This is a topic I have been long meaning to cover on the musings as it is a pretty core part of modern palaeontology but exactly the kind of thing that never makes it from the research papers into newspapers of documentaries and thus I suspect many will not have even heard of it as a concept, let alone its application. As ever, this will be a reduced and simplified version so for those who do know better, please forgive the glossing over of details, but essentially the EPB runs as follows – if you have an unknown characteristic in an extinct species, but there are living relatives of that animal that phyologenetically are both more basal and more derived, then you can fairly safely conclude (with caveats, inevitably) that this was also a feature of your extinct organism.

To put this into practical perspective with an archosaurian example, crocodiles are related to dinosaurs but a phylogentically basal to them, and birds derived from dinosaurs and are thus more derived than them. However, while the non-avian dinosaurs are extinct, both crocs and birds are still alive today. Thus characteristics shared by birds and crocs were likely shared by dinosaurs. For example, even without the extensive evidence for dinosaur nests, if we had never found any eggs it would still have been quite a safe assumption that dinosaurs laid eggs since both crocodiles and birds do.

This as a concept obviously has enormous benefits as we can use it to try and reconstruct missing data from direct observation of living animals. We don’t have dinosaur muscles to work from (although muscle scars on bones give us a good idea) but with guidance from the EPB we can be much more confident in our restorations. Furthermore we can also use it to prune out bad ideas (or at least challenge them) if you want to argue that all dinosaurs had no lungs (to take an extreme example!) without any physical evidence it should be pretty obvious that since both birds and crocs have this (and yes, quite a few other things too), it’s going to be a very odd to assert that they are missing in dinosaurs.

There are of course problems with the method and I’ll elaborate on just a couple since in day-to-day archosaur work these are not huge issues normally (i.e. for the average person reading a dinosaur story, they don’t have much impact but are worth watching out for). First off, just using ‘birds’ and ‘crocodiles’ is not quite true, to use the EPB properly one must try to use the living animals most closely related to dinosaurs which is the ratites for birds (ostriches, kiwis, rheas and so on) and gharials for crocs. This of course is a problem since if you want to look at say flight mechanics the ratites are a bit of a non starter and you’ll have to move up the tree a bit to get hold of some flying birds. In any case, there are obviously huge gaps of time and morphology going on between say the most basal theropods and living birds.

Similarly, one is also effectively trying to use these animals to reconstruct the condition of characteristics in dinosaurs, yet we know some things have changed which make these animals unsuitable. All living crocodiles are rather sprawling in posture, but not all of the extinct ones were and it’s unclear exactly what posture was adopted by animals around the time that crocs separated from the lineage that would become dinosaurs. As such just using them freely as a proxy is not always a good idea. In a similar vein, there are some things for which the EPB is wholly unsuited. For example if you want to (as I do) try and reconstruct the predatory behaviour of theropods the EPB is not a great way to go, modern crocs are largely specialised ambush or aquatic predators and most birds are not predatory (and those that are largely hunt in the air and the few that do not are rather derived and are certainly not basal taxa), so given the huge specialisations of these animals to their respective hunting methods it’s unlikely their behavioural adaptations can tell us much about an Allosaurus trying to take down a sauropod.

There are also times where the EPB is not so much problematic, as just not very helpful. Endothermy (or warm bloodedness to be less technical and less accurate) is an obvious example. Birds are endotherms, crocs are not – so how do you interpret dinosaurs? Were they endotherms or not, or only some and if so, which? Are the basal ones more likely to be ectotherms since they are closer to crocs and derived ones endotherms since they are closer to birds? Or were even basal birds ectotherms? And what about the orniothischians, they separated out from the saurischian (and ultimately bird) lineage over 50 million years before Archaeopteryx appeared so are they the same or different? Of a different note but equally an issue are things like pterosaurs – if these are indeed archosaurs then the EPB for them would be crocodiles and birds, though if they are actually more basal archosauromorphs then the EPB would be lizards and crocs – a very different consideration.

That in essence is the EPB, we can use living relatives to help reconstruct the missing in fossil data. These are inferences, not absolutes and you need to combine these suggestions with other information (is there a muscle scar present for where you think one should be, is that gait possible given the trackways we see, has this already changed in crocs making this inference problematic etc.) to come to a conclusion. It can be incredibly powerful and has been very influential in vertebrate palaeontology by providing a firm and reasoned foundation for making inferences about extinct animals based on real, observable evidence (living creatures).

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Anyone who has read a bunch of vertebrate palaeontology papers will by now (hopefully) have noticed that the description of various anatomical bits tend to be in the same order, each bone has it’s place in the queue so to speak. It’s a simple enough concept as it makes it easy to access details quickly – if you want to know what the hand looks like you need to know where in the paper you are likely to find it and not have to read the whole thing to find the information you want. This is an established protocol that is, sadly, not always followed (most especially in character lists of cladistic characters), but it worth spelling out for the interested.

Quite simply one starts with the front of the skull and describes it front to back, then the mandible, then the complete vertebral column front to back (so going through to the end of the tail, and including associated bits like ribs and gastralia), then the forelimbs from the body outwards (finishing with the last finger) and then finally the hindlimbs in the same manner (starting with the pelvis and finishing with the claw of the last toe). Of course this varies depending on exactly what bones you have both in terms of general biology (not everything has five toes, or a predentary or a palprebal, etc.) and of course preservation (you can’t describe a skull you haven’t got). The three sections being called the cranial (skull), axial (vertebral system) and appendicular (limbs and girdles).

