Trouble in the Message Centre
Once again, months have flown by without a new post: that wasn't meant to happen. I've got at least two new images that I want to put on here soon, but finding the time to write something of note about them has proved more or less impossible. A not unnoticeable affect on my free time has been the impending arrival of Christmas: this means it's obviously time for another E-card thingy to be posted up here. This one comes with a festive warning comparable to those given in Dickens' A Chirstmas Carol: if you're going to send said E-card to your friends, family, colleagues and acquaintances, it's a jolly good idea to make sure the E-card is attached. Otherwise you send out your biggest E-mail of the year and look like an ass.
Merry Christmas and Happy New Year to you all, anyway.
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Uploaded on Dec 17, 2009
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Becoming More Like Alfie
My housemates don’t quite understand my fondness for darkness. While it probably does my eyes no good at all and has led to more than one stubbed toe, I don’t put many lights on around the house. At best, I’ll put on a few lamps while drawing or reading, but I can’t stand ‘big’ lights. No, they’re too artificial, too orangey and somehow nowhere near as pleasing as genuine sunlight. I’m not one, y’see, for pretending that it’s not dark outside: in fact, there’s something quite comforting about being at home with the dark only held at bay by the localised glow of a little lamp. It’s the same feeling you get when sat indoors as rain lashes against your windows. You know the one: that warm, comfy feeling that’s amplified by the sound of rain peppering the glass and brings a smile to your face every time some poor bugger runs past, soaking wet and miserable, while you’ve got your feet up on the sofa and a cup of coffee in your hands. This means that as the nights draw in and temperatures drop in this October time of year, I’m quite happy to embrace the change. Still, it does mean that we’ve got to wave goodbye to all the summer hobbies and open the box on all the wintery, indoor counterparts. Goodbye snoozing on a lazy common under a clear blue sky, hello lazing on the sofa in front of the telly. Out goes watching bands on the seafront, and in comes piping your favourite tunes through the internet. So long to cycling around town looking as stereotypically French as possible and welcome to... well, actually, that will continue unabated: some things should persist all year, after all.
Of course, our transfer to winter conditions occurs quite slowly, caused by little more than successive subtle changes to rainfall and temperature over many weeks. In this respect, it operates in a similar manner to the classic model of evolution: successive generations of organisms build up incremental changes to their anatomy over time and, eventually, produce something radically different from their ancestors. We don’t see much evidence, certainly in the fossil record, of organisms dramatically changing isolated elements of their anatomy without effects elsewhere: they don’t, generally speaking, suddenly develop an entirely new skull structure or something without showing modification of other body parts. What’s weird, though, is that geneticists have found that genes – and the expression of them - often show signs of clumping together into genetic complexes or ‘modules’ that, in theory, could be modified independently of other modules to produce large changes to an organism’s bodyplan without affecting others. Typically, we don’t see such changes in the fossil record: organisms typically show a whole bunch of ‘advanced’ and ‘primitive’ features scattered across their anatomy, so called ‘mosaic’ evolution.
All this changes today, though. Stepping into the international spotlight is Frank, a new pterosaur from the middle Jurassic of China that combines features of pterodactyloid pterosaurs (classically defined as critters with reduced numbers of openings in their skull; long, simplified neck vertebrae; long bones in the ‘palms’ of their hands; short tails and reduced fifth toes) and their more basal ancestors (defined by the inverse of the criteria listed above). Of course, ‘Frank’ isn’t the animal’s real name: honouring 200 years since Charles Darwin’s birth and the 150th year since the publication of The Origin of Species, it’s been christened Darwinopterus; but the moniker ‘Frank’, used by the scientists studying Darwinopterus to refer to the animal while they were thinking up something more grandiose, does reveal something about it’s strange anatomical bauplan. Frank’s anatomy, see, is somewhat akin to the construction of Frankenstein’s Monster, looking like it was bolted together from different pterosaurs. More specifically, the head and neck are classically pterodactyloid, while everything below the neckline is a textbook basal pterosaur. Frank is therefore important for at least two major reasons: it’s the first time in over 200 years of pterosaur research that we’ve gleaned an insight into the transition of pterodactyloids from basal forms, and, perhaps more importantly, it shows that this modular evolution stuff did occur and can be demonstrated in the fossil record. Frank’s discovery has other implications too but, I’m afraid, we don’t have time or space to cover them here. Happily for you though, you lucky dogs, I’ve penned a full summary of how Frank will shatter the world over at the online science magazine Flesh and Stone: why not nip over there and read it now? Just be sure to come back.
Right: got the full lowdown on Frank? Pretty neat, huh? Such an interesting little critter clearly deserves an equally interesting press release image and, presumably because all the other palaeoartists were on holiday or something, Frank’s minders asked me to produce that image for them. I was asked to focus on two things: Frank’s hybrid pterosaur bodyplan and it’s proposed ecology of an aerial predator. I have to admit that this proposed ecology doesn’t sit entirely comfortable with me: it’s not that I’m saying the authors are wrong, but there’s been virtually no research at all into the functional morphology of non-pterodactyloid pterosaurs and, as such, their assumption of things like their poor terrestrial ability lacks backing. What’s more, for all it’s modular innovation, Frank’s anatomy is quite generalised and there’s no features to really suggest it was a specialist aerial predator. That said, a number of birds manage to hawk animals in mid air without specific adaptations for the job, so Frank’s proposed ecology may get through on this technicality. Plus, at least it’s not another suggested fish eater or, God forbid, another proposed skim-feeder, and that should be celebrated. And, undeniably, aerial predation makes for a more exciting PR image than, I don’t know, grubbing for worms.
