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 a 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, Tpuxuara 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
11 comments
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
10 comments
Your Time Is Gonna Come
To my constant shame, I don’t rate that highly on the Manometer. No, my Man Points are generally pretty low: I don’t get excited by fast cars or gadgets. I prefer chocolate to salty snacks. If I want to watch a film with cowboy hats, I’ll take Brokeback Mountain over True Grit. I reckon most clothes available in Burton or H&M are generally lacking in delicate fabrics and frilly bits, and, at times, my idea of a perfect evening is sitting down with a book listening to Thomas Newman soundtracks. Yup, the reading on my Man Point Scoreboard is worryingly stark most of the time, to the point where even my own parents have said ‘you know Mark, it’s really all right if you want to tell us something. Thank God, then, for Led Zeppelin, the most manly of all rock bands. Yes yes yes yes yes I know they owe a tremendous amount to The Yardbirds but that’s not the point: the important thing is that anyone who enjoys the beats of Misty Mountain Hop or swung around Gallows Pole has distilled testosterone pumping through their veins. I mean, we all like their quieter moments: Going to California, That’s The Way and the like, but nothing makes you want to put on your tightest spandex and do your best woman-toppling Robert Plant impression like, I don’t know... Immigrant Song, Kashmir, or Bring It On Home. Mmm: watch out, watch out now.
So, yes, Zeppelin are high on my list of good bands, and not the least because they give me some mild form of masculine credibility (although, let’s face it, if you need to wave Houses of the Holy at people to prove you aren’t really a very hairy woman, you’re in trouble anyway). So, imagine my shock when I heard late last year that the Zepper’s are touring without Robert Plant. I mean, what are they thinking? Sure, Black Mountain Side and Moby Dick show that Zeppelin can knock out good tunes without him, but you just know that Plant was simply out making the tea while they were recorded and would be back for vocals on the next track. I can dig the idea of playing without deceased band members if the vast majority of the band is still willing: that’s understandable, but to label yourself as the same band when only half of the original line-up is playing simply ain’t right. They’re missing too much to really be considered whole, and getting someone else in to replace them isn’t a substitute either, dangit.
Alas, I’ve also been operating as a mere shadow of what I should be. Y’see, this little corner of virtual real estate that I call my own has been running under the vague guise of a ‘pterosaur website’ for some time now: people chiefly know it and visit for images and rambly discussion of flying reptiles. Imagine my shame, therefore, for neglecting one of Pterosaurdom’s best known weirdos: the Early Cretaceous Argentinean ctenochasmatoid Pterodaustro. Everyone who’s ever picked up a pterosaur book knows this critter, having almost certainly stopped at whatever illustration was provided in said tome and uttered something like ‘that’s a weird one’. Leaving Pterodaustro off the running list of a pterosaur website is like a venue saying they’re hosting The Velvet Underground without Lou Reed or John Cale: it’s a sham, and one I’ve been getting away with for far too long.
So, in a vague attempt to recover some self-respect: what goes on with this Pterodaustro critter, then? Well, it’s not the world’s biggest pterosaur, growing up to a mere 2.5 m or so across the wings, nor does it bear an overly flamboyant headcrest like some taxa, but, obviously, that’s not what makes Pterodaustro a big deal. Nope: what turns heads for Pterodaustro is that it looks like it flew into a broomhair factory with its mouth open: it’s entire lower jaw is stuffed with incredibly long, bristle-like teeth that are arranged in rows akin to the baleen of modern whales. However, unlike our giant mysticete friends, Pterodaustro’s mandibular feeding apparatus is comprised of hundreds of genuine teeth with enamel, dentine and a pulp cavity, each one being about a third of a millimetre thick. In fact, there are so many teeth lining the lower jaw of Pterodaustro that they don’t have individual sockets: they lie in grooves running along the sides of the jaw. There are shedloads of teeth in the upper jaw, too: but these are small, spatulate things that don’t actually have any rooting in the skull whatsoever but are instead attached by some supportive soft tissue. If this weren’t weird enough, a series of tiny, tiny ossicles – small lumps of bone embedded in the skin – lie above each one of these. Neat.