Based on my own notes and a couple of papers I’ll try and do a full list of every archosaurian bone in order. Doubtless I’ll miss a few (even within archosaurs) and misplace a few since I don’t know every bone or where there are significant variations in where they are positioned (or specially absent or specially present), but it should be a general guide (e.g. no pteroids).

When describing the individual bones you should really start at the front and move toward the back and from the top to the bottom, beginning with an overall description and then moving to the details, then how they fit with other bones, then any accessories. When you have multiple parts, move in the same direction so in the hand start with digit 1 and go to the end, then back to digit 2 and so on.

Cranial:

Skull bones as follows – premaxilla, maxilla, nasal, lacrimal, prefrontal, frontal, postfrontal, parietal, postorbital, squamosal, jugal, quadratojugal, quadrate.

Fenesatrae (naris, anorbital fenestra, foramina etc.).

Braincase as follows – basioccipital, supraoccipital, epiotic, paroccipital, exoccipital, opisthotic, prootic, parabasisphenoid, laterosphenoid.

Palate as follows – vomer, palatine, pterygoid, ectopterygoids, hyoids

Teeth.

Mandible as follows – dentary, surangular, angular, splenial.

Mandibular teeth.

Axial:

Vertebrae – atlas, axis, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae.

Cervical ribs, dorsal ribs, chevrons, gastralia.

Appendicular:

Pectoral limb – scapula, coracoid, clavical, humerus, radius, ulna, proximal carpals, distal carpals, metacarpal I – ungual I, then II-V in the same manner.

Pelvic limb – ilium, pubis, ischium, femur, tibia, fibula, proximal tarsals, distal tarsals, metactarsal I – ungual I, then II-V in the same manner.

Additional Strucutres:

Osteoderms, scutes etc.

So there you have it. I imagine it’s of little interest to the readers who don’t already know it, but if nothing else it might yet serve as a reference for people in the future. It’s certainly useful for me to have a permanent record of it I can refer to. Feel free to suggest modifications or additions and I’ll try and keep on top of it, though do remember that while the basis of this is standardised as such, I have never seen a list like this published. Doubtless therefore, some people would do the ulna before the radius and others will include the limb girdles with the axial system on occasion too and just keep the humerus onwards and femur onwards on the appendicular side of things and that kind of difference is not likely to be important. The pelvis as a whole of course will never sit comfortably on either side of the divide given how intimately the ilium (and often the pubis and ischium) is bound to the sacrum, but this should be a decent start for any ‘describers’ out there.

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The fossils of vertebrates (with the possible exception of fishes and some marine reptiles) are only rarely complete. That is, when you find a fossil you don’t get a whole skeleton, but only bits of one. Fossils can of course range from a complete and articulated skeleton (i.e. not only are the bits there, but are have not come apart and moved, so the legs attach the hip and the head is on the neck etc.) to a fragment of bone or part of a tooth. Palaeontologists are obviously rarely interested in such fragments since there is very little you can do with them normally (though I have a paper in review on just such a set of fragments which *are* interesting) but it is well worth considering how and why you get fossils that consist of only a few bits, or why some pieces are often missing.

I have already posted about scavenging and degradation effects on skeletons and indeed about the related issues of bias in the fossil record (and these should probably be read before you start here). However, this post will deal with parts of the actual skeleton itself – what can cause toes and tails to vanish for example?

While it is perfectly possible to find a combination of almost any two (or a few) bones you care to mention (a claw and a rib, a humerus and a palatine, an ilium and a jugal) these are likely to be more or less random associations from a scattered skeleton taken apart completely by scavengers or transported in water. What is of interest here is finding a partial skeleton with only some parts missing. These parts are often the same ones, or part of an obvious subset so let’s take the skeleton apart and look at each section in turn.

Remember that to even become a fossil the carcass has to be buried by sediment, typically underwater, but also occasionally on land (e.g. in volcanic ash). This means we already have a combination of factors to contend with: did the animal die on land or in the water, was it killed and dismembered by a predator or just keeled over from age or disease, did scavengers get to it, was it transported in water or sank immediately, was it buried quickly or over days or even years, or exposed and recovered multiple times, and in what kind of sediments, was it an adult or juvenile, how big was it? Thus unless I want to sink into the quagmire of every single possible factor and how they affect every kind of vertebrate or archosaur, I’ll soon be buried in details and this will turn into a book. This is just a quick look at the primary factors based on the bones themselves rather than all of the possible interactions and combinations of circumstances that will affect them based around their likelihood of separating from a body, being preserved, transported and / or destroyed.

Skull: this (as a whole unit) can hang around since there is little meat on it and so scavengers can only do so much. That said the individual pieces of the skull can easily split apart and be lost, and of course the head can easily come off the rest of the skeleton, and the jaw can easily come off the skull, so both parts can often be found in isolation (either from a skeleton or from each other). Weak bits like the sclerotic ring, nasal turbinates, ear bones and so on are easily broken or simply have too little bone to be well preserved if the survive at all and thus are rare. Skulls in general aren’t too common as compared to say a nice robust femur, the bones are pretty weak and fragile.

Vertebral column (back and neck): individual bones can be well bound together with ligaments and so one and will be found as whole units while others can easily separate out and vanish (notably the axis and atlas that support the skull). While they are commonly found (they are very numerous and typically robust) often fragile bits like the neural spine get broken off or simply do not preserve.

