Our lives with pterosaurs, part 1

Not many mornings ago the lovely Georgia Maclean-Henry and I were discussing the the topic of 21^st century pterosaurs. Not, you understand, as a discussion of whether the reports of late-surviving, cryptid pterosaurs are genuine (they almost certainly aren’t, for reasons discussed in Darren Naish’s assassination of this idea), but a hypothetical premise that pterosaurs were commonplace components of our modern fauna, and what they would be like to live with. Though obviously speculative and completely juvenile, I thought this may be fun to blog on and discuss with others, so feel free to chime in at the end of the post with your own ideas. Who knows, we may even learn something in the process. (Image, above, shows what we're all now thinking).

Before we get going, though, some ground rules. Aside from the fact that we’re ignoring pterosaur extinction in this discussion, we’re basing everything else on fact as much as possible. For instance, we’re not ignoring the extinctions of specific pterosaur groups: if they went extinct before the terminal Cretaceous (when pterosaurs as a whole got the evolutionary chop), then they can’t exist in the modern day. Pterosaurs are also the only animals we’re hauling into the Modern: the biosphere is otherwise exactly as it is now, so there are no tyrannosaurs or anything running around as well. Also, the goal here is to consider pterosaurs as real animals, not hyper-aggressive movie monsters, so we don’t need to pay any attention to their Modern interactions with people in virtually all Silver Screen outings (which invariably boil down to said people being attacked and/or eaten) and start with a clean slate of ideas. Got that? On we go, then.

UPDATE: 24/04/12
Just one last rule, following on Mike Taylor's comment, below. I'm also focusing on pterosaurs as we know them in the fossil record, not as we may twist them through selective breeding or other genetic tampering. I guess this is an exercise in simply crashing pterosaurs into the Recent, considering what basic pterosaur palaeobiology would lend itself to in our modern world.

Roll call

The first part of this exercise, of course, is to determine what pterosaurs we would have running around today. Which lineages were present at the end of the Cretaceous that could, potentially, have survived until Recent times? Because pterosaur fossils are found within spitting distance, geologically speaking, of Tertiary rocks we assume that the last of their kind died out in the same mass extinction event that ruined the weekends for 75 per cent of life 65 Ma (Buffetaut et al. 1996), but the majority of pterosaur types were not witness to this event. Pterosaur faunas of the uppermost Cretaceous are almost entirely dominated by azhdarchids, the often gigantic, toothless and long-necked forms made famous by the likes of Quetzalcoatlus and Hatzegopteryx (see sketch, above, for a general guide to their appearance). These famous genera, incidentally, are some of the last pterosaurs we find in the fossil record, so giant pterosaurs are very much in for our consideration here. An incomplete nyctosaur humerus (if you’re not familiar with nyctosaurs, think Pteranodon, but weirder) from Mexico is the only record of non-azhdarchid pterosaurs in Maastrichtian strata (that is, name of the time interval representing the last 5 million years of the Cretaceous, 70-65 Ma), compared to literally dozens of azhdarchid occurrences (Price 1953). The pterosaur fossil record is noted for its incompleteness and preservational biases (Butler et al. 2009), but their reduced diversity at the end of the Cretaceous may not be an artifact of the fossil record as the number of pterosaur-bearing rock units at this time is relatively high, but diversity remains low. In short, then, while we may be able to identify dozens of different pterosaur groups across their evolutionary history, it seems that only the azhdarchids and nyctosaurs would have any hope of meeting us in the modern. (Image, below, shows a phylogenetic tree of pterosaurs using the major clades of Lü et al. [2010] mapped across time. The squiggly line shows the number of pterosaur-bearing rock units throughout the Mesozoic [borrowed from Butler et al. 2009] From my book).

With 65 million years separating us from the last pterosaurs, it is not unreasonable to assume that they may have developed into rather different forms by the time modern man appeared. Or would they? Evolutionary stasis spanning 9 – 10 Ma has recently been proposed for several non-pterodactyloid pterosaur clades (Lü et al. 2012) and, although admittedly suggested by rather fragmentary remains, several pterodactyloid lineages also do not appear to change dramatically over longer time frames. This may be true for azhdarchids as much as anything else: a vertebra representing the oldest known azhdarchid is known from Berriasian rocks of Romania (140 Ma) (Dyke et al. 2010) and looks, so far as I can see, no different from the vertebrae of Maastrichtian forms. Note that azhdarchid necks are very derived compared to those of other pterosaurs, so this comparison of their cervical anatomy suggests that the group was already fairly ‘evolved’ very early on in the Cretaceous. Maybe, then, modern pterosaurs would not be so dissimilar from the forms we know in the fossil record.