Now, the function of these teeth really couldn’t be clearer: it’s plain-as-day that Pterodaustro was some sort of filter-feeder, using its teeth to strain small bits of food from the water column – you know, seeds, invertebrates, that kind of thing. What’s not been looked at in detail, at least as far as I know, is how Pterodaustro really did this. Other than their teeth, there are two details of Pterodaustro’s jaws that are worthy of attention: one is that the retroarticular process, the bony extension of the lower jaw that extends behind the jaw joint, is quite robust and curves downwards, away from the cranium. This suggests that their posterior pterygoideus muscles – the big muscles you can see bulging from the side of alligator skulls – were probably quite big in Pterodaustro. A big posterior pterygoideus means that Pterodaustro would’ve generated relatively high bite strengths when it’s mouth was nearly closed: this is a bit weird as pterosaurs seem to generally favour the snappy-actions of jaw adductor musculature over the relatively slow, but more powerful, posterior pterygoideus. On top of this, you have an incredibly long- diagnostically so, in fact – and curved jaw. Curved jaws are brilliant if your intention is to bring the entire jaw together along its length simultaneously: you can try this out yourselves by hinging your hands at the wrists and then clapping them together with straight or curved hands – everyone see how that works? Good. What this might mean then, dear friends, is that Pterodaustro wasn’t simply moving forward through water with it’s jaws agape, trapping foodstuffs like a pterosaurian shearwater (so-called ‘ram filter feeding’): nope, Pterodaustro was probably pumping water through its teeth for its food, with the pumping action provided by that kick-ass posterior pterygoideus and the curvy jaw ensuring that water wasn’t just pushed forwards out of the mouth, but was pushed sideways through the teeth (try the same hand experiments in the bath and you’ll see where I’m coming from). Now, we don’t know enough about Pterodaustro’s anatomy to suggest how filtered food was taken off the teeth and moved into the throat, but I guess it’s possible they had a large tongue that could hold gathered food particles against the upper jaw, where those little-peg-like teeth and ossicles may have helped hold them in place. As in modern geese and swans, the food could’ve been moved backwards along the jaw over successive filter cycles, and then swallowed finally when it reached the throat. Well, possibly.
Now, looking beyond the skull of Pterodaustro, it’s obvious that it was a wading animal – like lots of other ctenochasmatoids, in fact – with big, broad feet that are almost as long as its shin bones. This, presumably, means it was feeding while standing, and hey – check that out – it’s got a long neck like our other favourite potential terrestrial feeding pterosaurs, the the azhdarchids. Is it possible, therefore, that all long-necked pterosaurs liked to feed when grounded? Well, maybe: something to look at in the future, I guess.
What’s more, by golly, Pterodaustro does occur in some abundance. There are, apparently, hundreds of Pterodaustro fossils out there, most of which stem from a site in which they’re so abundant that it’s been named after them: the Loma del Pterodaustro of Argentina. Presumably, if you travelled back to the Lower Cretaceous and wandered down to this ancient freshwater lake, you’d find whole flocks of these guys wading around in the shallows, filter-feeding their little hearts out. Pterodaustro fossils represent a suite of different ages, from embryos right the way up to burly adults, and recent work on this spectrum of differently-aged individuals has shed light on how quickly they grew. Like dinosaurs, Pterodaustro(and presumably other pterosaurs) grew like rocket-fuelled dynamos until they reached approximately two years old – about half their full size – before their growth rates slowed, taking another three-to-four years to gain their full adult size. Unlike some modern reptiles – your crocodiles, turtles and the like - Pterodaustro appears to have had determinate growth (that is, like us, it reached a certain size and then stopped growing altogether), but, like the same modern reptiles, Pterodaustro hit sexual maturity before they finished growing. Sexual maturity seems to coincide with that two year-old benchmark where a switch in bone texture (from fibrolamellar to parallel-fibred, histology fans) suggests that energy is partially redirected from growth to reproduction – hence the slow growth from that point on.
