Fall down mountains, just don't fall on me
For most men, bless us, everything is about size and quantity. Car engines, televisions, stereo wattage, houses (and associated drive space), computers, various dangly appendages... they’re all the same. If they’re bigger, more expensive or exist in greater quantity, they’re far better than their diminutive alternative. Being the simple, simple things that we are, men posture and flaunt their various oversize appendages to demonstrate their dominance over subservient men and impress the ladies. Perhaps the only exception to this is the gee-whizz world of gadgets and technology: mobile phones, MP3 players and that kind of thing. Here, smaller is better, right to the point where you can’t dial a phone number even with your pinkie finger without smooshing the entire dialling pad or loose your iPod through the seams of your trouser pocket. But hey, who cares: it’s smaller than the brick of a phone owned by Derek, who could only loose his should it fall into a rice sieve. Go figure.
We’re quite open-minded in the world of palaeontology, however, and we flaunt both ends of the size spectrum to harvest all the moneys, honeys and, er, bunnies that fill the life of a typical palaeontologist. Still, for all the neatness of tiny little fossils, nothing grabs headlines more than ‘biggest ever discovered’. Unsurprisingly, pterosaur researchers are just the same and willing to big-up any large flying reptiles they may find. I’ve spent much of the last few weeks piecing together the history of this (quite literal, in one view) bigging-up of pterosaurs, documenting the discovery of the largest pterosaurs known from 1871 until today (to clarify the specificity of that date, Dave Martill, my PhD supervisor, has the slightly more involved job of piecing together the pterosaur record-breakers from 1784 until 1870). For once, this was not research conducted as part of a futile effort to finish my PhD, but instead for a presentation: the results of this bit of historical research are to be published, in poster form, at the Dinosaurs - A Historical Perpsective meeting being held in London next week (for those living in the future, next week is the 12 – 16 of May, 2008). Unfortunately, due to desperate finances, I won’t be attending the meeting in full, but will be around to collect people’s coats on their way in on the Tuesday morning.
So, what’s the story with these giant pterosaurs, then? Well, prior to the 1870s, the biggest pterosaurs were not that magnificent, perhaps only 4 m or so across the wings, and therefore not much bigger than the largest modern birds. What’s more, they were only known from the most diminutive of fragments from deposits like the Cambridge Greensand of England, where the pterosaur fossils look like they’ve been chewed up and spat out by a rhinoceros with acidic saliva. Complete pterosaurs were known, of course, but only comparatively small critters like Pterodactylus and Rhamphorhynchus from German deposits that still, to this date, have yet to yield a real pterosaur giant. Hence, it appears that Europe was not the best place to look for giant pterosaurs. Unsurprisingly, it was the USA, land of Supersized fast-food, Supersized cars and Supersize waistlines, that provided the worlds’ first truly enormous pterosaur. Its discoverer was one Othniel Marsh, the palaeontologist famous for his rivalry with Edward Cope. Funnily enough, Marsh championed his discoveries American pterosaurs as the first of their kind, but Cope may have beat him to it by several years (a story for another night, perhaps). Marsh and his expedition found the first remains of these giants in the Niobrara Chalk of Kansas, a deposit laid down in the continental seaway that bisected North America in the Late Cretaceous. Marsh’s initial discoveries (1871, chronology fans) were fragmentary, but one bone – a bit of wing metacarpal (metacarpals, for those who don’t know, are the long bones that connect your fingers to your wrist: each pterosaur forelimb has one particularly large metacarpal to articulate with their massive wing fingers) – hinted at a form with a 6.1 m (20 ft wingspan). This is pretty damn big, being almost 50 per cent longer than a large family car. The next year saw Marsh’s teams find a complete wing that confirmed Marsh’s wingspan estimate and, more astonishingly, reveal even bigger pterosaurs with 6.7 m wingspans. But what were these winged leviathans? Marsh initially dumped these remains in the genus Pterodactylus in 1872, noting their similarity to this European animal including the shape of their teeth. Marsh had this a little around his neck, however: in 1876, Marsh described newly-discovered skull material of these forms that revealed they had no teeth at all. Like, anywhere. They were, as we say, edentulous. Presumably, Marsh was describing fish, bird or marine reptile teeth associated with the pterosaur remains, because, even in the 140 years since Marsh’s work on Niobrara pterosaurs, there’s not one tooth known from any Niobrara pterosaur. Anywho, the lack of teeth in the Niobrara remains gave Marsh enough taxonomic clout to name a new genus, Pteranodon in 1876, and new remains described in the same year gave Marsh his largest ever Pteranodon wingspan estimate, 7.6 m. It was suggested in 1966 that even larger, 10 m span Pteranodon once existed, but Marsh’s estimates are probably more accurate. We’ve now got something like 1100 specimens of this critter, Pteranodon is, without a shadow of doubt, the best known of all giant pterosaurs.
