How a giant ape nearly brought flightless pterosaurs to cinema screens

I've not kept it much of a secret that I’m a big fan of King Kong or, at least, the 1933 and 2005 versions (you can keep your ‘76 and Toho incarnations, thanks). There was something about the mythos of the film that excited me even before I had seen it so, when I was eight and my family saw the ’33 Kong being shown on late night TV, we grabbed it on video tape and I got up especially early before school to watch it. I only managed to see a brief glimpse of Kong himself before I had to leave for school, but that was enough to ensure that I resumed my viewing as soon as I got home. Almost 18 years later, I can still remember watching the charging Stegosaur for the first time, or that Brontosaurus chucking sailors around a swamp before chasing them up the tree. And, of course, the T. rex vs. Kong wrestling match, all framed by the wooden cabinet around our old TV and watched from our comfy blue sofa just left next to the patio door, with the heavy blue curtains closed to keep the glare off the TV.

Sometime later, my sister would record The New Adventures of Superman over virtually the entire thing and leave only Kong’s death atop the Empire State Building as my entire Kong experience. We’re still not talking.

Anyway, things turned out all right: I eventually got a proper copy of Kong and, hooray, Peter Jackson remade the original to generally great acclaim and success in 2005. Yesterday, my day was made when I received a copy of The World of Kong: A Natural History of Skull Island, essentially being a collection of the creature and environment concept art for Jackson’s movie. Tell you what: Weta Workshop, the chaps behind the 2005 Kong special effects, really went to town with their ideas. They literally imagined an entire world, or at least an entire island, for their movie to be based in. In essence, they embarked on a big speculative zoology project, imagining what may have happened if Skull Island (the mysterious land that the explorers of the film er… explore) held a whole bunch of Mesozoic critters that survived the K/T extinction and continued to evolve. The film shows a handful of the more charismatic creations and environments, but there was buckets more that could’ve gone in. There’s nasty-looking fish, birds, worms and insects, several flying rats, all manner of theropods, ceratopsians and sauropods and even – get this – flying (not gliding) frogs. But they didn’t just go for wild and spectacular stuff: apparently fully immersed in their world, the chaps at Weta imagined the quieter, more sedate biota of Skull Island, including the inclusion of pretty-standard looking storks, egrets and herons in swamps and wetlands. But, and here’s the really cool bit, they also toyed with the idea of flightless, cormorant-like pterosaurs.

How cool would that have been? Secondarily flightless pterosaurs on film! And pterosaurs that are really, really far removed from those that we know and love! Sadly, it wasn’t to be but, still, it’s closer than almost any other film project I know of. Christened Axiciacephalus curia (see image at the top of this post; by Weta artist Johnny Brough), the Weta flightless pterosaur is around a metre long, has naked skin and bears long, low jaws filled with isodont, regularly spaced teeth. The nostrils are positioned far back along the jaw and on the dorsal surface of the skull. The neck and body are short but the tail is long, deep and muscular. Weirdly, the forelimbs are heavily modified into short, flipper-like appendages while the hindlimbs are elongate, three-toed and digitgrade. It’s meant to dwell around streams and live in a cormorant-like fashion, diving underwater and propelling itself along with its long legs. It really is very far removed from all things pterosaurian and, frankly, if it weren’t for the text, I would’ve thought it was some sort of weird theropod. Still, it deserves acclaim for being totally different (I thought my goat-tapejarids were good, but they’re blown out of the water here) and, moreover, a short-armed diving pterosaur may not be as crazy as you’d think.


And here’s why
For one thing, while pterosaur forelimbs are considerably more conspicuous than their hindlimbs, most pterosaur legs are not under-developed. As Padian (1983), Bennett (1997) and Habib (2008) have noted, they only appear small in contrast to the enormous heads and arms that characterise pterosaurs: they’re actually proportionate to the torso size and mechanically suited for powerful, leap-assisted takeoffs (Bennett 1997). Moreover, pterosaur swimming trackways indicate that they propelled themselves through water with their feet, not their hands (Lockley and Wright 2003; see adjacent image from the same paper. Illustration by Judy Peterson). Therefore, it’s not impossible to imagine a situation where a specialist wader pterodactyloid – a ctenochasmatoid, say – became secondarily flightless and, as wading turned to swimming, developed longer, more robust hindlimbs. Simultaneously, a diving animal would almost certainly reduce the size of its drag-inducing and now largely-useless arms, but still maintained some of their aerofoil properties for use as flippers. It’s a stretch, sure, and I’m not really sure the final product would look like Axiciacephalus, but I wouldn’t rule it out.