Pelvis: the pelvis and sacral vertebrae is obviously a robust and chunky set of bones that are unlikely to be destroyed during feeding, or dragged away by predators or washed away with flooding. Other bones of the pelvis (like the pubic bones) can be separated and lost however.

Tail: the distal tail is almost always missing from a combination of factors – scavenging, small size or simply being washed away or missed during excavation. The bones tend to separate out (except linked / fused things like dromaeosaur tails) and thus can be easily lost, as can the chevrons for the same reason.

Ribs and gastralia: a quick burial of a dead body will likely ensure that everything is intact and articulated and that is by far your best chance typically of finding ribs or gastralia at all. They are obviously often fragile and while ribs can be big, they are also often thin and any predator wanting a decent meal is going to go through the ribcage to get to it, so it’s not surprising when ribs are often disarticulated, broken or lost.

Main limb bones: can be found intact and articulated, or broken and scattered, I’ve not noticed any obvious pattern here. One thing of not is how often one finds bird and pterosaurian wings articulated by isolated from the rest of the skeleton (and occasionally wingless bodies) since they clearly detach easily after death.

Fingers and toes: these again are often missing (or found in isolation) since being small they tend to detach, and are easily moved.

So there you have it, in general fingers and toes, tail bits, skulls and ribs tend to go missing or be found separated from the ‘main’ body. That means you should often find something consisting of part of a vertebral column, with a pelvis and a few major limb bones. That at least is my impression and is at least partly back by my experience in the field and just looking over collections and fossils, though it would be interesting if someone did (or has done) a specific study of this. As ever there are strong variables based on all kinds of things, (sauropods only very rarely preserve skulls at all but these are common in isolation for ceratopsians) so don’t take it as gospel by any stretch of the imagination, but it certainly illustrates a few problems (like getting accurate length measurements when you never have a full tail – how much is missing?).

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“Everyone is getting better at less and less, and one day someone is going to be superb at nothing”. Kenneth Williams.

Following on from my posts about the ever expanding literature comes the issue of specialisation in academia. In the olden days when science was forming as a concept most people dabbled in many fields – it was normal for people to work on mathematics, chemistry, botany, astronomy and philosophy all but simultaneously. Even within fields like zoology it was normal for people like Darwin to devote time to South American fossil mammals, barnacles, worm behaviour and more aside from his theorising and work on natural selection. Even as little as 20 or 30 years ago it was common to find researchers who worked on ‘whales’ or ‘dinosaurs’ when now one might find one researcher specialising in sauropod mechanics and another in sauropod feeding and yet another on their systematics. I think it fair to say then that over time there has been a pretty strong trend towards increased specialisation by researchers and while of course everyone dabbles well outside their supposed ‘main research theme’, the theme in itself seems to shrink in each generation of research.

There’s no doubt that greater specialisation allows researchers to do better and more detailed science. It’s hard to know everything about dinosaurs so if you try, your work on sauropod feeding mechanics might be a bit superficial – if you specialise in sauropod feeding mechanics then you likely have read every paper on the subject and in detail and will be able to bring that knowledge and expertise to bear on the problem. This is, of course, a good thing in general. More work of a more detailed nature will be done and it stops people from getting lost in the vast realms of literature and specimens of a much larger field (100 years ago one could probably easily see every dinosaur *specimen*, now it’s probably rare for someone to have seen a single representative of every family) and of tackling tricky areas that might require specialist knowledge.

However, I think there is a danger of missing the wood for the trees. Just as a spotlight lets us see into a dark and deep well of a scientific problem, a more general illumination of the area around us can be just as valuable, if not more so. It reminds me of the old tale of the blind monks and the elephant – details are all well and good, but you need someone to see the bigger picture.

To draw from my own experiences, I have found that some people have a very limited knowledge out things outside of their own narrow focus and that they can struggle when trying to integrate things from other branches of biology. Without the contributions of colleagues (themselves typically specialists) then it’s clear that people are in a position to produce less good science. In short, collaboration is (I think) becoming more and more important for more and more research as the specialisation of researchers continues.

You could call this a plea for generalists in science or a warning that over specialisation could harm future research. However, I’d prefer to see it as a discussion point (since although it’s fairly obvious what I think, it’s not something I’ve discussed much with my peers) – is there too much specialisation? Are ‘generalists’ (at whatever level) a dying breed? Is this a problem?

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A much underappreciated area of palaeontology this and one I should probably have mentioned months if not years ago, but the opportunity arises so here we go. Emma Schachner (who’s pursuing a PhD with Peter Dodson) was kind enough to let me use some of here pictures from an upcoming paper on the basal iguanodontid Tenonotsaurus to illustrate this post for which I am most grateful (and you can see more of Emma’s work here).

An obviously important part of palaeontological papers is illustrating them to show off your ideas. Pictures can indeed be worth thousands of words and when you are striving for the accuracy and clarity that is an anatomical description they can be essential. Obviously if you have a specimen then a photo is a damned good start in terms of getting across what it looks like, and how big it is etc. but it is not the only way, and technical drawings are often as good if not better.

The foot and lower leg of Fodonyx (left) and reconstruction of the tibia (right).

While obviously there is no set terminology and continuum of levels of detail and so on, I’m here tying to refer specifically to work that is designed to clarify and show off various features of a specimen. That is, something more than just a very simple outline with minimal shading or other features being recorded (like this lower leg and foot of Fodonyx on the left, contrasting with the technical reconstruction of the tibia on the right). While photos are of course rather by definition exceptionally accurate renditions of fossils, they do have their drawbacks and that is where technical drawings can come in.