Bird brains

What sort of behaviour would we expect of our modern pterosaurs? To best answer this we may want to assess some likely basic aspects of pterosaur physiology and neurology, as this may provide  an insight into how active and intelligent they may have been. There’s scant discussion of pterosaur physiology in pterosaur literature, but their flight adaptations, erect carriage (in at least pterodactyloids, and probably some non-pterodactyloids too), insulating fuzz and relatively large brains all seem to correlate with modern animals that have elevated metabolisms. Pterosaur brains are known from specimens spanning much of their phylogenetic range, and they all seem fairly bird-like, but especially so in later forms (e.g. Witmer et al. 2003; image and caption, below, from this study). There are some differences, such as the pterosaur flocculus (the region of the brain primarily dedicated to motor coordination) being relatively enormous, (perhaps because the muscle-laden wing membranes of pterosaurs were being directly controlled and shaped during flight, requiring some extra computing power [Unwin 2005]), and bird brains are, on the whole, a little larger, but they are otherwise fairly similar. 

It may not be unreasonable, then, to predict that all pterosaurs – including our hypothetical modern ones – would be active, fairly intelligent beasties that, with warm bodies and big brains to fuel, may spend much of their time foraging. This leads us to a further analogy with birds: the requirement for lots of food does not sit well with flight, as a full belly is more mass to shift about. Hence, pterosaurs – like birds – may have dumped their waste as often as possible, presumably in the same form of acidic paste that common to all archosaurs. Such waste can be very damaging to architecture and car paint, so the existence of giant pterosaurs dropping vast quantities of crap on our cool stuff is not an appealing one. Plus, we’ve all been hit by stray bird guano on occasion, which is unpleasant enough, but imagine the same experience when the offending animal is several hundred times the size…

My pet pterosaur, and pterosteaks

As with most things in life, it probably wouldn't be long before the economic potential of Modern pterosaurs was tested. Could we farm them for meat and eggs, or breed them as household pets? Pterosaurs would probably be lousy sources of food for several reasons. The amount of meat offered from pterosaur carcasses is tiny compared to their overall size, providing minimal returns to pterosaur farmers for the space required to rear them. Pterosaurs have tiny, tiny bodies, with their edible soft tissues tightly concentrated around them. Even the biggest azhdarchids probably only had bodies 70 cm long (Witton and Habib 2010) with around 60 kg of flight muscle (Paul 2002), despite standing tall enough to look into a first floor window. Ornithocheiroids are even more disproportionate, with torsos barely longer than their humeri (near-enough the shortest bones in their wings). Some pterosaurs may offer better options, such as the relatively long bodied ctenochasmatoids, but they were long gone before the KT boundary, and therefore out of the game here. 

Keeping ourselves stocked with pterosaurs may require a lot of careful planning as their development times appear more extended than we're accustomed to with modern livestock. Because pterosaurs lay parchment-shelled eggs like most modern reptiles, it’s assumed that they required similarly long incubation periods of two or three months (Unwin and Deeming 2008). Once hatched, it seems that neonate pterosaurs did not rocket to full adult size like modern birds (a trait we’ve artificially enhanced in poultry to have large, fully-grown chickens within weeks of hatching), instead slowing their growth rates once they reach half size (Chinsamy et al. 2008). It's predicted that, for some pterosaurs, this threshold may take several years to reach (Bennett 1995; Chinsamy et al. 2008) As such, we could be looking at several years between pterosaur generations, which is a little on the slow side for big business. We don’t know much about pterosaur clutch sizes or reproductive rates, so it’s not clear how many animals you’d need to sustain a harvestable, breeding population but, regardless, it seems that you’d need a pretty substantial operation to get any profit out of space-demanding animals with awkward reproductive mechanisms.