So, Pterodaustro is a pretty durned-interesting pterosaur, then, and one that I definitely should’ve covered a long time ago. However, that’s not all: oh no. If you’re the sort of person who would have a pterosaur as a pet if they weren’t so inconsiderately extinct then you should stick a pole in the ground, grab some ribbons and have an early May Dance of Joy because pterosaurs are, officially, Fossil Animals of Choice for January. Oh yes: a collection of papers has just been published following the proceedings of the 2007 Munich Wellnhofer Pterosaur Meeting and, by jingo, the Interweb is going crazy about it. Chief party venue is Dave Hone’s Archosaur Musings, recently voted one of the top 100 Earth Science Blogs on the ‘Net and home of the volume’s editor, um, Dave Hone (the giveaway’s in the blog title, see). The Musing’s are running a series of blogposts across this week: there’s an introduction to Peter Wellnhofer, the Godfather and Don of modern pterosaur research; an essay by yours truly about a paper in which I, along with my ex-PhD supervisor Dave Martill, describe a particularly strange specimen of Tupuxuara that looks like it flew into a wall and an overview of the Chinese istiodactylids, those pterosaurs with muzzle-like jaw tips. What’s more, Mike Habib has recently guest-posted on the musings with his own take on his paper from the volume about how pterosaurs may have taken off using their forelimbs rather than their hindlimbs. There’s some great coverage of this particular story as MSNBC, featuring opinions from Mike himself, Sankaar Chatterjee, noted expert on animal flight, and some hack they found on the internet. Personally, seeing as Mike’s been telling the world that he can launch a 250 kg azhdarchid into the air without any problem (well, maybe not him personally, but you know what I mean), I’m all in favour of his ideas and am dead-chuffed to have my own work on pterosaur mass estimation sitting side-by-side with Mike’s paper in the same volume. That’s all great stuff, then, and should give you plenty to do look at sneakily in your office when your bosses’ back is turned.
Oh yes, one more thing for those who’re still here: this is going to be quick because this mess is already w-a-y over 2,000 words. in fact, I’ll do in my best, unpunctuated telegram style of English to save time and words:
[START] picture above is Pterodaustro [STOP] note the size of the feet in the flying critter to the left – I told you it was a wader [STOP] avoided pink colour because the flamingo analogy has been done to death [STOP] once had considerably more acid coloured skies but was toned down because it looked too much like the trippy scene at the end of Easy Rider [STOP] i mean, it was cool but too funky to be realistic [STOP] like too much James Brown [STOP] might have messed up the blurring on some animals [STOP] but never mind [STOP] you may not have noticed if i had not brought it up [STOP] own worst enemy [STOP] anyway i need to get on with something else now so will stop typing [STOP] no really my back is hurting from hunching over this keyboard [STOP] am going now [STOP] bye bye [STOP] [END]
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Uploaded on Jan 8, 2009
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And baby, it was all right
Not much time to write today: been rather busy over the last few weeks with lecturing, talking to the press about Lacusovagus and, somewhere around all this, having my PhD viva. With that over, you can now say goodbye to 'Mr Witton' and welcome in the new, sleekly-contoured 'Dr Witton'. Which is nice.
Anyway, there's no time for wallowing in my own ego: it's time to get on with this whole Christmas thing: Christmas shopping this morning, Christmas lunch with the department this afternoon, festive drinking at the pub this evening. On that note, I should really get on with things. Thanks to all you folks in Internetland who've been so nice and supportive this year and, heck, throughout the three years of my PhD: it's entirely appreciated. Best wishes for Christmas, the New Year and anything else you may get up to in the next few weeks: see you all in 2009.
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Uploaded on Dec 18, 2008
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You’re dirty, sweet and you’re my girl
Tell you what: of late I’ve done nothing but talk. Thanks to covering my PhD supervisor’s teaching load while he’s away on fieldwork for a month, I’ve been delivering 3 hour lectures, tutorials, assisting in practical classes, invigilating in-class tests and all sorts: I’ve been rambling on at students more than Led Zepplin II. The funny thing is, save for one seminar I’ve given on my own research, none of what I’ve said has been my own words. No, instead I’ve been regurgitating the songs of other researchers, putting what they’ve said into my own words and launching them at students. It’s a bit weird, really: I must’ve said thousands of words more than normal over the last week and yet, in a strange way, I feel like I haven’t really spoken to many people at all.
