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Exclusive: Finding Lacusovagus by Mark Witton

Posted Jan 07 2009 4:39pm

Like most folks who’re rather chaotically organised and cannot say ‘no’ to extra work, my office desk isn’t the tidiest of places. In fact, it’s less of a desk and more of a utilitarian storage platform, separating piles of paper, books and specimens on its top from the boxes, old shoes and God-knows how many forgotten knick-knacks underneath it. I’d like to say that it’s only a mess to the untrained eye and that it’s actually a sophisticated filing system that only its owner can fathom, but that would be a blatant lie: frankly, to say it’s a pigsty would insult the housekeeping skills of pigs across the world. What’s more, this mess will probably only be cleaned when alternative activities are something like sorting out my tax details, filing my utility bills or cleaning the rest of my office, the state of which makes my desk look as tidy as Buckingham Palace in comparison.  

Still, at least there’s some relatively interesting junk buried in the paper mire of my desktop. There’re odds-and-sods from old science exhibitions I’ve participated in, casts of fossil bones, thin-sectioned fossils, the odd pickled turtle, and some stray bird bones collected from local beaches and marshes. All neat stuff, but the most interesting object I have lying on top of my desk is a slab of cream-coloured limestone. This thing is almost a metre long, 30-40 cm wide and has been hanging around my office for well over three years – I’ve come to see it as much as part of my office furniture as my bookshelf or chair. This oversize paperweight is more interesting than it first sounds, however: half-buried in the slab is the fossilised remains of a pterosaur, a flying reptile that existed alongside the non-birdy dinosaurs.   

Affectionately known to its friends as SMNK PAL 4325, this lump of rock and its fossil content represent the only known specimen of the world’s newest, sexiest pterosaur: Lacusovagus magnificens, a brand-spanking new pterosaur from Lower Cretaceous deposits of Brazil. Now, the Lacusovagus story has been told in a surprising number of places: what was initially a tentatively launched press release and accompanying illustrations became something of a media monster, appearing in the national press and spreading across the Internet like a highly contagious pterosaur-shaped rash. It was everywhere: National Geographic, The Times, The Sun, and numerous other papers featured the story in print and on their websites. I was interviewed for local and national radio in Britain and Canada; the Blogsphere and Internet mailing lists was buzzing with Lacusovagus -themed discussions, and even the BBC’s online magazine used one of the press release images for their weekly caption competition.   

As you might expect, the reporting quality varied widely. Sometimes the information gleaned from the press release and interviews was regurgitated precisely, but at other times made you want to slap your forehead with the despair of it all. Some folks have made howling claims that Lacusovagus was the only toothless pterosaur or that it was the biggest ever. Following these reports, I’ve had piles (well, a few) e-mails from people asking who was correct: the press reports or their own knowledge? Hence, when Flesh & Stone asked me if I could lend them a few words of my own about Lacusovagus, it seemed the perfect opportunity to put the Lacusovagus story straight: what, then, is Lacusovagus and where does it really fit into the rest of the pterosaur picture?   

Well, firstly, I guess we should address how old Lacusovagus is -- not the age of the individual represented by the fossil, you understand, but the age of the fossil itself.  SMNK PAL 4325 was sourced from the Crato Formation of Brazil, a limestone deposit of somewhat uncertain age. Based on fossil spores and pollen, the Crato limestones seem to have a ballpark age of about 110 million years, placing them towards the top of the Lower Cretaceous Period. 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 10 major groups of pterosaurs around at this time, and God-knows how many different species. In this regard, Lacusovagus doesn’t exactly rewrite our knowledge of pterosaur temporal distribution; 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 (that is, the specimen to which the scientific name of an organism is attached – SMNK PAL 4325, in this case). 

SMNK PAL 4325 is, y’see, 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).   

