Guest post: Your Pretty Face Is Going To Hell

So first off in the ‘Wellnhofer’ series, Mark Witton takes time out of his busy schedule of not frantically finishing his PhD (since he’s actually done it now – well done again Mark) to tell us about a fantastically well, broken, pterosaur that he and Dave Martill have described. It’s not often busted pterosaurs are that interesting so take it away, Dr Witton:

For shame, I’ve only ever read one Sherlock Holmes story: The hound of the Baskervilles. I did enjoy it thoroughly: it’s a dead-good read and very hard to put down, so I thoroughly encourage you to track it down and read it for yourself if you’ve not done so already. Baskervilles reads in the highly accessible manner typical of other Conan Doyle tales: noble, relatively straightforward characters performing muted acts of heroism, a clearly and precisely delivered plot with elements of the fantastic but a firm foothold on reality, a sprinkling of Edwardian righteousness and the sensation that, although things may look a bit hairy before the novel ends, everything will work out all right by the final page. Being my first Holmes story, it was interesting to note that everyone’s favourite sleuth was presented in more-or-less exactly the manner you might expect, with his best party trick being his ability to deduce the habits of other characters with only a cursory glance of their appearance. You know: with a single look at your walking stick he could figure out where you work, where you live, whether you went to public school and which member of Girls Aloud you fancy most. That sort of thing.

Now, it seems to me that sleuthing abilities of that calibre would be very handy to have in real-life. Not only would it mean that you could, immediately, figure out who really did steal your last Rolo but, as a palaeontologist, it would make certain fossils make so much more sense. Enter, stage left, the strange mystery of SMNK PAL 4330…

Ickle Tupuxuara meets not-so-ickle Tupuxuara

An unassuming limestone nodule from the Santana Formation of Brazil, SMNK PAL 4330 kept both myself and my former PhD supervisor Dave Martill scratching our heads for some time. Within the nodule, see, is the skull and two partial neck vertebrae from a pterosaur known as Tupuxuara leonardii: for those of you who don’t know, Tupuxuara is a sail-crested pterosaur found exclusively in Lower Cretaceous deposits of Brazil, and is closely related to the larger Thalassodromeus, the critter all that reinvigorated all that skim-feeding nonsense a while back. SMNK PAL 4330 contains the bones of a juvenile individual, with an estimated skull length of about 30 cm or thereabouts (other Tupuxuara skulls are over twice this length – take a look at the accompanying picture to see just how much bigger SMNK PAL 4330 could’ve got). While this is moderately interesting in itself, the real intrigue of this specimen is that the pterosaur remains look like they’ve been run over by a truck: the rostrum has been shoved back into the nasoantorbital fenestra (the big hole in some pterosaur skulls formed by a fusion between the naris and another pneumatic opening); the cranium has been smashed to smithereens beneath the topmost margin of the eye socket; the palate of the mouth has broken away from the rest of the skull and the lower jaw – the mandible – has been broken in two places to lie in three separate pieces. Simply put, it’s a real mess, and Dave and I spent longer than I’m willing to admit trying to figure out just what happened to it. We could draw several conclusions about the fossil: it’s clear, for instance, that the animal was either dead or close to death when its skull smashed: if the animal was alive during the event that smashed its skull, you can bet that it wasn’t alive for much longer after. We can also deduce that some degree of soft tissue had to be left on the skull, or else all these separate fragments would’ve disassociated: this also suggests that the event happened with some temporal proximity to the animal’s death (soft-tissue rots away over time, after all). As for the nature of the damage, the oblique breaks across the mandible and the telescoping and microfracturing of the rostrum indicate that the skull received a very forceful impact from the front: while it’s possible that two separate events could’ve independently snapped the mandible and skull, it’s far more likely that the same event did both. Finally, being found in what was once the Santana Formation lagoon, the skull occurred in an environment where the nearest shoreline was several kilometres away. Hence, the skull had either drifted some distance from land or else the catastrophe had happened on the lagoon itself.