While I’ve been busy putting other people’s words into my mouth, a milestone in my career has drifted by virtually un-noticed. Yup, last week saw not only the publication of my first ever solo paper, but also my first ever contribution to the big list of animal species known to exist across time. Enter, stage left, Lacusovagus magnificens, a brand-spanking new pterosaur from Lower Cretaceous deposits of Brazil, described, illustrated and named entirely by yours truly. Given that a half-decent new taxon will be forever referenced and discussed in scientific literature until kingdom-come, this is, I guess, a reasonably big deal. Shame, therefore, that my reaction to its publication was something more akin to ‘oh, that’s nice’ than ‘hot-damn, I’ve been immortalised in the scientific literature’. Even as I write this, I can’t shake the feeling that I really have more pressing concerns to address like putting a lecture together or reading through some proofs but, dammit, it’s been ages since I wrote anything other than some hastily worded E-mails, so write I will: the words of other people will have to wait for a few minutes longer.
So, what is this Lacusovagus beastie all about, then? Well, the holotype specimen (that is, the specimen to which the name Lacusovagus magnificens is attached to) was sourced from the Crato Formation of Brazil, the age of which isn’t entirely clear. Based on fossil spores and pollen, the Crato Formation seems to have a ballpark age of about 110 million years old, dumping it towards the top of the Lower Cretaceous. This stretch of time records one of the richest, most diverse pterosaur faunas we know of: between the famous Jehol Group of China (you know, the place that's blossoming with all those fuzzy dinosaurs you see splashed across the news every-so-often), the Crato Formation, the neighbouring Santana Formation and a few other sites, we know of at least ten major groups of pterosaurs around at this time, and God-knows how many different species. So, Lacusovagus doesn’t exactly rewrite our knowledge of pterosaur temporal distribution, then: in this respect, it simply adds another name to the already-long list of pterosaurs known from this time.
What is a bit more exciting, though, is what Lacusovagus is. It took a little while to verify exactly what Lacusovagus was because of the, frankly rather crappy, nature of the holotype. Affectionately known to its friends as SMNK PAL 4325, the only known specimen of Lacusovagus is simply a fragmentary rostrum – essentially the front end of the upper beak and elements of the bars making up most of the skull length (to be all technical, we’ve got the complete pre-nasoantorbital fenestral rostrum, most of the right maxillary bar, some of the left maxillary bar and a short stretch of the posterodorsal extension of the premaxillae). Unusually for a Crato pterosaur, SMNK PAL 4325 is preserved with the roof of its mouth flat in the sediment, making it damned difficult to see even the most basic features of it - like the presence of absence of teeth. Adding to this problem was the fact that the chaps who collected the specimen decided that, because the limestone slab housing the skull was quite thin and delicate, they would secure another slab to the underside. In theory, this is an excellent idea because, hey, no-one wants their sexy new pterosaur skulls to split in two, but they used car body filler to cement the slabs together. We removed a section of the bottom limestone slab pretty easily, but the infernal car filler was a real cow to get through. In fact, only a tiny portion was removed before the juxtaposition of bloody inert car filler and delicate fossil became too much of a liability for preparation to continue. What you can see of the underside of the jaw shows no sign of teeth, and we later CT scanned the specimen to find a similar result. Thus, whatever Lacusovagus was, it didn’t have any teeth.
Thankfully, other aspects of Lacusovagus ‘s skull weren’t so difficult to see. Although pretty fragmentary, we’ve got enough of the skull preserved to show that the skull was quite long – at least 655 mm and probably well-over 700 mm when complete – but, based on doubling the width of the widest part of the skull, it’s also unusually wide. This is something you don’t get too often in pterosaurs: their skulls are typically quite slender (though no-where near as paper-thin as suggested by some workers), with only aberrant, derived things like istiodactylids and tapejarids having proportionally wide skulls. Lacusovagus stands out with weird skull proportions, combining a long snout with a relatively wide skull. In fact, only one toothless pterosaur, Tapejara, has a wider skull for its length than Lacusovagus.
And that’s not the only weird thing about Lacusovagus. For a long-jawed pterosaur, its rostrum – the bit of the beak in front of its nasal opening (although, of course, pterodactyloid pterosaurs have fused nasals and antorbital fenestrae – but you knew that already, didn’t you?) is pretty short. Given that the jaw is not entirely complete (but I figure most of it is there), the ratio of jaw length to rostral length will be even shorter in a complete specimen. The unusually wide skull is also reflected in the rostrum, which is pretty chunky along much of its length. However, unlike an awful lot of edentulous pterosaurs from the Lower Cretaceous, there’s not a hint of a headcrest anywhere along the skull. Given that the specimen is osteologically mature, it’s unlikely that it’s crestlessness (um... that may not be a real word) can be put down SMNK PAL 4325 being an immature individual still awaiting the crest development, shoegaze music and moodiness that would arrive with puberty.