Frank’s portrait went through quite a few drafts before the version you can see here. The first decision involved deciding on a prey item: if you’re a mid-Jurassic aerial vertebrate predator, your menu will consist of gliding dinosaurs, mammals or other pterosaurs. The obvious choice had to be a dinosaur because, in these cynical times, dinosaur-eating animals tend to get more press interest. Once this was decided, composition had to be considered. Initially, Frank was powering in from the right of the image, mouth agape and wings at the end of their downstroke. The prey item was different, too: rather than the gliding troodontid Anchiornis seen here, Frank was chasing a tiny scansoriopterygid, a group of very birdlike dinosaurs that appear to have been adept climbers. In fact, the first draft of Frank’s image saw Frank about to engulf one of these chaps as it ran up a tree, but my commissioners were dead keen to retain Frank a predator of other aerial animals, so the scansoriopterygid took to the air in a parachuting fashion for the next draft. This version almost became the final draft, but two big changes were then asked for that resulted in the whole thing being started again. Firstly, Frank was found to look much better at the top of the image, looming over his prey with raised wings and using it’s long neck to reach beneath it. Then, re-dating of fossil beds containing Anchiornis gave us the opportunity to jump on the ‘isn’t it cool to have genuine dinobird in the mid-Jurassic’ bandwagon, and gave us a more topical and likely prey item. To begin with, this version had Frank flying directly at the viewer, meaning his chest obscured much of the detail of his anatomy. This didn’t really cut the mustard for showing off Frank’s chimeric characteristics, so he was repositioned again to appear as in a dive. Anchironis, too, once looked more birdlike, but this was toned down to ensure that people recognised it as a dinosaur. Once all this was settled, colouring finally commenced and, in tribute to the cut-n-shut processes taking place around Frank’s neckline, I thought it made sense to have a clear division between the dark basal pterosaur anatomy at the rear and the considerably brighter, funkier pterodactyloid anatomy ahead. Anchiornis was made deliberately bland to contrast with all those dinobird images that have them painted in the same schemes as the most brilliant birds of paradise: I’m sure there were fantastically coloured Mesozoic dinosaurs, but there were probably plenty of dull, brown ones too. I figure that I’m already working on a reputation for making pterosaurs less interesting (they weren’t hyperlightweight, had relatively uninteresting feeding strategies etc...), so I may as well try to make dinobirds boring, too.
Beyond this, a background had to be painted. The Tiaojishan Formation rocks that yielded Frank are much better known for their palaeoflora than fauna, suggesting that it would’ve been very, very green around there 160 million years ago. A lush, vegetated background was clearly needed then, and my initial plan was for the backdrop to be painted with a directional blur. You know, as if the image were a tracking photograph of Frank and his prey that grabbed the animals in focus but blurred the background. However, I opted away from that in favour of experimenting with some depth of field stuff that, with it’s grading into mist and fog, also serves as a subtle nod to old Chinese ink and wash paintings. I think it works. Sort of. That being done at the end of several weeks – maybe even a couple of months – of sketching and redrafting, the image was ready for presentation at the big SVP conference in Bristol last month. I think it’s generally all right, but there are some bits that could be better: Frank looks a little flat and undershaded, and some parts just look unfinished (apologies to the authors – deadlines and all).
And on that note, I’ll finish. Don’t forget to check out Flesh and Stone for more Frank-related goodies if you haven’t already, as well as their other articles on all things science. As for me, this year’s transition from summer to winter has churned up a very nice looking day, so I’m going to have a shower and enjoy the warmth of the sun for a while. Probably while drawing one of the dullest pterosaur fossils in the world. Oh well: can’t have everything.
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Uploaded on Oct 13, 2009
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Mis-shapes
I dance a lot in secret. I like dancing, see, but I’m too nervous to do it regularly in public. With an iPod beaming music into my head virtually all the time, I’d be dancing in very inappropriate places if I were totally unabashed about dancing in front of others – grooving along the fruit aisle in Tesco, sliding around Portsmouth’s Guildhall Square and that sort of thing. No, I keep my public dancing subtle - little flairs of my hands when typing, striding in time with the beat when walking, virtually indiscernible wiggles of my hips when at the gym (whoever designed exercise machines clearly thought nothing of their more flamboyantly minded customers, I tell you – try wiggling your ass to David Bowie’s Cracked Actor on a cross trainer and you’ll see what I mean).and so fourth. The story only changes in two places: if I think I’m on my own, suddenly, cooking dinner resembles the end of Saturday Night Fever or when I’m out with chums at some retro-music evening, and perhaps somewhat jollier for my intake of beverages. There, and typically to the sounds of The Rolling Stones more than others, my shyness disappears and my mojo, whatever I may have of one, does its stuff. My dancing, similarly to my good friend Richard Hing, requires lots of space: there’s all sorts of sliding, strutting, leg crossing, kneeling, enormous arm/hand movements and no shortage of considerable movement around the dance floor. Forget getting my PhD: my favourite memory of last Christmas was literally clearing a dance floor whilst jaggering around with my girlfriend to Brown Sugar. Not many people I know have done that, and I didn’t even have any shoes on.