Thing is, while Pteranodon is the best known giant pterosaur and had a wingspan certainly not worth sneezing at, it was most certainly not the biggest pterosaur. The first hints of even larger animals were found but not recognised by C. A. Arambourg in the late 1930s or early 1940s: this Jordanian material, thought by Arambourg to be a wing metacarpal, gave a wingspan of 7 m and was named Titanopteryx in 1959. Arambourg’s pterosaur was not really understood properly until the 1970s, when Douglas Lawson found a truly gigantic pterosaur remains in Late Cretaceous deposits of Texas. Several kilometres away, a bunch of smaller, but considerably more complete pterosaurs were found that bore remarkable similarity to what Times Magazine dubbed ‘Lawson’s Monster’. Lawson named them all Quetzalcoatlus in 1975 and estimated that the wingspan of the biggest was anywhere between 11 and 20 m: at very least, that’s 30 per cent larger than the biggest Pteranodon. Quetzalcoatlus then fell into the hands of Wann Langston Jr., who favoured the lower wingspan estimate In 1981 based on comparisons with the relatively small (6 m span) Quetzalcoatlus and biomechanical issues acting on 20 m span pterosaur wings.
Now, Quetzalcoatlus proved a key role in unlocking the secrets of Arambourg’s Titanopteryx. The smaller Quetzalcoatlus skeletons revealed that this taxon had an enormously elongate neck comprised of relatively few vertebrae, and the longest of the neck bones was a dead-ringer for the Titanopteryx ‘wing metacarpal’. Lawson realised this in 1975 and, with the 1984 discovery of another pterosaur with an absurdly proportioned neck in Uzbekistan (not a giant, mind), it dawned on pterosaurologists that a whole bunch of these fellows once existed. L. Nessov appropriately named this group Azhdarchinae in the same year, basing the name on the Uzbek word for ‘dragon’ (we’ve now raised the taxonomic rank of these guys to Azhdarchidae, by the way. That’s yet another story, however). Because it soon became apparent that the name Titanopteryx had already been applied to a tiny, tiny fly, Nessov, along with A. Jarkov renamed Titanopteryx as Arambourgiania in 1989, and seven years later, Eberhard ‘Dino’ Frey and my PhD supervisor re-described the vertebra and the size of the animal it represented. With refreshingly frank admittance of their inability to resist the urge to scale-up Arambourgiania despite having next-to-no-remains, Frey and Martill estimated a whopping 11-13 m wingspan for this animal, possibly dwarfing Quetzalcoatlus by 2 m.