Tenontosaurus ulna. Courtesy Emma Schachner.

For starters it is incredibly hard to light and shoot some things well and certainly some institutes or researchers lack the facilities to do this, but pretty much anyone can find a pen and paper. Secondly, some things can be cryptic in photos – no matter how well shot it is, a black coloured bone in a black matrix will not reveal it’s subtleties well as contrast goes out the window. Drawing this in clean black and while can clear up this problem, and using different styles or pen sizes etc. can help distinguish between breaks and sutures, or show where matrix is adhered to the bone or whatever. One can also use techanical drawings to make things in a sense ‘more real’ – by highlighting important features of a bone or leaving out the unimportant or distracting to make the image clearer. Similarly, while restorations of broken and distorted bones can be done in a simple manner, where the morphology is important or complex, a more detailed image can really help.

Tenontosaurus phalanges. Courtesy Emma Schachner.

I think the ability to produce these is much undervalued especially as now often perfectly acceptable images can be produced pretty easily on a computer by someone with minimal artistic ability. However, good or great drawings really add to a paper or description and it would be a shame if this was lost to us. I still produce all of my own images like this by hand, and while I’m not a patch on someone like Emma, I do think that they are generally better than most electronically produced ones. Many students even have access to professional artists and can end a higher degree without having drawn a single bone which I can’t help but think will be a problem for them one day. Sure we have to move with the times, but I think that drawings are still much better than computer generated outlines and this is something we should make an effort to hang on to.

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One thing I did not cover at the Sino-German fossil park was their excellent collection of pterosaur mounts. Obviously I do like my pterosaurs and I wish they would get a little bit more attention in the average museum ‘dinosaur’ hall since this is often limited to a token Pteranodon and some facts about Quetzalcoatlus being really big. Here they have made a good effort and not just to include them as hanging models* but also on the ground and mixed in with the other exhibits. Naturally a I took a bunch of pictures of them and here are some of those for your interest – since these are all hand-made they include taxa not normally featured in fossil displays since if you are making the thing from scratch, not having any bones to cast from is not much of an issue and you can make what you want.

Tapejara (for a given value of Tapajara – I’m not entirely sure which taxon this is supposed to be, probably T. wellnhoferi and the taxonomy of the group is a bit up in the air right now).

Tupuxuara (again, slightly uncertain taxonomy – pretty common for pterosaurs – and several closely related taxa are known with various crest morphologies).

Azdarcho (a real composite mount, not much is known of this genus).

*I have heard that often it’s a big problem for many museums to string their pterosaurs from the ceiling because (inevitably) ‘health and safety’ regulations. Which is a shame as it can help make really good displays and show off these animals in the air. However, I do think a mixture is best where you can see pterosaurs in flight and on the ground as they are pretty unusual animals in either locomotory mode.

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It’s all too easy to pick upon cheap plastic toys and complain about how bad they are, so I will. However, despite the withering criticism and scorn I am about to pour onto this awful excuse for a ‘pterosaur’ there is a more pertinent point to be made, so either enjoy the bile and then stoke one’s chin thoughtfully over the social commentary / science / dinosaurs bit, or just skip to that now if you can’t be bothered too wade through the ‘look at the bloody carpus, it’s rubbish!’ rubbish.

I picked this thing up in Mexico as part of my trip last year and despite the proto-post languishing for the best part of a year I have been re-inspired to write about it thanks to some photos of a colleague of mine. First off, what’s wrong with this? Well, anyone who has read my ‘top 10’ pterosaur mistakes will be familiar with most of them already. But in short:

The head is too small (of if you prefer the body is too big)
The shape of the crest is wrong
The neck is too short
There’s no propatagium / pteroid
The fingers face the wrong way and are the wrong lengths
The wing finger is too short
It has bat wings (and by extension some six fingers)
The wings have scales on them
The shape of the body is wrong
The legs are too short
It has a weird reversed toe
There is no uropatagium
There is a long tail
The tail vane should not be present, and even if you want to argue for a rhamphorhynchoid tail, the vane is the wrong shape.

In other words, this is really, really bad. I’m honestly not sure I’ve ever seen worse and I have looked. It pretty much fits every ‘top 10’ of bad pterosaurs which in itself is quite and achievement. However, the important thing here that I want to note is not how bad it is, but the fact that it came in a big pack of dinosaurs most of which were actually pretty good. OK, so the colours were lurid and most were a bit too upright in stance so they balanced on their tails, but really the proportions and details were about right (raptorial claw, long arms and stiff tail for the dromaeosaur, huge skull and just two fingers for the tyrannosaur, non-dragging tail for the sauropod and so on). Why then such a disaster when we reach the pterosaur?

I have touched on this before, but I think it is ultimately an artefact of public perception. Thanks largely due to Jurassic Park, but also any number of associated projects (other dinosaur films, new books, documentaries etc.) that spawned from its popularity, dinosaurs have had a new lease of life. The public (like it or not) have been exposed to lots and lots and lots of ‘modern’ upright, feathered, active dinosaurs. As such, if only subconsciously, they have a new perception of dinosaurs.