Thing is, I need a particular type of music to dance. I need something with beats that you can move between, some change in tempo, a little melodrama and, more important than anything else, a dash of flamboyance. Yer glammy Bowie tracks, less pretentious Doors numbers and Beatles singles are perfect dancing fodder. You can imagine my dismay, then, that nowhere, virtually nowhere plays this stuff. Yes, all right, I’m several decades late to such a party but, really, would it kill people to throw these things onto their playlists once in a while? Instead, we have to make-do with clubs that play the tightest, most repetitive dancey-trancey tracks you could possibly imagine, the sort of thing that you could either subtly bounce to if you’re shy, go all trippy and arm wavy if you want as you loose yourself to the deafening beat or, if you’re of a looser disposition, grind your nether regions against those of a perfect stranger in the hope that they’ll take you home for cookies and beer later on. The flamboyant dancer is left out in such a place: there’s no musical or physical room to do anything, and defying your surroundings to be all flamboyant would almost certainly land you in a fight. In years gone by, I would’ve thought there was something wrong with me and shuffled around the edges of the venue until, at last, my less self-conscious friends left and I could escape with them under the guise of still being popular. Now, at the confidently cynical old age of 25, I happily left the last club I went to early. Let the fools dance their tight, constrained jigs as long as they want, thought I. Put on some Pulp or Iggy Pop and I’ll show them how it’s done. So, I wound my way home to the world of bad late night TV and nice beer, content with the fact that I’m different to the rest of the world.
Predictably, this long tale has some relevance to the world of palaeontology. Ages and ages ago, some chums of mine decided that they just weren’t happy with the cheap beer, crap music and overcrowding of the surprisingly controversial dance club of sauropod dinosaur neck posture and decided to do their own thing. The short version of the tale, covered in considerably more detail here, is that most folks for the last twenty years have assumed that long-necked dinosaurs habitually held their necks slung out horizontally from their bodies – you know, like they did in Walking with Dinosaurs. This was in stark contrast to how sauropods were originally reconstructed when, for giggles, they were always reconstructed with their necks arching into the air. The horizontal sauropod neck idea wheeled out in the 1980s sort of made sense in a strictly mechanical way: neck bones, like most vertebrae, have overlapping processes known as zygapophyses that, if you were to design such a system, would be in their most energetically effective position when they were held halfway between flexion and extension (the so-called neutral posture). This way, muscles running along the neck could be relaxed, letting the sauropod nuchal ligament (the strong, elastic tissues running along the upper surface of a tetrapod neck – you can feel your own on the back of your neck or, alternatively, go pinch the top of a horse’s neck) hold the vertebrae with minimal effort from the neck musculature. Both actual fossils and sexy computerised versions were thought to verify this posture and, before you new it, every sauropod from here to the Caucus Mountains was being reconstructed with a long, horizontally held neck.
However, at least three sauropodophiles weren’t keen to dance to this track. The chaps in question are the proud owners of the SV-POW! blog or, in full, Sauropod Vertebra Picture of the Week. For those of you unfamiliar with their neck of the interwoods, SV-POW! is an, uh… dedicated website dealing almost exclusively with the vertebrae of sauropod dinosaurs. You can tune in every week and see a new view of a Camarasaurus fourth cervical or something and learn a new fact or two about dinosaur anatomy. Clearly, it’s totally barmy and has no right to be anywhere near as good as it is, but the talents of Mike Taylor, Matt Wedel and Darren Naish somehow keep it not only informative and interesting, but fun and exciting. These guys have a passion for sauropod vertebrae that really makes you wonder if their wives know what they’re getting up to: eventually, one of them is bound to leave a note addressed to their family on their kitchen table explaining that they’ve run off with the Xenoposeidon type specimen or something. Anyway, the SV-POW!-er Rangers decided to test the notion of habitual horizontal neck postures in sauropods through some forehead-slappingly obvious science: how to modern tetrapods hold their necks?
Well, from salamanders to bunnies and crows to cattle, the answer is that virtually all extant tetrapods necks are almost always extended at their bases, with the skulls flexed on the foremost vertebra. In upright-standing critters such as mammals and birds, the neck is held vertically at rest even if the rest of the body is held horizontally (as is the case for most tetrapods – we have a pretty weird posture, after all). This has very, very few exceptions, so we can infer that fossil terrestrial tetrapods should’ve had inclined neck postures and flexed skulls too or, to put it another way, would have habitually have held their necks above their backs and rotated their heads downwards to see what was in front of them. Now, sauropods have crazylong necks, but there is no reason at all to assume that they were any different from modern animals: they too probably held their heads up high a lot of the time, bringing them down to earth when they had to drink or (in some cases) feed or whatever. What’s more, the idea of a horizontal neck being mechanically advantageous just ain’t right: as we all know from carrying virtually any heavy object, it is far easier to support the load when it is close to your centre of gravity than when held as far away as possible, which is the effect achieved with a horizontal neck. In my view, it all makes perfect sense and, because the SV-POW!-erpuff Girls have really gone to town on explaining their paper in excellent detail, I recommend that you point your browser this way to read all they have to say about it.