There's loads more we could say about this, but I don't really have the time. Still, it's pretty neat that flightless diving pterosaurs came close to being put on film and, actually, are a pretty groovy idea. In retrospect, you can see why Axiciacephalus didn’t make it into Kong 2005: although neat in its own way, it’s hardly as attention grabbing as the big tyrannosaurs, brontosaurs and gorillas that lived nearby. Certainly, it would’ve been a very different movie if Axiciacephalus and his more sedate chums had featured heavily. Anyway, must dash: I’ve got to go flip a giant pterosaur.

References

• Bennett, S. C. The arboreal leaping theory of the origin of pterosaur flight. Historical Biology, 12, 265-290.
• Habib, M.B. 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana, B28, 161-168.
• Lockley, M. G. and Wright, J. L. 2003. Pterosaur swim tracks and other ichnological evidence of behaviour and ecology. In: Buffetaut, E. and Mazin, J. M. (eds.) Evolution and Palaeobiology of Pterosaurs, Geological Society Special Publication, 217, 297-313.
• Padian, K. 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Musuem. Postilla, 189, 44 pp.
• Weta Workshop. 2005. The World of Kong: A Natural History of Skull Island. Pocket Books, London, 223 pp.

Embarrassing questions on Quetzalcoatlus

You can’t queue up at a supermarket checkout nowadays without being bombarded by celebrity lifestyle magazines. They glare at you from the impulse-buy shelves with paparazzi shots of stars looking flabby, pregnant, boozy or unhappy and garish, block capital headlines scorn celebs for revealing their mortal flaws. There is probably a deep-seated psychological reason to their popularity, perhaps reflecting the desire people have for gossip or reassuring somewhat insecure readers that it’s OK, people with stars on Hollywood Boulevard aren’t perfect either. The thing that strikes me, though, is that a lot of the people splashed all over the front pages of these rags have very little substance behind their fame, becoming famous because they took they posed semi-nude for a tabloid newspaper, are related to someone else in the public eye or appeared on telly for five minutes on a reality TV show. These are the empty celebrities, the ones that you assume have some reason for being known but, when investigated in more detail, are actually quite devoid of substance. It’s rare that these tabloid-fodder achieve international fame: to do that, you’ve at least got to be associated with an internationally-released product or hung-out in high-profile political circles. In some respects, then, becoming a real international household name requires a little more substance than your local, lower-grade celebrities. Talent, though, is handy but not strictly necessary.

There are definitely fossil animals that are the equivalent of A-list celebs, the sort of critters that every five year-old knows and that press releases strive to mention, no matter how tangential their work is to them, to gain more kudos. They’re the animals that the public know and love, the likes of Tyrannosaurus, Triceratops, woolly mammoths and sabre-toothed cats. Typically, these animals do have some substance to them: while their taxonomy may be confused or controversial, they definitely ‘exist’. Some pterosaurs are in this club too, with Pterodactylus (or probably ‘pterodactyls’) or Pteranodon being at the top of the list, and Quetzalcoatlus, everyone’s favourite superpterosaur, just behind (detail of a new image above). Thing is, though, Quetzalcoatlus may be a fraud. Yes, that’s right: there may be so little substance to its existence that its status as a household palaeontological name is undeserved: it’s a local celeb masquerading as a big shot. That’s controversial stuff and, no doubt, several of you have just sprayed your monitor with coffee shot through your nose at the very idea of such a thing. But mop up that liquid, dry the screen off, and we’ll see why I’m suddenly being so nasty to one of the cornerstones of Azhdarchidae.


Giant, yes; diagnostic, maybe not
As I’m sure you all know, Quetzalcoatlus stems from the Maastrichtian Javelina Formation of Texas. Remains of several animals that would be referred to this genus were found from 1972 – 1974 and were briefly described by their discover, Douglas Lawson, in 1975 (Lawson 1975a). Quetzalcoatlus was erected in the same year (Lawson 1975b) with fragments of a giant left wing (including a famous complete humerus, TMM 41450-3; see image, above) being used as the holotype for the type species, Q. northropi Lawson, 1975b. A bunch of smaller individuals that were represented by substantially more complete remains were discovered at the same time and initially referred to the same species (Lawson 1975a, b) but, later, were said to be sufficiently distinct from Q. northropi to deserve their own species (Kellner and Langston 1996). Pending their complete description, however, Kellner and Langston simply called them ‘Q. sp.’ for their work on the Quetzalcoatlus skull.