So, pterosaurs would probably make for lousy food sources, but what about pets? It would certainly be cool to keep your own little azhdarchid that you could take out for a flap, train to fetch the morning paper and perform tricks, but the ‘little’ part may be a problem. Pterosaurs are said to demonstrate Cope’s Rule, the controversial idea that the average body size of individuals within a given lineage will increase over time (Hone and Benton 2007; see graph from this study, above, showing the increase in average pterosaur wingspans over time). Whether you agree with the notion of Cope’s Rule or not, it’s hard to ignore the steady increase in average pterosaur body size throughout the Mesozoic, leading to the smallest known Maastrichtian taxon (the oddly-proportioned Montanazhdarcho) being 2.5 m across the wings. A 2.5 m span may seem small compared to its 10 m span contemporaries but, for a homeowner, it would still be far too large to have in the house. Standing upright, said diminutive azhdarchid would have a shoulder height of over a metre and, with its long neck, be nearly as tall – if not taller - as you. That’s hardly a little animal, and probably one that would scare the bejesus out any other pets you have, and may even see them as potential lunch. Perhaps best to leave the pterosaur wrangling to zoos, then.

The biggie: could I ride a pterosaur to work?

Almost certainly the most important consideration in this concept: were pterosaurs strong enough fliers that we could saddle them up fly them places? Well, possibly.

Pterosaur.Net regulars are no doubt aware that some pterosaur workers now think that pterosaurs launched quadrupedally, using their powerful flight muscles to propel themselves into the air (Habib 2008). Part of the rationale for this idea is the strength of the forelimbs compared to the hindlimbs, as the launching limbs tends to be proportionally large in any flying vertebrate you care to look at over a certain mechanical threshold. As with most animal skeletons, it seems that the pterosaur forelimbs came equipped with large mechanical safety factors to accommodate for any atypically heavy loads that may be placed on the limbs. The humeral safety factors against bending in the largest azhdarchids – which we would possess in the Modern in our hypothetical scenario here, remember – are around 2.5 – 1.8, depending on how heavy you consider the animal to be between 180 - 250 kg (Witton and Habib 2010). Thus, the pterosaur skeleton could take weight of a person without crumpling, but could it take off? It seems so: Marden (1994) calculated that a giant azhdarchid would find launch no more strenuous than a 1 kg vulture, suggesting that one could, theoretically, take on the extra burden of a person on its back. Perhaps only relatively small folks would be suitable pterosaur jockeys to reduce the strain as much as possible but, hey, that’s still something, right?

This is not the end of the story, however. While the azhdarchid may be able to sustain flight with a jockey when flapping vigorously, it would not be able to endure this indefinitely. Mike Habib predicted for our 2010 study that a giant would have a few minutes of burst flight, tops, before it had to rest in a gliding phase. To avoid merely landing at the end of this, an alternative source of lift would be needed, and this is where a potential fly in our ointment appears. Long distance travel for azhdarchids was probably achieved by soaring (Witton and Habib 2010), which would be reliant – as it is with modern birds and bats – on climbing to high altitudes (many thousands of metres in some cases) on uplifts of air before gliding on. This would be a significant problem for our jockeys. Mammals are far less tolerant of hypoxia than birds (and, perhaps, by extension, pterosaurs) and, at altitudes that even little birds like sparrows are alert and lively, mammals are comatose (Faraci 1991). Hence, to fly with azhdarchids we may have needed to curb their flight styles a bit, keeping them at lower altitudes and, presumably, making more frequent use of areas of uplift. Alternatively, we supply them with oxygen tanks and warm clothing to keep them alive, but this all adds weight and reduces our azhdarchid's flight ability. Hmm... perhaps this is more complex than we thought.

Gosh, look at the time. There’s a lot more we could mention about riding pterosaurs, but I think we’ll stop there for now. This has already gone on too long and I’ve not even covered the most exciting bit: living alongside wild pterosaurs. Would we be potential pterosaur prey? Could they be pests of annoyances to us? All things to be discussed soon...

References

Buffetaut, E., Clarke, J. B. and Le Lœuff, J. 1996. A terminal Cretaceous pterosaur from the Corbiéres (southern France) and the problem of pterosaur extinction. Bulletin de la Societe Geologique de France, 167, 753-759.