Now, I was privileged enough to be invited to the first official SV-POW!-wow dance before most other folks when the chaps asked me to draw their big press release image. Being asked to draw dinosaurs is quite a big deal for me: there aren’t that many chaps out there specialising in pterosaur art, but there is a whole truckload of really, really excellent dinosaur artists. Many of them manage to combine a real artistic flair with pinpoint anatomical accuracy: they won’t put claws on (most) titanosaur hands or leave the jaw of Tyrannosaurus without an enormous, bulging posterior pterygoideus muscle. This stuff is important: irritatingly, many palaeontologists pay little attention to such details when working with artists: they give them a skeletal reconstruction, leave them to their paintbrushes and then come back later with a pat on the back regardless of whether the depicted animal looks anything like it should or not. Sure, there may be talk of colour and composition, but scientific accuracy is pushed down the list of importance. A good palaeoartist, then, can almost work independently of a scientist (although, obviously, good communication between the two is best) and folks like Todd Marshall, Mike Skrepnick, Luis Rey and many more manage to produce work that is not looks exquisite, but also is scientifically savvy. In such company, then, it’s something of a surprise that all these folks were bypassed for the palaeoartist hack writing this. Maybe they made a mistake when sending the E-mail and didn’t want to feel embarrassed after I’d said yes to the commission. Maybe all the other palaeoartists were busy. Or maybe they liked my price tag.
Whatever the reason, once the neck-posture paper was in the publication mill, we began the process of putting the image together. A surprising amount of thought went into most aspects of it: Diplodocus was chosen as the animal because of its familiarity and to counter the BBC-produced low-slung versions appearing everywhere. Colour was unanimously decided as being drab: we all think sauropods are exciting, but big animals tend to be much duller than their smaller counterparts, so their shades of integument probably weren’t much to write home about. The position of the soft-tissue spines along the neck was debated, as was the position of the nostrils. With all of us being too geeky to resist at least one in-joke, we discussed the possibility of including a small, red Rhamphorhynchus alongside a sauropod neck a la Rudolph Zallinger’s Age of Reptiles mural. Alas, the Diplodocus bearing Morrison Formation hasn’t yet yielded any rhamphorhynchine pterosaurs, but, happily, we could substitute this for the Morisson rhamphorhynchid Harpactognathus - the fact that these pterosaurs are tiny specks on the page is obviously irrelevant. Different genders for the sauropods and a tripodal Diplodocus in the background were also discussed, but all were abandoned in favour of keeping the image as simple as possible. A drinking sauropod was realised as mandatory early on: we all figured that people would almost certainly misread the press releases and start harping on about sauropods needing to drink and all that. Hence, putting one slap-bang in the middle of the image graphically demonstrates that the SV-POW!-busters never said sauropods held their necks erect all the time, just that they would do by default. Even purely arty things like the framing of the animals in the background and the degree of contrast to loose when viewing sauropods from a distance was considered. Trees and other vegetation were included for scale and, for kicks, I went to town with some wibbly-wobbly reflections in the water. Having done work with several different palaeontologists now, I can reflect on this image as one of blissful efficiency: happily, the first concept sketch I drew was accepted as what we wanted (in fact, Mike was a little bummed that he couldn’t show the development of the idea in a series of blogposts) and, unlike some images I’ve drawn where people have proven very difficult to please or prone to changing their mind until you finally refuse to keep modifying the damn thing, the SV-POW!-trotters simply said what they wanted, what they liked and didn’t like and, well, we had the whole thing wrapped up within 10 days or so. The results, as you may have guessed, are above, and you can find a high-resolution version here.
And there, dear friends, ends the story of how to be different in the world of palaeontology and have someone with chronic verbal diarrhoea draw you a picture about it. Apologies to Mike who asked me to write up my thoughts on this way back in early July: blame all the dancing I’ve been doing in a certain workshop on my supersecret project involving my own long-necked creatures. What workshop and supersecret project is this? Point your interweb viewer at this and then join me in reciting my new mantra: No Pressure.
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Uploaded on Aug 24, 2009
7 comments
Shine on
It’s summer blockbuster season at the cinema. This year, we’ve already had another superhero flick, a new Terminator doing the rounds at the moment, giant transforming robots hot on his heels, and an angsty teenage wizard following behind that. Depending on your point of view, this is either the best time of the year to visit the silver screen or good reason to stay outside and work on your suntan. For me, it’s got to be the latter: sure, I loved the blockbusters of my day: Ghostbusters II, Independence Day and Jurassic Park stand out as memorable cinema trips from yesteryear, but, even though the same people are still making the movies, I’ve grown out of them. The Jurassic Park guys had a heavy hand in the new Indiana Jones movie, and it was crap. Likewise, the Independence Day boys have filled our screens with several unadulterated pieces of tripe, Godzilla, The Day After Tomorrow and 10,000 BC. I figured that it was them doing something wrong, that they’d lost some of their magic in the way that musicians can loose their spark over time. Unfortunately, I checked: their old movies are just as bad, it’s just that I’m no longer a puppydog that laps up any onscreen action as long as the movie as plenty of roary-roary creatures and some lasers.
Nowadays, being a whole week and a bit from 25, I’d rather watch a movie based on Chekov than Clancy, or be confused by Lynch than bored by Bruckheimer. The difference is the emphasis on scale: I don’t need big set pieces, action and devious plots to overthrow the world as we know it to be entertained: I just need two people in a complicated relationship, perhaps an edge of surrealism, and I’m very happy. I want to be emotionally challenged: I’ve seen enough celluloid explosions already, now I want to see real life. Give me longing and desire, or explore the brevity of happiness. Show brooding revenge and darkness, or people struggling with their own salvation. Instead of chases involving gruff men in black cars, I want people running away from their pasts. This is the stuff that makes for a rewarding film. American Beauty or, say, Mulholland Drive may be stories set within a narrow space and feature only a handful of players, but they offer a reward that just can’t be paralleled by any globe-trotting, high-octane thrill-seeking adventure with dozens of characters.