That all looks above board on the surface, but it doesn’t take much digging to find several massive holes. Firstly, despite the wealth of material that has been referred to it, neither Quetzalcoatlus or Q. northropi have ever been given a rigorous taxonomic definition*. To my knowledge, only Nesov (1991) has had a stab at a Quetzalcoatlus definition but his listed characters are either not unique to Quetzalcoatlus or of questionable validity, so his work is not really useful here. This leaves us without a diagnosis and, accordingly, we simply cannot know if Q. northropi is a valid species or not. What’s more, with Q. northropi being the type species of Quetzalcoatlus, the entire genus must go if the former is sunk.

*You could get away with this sort of stuff in the 1970s, but it’s much harder to be taxonomically slack nowadays. The ICZN (the body that regulates naming of zoological specimens) has recently tightened its rules considerably to make sure that new taxa come with proper holotype allocation, diagnoses and all other due practises (e.g. article 16, International Commission on Zoological Nomenclature 1999), so messes like the one under discussion here should – in theory – eventually become a thing of the past.

In my eyes, this is quite a real possibility. Pterosaur limb elements aren’t normally named because they are not considered diagnostic at generic or species levels: taxa that are based on limb elements alone have been considered nomina dubia by later authors. ’Santanadactylus’ spixi - a set of wrist bones - and Palaeornis cliftii - an isolated humerus – have both fallen into this trap (Unwin 2003; Witton et al. 2009). Unless Q. northropi is unusually distinctive, it’s possible it may be binned too. Adding more concern to this worryfire is that, so far as I can see, the Q. northropi humerus doesn’t look that different from other giant azhdarchid humeri (e.g. Padian and Smith 1992; Buffetaut et al. 2002) and the existence of these other giants nullifies the possibility of using size as a diagnostic feature (though this would be dodgy anyway). The other Q. northropi elements are so scrappy that they’re probably of very little taxonomic utility and preclude the use of limb element proportions in a diagnosis, too. Call me cynical if you like, but it looks like this could be an uphill struggle to me.


The plot thickens
There’s more. With no definition for Quetzalcoatlus, the referral of the Q. sp. material (including that depicted above, from Kellner and Langston 1996) to this taxon is also questionable. The Q. sp. material is what people refer to when talking about the detailed anatomy of Quetzalcoatlus, but we need to be careful: there has never been any justification printed for the allocation of Q. sp. to Quetzalcoatlus: we’ve just been told it’s similar to Q. northropi and can therefore be placed in the same genus. Thing is, Hatzegopteryx, Arambourgiania and Zhejiangopterus are pretty similar animals to Q. northropi too, so why can’t the Q. sp. material been popped in one of these genera instead? You can't argue taxonomic provinence in this instance, either: it's highly likely that there is more than one azhdarchid genus in the Javelina Formation (see my thoughts on this here), so you can’t suggest allocation of Q. sp. to Quetzalcoatlus through association alone.

To be clear, I'm not saying that Q. sp. itself is of questionable validity - whatever you want to call it, Q. sp. is definitely a valid, diagnosable species, I’m just iffy about its allocation to Quetzalcoatlus at present. Note, however, that the story continues outside of material referred to Quetzalcoatlus, too: the status of Hatzegopteryx may also hang in the balance. I don’t have time to go into that now, though.

So, what next?
The resolution of all this is, in my view, quite straightforward. Eagle-eyed readers may have read between the lines of this post and realised that, despite it’s fame, popularity and unearthing almost 40 years ago, there is almost nothing written or illustrated of Quetzalcoatlus. The issues highlighted here will not be resolved without this data and, frankly, a few good photographs and descriptions of Q. northopi would give all the information we need to get started. There is, in fact, a bit of an elephant in the room about Quetzalcoatlus and, foolish though it may be for a bloke looking for a job in the pterosaur corner of palaeoindustry to be so outspoken, it should be flagged up. Without mentioning any names, the Texas Memorial Museum has placed a strict embargo on the release of information about Quetzalcoatlus until the full monographic description has been properly published. This has been promised since at least the 1980s (Langston 1981; Kellner and Langston 1996) and, in the meantime, getting access to the material seems to be extremely difficult. I asked to see the material back in 2006 and was told no. Colleagues of mine have asked the same, and got the same answer. The few friends of mine that have seen the specimens are sworn to secrecy and, if they want to publish even itty-bitty snippets of information about them, they have to ask permission first.