So, are these features enough to give an idea of what SMNK PAL 4325 actually is? Well, it looks like Lacusovagus can be quite reliably shoved inside the pterosaur group Azhdarchoidea, the social club that also features thalassodromids, tapejarids and azhdarchids. However, it can’t be placed in any of these ‘classic’ azhdarchoid groups: no, Lacusovagus finds its closest chums in a relatively new pterosaur group, Chaoyangopteridae. These chaps – like Lacusovagus - have long, edentulous jaws with shallow, crestless rostra, big nasoantorbital fenestra and - a bit like azhdarchids - long neck vertebrae. Now, when I submitted the Lacusovagus manuscript to Palaeontology I hadn’t verified the chaoyangopterid affinities of SMNK PAL 4325 with any kind of cladistic analysis, but I managed to work one into my PhD thesis: in all recovered trees, Lacusovagus hangs out with the likes of Jidapterus, Eoazhdarcho, Eopteranodon, Chaoyangopterus and Shenzhoupterus - certified chaoyangopterids - to the exclusion of all other azhdarchoids. Interestingly, I found Chaoyangopteryidae to form a little clade with Azhdarchidae, suggesting that long necks only evolved once within Azhdarchoidea. Neat.
Now, if pterosaur palaeobiogeography floats your boat, finding a chaoyangopterid in Brazil is extremely cool. Chaoyangopterids, y’see, have thus far only been found in the Jehol Group of China. Lacusovagus, therefore, provides the first record of these guys outside of Asia and suggests that this otherwise poorly-known group were far more widespread than previously realised. It also heightens the faunal similarity between these two localities, suggesting that we should expect pretty similar pterosaur diversity between China and Brazil. All in all, it goes to show that we’ve still got a hell of a lot to learn about pterosaur diversity and biogeography and emphasises just how reliant we are on fossil lagerstätte – sites of exceptional fossil preservation like Crato and Jehol – to tell us what pterosaurs were up to at any given time in their evolutionary history.
Anyway, that’s about all I’ve got time to tell you about Lacusovagus for now. Only two more things are worthy of mention: with an estimated wingspan of 4 – 5 m, Lacusovagus is the biggest chaoyangopterid yet known and the biggest pterosaur from the Crato Formation (estimated mass of 20 kg, wingspan-mass regression fans). I mention this because, like all palaeontologists, my main concern is that any animal with my name attached will kick the asses of its contemporaries and closely-related animals. Finally, a quick word about the name: I really wanted to avoid another terribly dull place-name-opterus or something like that with my first scientific moniker. Hence, Lacusovagus magnificens translates from Latin to ‘magnificent lake wanderer’, a reference to the fact that the specimen comes from the Crato water body and was of some magnitude in size. This name, for some reason, really makes me want to listen to The Beatles’ Magical Mystery Tour album. Hmm: probably just me, that one.
Oh, and as usual, there's been no mention of the picture at the top of the text: what you've got there is the first ever restoration of Lacusovagus, suitably wandering around the margins of the Crato lagoon. Which is nice. Anywho, thanks to all those who helped out on the paper and with figuring out the specimen. Much appreciated.
--
UPDATE (4/12/08): Well, bugger me: this whole Lacusovagus thing has gone crazy in the last few days. It's been in the national papers, national radio, is all over the internet like a cheap suit and may even end up on the TV. It's funny to think that I only contacted our press office with the idea that someone - maybe, one, two bloggers, tops, would find Lacusovagus interesting: now it's a bona fide international megaevent. Crazy stuff. The best bit, is though, that the BBC have used my scale graphic for their picture caption of the week competition. So far, I've been likened to John Lennon, David Bowie, Rod Hull, Noddy Holder and at least two people can't figure out what sex I am. Superb (the BBC stuff, that is: not gender confusion. Not that there's anything wrong with that, you understand - I'll freely admit to dressing in a rather androgynous fashion on occasion and am perhaps favourably compared to women somewhat more often than I should be comfortable with. And I do moan about men a lot, so, hey, gender confusion is savvy with me. Um, where are we going with this? This is a sort of corner I've written myself into here: best trail off...)
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Uploaded on Nov 27, 2008
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