The same can be said for your world of pterosaur research*. There well over 100 pterosaur species now known and you can make a good name for yourself by studying the whole lot of them at once. Work on, I don’t know, an epic comparison of flight styles or some sweeping study of their systematics. Tell the world that everything they thought they knew about one aspect of pterosaur palaeobiology, mass estimation, say, is wrong, or reveal a finding from one critter that has implications for the whole clan. Alternatively, you could be really, really specific and work on just a few species at once. This is also kind of cool, because you become a total expert on that one little clique: you know everything of note that’s ever been said about them, and can spout streams of information to anyone foolish enough to ask. While this doesn’t really put you in excellent stead for conversation at parties, it does mean that you begin to feel a real affinity for your little corner of the Big Picture and you can tell the Big Boys doing the grand, epic work things that they just haven’t had time to notice.
*Yes, yes, I know: flimsiest link ever.
This brings us neatly to one little group of pterosaurs, Thalassodromidae. They’re the sexy-looking pterosaurs with stonking sail-like headcrests made entirely from bone and, for the moment, we only know of two genera: Tupuxuara and Thalassodromeus. They both come from the Cretaceous Santana Formation of Brazil and, to date, there’s no conclusive evidence that they existed anywhere else. There are some pterosaur arm bones from Europe and Texas that could be thalassodromid, but they could also be something else. Regular readers, if I’ve got any left after such a long posting hiatus (I have good reasons, honest) will recognise them as reasonable regulars of this corner of cyberspace: they appeared yonks ago in my first-ever press release image (the consequences of which are another reason for my lack of posting – fair number of folks after original artwork, these days) and then appearing several more times, most notably in the ‘down with skim-feeding’ press work of 2007. They were also a focal point of my PhD, as I not only discussed their feeding habits through research into skim-feeding, but also looked at virtually ever aspect of their taxonomy. Turns out, y’see, that the thalassodromid story is far more complicated than you might expect, full of enough twists, turns and heightened emotions to fill a period drama. Here's why.
Firstly, their name: Thalassodromidae. Not much can be controversial about a name, right? Well, there’s been some disagreement about whether the group should be christened this or another moniker, Tupuxuaridae. No one’s actually come to blows over this yet, but different teams of authors have firmly stuck to one name or the other. While you may imagine that there’s no real issue with using different names for the same group, it defies the weighty International Commision of Zoological Nomenclature, the institution that has governed the naming of animals since 1895. These chaps state that you cannot name the same animal, or the same group of animals, more than once. This is sensible enough, especially when you’re trying to write specifically and scientifically, and both Tupuxuaridae and Thalassodromidae are exactly the same thing, so there should only be one name. Thankfully, the ICZN provides guidelines to suss this sort of thing out, and, typically, the earliest name wins out. This would make Tupuxuaridae the winner, as this was first coined in 2006. However, it was only mentioned in passing as part of a discussion over pterosaur phylogeny and, in fact, it was almost certainly an error: the authors of the paper were paraphrasing another set of authors who mentioned tupuxuarids, not the formalised term Tupuxuaridae. Is this a big deal? In the eyes of the ICZN, yes: their code explicitly states that names need to be erected explicitly, and the casual naming of the group in the 2006 doesn’t cut this gravy. Or mustard. Whatever, the important thing is that Thalassodromidae, despite appearing a year later (2007) was erected explicitly, and therefore takes priority.
So, now we know what to call them, then, but what are they? There’s no disagreement that they belong to Azhdarchoidea, the same pterosaur group as the short-faced tapejarids, stork-amatic azhdarchids and slender-skulled chaoyangopterids, but which one of these groups are they most closely related to? This argument has been raging since at least 2003, with some authors saying their crest structure ropes them to Tapejaridae, while others argue that other aspects of their skulls and skeletons tie them to azhdarchids and chaoyangopterids in a group termed Neoazhdarchia. The jury is perhaps still out on this, but I think the weight of evidence places thalassodromids in Neoazhdarchia: all pterosaurs in this group have long, straight jaws with shallow mandibles, relatively long snouts in front of their nasoantorbital fenestra (that big hole positioned in front of the skull in pterodactyloid pterosaurs), eye sockets significantly positioned below the top of the same opening, straight or concave margins along the top of their snouts and a fused shoulder region (the notarium). Several features have also been used to lump thalassodromids with tapejarids, but the only remaining valid character of this pairing is that their headcrests start at the front of the skull. Compared to the number of characters that suggest the contrary, this is argument is pretty weak and, for my money, nowhere near as well supported as the Neoazhdarchia hypothesis.
OK, so we’ve got a name, and a good indication where they fit on the pterosaur tree, but how many thalassodromids are there? We've already mentioned the two genera of the group, Tupuxuara and Thalassodromeus, but how many species were there? Well, more than most have suggested, in my view. Circa 2002, we recognised two species of Tupuxuara and single speceis in it's sister genus, Thalassodromeus. Then, the controversy wand was waved again and it was suggested that all these taxa represented different ages of one Tupuxuara species. This has since been proven not be the case, and we’re back to at least three species again. At least? Yes, at least: there’s two Tupuxuara skulls with unusually reclined crania, particularly low orbits and angular, diamond-shaped nasoantorbital openings. These features aren’t known in any other Tupuxuara material, suggesting these skulls may represent a third Tupuxuara species. Problem is, one Tupuxuara species is only represented by rostral remains, and these elements are unknown in the two Tupuxuara skulls with peculiar crania. Hence, the two morphologies cannot be compared and we’re left wondering if we’ve got three or four thalassodromid morphs in the same locality. Sheesh.