If you ask me, this is all a bit rotten. The Society of Vertebrate Paleontology’s ethical mission statement states that vertebrate palaeontologists of the world are here to:

1. To advance the science of vertebrate paleontology throughout the world;
2. To serve the common interests and facilitate the cooperation of all persons concerned with the history, evolution, ecology, comparative anatomy and taxonomy of vertebrate animals, as well as the field occurrence, collection and study of fossil vertebrates and the stratigraphy of the beds in which they are found;
3. To support and encourage the discovery, conservation and protection of vertebrate fossils and fossil sites;
4. To foster the scientific, educational and personal appreciation and understanding of vertebrate fossils and fossil sites by avocational, student and professional paleontologists and the general public.
   

From the SVP Constitution, Article 12, Code of Ethics.

Aside from the point 3 in this list, it seems that the decades-long embargo on the Quetzalcoatlus material isn't really in keeping with these guidelines. I mean, I get embargoes. I get 'gentlemen's agreements' about publishing rights. But 40 years to publish a specimen description while simultaneously being very cagey about giving access to the material? Seriously guys, what's going on? I'm not sure there's quite enough ground here to go stampeding to the SVP ethics committee or anything, but when is this material going to be properly published and freely available to see?

References

• Buffetaut, E., Grigorescu, D. and Csiki, Z. 2002. A new giant pterosaur with a robust skull from the latest Cretaceous of Romania. Naturwissenschaften, 89, 180-184.
• International Commission on Zoological Nomenclature. 1999. International Code of Zoological Nomenclature (4th Edition). The International Trust of Zoological Nomenclature, 1999.
• Kellner, A. W. A. and Langston, W. Jr. 1996. Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from Late Cretaceous sediments of Big Bend National Park. Journal of Vertebrate Paleontology, 16, 222-231.
• Langston, W. Jr. 1981. Pterosaurs. Scientific American, 244, 92-102.
• Lawson, D. A. 1975a. Pterosaur from the Latest Cretaceous of West Texas: discovery of the largest flying creature. Science, 185, 947-948.
• Lawson, D. A. 1975b. Could pterosaurs fly? Science, 188, 676-677.
• Nesov, L. A. 1991. Gigantskiye lyetayushchiye yashchyeryi semyeistva Azhdarchidae. I. Morfologiya, sistematika. Vestnik Leningradskogo Gosudarstvennogo Universiteta. Seriya 7, 2, 14-23.
• Padian, K. and Smith, M. 1992. New light on Late Cretaceous pterosaur material from Montana. Journal of Vertebrate Paleontology, 12, 87-92.
• Unwin, D. M. 2003. On the phylogeny and evolutionary history of pterosaurs. In: Buffetaut, E. and Mazin, J. M. (eds.) Evolution and Palaeobiology of Pterosaurs, Geological Society Special Publication, 217, 139-190.
• Witton, M. P., Martill, D. M. and Green, M. 2009. On pterodactyloid diversity in the British Wealden (Lower Cretaceous) and a reappraisal of “Palaeornis” cliftii Mantell, 1844. Cretaceous Research, 30, 676-686.

On the nature of palaeontology and throwing away years of training for a career in artistry. Oh, and something on pterosaurs, too.

Every now and then it occurs to me just how silly vertebrate palaeontology is. Consider the following: access to specimens is extremely competitive, but, despite this, a vast wealth of material remains undocumented; chances of scoring funding are less than 5 per cent; a high proportion of the work you perform is unpaid; there are all sorts of political considerations when reporting new finds or sharing information and, aside from ‘being nice to know’, there’s very little reason or rationale to investigate most extinct vertebrates – invertebrates and microfossils have utility in stratigraphy and hydrocarbon work, at least. All the same, people are falling over themselves to work in this profession, which means you have to be bristling with qualifications to even think of applying for an academic palaeo position. These qualifications don’t come cheaply: in Britain, you’re looking at three years of a relevant degree study, probably another year earning a Masters, then at least another three of PhD study. Tuition fees alone across this seven year period will set you back well over £20,000 and, while you’re studying, your earning power is significantly reduced: while all your school friends are off earning proper money in real jobs, even funded students will be just about be breaking even. As such, these seven years are not just spent acquiring the skills you need to be a palaeontologist: they're also seven years off the property ladder and seven years of not really putting any money into personal savings, and there’s little guarantee of a job at the end of it. What’s more, your fancy doctor’s title can become a burden as, while academic jobs become (theoretically) open to you, doors close on most menial jobs as, frankly, employers realise - probably rightly in many cases - that a PhD in a menial job will fly the nest as soon as they can.