Thing is, these deductions don’t really tell us what woe befell SMNK PAL 4330 on their own. Instead, Dave and I did our best Holmes impressions with deer-stalkers, calabash pipes and the most spiffing morphine available* to rationalise several different hypotheses that could’ve resulted in SMNK PAL 4330 becoming the mess it is. With night drawing in and the storm intensifying outside the drawing room windows, we confronted each of our hypotheses head on, keeping in mind that SMNK PAL 4330 could record a dark, dark pterosaurian murder (thunder rumbles, lightning flashes), a terrible, grave accident (more thunder), or, most innocently, simply violent transportation to its site of deposition (er… slight intensification of the rain on the window panes). So, my figurative Watson, light your pipe, sit back in your lounge suit and let’s see if we can’t get to the bottom of this bizarre mystery.

*Not really. We just drank lots of coffee.

SMNK PAL 4330 in all its (un)glory

SMNK PAL 4330, Tupuxuara leonardii, in all its (un)glory. A, main slab; B, counter-slab; C, interpretive drawing of main slab (Cv, cervical vertebrae; Fr, frontal; L, lacrimal; Mdr, mandibular rami; Mds, mandibular symphysis; Nas, nasal; Pal, palate; Pmx, premaxilla); D, cross section of counter-slab revealing histology of mandibular rami (section taken along dotted line in B; arrows indicate thickened bone walls identified as dorsal margins of mandibular rami); E - F, tentative reconstruction of skull (light grey) based on preserved elements (dark grey). E, based main slab; F, based on counter-slab. Scale bars represent 50 mm (A - C, E - F) and 5 mm (D).

Hypothesis number one: predation/scavenging by other animals

There are shedloads of fossils that demonstrate pterosaurs were devoured by other animals. Bony fish, sharks and dinosaurs have all left unquestionable evidence of their taste for pterosaur meat: regurgitated, partially-digested pterosaur bones; tooth marks, or shed teeth embedded in pterosaur skeletons. Hence, it’s entirely plausible that SMNK PAL 4330 could represent a pterosaur that was chewed on by another animal. If this were the case, it’s clear that this pterosaur-muncher had to be a large animal: it’s hard to imagine how a small carnivore could’ve have broken the skull of even this half-size Tupuxuara so spectacularly. Happily, there are some good candidates for pterosaur devourers from the same deposits as Tupuxuara: the enormous spinosaur Irritator (a dinosaur known to have a taste for pterosaurs, too), a respectably-sized crocodile and several species of fish that would impress even the most world-weary anglers. Any one of these probably would have enough bite force to shatter a lightly constructed pterosaur skull, and Dave particularly liked the idea of a fish or crocodile grabbing our hapless Tupuxuara while it flew low over the Santana lagoon. Problem is, there’s no evidence of digestion, shed teeth, tooth marks or, basically, any calling cards left by any predatory animal on the pterosaur remains. What’s more, the telescoping of the rostum and transverse fractures across the mandible may be hard to generate by biting actions that would, presumably, splinter the skull from its sides or top and bottom. Thus, predatory acts have to be rejected because, being evidence-led scientists and all, we simply have no supportive evidence for this idea.

Hypothesis number two: trampling

As scuffed shoes and battered toes across the world can testify, animals – including people – aren’t always too careful where they land their feet. Is it possible that SMNK PAL 4330 assumed such a roadkill-like appearance because it was run-over by a large animal? Well, that certainly may explain why the cranium is so entirely shattered: there really is barely anything recognisable left beneath the top margin of the eye socket, suggesting it could well have been smashed to nothingness by the footfall of a giant dinosaur or summit. However, it’s hard to imagine how the trampling would push the skull and mandible back on themselves, save for some very, very particular circumstances. Equally, apart from the major breaks on the specimen, the bone is actually in pretty good shape – there isn’t any of the radial fracturing or breakage you would expect from a skull that was stood on by another animal. Hence, trampling also looks unlikely and, with predatory acts also ruled out, it looks like other animals had little to do with the creation of this pterosaurian Picasso.

Hypothesis number three: violent post-mortem transportation

When an animal dies, it’s rare for its remains to lie totally undisturbed. Even without the effects of decay and scavenging, water flow, gravity and other abiotic environmental factors have their say on the final resting place of animal remains, and sometimes the movement of bones or carcasses can be violent and traumatic. It’s certainly conceivable that SMNK PAL 4330 was battered about a rocky shoreline or riverbed by swirling, tempestuous currents or floodwaters: these events would easily generate the kind of forces necessary to shatter the cranium and force the jawtips back on themselves. Is there any evidence for this, though? Well, not really: as well as the major fracturing of seen across the skull, we’d expect signs of other, minor damage too: radial microfracturing, abraded bone textures – that sort of thing. What’s more, the Santana lagoon shows no sedimentological evidence of ‘high energy conditions’ – that is, high current velocities, storm activity and such. There’s therefore little reason, my good friend, to suspect that SMNK PAL 4330 was simply given a rough ride en route to its final resting place.