So, thalassodromids are clearly a taxonomic minefield, with disagreements over just about every aspect of their systematics. Do details of their palaeoecology fare any better? Well, not really. My Portsmouth chums published a paper a few years back about growth in thalassodromid headcrests, noting from an immature specimen that the top-portion of the crest appears to grow along the skull as the animal aged, suggesting only fully-developed adults would sport the full flamboyance of a thalassodromid headcrest. This isn’t the fist time such a finding has been made, of course: we know that at least some other pterosaurs underwent similar growth patterns, and thalassodromids seem pretty typical in this regard. Even this finding is tinged with a caveat, though: the specimen that showed this growth strategy, identified as Tupuxuara by my buddies, is very probably a piece of Thalassodromeus. D’oh.
And then, of course, there’s the skim-feeding stuff. Thalassodromeus, y’see, was meant to be the Pterosaur Skim-Feeder Extraordinaire, and it’s descriptors were so confident of it’s proposed feeding habits that they named it, accordingly, ‘sea-runner’. It’s no secret that I think this is hokum, but I’m not going to write out why again: it will suffice to say that biomechanical modelling and comparative anatomy have clearly demonstrated the total lack of substance behind the proposed skim-feeding habits of Thalassodromeus and all other pterosaurs, for that matter (and yet, bizarrely, it still crops up from time-to-time in the technical literature).Unfortunately, there has been no further investigation into exactly what thalassodromids did do for a living, but some loose conclusions can be drawn from their skeletal bauplan. Like other azhdarchoids, their wings are relatively short and, bearing a relatively low aspect ratio, would’ve been handy for flight in terrestrial settings (what with the high lift such wings produce, not to mention the fact that their stunted ends will clip less vegetation). Their hindlimbs are pretty typically developed for non-ornithocheiroid pterodactyloids, meaning they were probably quite comfortable when milling about terrestrially. The neck of Tupuxuara is pretty short but otherwise strong and flexible: it bears no indications of dip-feeding, but it presumably didn’t place as many lifestyle-restrictions on its owner as the necks of azhdarchids probably did. Thalassodromid skulls show some variation: the Tupuxuara skull is quite slender and delicately-built with flat occlusal surfaces at the jaw tip, whereas the skull of Thalassodromeus is pretty durned chunky and has laterally tapered, superficially scissor-like jaw tips. Presumably, this reflects niche partitioning between these contemporary genera, with Thalassodromeus perhaps capable of taking relatively big prey compared to the delicately-built Tupuxuara. In fact, I’ll bet that the bladed jaws of Thalassodromeus were quite a limiting factor on prey size: while they would increase bite pressure along the occlusal margins, bladed jaws might make handling small foodstuffs awkward – imagine substituting chopsticks for two knife edges and you’ll see where I’m coming from. There’s nothing noted in their skeletons to suggest a preference for any type of prey however, so we may provisionally conclude that thalassodromids were generalists that ate anything from fish through to small dinosaurs. However, seeing as excellently, excellently preserved, complete thalassodromid skeletons are still sitting on museum shelves awaiting description, we may eventually be able to pin down their habits more specifically when more details of their anatomy are known.
And that, dear friends, may be all we can sum-up about thalassodromids for the time being. Like a Gore Verbinski movie, it's been a tale of frustration and convolution and there’s clearly some way to go before all the loose ends are wrapped up. However, the point here, I suppose, is that so much drama has been got out of so few species from one point on the map, and that sorting out these relatively minor controversies can be just as rewarding as figuring out some enormous, pan-palaeontological issue.
And, speaking of very focused views, there’s a profile up top of the aforementioned Tupuxuara with a strange skull, complete with a frog dangling from its mouth. It’s not the most exciting contribution to my portfolio and, what with the lighting and all, you can only just see the low orbit and reclined crania. Oh well: at least it’s something new and, hey, I’ve never seen a pterosaur depicted in lateroventral view before. And that’s important. Like recycling.
And on that note, I’m starting to yawn with alarming regularity and should shove off to bed. Before I go, though: apologies to all those who've tried to contact me with no success in the last few months: I'm not deliberately being rude or lazy, just a bit swamped. Accordingly, this leaves me a bit knackered most of the time, just like now. Hence, with the Sandman a callin', toodleoo for now.
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Uploaded on Jun 22, 2009
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Stormy Clouds, New Horizons
It’s hard to escape the increasing realisation that my friends and I are twenty-somethings. When you’re, say, 22-23, you can dump yourself in the ‘early-twenties’ category and be content that youth and vigour are still happily with you, albeit without the angsty energy of adolescence. Then you hit the 24-26 category, where you’re around the cusp of your third decade on the planet and it slowly dawns on you that time is getting on. A quarter of a century has passed since you were born and doubts start creeping in. You spend a bit of every day wondering if you’re on the right career path; whether you should have your own place by now; thinking a bit more seriously about having some little versions of yourself running around and when, Jesus when will you loose that gawky physique you gained when you were 16 and turn your naked self into something resembling a man rather than a baby chimp.