Butler, R. J., Barrett, P. M., Nowbath, S. & Upchurch, P. 2009. Estimating the effects of the rock record on pterosaur diversity patterns: implications for hypotheses of bird/pterosaur competitive replacement. Paleobiology, 35, 432-446.

Bennett, S. C. 1995. A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: year-classes of a single large species. Journal of Paleontology, 69, 569-580.

Chinsamy, A., Codorniu, L. and Chiappe, L. 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guiñazui. Biology Letters, 23, 282-285.

Dyke, G., J., Benton, M. J., Posmosanu, E. and Naish, D. 2010. Early Cretaceous (Berriasian) birds and pterosaurs from the Cornet Bauxite Mine, Romania. Palaeontology, 54, 79-95.

Faraci, F. M. 1991. Adaptations to hypoxia in birds: how to fly high. Annual Review of Physiology, 53, 59-70.

Habib, M.B. 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana, B28, 161-168.

Hone, D. W. E. and Benton, M. J. 2007. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology, 20, 1164–1170.

Lü, J., Unwin, D. M., Jin, X., Liu, Y. and Ji, Q. 2010. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society B, 277, 383-389. 
Lü, J., Unwin, D. M., Zhou, B, Chunling, G, and Shen, C. 2012. A new rhamphorhynchid (Pterosauria: Rhamphorhynchidae) from the Middle/Upper Jurassic of Qinglong, Hebei Provine, China. Zootaxa, 3158, 1-19.

Marden, J. H. 1994. From damselflies to pterosaurs: how burst and sustainable flight performance scale with size. American Journal of Physiology, 266, 1077-1084.

Paul, G. S. 2002. Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. John Hopkins University Press, Baltimore, 472 pp.

Price, L. I. 1953. A presença de Pterosáuria no Cretáceo superior do Estada da Paraiba. Divisão de Geologia e Mineralogia Notas Preliminares e Estudos, 71, 1-10.

Unwin, D. M. 2005. The Pterosaurs from Deep Time. Pi Press, New York, 347 pp.

Unwin, D. M. and Deeming, D. C. 2008. Pterosaur eggshell structure and its implications for pterosaur reproductive biology. Zitteliana, B28, 199-207.

Witmer, L. M., Chatterjee, S., Franzosa, J. and Rowe, T. 2003. Neuroanatomy of flying reptiles and implications for flight, posture and behaviour. Nature, 425, 950-953.

Witton, M. P. and Habib, M. B. 2010. On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PLoS ONE. 5, e13982. 

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.

Actinopatagia percussion and sketchy speculation

I’ve been enjoying the previously unreported sonic qualities pterosaur wings a lot this week. Thanks to the need to paint some fibreglass pterosaur wing membranes and a newfound obsession with the heavy beats of Florence and the Machine, I’ve been smacking out tunes with paintbrushes on the folded wings of our giant male azhdarchid model, tastefully named Bamofo, all week. Hit them hard enough with a paint-slopped brush and they make a noise unlike that of a walloped bass drum, albeit one that splashes paint everywhere and renders the artist and workshop looking like a Jackson Pollock canvas. With the amount of paint I find on the walls, floor and my hands, arms, shoulders, chest, neck and face after a particularly enthusiastic rendition of Dog Days Are Over, I’m surprised any colour has made it onto the model at all. Seriously: given my choice of using blue shading on Bamafo’s leading wing edges, a good day at work means I could easily pass as an extra in Braveheart.