However, the pterosaurs seem not to have enjoyed the same shift in perception. They still lumber about with bat wings and scaly bodies, perched on tree branches or gliding through the air. I’m not foolish enough to think that pterosaurs will ever get the attention that dinosaurs do (and I’m happy to admit that at some level they don’t deserve that attention – the average dinosaur is more interesting and / or important than the average pterosaur) but this in itself is odd. To many people, pterosaurs *are* synonymous with dinosaurs so you would think that they might get dragged into the 21st century of public perceptions if only by accident. Even if not, many people accept and recognise that our understanding of dinosaurs has and continues to change rapidly, yet bizarrely they seem not to realise that this *also* happens to all the other prehistoric beasties.

It is I think an odd situation. The public seem to have accepted a ‘new’ vision of dinosaurs with all that entails while steadfastly refusing to budge on anything else, including pterosaurs which many consider to be dinosaurs. It’s a rather odd state of affairs and leaves us with this terrible pterosaur in an otherwise satisfactory collection of cheap dinosaur toys. I’m forced to conclude that, sadly, it may simply be that the average member of the pubic pays so little attention, and gives so little thought, to anything not explicitly put in front of them (be it in the cinema or a textbook) that they miss the point that lots of research on all things is going on all the time. This (I guess) filters down to the point that anyone not actively interested in pterosaurs or palaeontology as a whole might not be aware of this, to the point that even someone designing model dinosaurs knows about dromaeosaur claws, but not pterosaur wings.

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Have an ankylosaur skull. Euoplocephalus apparently (I would not claim to know much about ankylosaurs so I’m going with what it said on the sign).

You want *more* than this? OK, well ankylosaurs are actually quite interesting but in their own way they rather suffer from the same problem as pterosaurs. That is that their taxonomy is rather problematic since a lot of the characters you might expect to find to help sort them out are concealed. In pterosaurs its due to the way the bones are sutured in the head and because they have a very conservative bauplan, in ankylosaurs it’s the armour getting in the way. As you can see here, the cranium is essentially a box with holes for the eyes and nostrils and so you can see how it might be tricky to find out how all the underlying bones are moving around and changing shape (evolutionarily) and thus work out which features various taxa have in common or were they differ (or even if two animals are the same species or not).

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Today’s post comes courtesy of Tom Holtz. Obviously being British, Thanksgiving passes me by at the best of times and living in China, I usually only register it when suddenly blogs and websites go very quiet for a few days. However we do usually revel in the Christmas turkey this is hardly an inappropriate post on the theropod ancestry of turkeys.

Thanksgiving is a great opportunity for a reminder of theropod anatomy. Of course, every roast bird offers this possibility, but since the number of people who are likely to encounter a turkey on Thanksgiving is very high, this time of year makes it easy for a vertebrate paleontologist to schedule a timely review of dinosaurian characteristics found in modern birds for their students.

As with any living thing, Meleagris gallipavo has a body that is a record of various traits acquired throughout its long evolutionary history. For example, it has DNA (inherited from the long distant ancestor of all living things), mitochondria and nuclei (from the common ancestor of all eukaryotes), multicellularity (from the earliest animals), enterocoely and determinate embryological cleavage (from the earliest deuterostomes), and on and on up the ever-branching Tree of Life.

Of interest for an instructor in a course on dinosaurs, of course, are traits preserved in a turkey relevant to dinosaur history. A number of paleontologists have used turkeys as teaching tools. For example, the skeleton that is the basis for this figure was taken from a University of California Museum of Paleontology website by Matt Wedel. The figure here (with its label) comes from my own course for non-majors.

Some of the relevant traits aren’t immediately obvious from a roast bird, given that they are typically served headless, footless, featherless, and with the neck separated from the rest of the skeleton. Even so, what osteological features remain records evolutionary events from before the initial divergence of the various dinosaur lineages through the extant (crown-group) bird radiation.

I’ve highlighted many of these. You can see the relevant cladograms and the taxonomy I am using on these various web pages.

As for flavor, though: given that turkey, chicken, guinea hen, duck, and goose meat all tastes different from each other—and these birds are all within one subclade (Galloanserae) of crown-group birds—it is unlikely that any Mesozoic dinosaur tasted exactly like turkey (or any other modern species of Aves.) Lacking a time machine, we are unlikely to ever know how tasty roasted Velociraptor was.

I suspect given the ‘general interest’ nature of much of my audience this will be rather too technical, but even if the names are meaningless, the sheer number and variety of characters should be interesting and perhaps even convincing in their own right.

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I’ve been brushing up on a few museum and zoo reviews for posting and it occurs to me that often my biggest complaint with an exhibition is a lack of good signs. I’m not talking here about absolute basics (“This is a Brachiosaurus” – though even some places seem to eschew this minimalist approach) but pretty much anything more detailed than that – be it the age and geographical origin of the organism or a complete display about the phylogeny of the clade and it’s more interesting anatomical features.

A great many places of supposed public interest and education seem to rather lack that second aspect because of a lack of signs. Sure it’s educational to stand in front of a hall of bones or a paddock full of antelope, but signs add so much more. It is, let’s face it, uneconomical to have people standing around answering questions and interfering with people’s days (and indeed these can be intrusive and annoying) and a good sign can communicate lots of information without being dull or taking up a lot of space.

The obvious point to make might be that not many people *want* to read the signs, but this is misleading. I can’t imagine anyone buys a newspaper and reads it cover to cover – some people want the sport, some the stock indexes, other the comments, or the lifestyle section and so on. Everyone will likely get something different from the paper in differing combinations and amounts. If you don’t *want* to read a sign, then fine, don’t. But even if it’s a minority, I’m sure that lots of people *do* want to learn more about what they are looking at.