However, if one thing comes with age, it’s a taste for good beer. As an underage teenager trying to be served in my local pub – complete with a soft teenage-moustache and enormous goggle-glasses - I was an avid lager drinker. You know: the likes of Kronenberg, Stella and, as a special treat, big bottles of Budweiser. Nowadays, though, I’m really not a lager fan at all. Nope, I’ve moved away to the considerably more interesting and mature world of ales and bitters. Ignoring the weak, crappy taste of Boddingtons and the like, ales are the way to go. Each has its own unique flavour and strength: some are very watery, some pack strong tastes that linger in your mouth for minutes, and others taste so flowery that I suspect brewers have been liquidising and bottling their local florists. Compared to lager, they’re incredibly flavoursome and rich and, once you’ve matured to Ale Age, there’s no going back. Still, as I watch my younger chums sucking up their lagers, I don’t judge or try to change them: nope, I quietly know that in a few years they’ll be watching other young men through the same, ale-distilled eyes. It’s all right, lager drinkers of the world: we were all there once, we understand, and we’re just waiting for you to join us.
Now, believe it or not, the professional interests of palaeontologists go through a similar maturation. 90 per cent of fresh-faced, first-year palaeontology students are only interested in one thing: dinosaurs. It’s dinosaurs this, dinosaurs that: they tolerate the molluscs and echinoderms put in front of them for description, they begrudgingly look at sediments and will consider basic geological principles like Walther’s Law of Superposition and continental drift but, given any freedom of choice over their topic of study, and they want dinosaurs. Some palaeontologists never grow out of this and, for them, they’re only interested in a fossil animal if their remains are big enough that you can wield them like guitars and pose on the front cover of scientific rock magazine equivalents, National Geographic and New Scientist. Thing is, though, this blinkered view obscures some of the true marvels of the fossil record. Some of the most fantastic, amazing things require more patience and contemplation to appreciate. The mysterious Ediacaran fauna. Small but intricately-spiralled graptolites or spiny trilobites. 30 million year-old molluscs and beetles with bona fidecolour patterns. It’s frustratingly incomplete, but, for the mature palaeontologist, the fossil record is freaking awesome even without its A-listers like dinosaurs and enormous marine reptiles. Sometimes it’s the richness of a particular fossil deposit that is fantastic, and not necessarily the likes of the Chinese Jehol Group or German Solnhofen Limestones which, with their fantastically preserved early-birds and whatnot, are predictable headline fodder. No, given enough time and patience, even the most unassuming fossil-deposits can be veritable goldmines, assuming you know what you’re looking for and where to find it.
Step in, then, my University of Portsmouth colleague, Dr. Steve Sweetman. Clearly not interested in discovering fossils that you can pose alongside while being circled by expensive photographers, Steve’s spent the last several years working on the microfossils of the Lower Cretaceous Wessex Formation of the Isle of Wight. To find them, he dried samples of silty clay taken from lignite-infested plant debris horizons found within the Wessex, washing the clay away and painstaking sifting through the remaining plant material to find the animal fossils. This required literally hundreds of hours of work to retrieve the fossils alone, let alone figure out what they were. As you might expect, such a project is worthy of a several-hundred page book, and, indeed, it’s results formed the subject of Steve’s Ph.D. thesis. However, the God-knows how many hours spent identifying his fossils have, thus far, only allowed him to review the Wessex tetrapods – vertebrates with/that once had four limbs – without even approaching the fish discoveries. Thing is, this alone has, by Jingo, totally changed what we know of the Wessex palaeofauna. Essentially doubling the number of known tetrapods from the Wessex Formation, Steve found a whopping 48 new types of critter from the Wessex, including dirty-big dinosaurs, tiny amphibians and mammals, and more middling-sized lizards, birds and mammals. His work allows for a much more complete picture of the 115 million year-old ecosystem record in these deposits, and, luckily and very honourably for me, Steve asked yours truly to paint a picture of the ecosystem that he is now more acquainted with than anyone else in the world. The result is above: it’s the biggest picture I’ve ever painted digitally and took 7 days to get from rough paper to your screens. There’re lots of things I would change if I had a few more days to work on it: some details of the water need work, there’s not nearly enough shading, everything looks too clean, some areas have been really, really, roughly coloured… Thing is, with a tight deadline to meet, I had to draw the line somewhere: eventually, you have to concede that you’re out of time and a project will have to be presented as it is. I guess it’s all right, but I reckon it could be better. Ho hum.
Anyway, enough moaning about my lack of artistic finesse: what’s going on in that crowded scene? Well, the picture can be divided into two parts. The top-half of the image is pure, Classic Wessex, full of big dinosaurs, big trees and big crocodiles. It also presents the Wessex palaeoenvironment, showing the kilometre-wide river that was responsible for depositing the clays of the Wessex Formation. This river meandered its way eastwards across a vast, seasonal floodplain through a landscape covered with ponds, conifer trees and ferns, with the biggest trees localised on the low hills found to the west of the floodplain. To the right of the image, the vegetation on these hills is being set alight by lightning storms that seasonally ravaged the floodplains, burning off the canopy and creating the floods that filled ponds, river channels and what-have-you with the sediment and plant muck that would eventually form the plant debris beds. En route, these floods would pick up animal carcasses and other remains – shed teeth, loose bones - and deposit them in the same plant debris horizons. As such, these storms played a vital role in recording the story of the Wessex fauna. Hooray for ancient storms, then.