Even bigger azhdarchids were to come, however. In 2002, E. Buffetaut and friends revealed yet-another poorly-known but clearly gigantic azhdarchid to the world: Hatzegopteryx. This animal, from Late Cretaceous deposits of Transylvania, is only represented by scrappy skull and limb material, but is thought to have spanned at least 12 m and, by my estimation, stands about 3 m tall at the shoulder. Thing is, while the remains of Quetzalcoatlus and Arambourgiania hint at relatively slender, lithe creatures, Hatzegopteryx is built like the proverbial fired-clay outbuilding. What little is known of its jaw is massively constructed and indicates a skull width of at least 50 cm. That’s half a metre. I’m barely 50 cm across my shoulders: Hatzegopteryx could probably swallow me, a fully grown, 23-year old man, whole. If we scaled this up to the skull proportions of the small Quetzalcoatlus, we’d have a skull 5 m long. Now, because skulls of this size are typically reserved for monstrous marine reptiles or filter-feeding whales, it’s thought that these estimates may be a bit wrong. However, even more conservative estimates of 2.5 m give Hatzegopteryx one of the longest skulls of any land-based animal, and certainly the largest of any flier. It also bears thought that the record holders for the longest skulls of land animals, the elaborately frilled horned-dinosaurs, are cheating to get their place in the record books by having much of their skull length occupied by accessory frill. The length of the Hatzegopteryx skull is almost entirely jaw, however, making it more comparable with the long-jawed skulls of big predatory dinosaurs like Giganotosaurus and Spinosaurus. Seeing as the latter has a skull of around 1.8 m length, it appears that a twiglet-boned, lanky pterosaur had longer jaws than any dinosaur. Who’d have thought it?
Alas, the rest of Hatzegopteryx is virtually unknown. We have the occipital region (the part of the skull that connects with the neck), which is deeply-sculpted for anchoring powerful neck-elevating ligaments and muscles. The humerus is poorly preserved but comparatively more robust than that of the giant Quetzalcoatlus. That’s about it, but the bottom line is clear: Hatzegopteryx was absolutely enormous and it remains the largest pterosaur we know of. In fact, I have it on good authority that, based on our current understanding of pterosaur biomechanics, the pterosaur skeleton would have to be dramatically altered to facilitate much larger forms. Despite this, there were rumblings in 2005, however, of an even larger pterosaur being found. Y’know: something in the 20-25 m range. Unfortunately, this beastie was mentioned to the public well before it should’ve been: the alleged remains of this creature have since proven to be non-pterosaurian and several pterosaurologists (some of whom I know quite well – but no names mentioned) retire sheepishly at its mere mention. For the less squeamish, Cameron McCormick has crafted a diagram and blog post discussing this most monstrously unreal pterosaur.
So, there you have it: highlights of the history of giant pterosaurs in 1,780 words. There’s a whole lot more to go with this stuff: giant Jurassic pterosaurs, giant pterosaurs in the Lower Cretaceous, giant pterosaur footprints, giant palaeontologists vs. giant aeronautical engineers on the mechanical constraints facing a giant pterosaur… if only there was a giant amount of time to tell it all (dy’see what I did there?). For the moment, you’ll have to be content with the image accompanying these words: it depicts the 1.75 m tall author, somewhat shaggier than his last comparison with a giant pterosaur, being dwarfed by the mighty Pteranodon (on the right) and the monumentally-sized Hatzegopteryx on the left. Note that Pteranodon, for all this talk of being much smaller than the largest azhdarchids, is no midget itself. No giraffe this time – it was eaten by Hatzegopteryx. Oh, that reminds me: big things - big, Earthshaking, city-levelling things - are about to happen in the world of azhdarchid palaeobiology. What’s that, you ask? Well, that would be telling. Come back soon, dear friends, and all will be revealed…
UPDATE (12/05/08): As is customary with these things, the ever prompt Dr. Naish has written a review of the aforementioned conference, which you can find here. It even has a daft pictures of me and Darren, plus a picture of the poster that kick started this whole essay off. Now that's value for money, especially when you don't have to pay a penny to see it.
UPDATE (21/05/08): Of course, giant pterosaurs are all very impressive, but the crazy guys at Sauropod Vertebrae: Picture of the Week (or SV:POW! to those on the scene) have just graphically pitched the planet's most enormous animals against each other: sauropod dinosaurs vs. whales. Who wins? Head here to find out.
(While you're over there, don't forget that their animals of choice can't fly: pterosaurs are far cooler [maybe drop a comment or two to point this out to them]. And I'm much better looking than either Matt Wedel or Mike Taylor: see for yourself.)