At the very least it’s almost criminal in a zoo or museum not to tell you the name of the species you are looking at. The one thing you hear more than anything else in these places is a kid asking a parent “What’s that?” and without a sign to hand often there’s no obvious answer forthcoming (or a wrong one – I one, honestly and truly, saw someone call a giraffe a ‘zebra’ once). Kids who get their questions answered are going to learn something and might keep up that interest / trait to ask questions. Those that don’t, will not. Even if they don’t take much in at the time, the name will likely be remembered and can be looked up later. And this hardly takes into account adults – plenty of people do read signs and want to learn more and that’s tricky without the information being provided.

There are of course some truly great signs out there, original, inventive, informative and exciting (like this dinosaur tree I have been meaning to show off – a complete dinosaur phylogeny with little models to represent the various clades). But signs need not be huge or dramatic or expensive to be informative. Something simple to say the same of a species, which family or higher group it belongs to, how big it got, when and where it lived and what it ate need not take up more than 6 inches of wall or display space and actually tells you quite a bit.

I really think there is almost no excuse for this kind of sign not appearing next to pretty much every single display – it’s simple and informative and unambiguous and is hardly likely to go out of date (unlike say the average sign of dinosaur behaviour, or the names of all the meerkats in the enclosure) making it cheap and easy to install. These should be used in conjunction with bigger displays and signs with greater depth, but something small and unobtrusive that will both no-one while informing many, and is quick to scan and digest should surely be essential for just about anywhere that wants to inform its audience.

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I have commented on here before about the theft of various fossils (most notably dinosaurs) and their illegal export and sale. However it seems that for once the media has realised that actually selling tyrannosaurs at suction may not be a good thing and that the theft and illegal trade in scientific specimens is bad. I’m very pleased therefore to see this article in The Independent in the UK and I hope that this is not just a one-off and that other outlets pick up the story and get the point across that this is harming researcher and denying both scientists and the public access to the heritage of our planet.

So being eight hours out from the UK and 12 from the US east coast it’s perhaps no surprise that I missed (forgot) that yesterday was the anniversary day of the publication of the Origin. While I totally failed to celebrate, Scott Sampson did not and chose this rather auspicious day to launch his new blog – The Whirlpool of Life. Scott will be covering mainstream science education and communication as well as all aspects of nature and biology and not just palaeontology and the dinosaurs on which he usually works. Nip over there and take a look when you have five minutes.

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Beijing is actually home to three public aquariums, but the one I’m covering here is actually inside the Beijing Zoo, though it can be visited separately hence the separate review. It’s also big enough in its own right to warrant a separate review since it can easily occupy three or four hours of your time. It’s rather new having been open only since 2003 I believe.

The layout is one that seems to be increasingly common – a series of relatively small tanks designed to cover the variety of a given ecosystem and then a mammoth tank or two occupied by huge animals or a massive array of species. It starts in the ‘Amazon’ with the usual fare (and some nice oddities like giant salamanders) with numerous small exhibits and two large ones containing giants like arapaima and pacu and then a whole host of several hundred arowana.

We go from here to an open-top reef tank and the first major set-up – home to several dozen sharks and rays with massive windows and rather nice ‘bubble’ windows that allow you to stick your head into the tank. To the side of this area is the marine mammals hall which features just sealions and bottlenose dolphins. Though I freely concede that I’m generally not happy to see dolphins captive, they certainly have lots of room and seem to be doing well enough.

The central attraction however is the main reef tank, all three stories of it with two viewing tunnels and several huge windows. It’s filled with a large number of reef fish, turtles, big eagle rays, groups and more. It is exceptionally well constructed and unlike many tanks of this kind, has lots of smaller fish and not just the bigger ones so it really feels like a community and not just a display. Again, laid out around the main tank are numerous smaller ones with various sealife (though as elsewhere here it’s mostly just fish – not that there’s anything wrong with fish in an aquarium I should hasten to add, but the odd invertebrate beyond coral would be nice).

That’s it really. It’s pretty big, it’s pretty good, it’s pretty well set up. One major quibble would be the cost (compared to other Chinese days out it’s steep – 10 times the cost of the entry to the zoo it’s in for example) and as ever there were very few signs for anything which is always annoying. Still, well worth and afternoon of your time if you have noting better going and it certainly holds up for repeat visits.

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Having covered the ongoing saga (though to be honest it’s less of a saga than a small novella) of the ‘cranial-caudal’ descriptions issue, it seemed an appropriate time to bring up the ideas of directions in anatomical descriptions. As I noted in the earlier post, the point about directions in anatomy are to be clear and concise and to provide an unambiguous definition of something to avoid confusion for the readers and researchers who want to follow what you have written accurately.

It should be easy to see how people can get confused without being careful about terms. You could describe a feature on a humerus say as being on the same side as the thumb, but rotate your wrist and suddenly that point of reference disappears. Most people would describe their chest as facing forwards, but in a quadruped that same structure (the ribcage) would be facing down towards the ground, and while the metatrsals in our feet face flat down on the ground in most other animals they would face backwards. If you used terms like this it would be easy to get lost or end up comparing the wrong things hence the general standardisation of terms. I say general of course as there are still issues here and there that crop up, like the cranial-caudal one, or those of the scapula.

So here as a brief guide / aid memoire, are a few of the basic directions used in anatomical descriptions for the orientation and position of bones and their features. Please excuse the very basic outline drawing, it was the best I could do* quickly:

Anterior (or cranial) – towards the head end of the animal.
Posterior (or caudal) – towards the tail end of the animal.