The back- and midground of this scene holds some familiar characters - in fact, these well-known critters have already featured on this corner of the Interweb (check out this set here for some old sketches of vanilla Wessex forms). In the far distance, there’re a couple of titanosauriform sauropods: big ‘Angloposeidon’-type brachiosaurs and more derived titanosaurs next door. To the right of these strapping chappies is a lone Caulkicephalus, an ornithocheirid pterosaur surveying the water for fishy morsels (see this for a discussion of dip-feeding in ornithocheirids). To the right of him, moving into the middle ground, is a small group of Iguanodon-like ornithopods, though they aren’t necessarily Iguanodon proper. Why? Well, bucko, the taxonomy of iguanodonts was overhauled recently, suggesting that many of the large ornithopod remains lumped into Iguanodon actually represent several, highly-distinctive forms. Hence, the slender forms shown in the picture here aren’t Iguanodon, but the smaller, recently-christened Dollodon.
Just in front of the wading Dollodon is another group of ornithopods, the 2 m long Hypsilopohodon, some of which are being harassed by the large crocodilian Goniopholis (oh, and look closely and you can see some baby Hypsilopohodon amongst the adults, too). Just right of the central midground and around the Goniopholis are basking and swimming Bernissartia, crocodilians that specialised in grubbing-out and eating molluscs. Left of these, in the mouth of the tributary feeding the main river, is the back of Lepidotes, a metre-long armoured fish being eyed by the biggest predatory dinosaur yet known from the Wessex, Baryonyx. The fish-eating habits of Baryonyx are well-documented, being based on gut content (including digested remains of Lepidotes, dontchaknow), tooth morphology, skull biomechanics and other observations of spinosaur functional morphology, so it’s interest in the Lepidotes here is well-founded.
Now, these chaps are undeniably interesting, but they’re nothing new. No, the real interest of this picture is found in the foreground and in the skies. Looking skywards first: Steve’s found that Istiodactylus, a pterosaur found in the Isle of Wight’s lagoonal Vectis Formation, also occurred in the terrestrial deposits of the Wessex. Next to this critter is a mysterious ‘early bird’, here suggested to be an Archaeopteryx-type thing but, in actuality, only represented by teeth that, while undeniably avian, could belong to a number of basal birds. Moving to the bottom of the image, you can find a pond in the bottom-left corner that features a bonzanza of new Wessex forms: salamanders and frogs sit on the pond margins and swim beneath the water (and, hey, check this out: I found one of Steve’s best salamander specimens during my dissertation studies); ctenochasmatoid pterosaurs sieve the water for prey; lizards of all shapes and sizes bask on a dead tree and rare turtles watch the river slink by. Alongside our anapsid friends are a pair of hesperornithiformes, two sitting on the riverbank and another swallowing a fish in the river itself. Some derived hesperornithiformes famously lost all ability to fly, becoming specialised diving predators in the process. However, early Cretaceous hesperornithiformes weren’t anywhere near as specialised and, to my shame, I probably should’ve drawn such early forms instead of fully-fledged, aquatic forms – whoops. Another mistake is to be found in the foot morphology of these chaps: rather than goose-like webbed feet as I’ve drawn here, hesperornithiformes are known to have individually lobed toes like grebes and coots. Annoyingly, this thought crossed my mind when drawing them, but I thought I was confusing them with something else and didn’t think to verify it. Grr.
Anatomical and temporal blunders aside, the middle foreground features a small maniraptoran dinosaur - suggested here to be a small troodontid. Dangling from its mouth is a tiny, tiny albanerpetontid; an amphibian that, if it weren’t busy being lunch, would be happy burrowing through damp soil. Beneath these fellas is yet another lizard, while to their right are the flagfliers for Wessex Formation Mammalia: rat-sized multituberculates and a shrew-sized dryolestid. These chaps are climbing over lumpy termite mounds, things that, to my knowledge, are yet to appear on reconstructions of the Wessex palaoenvironment. Now, no termite mounds have been found in the Wessex, but the sheer abundance of termites is clear from the masses of termite droppings that Steve sifted through in the course of his studies. The morphology of these mounds is very speculative: while there are some Late Cretaceous termite nests known, we known next-to-nothing of Mesozoic termite mound structure because their fossilisation potential is pretty poor. It’s entirely possible that the Wessex termites were entirely subterranean, but the Wessex clays weren’t kind to terrestrial trace fossils and any evidence of such termites has probably disappeared entirely. Hence, while we know that termites were swarming all over the Wessex floodplain, the jury’s still very much out on their accommodation of choice: the depiction you see above is merely to demonstrate their presence, not infer their way of living.
And that’s just about it, I suppose. I should re-emphasise that the animals you see here are only representative of the kinds of animals in the Wessex Formation: they were considerably more speciose than depicted here, but, hey, you can only fit so many types of critter on a sheet of paper before it becomes overcrowded. Still, it’s a far richer scene than anyone would’ve been able to paint years even four years ago, so hats-off to Steve for taking all that time and effort to turn the Wessex from a bland(ish) lager to a deep-tasting palaeontological ale. On that note, it’s time to finish my nice, floral-tasting beer and get myself to bed. Hence, I’ll thank Steve for asking me to help present his findings to the world – I’m genuinely honoured that he holds my work highly enough to ask me to illustrate what I think is a real scientific achievement – and point out that full-size versions of this image can be found on various news websites around the ‘Net, including this one here. Oh, and Steve and I have produced a visual key to the different forms if you’re having trouble finding them: in fact, one look at this and you'll realise that you needn't have read the last 2000 words.
Anyway, ‘night all.
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Uploaded on Feb 17, 2009
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