To date, there’s not been any indication that any pterosaurs lost these impromptu percussion devices, nor scaled back their wing anatomy enough to assume that, winged or not, they had abandoned flight. Accordingly, I’m not aware of many – if any – pterosaurologists who consider that any known pterosaur was secondarily flightless. Unlike theropod dinosaurs, which seem to have developed and lost flight numerous times in their evolutionary history, it seems that all pterosaurs - even the biggest 250 kg jobbies - were able to takeoff and fly about with minimal fuss (Marden 1994; Habib 2008). Buffetaut et al. (2002) raised the possibility that the giant azhdarchid Hatzegopteryx may have been flightless, but ruled it out on grounds that the holotype humerus bears the same volant characteristics as it’s smaller brethren. Sato et al. (2009) suggested that pterosaurs spanning more than 5.1 m and massing more than 41 kg would be incapable of flight, thereby grounding a good number of forms including many long-winged, tiny legged ornithocheiroids. Without going into too much detail, this work is quite problematic and I’m pretty sure these conclusions have not been accepted by the pterosaur community: a rebuttal paper, penned by Mike Habib and myself, is under review, and Ross Elgin has posted similarly-minded comments on the Dragons of the Air blog. I suggested that mass and wingspan of Dimorphodon may have combined to produce a relatively ineffective flier that only took to the air to cover ground quickly or escape predation (Witton 2008): this could be taken as a suggestion that dimorphodontids were moving towards abandoning flight, but there’s no reason to assume that it had been totally lost.

Despite this, the subject of flightless pterosaurs has been brought up in informal circles a number of times: along with numerous discussions of the topic on blogs and the Dinosaur Mailing List, flightless pterosaurs have appeared on Tet Zoo here (along with being discussed in the comments of several other Tet Zoo posts) and were famously depicted as giraffe-like critters in The New Dinosaurs by Dixon (1988). In such discussions, it seems generally accepted that there’s no reason why pterosaurs shouldn’t have abandoned flight given the right selection pressures: as long as they could find enough to eat, reach suitable areas for reproducing and, by whatever means, achieve relief from predators, the terrestrial abilities of pterosaurs were probably sufficient to let them hang up their wings and let them become fully terrestrialised again. I’m in full agreement with this and, here, want to share some old speculations (drawn at the end of 2008) of flightless pterosaurs, complete with horrible, unimaginative Latin and Greek names. The drawings are a bit crude, but I’ve not had time to spruce them up – nor will I in the foreseeable future. Unlike most speculative flightless pterosaur creations, though, I haven’t just picked on azhdarchids: although they may have been more terrestrially proficient than other pterosaurs (Witton and Naish 2008), I’m sure other clades would be equally capable of abandoning flight. As such, some of imaginings here would not necessarily post-date the known pterosaur record: many would have existed side-by-side with flying (and Mesozoic) pterosaurs.

Apterigulo
Found in Early Jurassic forests (and decorating the top of this post), this metre-long bundle of fluff has ancestry lying with dimorphodontids: continual development of their large heads and hindlimbs (these attributes already make genuine dimorphodontids quite heavy for their size [Brower and Veinus 1981; Witton 2008] but retention of short wings rendered some members of this clade capable of only the most limited burst of flight, and, eventually, even this ability was lost. While the terrestrial ability of basal pterosaurs has generally been considered to be poor at best, this loss of flight didn’t leave Apterigulo and it’s kind up the proverbial locomotory creek: although the limbs are somewhat sprawled like it’s ancestors (see Unwin 1988), Apterigulo can move like dynamite with saltating, or rather bounding, around like a giant, reptilian squirrel. While this method of locomotion doesn’t permit Apterigulo to run marathons, it gives it a neat burst of speed over short distances and, what’s more, it could happily chase you up a tree: the exaggeration of its massive appendages and claws make it even more proficient at climbing than its ancestors (Unwin 1988). The skull, teeth and neck have become more robust and powerfully muscled, giving what was ancestrally a nasty bite even more force. Being derived from a flighted ancestor also gives Apterigulo an unusually strong but lightweight skeleton: this not only facilitates quicker movement, but means it’s capable of considerable rough and tumble. It uses these attributes to ambush and chase vertebrates across a range of size classes, mainly eating smaller forms but occasionally subduing prey of equal or even larger size. Burrowing dinosaurs are particular favourites: with its massive bulk blocking the burrow entrance, the experience is akin to being stuck in a train carriage with a hungry tiger. Once subdued, the carcasses of big animals are dragged into the treetops to keep them out of reach of other carnivores but, if their carrion is threatened before this can happen, little Apterigulo will stand firm against even the biggest scavengers. It would not, therefore, be an ideal house pet.


