings abound. This really is absolutely horrible. The only obvious thing I expect was the ‘pterosaurs are dinosaurs’ schtick which they avoided only by calling them birds and lizards. Genius. Good work lads, now, please never, ever write anything about science ever again. Because if you can’t even get this kind of stuff right, then I can only pray that you never have to cover string theory.

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Pachycephalosaur head butting

Despite my interests in dinosaur behaviour I have rather managed to avoid the question of pachycephalosaurs so far and with a couple of nice photos on cue it seemed a good time to discuss this at least superficially. I don’t think this clade has actually even been mentioned here at any point so this is longer overdue.

Since I try to cover even the basics of archosaur palaeontology on here I should probably give a bit of background to these bone heads (as they are occasionally know – the literal translation of the name being thick headed reptiles). Pachycephalosaurs are a group of ornithischian dinosaurs closely allied to the ceratopsians (the horned dinosaurs) and with them make up the large and important clade the Marginocephalae. They were herbivorous bipeds that only spanned a relatively small range of sizes from small to medium (compared to many of their relatives) with the largest genus, Pachycephalosaurus, being up to around 5 m long.

Obviously their most prominent characteristic is the massively thickened skull roof and the occasional fringe of spines and knobs that run around the crown of the skull. What these were actually used for has long been contested with the most obvious suggestion being that these were used to fight with, either with each other or to attack other animals (like predators). Evidence has gone backwards and forwards over this with papers saying the head could not have absorbed impacts of fighting, or could have done, that they would clash heads or would not and would target flanks and that these were ornamental or not. In short, the only real consensus is that there is no real consensus as yet.

This may come as a surprise as despite the obvious controversial nature of many questions in palaeontology many are at least close to a consensus or the evidence has started to tip decisively but here this is not really the case. Part of the problem is likely to be the sparsity of material – pachycephalosaurs are not known from many good specimens at all (half a dozen are known from only skulls, partial skulls, or just the domes) and some aspects of their anatomy are thus not well understood. Combined with the relative lack of interest in this clade (since almost everyone seems to prefer theropods) it is perhaps less of a surprise.

The lack of material in Europe especially and the fact that the group is not half as well known as the ‘classics’ like tyrannosaurs and ceratopsians, and their relative small size means that they rarely make it into dinosaur halls outside North America so I was pleased to see two different displays of them in Japan – the first time I’d actually seen any. At the top we have a butting pair from Tokyo and below the front/side and back of a skull from Fukui (both images used with permission). I hope more research goes into this area as it is genuinely fascinating and covers various aspects of mechanics, ecology and behaviour that integrate well and of course the application of data and studies from living animals would be especially useful.

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Reversing the hallux

The reversed hallux has long been an important aspect of the discussion of dinosaur habits, and more specifically the origin of flight though it might not seem so at first glance. The hallux is basically the technical term for what most people would call the big toe, that is, the first digit on the foot and its reversal (or otherwise) basically relates to the orientation it holds – does it point forwards with the other toes, or sideways, or has it reversed to point behind?

The reason this point is so often contested or debated lies in two simple truths. Firstly, birds with a reversed hallux are mostly perching birds – those that live in trees and perch on branches and by extension are generally decent fliers. Secondly, the orientation of the hallux is incredibly difficult to determine in flat 2-D fossils such as those we generally get for things like early birds and close relatives in the non-avian dinosaurs.

The result as you might have guessed is that palaeontologists are incredibly interested in reversed halluces since this may allow us to determine if early birds and (perhaps more importantly) their likely ancestors were hanging around (so to speak) in trees. However between the tendency for the hallux to come free from the rest of the toes and the fact that compression can lead to it lying in a misleading orientation on a slab means that reconstructing the original position accurately is difficult at best.

It will be no surprise therefore to learn that this has been controversial at best and for things like Archaeopteryx with multiple good, and conflicting, specimens know the debate has been long and remains (largely) unresolved. The picture here is of a birds from Liaoning that I saw recently and clearly shows the hallux facing behind on each foot with no obvious signs of dislocation. Convincing is this case, but unhelpfully this is rarely in the more interesting taxa.

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Catharsis

So having dealt with both the failings of the press and the nature of the comments that followed in their wake I though it time for a final purge and go for some of the actual ‘errors’ that were highlighted by those who felt they knew enough about theropod predatory habits without reading the paper to actually read what had been said. As such, I highly recommend that you do not bother to read the rest of this as it will reach a mosquito-in-your-ear-at-3-am pitched whine in about half a paragraph and only ascend from there, whilst telling you things you probably already know. I make no apologies for this, you have been warned but some of these really got under my skin, while of course providing clear and concise examples of the kind of mistakes that seem to be made every nanosecond by the public. Thus we (i.e. you, since you are still reading) can learn what we need to address as communications while I blow off some steam…

Another decaying carcass

Long term readers will be familiar with my post on decaying donkeys in Mexico (that also prompted this diagnosis for palaeontologists) and this summer in Inner Mongolia brought me another large mammalian carcass – a camel. Thankfully this did not smell as bad as I had feared but nevertheless I did not get too close and only took a couple of photos with the better one shown here.

The point I want to highlight here is the way the fur has stripped off of the skin leaving huge patches bare. Given the way things had gone already it would not be a surprise if most of the rest of it went before the skin decayed to any significant effect. While obviously there are no big predators out in this part of the desert, there are foxes and various birds of prey (as well as smaller scavengers and insects) that might have had an effect though the animal could only have been dead a few days since I had been to that spot before previously when it was not present.

Interestingly this contrasts sharply with the effect we see in birds, (which I don’t have any photos for), whereby the feathers stay articulated with the skeleton long after the skin itself has gone. One study found that feathers could stay on the carcass even after 3 months of the body floating at sea. Unlike mammalian fur at least, they don’t come off easily and should be considered when comparing fossil remnants from exceptional deposits like Liaoning.

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Ghost lineages

Ideally I would have introduced the concept of ghost lineages here before but I never quite got round to it and as something is coming up soon-ish that requires some discussion of the situation it seemed a good time to get stuck in. This is one of those areas of palaeontology that seems to be more controversial that it should be, and though I am not sure why, I suspect it is down to a misunderstanding of the fossil record in general or phylogenetics specifically.

Pterosaur trabeculae

Time for another obscure word in the annals of vertebrate palaeontology and here is one that ties together birds and pterosaurs, if only in a nomenclatural sense. For those that do not know, both pterosaurs and birds have hollowed out, pneumatic bones which in life were filled with air sacs that were extensions of the lungs. However, this obviously could potentially weaken the bones and make them vulnerable to being broken and given the kinds of high forces that many of them would have to deal with (like the bones of the wing or legs for flight and landing respectively) you want to keep them strong.

Evolution has evolved an elegant way around the conflict here – keeping things hollow (and thus light) but strong with some biological scaffolding. The trabeculae are therefore the various small and often intricate little webs and buttresses and spars of bones that populate the insides of various bird and pterosaur bones, providing strength and support to the bone with the minimum of extra mass. These naturally tend to be denser in number and more complex in the ends of bones such as the one pictured here or those with higher stresses and strains, but they can be quite sparse in others.

Inevitably they are little discussed in the literature since in a well preserved bone you can’t see them and even in those that are broken open they are not always visible. Even if they are visible are themselves broken, or as shown here, so complex as to be beyond description. As a result they receive little attention though they are potentially very important as they may help show which bones are taking which stresses where and even in what orientation. As such there may be much functional anatomy hidden in the trabeculae and we have yet to investigate them properly, though with modern scanning methods and further interest beginning this may not be the case for too many more years.

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