Dorsal – towards the back.
Ventral – towards the front.

Medial – towards the midline (something can also lie medially like vertebrae).
Lateral – away from the midline.

Proximal – towards the body.
Distal – away from the body and towards an extremity (so you can also talk about the distal tail for example).

Palmar (or plantar)> – towards the palm of the hand / sole of the foot.
Dorsal – towards the back of the hand / top of the foot.

Labial – towards the lips or outer part of the mouth.
Lingual – towards the tongue or inner part of the mouth.

These rather obviously all come in pairs of opposites but they can be used together or in combinations. So your spine is medially positioned and runs anterio-posteriorly (from front to back) and while your orbits face anteriorly (or rostrally if you prefer) you can swivel your eyes to face dorso-laterally (up and to the side) or medio-ventrally (down towards the middle) if you so choose.

The point is, and should be, that even as joints move and rotate and even whole body plans change and evolve (humans stand rather differently to monkeys, let alone cats or mice) the points remain relevant and accurate and directly comparable. Thus providing a secure set of references to make both descriptions and comparisons accurate.

*and by ‘do’ I mean ‘bother with’, but for this it should be more than sufficient.

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This is something I have been avoiding for a while as I know for a fact that this is divisive in the dinosaur / archosaur community and incidentally I’m probably on the minority side. However, regardless of the divide, it is important to know that the division in there and why.

Although I have not really covered the issue of directions in detail before, the central idea that scientific writing should be clear and concise is something I have expounded on before. In short, when describing bones (or teeth, positions, rotations about joints etc.) anatomists use a series of words to accurately describe directions to make things clear and concise. Obviously terms like up, down, left, back, rear and so on can vary depending on your point of view or if something can rotate (you can hold you palm facing up or down for example) so having a set of directions based around the skeleton itself eliminates much of the confusion.

However since palaeontology and anatomy as subjects evolved well before phylogenetics, initially different groups of animals ended up with different shorthands to reflect the different people working on them and the different issues at hand. Thus while reptile (and dinosaur) researchers largely used anterior and posterior to denote a direction towards the front or rear, most bird workers used cranial and caudal (literally towards the head and towards the tail) to mean essentially the same thing. Of course once it became clear that birds were dinosaurs, many dinosaur researchers started to use cranial and caudal as opposed to anterior and posterior (the situation is of course more complex than this, but that’s my take on it in as few words as possible).

The consensus seems to be moving towards this as the right thing to do but I have to say I disagree. I think the clarity issue is at stake with these terms for two slightly different but related reasons:

1. Frankly I think the terms can sound silly when in use the beak or rostrum of a skull is anterior (i.e. in front of) the orbit (eye socket). Under the ‘avian’ system you would say that the rostrum is cranial to the orbit, but both of them are in the head itself, so essentially something is in the head direction of the head relative to something else in the head. Sure you know what it means, but I don’t think it is as clear as it can be and it is almost oxymoronic.*

2. Similarly but even worse, we have the problem with vertebrae. Vertebrae in reptiles are typically divided into cervical (neck), dorsal (back), sacral (in the pelvis) and caudal (tail) vertebrae – you may therefore have already spotted the issue. If you want to talk about posterior dorsal vertebrae these are caudal dorsals, and posterior caudals are caudal caudals. How can this possibly be considered clear? You actively have to stick the word caudal into positional details of vertebrae that abut the caudals or relate to the caudals but are not caudals? You can end up saying that the caudal dorsal vertebrae resemble the cranial caudal vertebrae but not the caudal caudal vertebrae or the caudal cervical vertebrae. Oh good.

That’s it really. In short cranial = to the front and caudal = to the rear. These terms are common and indeed are increasingly so, but I often find them awkward and as such I don’t think they serve the community as well as they could. Perhaps I’m just slow, but I really often do have to re-read phrases about ‘caudal cervical vertebrae’ to remember that we are dealing with the neck and not the tail and it seems so unnecessarily complex. I suspect at least a couple of readers will try to correct me in my thinking and I’m willing to be persuaded, but I’ve yet to hear a convincing argument as to why ‘cranial-caudal’ is better than ‘anterior-posterior’.

*Note: here ‘rostral’ meaning ‘towards the snout’ can also come into ply in place of ‘cranial’ though of course this still does not help when you want to say that the rostrum is rotrally positioned (OK, that’s obvious, but the point is valid), and of course a horn say that extends in front of the rostrum becomes very hard to describe!

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I got into a discussion with my colleagues the other day about the merits of collecting multiple specimens of taxa versus collecting something new. The reality of course is that there is rarely a choice to be made – you bring back everything you find in the field that you can. However, as a hypothetical discussion it is interesting since of course you can do very different science with 10 specimens representing 10 different species and 10 specimens of a single species.

This debate aside (one for another time) it led me to get around to writing this post which I have long intended to complete on the differing importance of different specimens. It is understandable that some people might think “so you have 25 Triceratops, so what? Surely once you have one good, complete one, there’s not much more to learn?” but of course this is far from the truth.

As I have covered before on my series of posts on taxonomy, multiple specimens can give you a huge insight into the variation of fossil animals as living organisms – be it intraspecific or sexual. If animals are of different ages then you can learn about ontogeny and growth and of course there is always the change that a new specimen shows off some odd characteristic like a pathology, bite marks from a predator or something like this.