Now, I’m not saying it’s all bad - vertebrate palaeontologists work hard at what they do because it brings enormous personal satisfaction and, ultimately, they’re being paid to do something they like – but the points made above are worth thinking about if you’re looking at a career in vert. palaeo. I stress that I'm genuinely not trying to put people off aspiring to palaeo jobs, but there are equally rewarding professions that are better paid, considerably more accessible and, at times when unemployment is looming on the horizon, considerably less stressful. I’m faced with the latter situation at the moment: thanks to greedy bankers around the world, British university budgets have been squeezed and, to slash costs, the University of Portsmouth is not renewing my contract post July. As such, I’m looking at joining the dole queue unless I can find a job before then and, without going into detail, pickings are slim at best. So slim, in fact, that I’ve been giving serious thought to leaving science and pursuing a career teaching art: I really enjoy teaching and, at times, I do wonder what I’m doing in science anyway. My dress sense, working methods and hobbies make me pretty unusual amongst the scientists I hang around with, but appear to be pretty typical of artier folks. But then, of course, I write something like the piece below and, by the end of it, I’m feeling pretty scientific. Maybe I should perform a cladistic analysis on interests and character traits and, plotting myself onto the tree, follow the career picked out for me in the consensus analysis. Until I do that, though, exactly where I should put myself professionally is a mystery, and one I’m quite keen to get to the bottom of.


The bit where I start talking about pterosaurs
Thankfully, I’m not alone in not being sure where I fit. An unusual pterosaur skull, nicknamed the Painten Pelican, has caused a lot of discussion amongst pterosaur palaeontologists because it is, superficially at least, so danged weird (see image, above). The specimen comprised a complete skull, mandible and cervical vertebra and, if you’re around in Southern Germany, you can see it for yourself: it’s on display in the Solnhofen Museum. A cast and UV photographs of the specimen were making quite a buzz at the 2007 Flugsaurier Meeting, and, apparently, the specimen is very slowly being written up. The Pelican has been mentioned in an abstract by Tischlinger and Frey (2007) but, this aside, it’s not been mentioned in the literature at all. This abstract describes the specimen as ‘a recently discovered skull of a very large azhdarchoid pterosaur from the locality Painten (Upper Kimmeridgian)’, but there are several reasons to think that this identification is wrong. In fact, amongst my colleagues at least, there seems to be some real confusion as to where this specimen should fit into pterosaur phylogeny. Thing is, I’m not sure we really need to be that confused about it, and here’s why.

The Painten Pelcian is, undeniably, something to get very excited about. The specimen is fantastically preserved, around 30 cm long and most notable for its strange jaws that are dorsally deflected and markedly divergent towards the jaw tip, forming a region where no direct occlusion of the bony jaw elements could occur. The jaw tips themselves, though, could occlude and bear a few (less than a dozen?) rounded, peg-like teeth in both the upper and lower jaws. The rest of the jaws are toothless, but a strange growth - presumably soft-tissue of some kind – appears to be present on the upper jaw and filled the gap made by the diverging jaws. It’s important to note how neat these features are: there’s no indication that they are pathological and, to date, there’s never been a pterosaur reported with such an odd looking jaw apparatus. The rest of the specimen shows a large fibrous crest along the mid-length of the skull, a nasoantorbital fenestra, an inverted-teardrop shaped orbit and a reclined occipital face with a prominent, rounded supraoccipital crest. The palate is prominently distended along for much of the jaw length and the jugal has an unusual posterior ventral deflection, extending ventrally so that the jaw articulation is in line with the base of the palatal surface. Sclerotic rings and hyoid apparatus are also preserved. The vertebra, so far as I can make out, is somewhat elongate, but other features are hard to discern from the photographs I have of the specimen.