Hypothesis number five: skim-feeding

Forwardly-derived, high impact forces? Occurring over water? Could it be… finally… the evidence for pterosaurian skim-feeding?

Don’t. Be. Stupid.

Hypothesis number five: ‘the ground is a hard target to miss’

So, what’re we left with? There seems to be no evidence of activity from other animals, nor is there any indication that the Santana environment mistreated SMNK PAL 4330 prior to its settlement at the base of the Santana lagoon. What else, then, could’ve churned the specimen into such a mess? Well, it seems to me that a single, severe, forwardly-derived impact like that recorded on SMNK PAL 4330 might have originated from the animal simply flying into something, smashing its skull to pieces and killing itself in the process. This meets the criteria for the catastrophe to coincide roughly with the time of the animals death, the retention of so much soft-tissue to hold all the loose skull fragments together and the absence of smaller-scale damage to individual skull components. What’s more, we can see similar damage in modern bird skulls that have flown into windows. Birds that have suffered such trauma show busted mandibles and telescoped rostra like those of SMNK PAL 4330 and subsequently lend some support to this idea. However, there probably weren’t many windows around in the Lower Cretaceous, and the only other head-on avian collisions I’m familiar with are between said birds and aircraft: there weren’t many of those around in the Mesozoic either. Hence, while I reckon the fracture signatures of SMNK PAL 4330 suggest a head-on collision, I’m a bit perplexed as to how this event may have happened beyond suggesting that the pterosaur simply blundered into the ground. That said, you just don’t see modern animals blindly flying into things nowadays (windows and planes excepted, the former being almost invisible and the latter flying into relatively slow-flying birds), so I’m still not entirely convinced. However, in spite of own scepticism, I just can’t see how else the skull could’ve ended up in such a mess: the other hypotheses are simply not as consistent with the damage to the skull as this one. I suppose I could do well to take on board one final bit of wisdom from that Mr. Holmes: “When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth”.


So, that’s your SMNK PAL 4330, then: a strangely messed-up pterosaur skull that confounds explanation but may, if our reasoning is sound, record an astronomical pterosaur blunder. Whatever did happen to this critter, it appears to be a rarity: as far as I’m aware, there aren’t any other pterosaur skulls like it anywhere, suggesting we’ve got a genuine fluke of preservation. On that note, I suppose it’s time to sleuth off elsewhere to solve some other mysteries. Top of my list: just what will I cook for dinner tonight? Someone fetch my pipe and deerstalker: I suspect my first clues will lie at the supermarket.

Oh yes, and Happy New Year to you all, too.

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12 Responses to “Guest post: Your Pretty Face Is Going To Hell”

  1. 1 neil 06/01/2009 at 3:21 pm

    And…Mark manages to score/steal a google hit from Iggy. I beginning to see a pattern.

  2. 2 Neil 06/01/2009 at 4:22 pm

    I learning to use linking verbs.

  3. 3 Michael 07/01/2009 at 1:34 am

    Is it possible that this juvenile was
    leaving the nest for the first time?
    If the nest was high above a shallow
    section of the lagoon, and the poor
    wee beastie didn’t really understand
    how to use its wings, it may have simply
    fallen straight down and met the ground

  4. 4 David Hone 07/01/2009 at 11:15 am

    I think it’s far too large to be a hatchling (though I’ll let Mark discuss that), but pterosaurs were probably precocious and left the nest (and were flying) shortly after hatching, and no hatchling would be half the size of the adult.

  5. 5 Mark Witton 07/01/2009 at 7:58 pm

    Yup, I agree with Dave. If Tupuxuara grew like other pterodactylodis it would’ve taken a couple of years to reach half size: given that SMNK PAL 4330 is about 40 per cent of adult size, it’s probably at least – and perhaps well over – a year old (again, assuming a similar growth rate). That would be a long time to hang around in a nest, so I doubt SMNK PAL 4330 is a nestling.