Caprajarids
At some point in the middle Cretaceous, some tapejarid populations began to favour the herbivorous side of their omnivorous diet so much that their guts required some development, including the expansion of their gizzard (it’s likely all pterosaurs had a gizzard of some kind – Reily et al. 2001) to house bulkier quantities of gastroliths. Their beaks became more robust with rounded tips and sharp tomia, making them suitable for cropping all manner of vegetation before their guts began the real processing procedure. Living in relatively bleak environments that excluded the existence of large dinosaur herbivores ensured that movement over harsh, craggy terrain was a constant issue, but the retention of the large foot pads of their ancestors (Frey et al. 2003) ensured good traction on even perilous slopes. Their pycnofibres – or fuzz – grew particularly long and shaggy to withstand the cool nights and winds of such environments and gregarious living ensured protection from the large azhdarchids that occasionally preyed upon the smaller individuals. Living in such groups encouraged the development of even more elaborate cranial crests than those of their flying ancestors as males sought breeding rights over the females. Free of aerodynamic considerations, male caprajarids went to town with bifurcating (males and females of this sort can be seen above), spiralling and even horn-like crests. If these visual displays could not sort out competition between males, violent shoving, punching and biting matches, often conducted whilst balanced on their hindlimbs, would take place.


Jacanazhdarchines
While the big azhdarchids were denizens of the open plains, smaller, more basal variants kept to the forests. One clade of these forest forms lost their ability to fly in the Late Cretaceous and, while some flightless developed into seriously lanky limbed, sloth- or monkey-like arboreal forms, others began to specialise in foraging around ponds and streams, these being obvious sources of all manner of foodstuffs. The smallest forms, the jacanazhdarchines (above), were only 20 cm in length and defied the reduction of foot size and non-flight fingers seen in their larger cousins (Hwang et al. 2002) and instead developed large, weight spreading appendages that made movement across soft substrata easy. The bulk of the flight apparatus was lost comparatively recently in these forms and, although the wing membranes were lost, the wing finger was retained and served as an additional weight spreading devices. The limbs were also lengthened, facilitating movement through deeper water and, when splayed, distributing their weight over an even larger area. With such weight spreading abilities and such small size, jacanazhdarchines could be entirely supported by even flimsy vegetation growing over water bodies and, with a turn of speed, could literally walk on water. The already hypertrophied azhdarchid rostrum was elongated further for swishing through the water in search of food, though the fused pterosaur skull and poor gaping ability of such a long rostrum means that their probing abilities were limited, however.


Aliazhdarcho
The pterosaur equivalent of putting a jet engine in a Land Rover, Aliazhdarcho (above) applied the powerful musculature, skeletal morphology and physiology of its azhdarchid ancestors to the sort of carnivory typically reserved for big, predatory theropods. The largest member of this clade was Aliazhdarcho, a 4 m tall monster with a deepened, robustly constructed metre-long head and stout limbs. This latter point is crucial to the hunting strategy of Aliazhdarcho: retaining the highly pneumatised skeleton of its ancestry means that it combined strength with lightness (despite its size, Aliazhdarcho weighed just under 500 kg), increasing the power/weight ratio and allowing the animal to move like the clappers during a sprint. The massive shoulder muscles that once propelled azhdarchids into the air were retained, but modified somewhat to prioritise grounded locomotion over aerial. The principle role of these muscles is a modified quadrupedal launch (Habib 2008) that, rather than being used for takeoff, provided a dynamite sprint start. With shoulder musculature used to high anaerobic loads, Aliazhdarcho was capable of moving at great speed for up to a minute before tiring, so ambushing it’s prey was the order of the day. Once within range, Aliazhdarcho would employ its long neck and head to strike its target prey, ramming or biting the haunches to prevent its escape and, ideally, tripping or crippling it. Once immobilised, the powerful jaws and deep, sharpened beak would remove chunks of meat from the dying animal, though the jaws weren’t quite strong enough to shatter bones. It would not, therefore, be a good idea to be a mid- to large-size animal in the same area as Aliazhdarcho: in short, wherever it was, you didn’t want to be.

And that’s it. Once again, that’s gone on far longer than I intended, but hey ho. Happy Easter to everyone and now, with the sun high in the sky, I’m heading off to my workshop. I just had a wicked idea involving our fake pterosaur fur and the bassline from David Bowie’s Stay.

References

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