So, it’s definitely a bit weird, definitely exciting, but what actually is it? Thanks to Darwinopterus, we can’t definitively say that the Painten Pelican is a pterodactyloid as we lack postcervical material that would show the only strong synapomorphies of this group (Lü et al. 2009). The skull is quite derived, though, and all basal monofenestratans found to date have pretty conservative skull morphology, so, until we see reason not to, it is probably safe to consider the Pelican as a pterodactyloid. The allocation of the Pelican to Azhdarchoidea by Tischlinger and Frey (2007) is, frankly, baffling, however: azhdarchoid skulls are readily identified by their edentuly and orbits positioned below the dorsal margin of their particularly large nasoantorbital fenestrae (see, for instance, Lü et al. 2008). As none of these features are seen in the Painten Pelican, it almost certainly is not an azhdarchoid. Elsewhere in Pterodactyloidea, the dental configuration is entirely opposite of what would be expected of a dsungaripteroid, ctenochasmatid or lonchodectid and the specimen lacks the elongate skull and derived dental characteristics of all ornithiocheiroids (e.g. Unwin 2003). It appears that we’re running out of places to put the Pelican then: is it something really, entirely new?

Probably not

While getting very excited about how kooky the Painten Pelican skull is, no-one seems to have noticed how favourably it compares with the Upper Jurassic French pterosaur Cycnorphamphus (= Gallodactylus; see Bennett 1996). This rarely discussed basal ctenochasmatoid, known from deposits in Canjuers and Solnhofen, contains two very similar species C. canjuerensis Fabre, 1974 (above, from Fabre 1974) and C. suevicus Quenstedt, 1855 (see photograph of skull and neck cast, below) and both bear dorsally sweeping upper jaws, kinked jugals, broad supraoccipital crests and elongate cervical vertebrae that are just like those of the Painten Pelican. What’s more, C. canjuerensis has a ventrally deflected mandible and robust cranial bones that are strikingly similar to the Painten specimen but, unfortunately, the holotype of this species also has broken jaw tips that prohibit comparisons of tooth morphology. Happily, C. suevicus shows that the dentition of at least one Cycnorhamphus species is confined to the jaw tip, though it does extend somewhat further back in the jawline than that of the Painten specimen. No Cycnorphamphus material has the strange structure on the upper jaw or large fibrous headcrest of the Pelcian, but this may reflect a imperfect preservation rather than their actual absence. The bottom line, though, is that the aspects of the Painten specimen that seem so odd are actually already known, almost identically so in fact, in another pterosaurs. Given that Cycnorhamphus and the Pelican stem from the very closely related depositional basins (see comment from Valentin, below), I think it’s very likely they’re one and the same. In fact, shoot: if the Painten Pelican isn’t just a complete skull of C. canjuerensis, I’ll eat my hat. The three corner job. With the feathers.


This could be another mystery solved, then, but I stress that this article is based on a brief period spent with a cast and numerous photographs of the Painten specimen, not the actual thing itself. I could, therefore, be very wrong and suggest waiting for the eventual technical documentation of this paper before getting too excited about what is said here. Still, it’s food for thought and, frankly, leaves me wishing that everything in life could be a bit more straightforward. Back to the work hunt, I guess.


References

• Bennett, S. C. 1996. On the taxonomic status if Cycnorhamphus and Gallodactylus (Pterosauria: Pterodactyloidea). Journal of Paleonotology, 70, 335-338.
• Fabre, J. 1976. Un noveau Pterodactylidae sur le gisement “Portlandian” de Canjurs (Var): Gallodactylus canjuersensis nov. gen., nov. sp. Comptes Rendus de l’Academie des Science, Paris, 279, 2011-2014.
• Lü, J., Unwin, D. M., Xu, L., and Zhang, X. 2008. A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications for pterosaur phylogeny and evolution. Naturwissenschaften, 95, 891-897.
• Lü, J., Unwin, D. M., Jin, X., Liu, Y. and Ji, Q. 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society B, 277, 383-389.
• Quenstedt, F. A. 1855. Über Pterodactylus suevicus im lithographischen Schiefer Wüttembergs. Tübingen. 52 pp.
• Tischlinger, H. and Frey, E. 2007. “Solnhofen” pterosaurs with soft-part preservation: Soft-tissue crests and occipital cones, preservation of muscles and hairy structures. In: Hone, D. (ed.) Flugsaurier: The Wellnhofer pterosaur meeting, Munich, Abstract Volume, 32.