Some specimens (and the fighting dinosaurs are a great example) cannot easily be prepared for research, no matter how good they are (or in this case, not without losing a lot of other important information). Another specimen where all the bones can be separated out and viewed and analysed in 3D is great therefore allowing all kinds of extra information to be accessed and things like range of motion in joints to be examined firsthand. Similarly, having a ‘sacrificial’ specimen is great – no one wants to chop up a brilliant holotype to look at the bone histology or look at replacement teeth or the braincase, but a second specimen allows you to be a bit free-er with your methods and destructive sampling becomes a serious option – even a very fragmentary partial bone can be enough for this.

OK, maybe we don't need to collect this.

So while obviously for most palaeontologists a single complete skeleton is a great find, every little specimen is valuable. However, it would be a mistake to consider each of equal value – a single broken femur is good for destructive sampling, but an articulated leg is more useful and obviously several complete animals are better still. Even this varies from researcher to researcher – histologists are likely overjoyed by a bunch of otherwise largely unimportant partial specimens that they can sample while behaviourists won’t get too worked up until they hit a whole herd preserved together.

I imagine most of this is largely very obvious, but still there is typically always one more angle to think about and I hope I may have highlighted one or two here. It’s easy to get stuck in the mindset of ‘what would I do with that fossil’ which might be very useful for you, but not always that of your colleagues.

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A couple of months back I posted an image of a ‘flying’ mount of the odd pterosaur Dsungaripterus taken at the IVPP. I had intended to include, but completely forgot, this image of a walking mount from the Beijing Natural History Museum. There’s not much to say here since I have already covered pterosaur quadrupedality and at least a few more details on Dsungaripterus in the last post, so I’ll leave this as a short picture post.

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A while back I launched a rather unsuccessful appeal for archosaur images to use on the Musings since I actually don’t have that many that I have not already used. These are of course still welcome, so if you have any photos that you own the copyright for, and don’t mind me using publicly, and if they are of archosaur fossils / casts / mounts then do please send them to me!

However this appeal is of a far more general kind. As I noted recently my main ‘online’ project Ask A Biologist is about to undergo a big makeover and we are also looking for any images related to biology to include in a big online gallery. So basically the same appeal applies but on a much bigger scale – please send me ANY images related to biology / palaeo that we can use. I should note that I do have a rather a lot of dinosaur, bird and mammal images already and we need some variety! Thus lings like people in labs, plants, cells, inverts, molecules, fungi, medicine related stuff, fish, non-dinosaur fossils etc. are especially welcome.

Send anything you have to me at dwe_hone AT yahoo.com
Thanks in advance for your help, it really is greatly appreciated.

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Before my brief hiatus with a trip to Shandong (very worthwhile, despite the illness that stuck me down) I was talking about convergent characters and the importance of examining all the available evidence and not just a select feature or two. However, that post was written rather quickly and I didn’t have time to expand on it in the way I wished so now I’ll push on with a few more observations.

While last time I mentioned only specific characters like spines or claws that can arise convergently, it is course possible for entire suites of characters to evolve convergently. While a big and specialised ungual will help you break into a termite or ant nest, a well evolved termite eating animal will have modified arms to provide power to that claw, and have a long snout and / or tongue to reach those termites, perhaps specialised sticky saliva, digestion suited to large amounts of formic acid, lost teeth and more. Eating ant is more than just a claw, so animals that specialise for eating ant are likely to have whole sets of characters which all help to increase ant-eating abilities and thus evolve in the same way in multiple lineages – in other words convergence. After all, if you want to run fast, having a long lower leg is great, but having a long metatarsal too, and cutting down on the number of toes, and actually shortening the femur as well are even better.

This takes us nicely to the second point – that when those suites of characters combine in certain parts of the body this can cause taxonomic and systematic problems. Animals that are highly specialised for running often have the characteristics I note above, but what if you recover a fossil that is *just* a pair of legs? If you have an anteater arm then you will spot the big claw and modified ulna, but there are also some other features that should help reveal its true identity – pick up a maniraptoran theropod leg though and things get trickier. It is perhaps no surprise that there were early questions over the phylogenetic position of things like alvarezsaurs and oviraptorosaurs with their specialised cursorial legs – there is quite a lot of convergence there.

Finally, we come to a point about defining characteristics. Things can look very different from a general description or a very detailed one and apparent convergences can vanish in a puff of adjectives (like the flippers of penguins and turtles shown here). Both birds and pterosaurs have wings, but one has feathers and reduced fingers, the other a hugely elongate arm and membraneous wings. Bats can try and muscle birds out the way with their long wingers and ‘skin’-like wings, but again, closer examination shows that pterosaurs rely on a single finger to support their wing, not a whole hands worth. These are, of course, especially coarse examples, but I hope the point gets home.

That largely wraps up convergence, or at least as much as I wanted to say about it for now. Coming up soon, something else. For once I’m a bit bereft of pre-prepared posts so I’m not sure what I’ll get round to finishing up and posting. Stay tuned!

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This week Bob Nicholls celebrates 10 years as a professional free-lance palaeoartist. I’ve known Bob for a number of years now as he’s resident in the West Country and so used to see him semi-regularly in Bristol when he was working. For those at SVP who actually ventured deep into the Geology Department you may have seen his large mural-cum-collage thing that covers the walls around the museum part of the department. His work regularly crops up in books and museum guidebooks (and Luis Rey’s name badge) and he is increasingly becoming recognised as a very modern palaeoartist. So drop over to his website and take a look at some of his work when you have the time.

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