Unusual 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 some of the most basic features of it -- like the presence or 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. Probably.  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. In fact, only one toothless pterosaur, Tapejara,has a wider skull for its length than Lacusovagus, but this guy is clearly cheating at the skull length:width game by having a proportionally very short skull. Lacusovagus, on the other hand, combines a very long skull with great width, giving it very unusual proportions compared to other pterosaurs.   

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 (note that pterodactyloid pterosaurs like Lacusovagus have a what looks like a giant nasal opening, but this is actually a fusion between the naris and another opening – the antorbital fenestra. This huge opening, known as the nasoantorbital fenestra, probably had more to do with weight reduction and pneumaticity than permitting a particularly good sense of smell) 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) is due to SMNK PAL 4325 being an immature individual still awaiting the crest development, affinity for shoegaze music and moodiness that would arrive with puberty (other pterosaur fossils suggest headcrests only grew at sexual maturity, see). Rather, the bone texture of SMNK PAL 4325 suggests that this individual was all-grown-up, suggesting it was genuinely crestless in life.  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 thalassodromidstapejarids,   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 the Lacusovagus manuscript   was submitted for publication I hadn’t verified the chaoyangopterid affinities of SMNK PAL 4325 with any kind of systematic cladistic analysis, but I’ve recently managed to generate such a test: in all recovered analyses, Lacusovagus hangs out with the likes of Jidapterus, Eoazhdarcho, Eopteranodon, Chaoyangopterus and Shenzhoupterus - certified chaoyangopterids - to the exclusion of all other azhdarchoids. Interestingly, I also found Chaoyangopteryidae to form a little clade with Azhdarchidae, suggesting that long necks only evolved once within Azhdarchoidea. Neat.   

So, what does being a chaoyangopterid mean for Lacusovagus? Well, for one thing, it allows us to make a stab at guessing its size: 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 – 25 kg, pterosaur mass estimation 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, which Lacusovagus would no doubt have done admirably.   

That concern aside, identifying Lacusovagus as a chaoyangopterid allows it to be plugged into the picture we’ve built up of pterosaur evolution circa 110 million years ago. This is where things become really interesting because, for pterosaur workers, a Brazilian chaoyangopterid is extremely cool, see. To date, chaoyangopterids have only been found in the Jehol Group of China: L acusovagus, 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 in 110 million year old deposits between China and Brazil. There’s now better reason than ever before to suspect that Lower Cretaceous pterosaur-bearing deposits of Africa, Europe and Central Asia should contain pretty much all the pterosaur types we know of in Brazil and China. This expectation is slowly becoming reality with some new discoveries in Britain and the Middle East, and more will surely follow. However, Lacusovagus emphasises 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.  

So, that’s the real significance of Lacusovagus: in a way, it tells us more about what we don’t know than it does anything else. Before we go, I should add the obligatory explanation about the etymology of Lacusovagus magnificens: I really wanted to avoid christening SMNK PAL 4325 with a terribly dull place-name-odactylus or something like that. There are far, far, far too many scientific monikers formed around this tried-and-tested idea. Instead, I wanted something a little bit more romantic, so I settled on Lacusovagus magnificens, translated from Latin to mean ‘magnificent lake wanderer.’   It refers to the specimen’s deposition in the Crato water body and comparably large magnitude, and, for some reason, it really makes me want to listen to The BeatlesMagical Mystery Tour album.   So, on that note, I’ll let you go and get on with something else, and I’ll go be a walrus for a while. Who ever said palaeontologists were weird eccentrics, eh?

Mark Witton is a paleontologist at the University of Portsmouth (UK) School of Earth and Environmental Sciences. Many of his dinosaur illustrations can be foundhere. He can be reached at Mark.Witton@port.ac.uk

Citation:

Mark P.Witton,ANew Azhdarchoid Pterosaur From the Crato Formation (Lower Cretaceous, Aptian?) of Brazil.Palaeontology,Volume 51 Issue 6,  Pages 1289 -1300, Published Online: 19 Nov 2008


 

 
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