  6. 6 Richard 07/01/2009 at 9:29 pm

    What kind of force of impact would have had to occur for the skull to actually fracture like that? Birds that fly into windows seem to rarely do themselves that kind of extreme damage:

    Skulls are in general pretty resistant to impacts.

  7. 7 Jaime A. Headden 08/01/2009 at 11:38 am

    From the look of it, and given that not only are separate sections of the mandible and upper jaw cracked and displaced, which is usuall indicative of transport after fracturing of the parts broken thusly, you have shattered elements in the jaw while the skull is largely intact (i.e., all the parts are in place). Movement of the pieces while retaining stable associations to their parts, but along with what appear to be disintegrated shattered regions implies to me only one thing: The skull was crushed dorsoventrally while the animal was on some form of substrate. Shattering of the mandible, specifically, could imply it was placed between two hard points and simply snapped in three, during this event. I would actually go with the occurance of the skull being caught by a predator and crushed while the jaw was torn around. This could have been pterosaurian or theropodan, or huge-giant-fishian, but whatever.

    The idea that the animal hit something really hard face-first doesn’t make sense unless you imply the animal was preserved immediately where it hit (face-first diving? I thought you were avoiding skimmer hypotheses?), and even in which case the upper jaw should be subject to the same forces that seem to have torn the lower jaw around. Contrarily, falling straight down while parallel to the substrate (or surface watter) will pulverize tissue indiscriminately, and bones tend not to stay intact for much of their length at all.

    The skull actually resembles the acts of scavenging that many fossils from the Niobrara Sea end up in, as well as dessication of exposed bits that are torn up by primary predators. This usually leaves all sorts of large bones intact along with soft tissue since primary predators go for the limbs and internal regions, while secondary predators finish the innards, limbs, and move on to the bones. This is as true of aquatic and terrestrial predators (or aerial in the case of vultures, but they feed terrestrially). So in this case, the nodule looks like postmortem dessication and predation, and tells us little how the animal actually died.

  8. 8 Graydon 16/01/2009 at 1:23 am

    It’s easy to have it hit something.

    All you need is a new somewhat floating dead tree, big rock sticking out of a shoal, etc., and a foggy day.

    Alternatively, you have maneuvering limitations due to the presence of other, larger, pterosaurs, and the little guy getting the bad choice. (I will only go for a mid-air if you’ve got the other pterosaur fossil, too. 🙂

    Also, there’s no available soft-tissue data, and while it is rare for healthy volant animals to fly into things, there’s no particular reason the specimen in question was necessarily healthy; if it had the mesozoic version of brain-worms or something, flight control could have been compromised.

  9. 9 Graham King 17/03/2009 at 1:56 pm

    Thanks for sharing this mystery!

    You said it: “an astronomical pterosaur blunder.”

    Maybe it got in the way of an impactor – not THE impactor, but a small one, a bolide already well-decelerated in its passage through atmosphere – imagine this Tupuxuara hearing the whistling shriek from behind/above, turning its head to look round, then WHAM!

    Ok. As a more earthbound explanation, maybe it misjudged depth of a puddle where it saw (or thought it saw) a fish to spear? Or dived for a near-surface fish the very moment a big hard-shelled or bony-headed predator from below gulped it first, getting in the way…
    Or is the fishing idea out altogether (not just the skimming idea – which I agree is out, as well-argued by Naish and Witton)?

    If it flew into something wouldn’t the very tip of the bill be extra smashed/blunted, or something? is it? by the answer, can we guess then the consistency of what it hit (if it hit)? (ie a substrate resilient/tough (like flesh/hide), or, penetrable but resistive (like mud/gravel), or hard and unyielding (like shell, or rock)?) Do the vertebrae give any clues to the impact angle/force?

    Did this body of water ever freeze? Could the Tupuxuara have hit ice where it expected only water? Or was it a tropical environment? Could a hurricane or twister have flung it at something hard, or vice-versa?

    As you may tell, I am guessing wildly, way out of my depth… 😉

    Again, Thanks for sharing this mystery!

  1. 1 Terrestrial predators such as…oh « Dave Hone’s Archosaur Musings Trackback on 13/03/2009 at 3:38 pm
  2. 2 Your Time Is Gonna Come | The Day The Earth Stood Still Trackback on 30/07/2010 at 2:43 am
  3. 3 The National Aviary, Pittsburgh « Dave Hone's Archosaur Musings Trackback on 06/01/2012 at 9:18 am
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