Wednesday, April 25, 2012

It’s dumb, it’s awesome, it’s… Our lives with pterosaurs, part 2

If you’re wondering what’s going on here, or if you’re looking at the right blog, it’s probably because you haven’t read this yet. And yes, we are stooping this low.

Pterosaurs in the modern day! What would it be like if some pterosaurs survived the K/T extinction to coexist amongst our modern biota and in modern environments? Such are the questions we're attempting to answer here. Just to remind you, the only pterosaurs under direct scrutiny in these posts are azhdarchids and nyctosaurids as they seem to be the only pterosaur lineages that were present at the terminal Cretaceous. We spent a lot of the last post discussing how we may try to exploit pterosaurs for our own benefit, and in this concluding post we’re going to consider how we may succeed at coexisting with wild pterosaur populations. (Adjacent image: when stork-like animals go wrong)

NOTE: The Blogger upload system has been a real pig this evening, and formatting this post has been nothing short of a nightmare. Apologies in advance for any choppy bits of text or other issues. I have tried to correct errors as I go, but please let me know if I've missed any. 

Meeting the neighbours

Humanity would probably bump into wild pterosaurs fairly often. Azhdarchid pterosaurs, in particular, achieved very wide distributions in the Cretaceous, being absent only from Antarctica (Witton and Naish 2008; Ösi et al. 2011; see map, above, for the distribution of azhdarchid fossils. From my Ph.D. thesis). Azhdarchid fossils show very strong ties to terrestrial environments,either being preserved in continental freshwater deposits and, when they do occur in marine sediments, they tend to be components of mixed terrestrial/marine biotas (adjacent graph is a sexier version of the same data presented in Witton and Naish [2008] on this topic. I’ve not updated it with new data since then, but the statistics will not have changed significantly to my knowledge). Their distribution across the globe suggests they were versatile animals capable of living in different habitats and climates, and their palaeoenvironmental signature hints that they would preferentially frequent terrestrial settings. Modern azhdarchids, then, may be fairly familiar sights to us if they were around today.

We may even find that some single azhdarchid species were found all over the globe. Some of the recent findings on their flight ability are rather arresting, with the 10 m span giants seemingly capable of flight speeds exceeding 100 kph (62 mph; Witton and Habib 2010). Mike Habib's recent SVP talk suggests that they could remain aloft long enough to travel almost halfway round the world in one sitting (Habib 2010) and, to paraphrase him directly, (imagine this being said VERY LOUDLY for full effect. Those who know Mike will understand why), geographic boundaries would mean nothing to these guys. This may mean that the sort of provincialism we see in some modern fliers may not apply to these forms and, indeed, cautionary words on the implications of this have been said with regard to azhdarchid systematics.

We may not find ourselves quite so acquainted with nyctosaurids, however. Their fossils are generally rarer than those of azhdarchids and, to my knowledge, largely constrained the Americas. Their rarity is of particular interest because Nyctosaurus, perhaps the best known of all nyctosaurids, occurs in the Smoky Hill Formation of Kansas, a deposit that has also supplied over 1000 Pteranodon specimens since 1872. I’m not sure how many Nyctosaurus specimens there are around the world, but I get the impression that it may be dozens, not hundreds or thousands (please let me know otherwise if I’m wrong, though). Assuming that this does not reflect other sampling or preservational biases, it seems that nyctosaurids were simply rather rare animals. Their remains, unlike those of azhdarchids, are also found exclusively in deep marine deposits, suggesting they spent much of their time away from land. Nyctosaurid anatomy agrees with their lack of landlubber status: the loss of the three, small manual digits used in walking and embarrassingly small legs do not suggest proficient terrestrial abilities. By contrast, the development of ossified tendons in the forearms of some nyctosaurid specimens (Bennett 2003; Frey et al. 2006) suggests that they put tremendous, continuous strain on their wings, and the wings themselves are super-long and probably very glide-efficient. The impression one gets, then, is of highly volant creatures that probably spent almost their entire lives in the skies over seas and oceans, so perhaps only sailors and fishermen would regularly see them if they were alive today.

Garbage monsters
In developed countries where little or no primary habitats remains, our modern azhdarchids may spend much of their times in rural areas, as this is probably the closest approximation of their natural habitat, and would, perhaps, provide the largest amount of live prey. The feeding habits of azhdarchids have been controversial since they were identified in the 1970s, but, in what is probably the only thorough exploration of their feeding habits to date, Darren Naish and I concluded that they were most likely ‘terrestrial stalkers’, long-legged predators of relatively small animals sought out in sparsely vegetated settings (Witton and Naish 2008). This idea may not be unfamiliar to many of you: not only have Darren and I waxed lyrical about it repeatedly in various blogs and lectures, but it’s now been immortalised on on TV and even in excellent, excellent comic book format (you can also download the full paper for free). Accordingly, I won’t go into details here, but, for the uninitiated, the seemingly proficient terrestrial abilities and long jaws and neck of azhdarchids seem well suited for hunting small game on land and, often, poorly adapted for anything else. The bulk of modern azhdarchid diets may not be too dissimilar to their Mesozoic ancestors, as these ancient forms were likely to primarily dine on small reptiles, amphibians and mammals that would appear, superficially at least, not too different from their modern representatives. Of course, modern azhdarchid diets would lack a certain non-avian dinosaur flavour, and that would presumably be substituted by various mammal species.

Azhdarchid jaws are generalised enough that we cannot rule out some ocassional bouts of scavenging, and it would be silly to ignore the importance of carrion feeding to some modern azhdarchid analogous, the ‘giant’ storks. Some of these birds – particularly the larger Leptoptilos species (e.g. the adjutant and marabou storks) – frequently forage on carrion (Kahl 1987) and, because we humans are disgusting slobs who do not dispose of our garbage properly, they have expanded their taste for lousy food to leftovers on rubbish tips. Other, more familiar birds are also keen rubbish raiders: I’m sure we’ve all seen local crows and gulls riffling through bins or splitting open refuse sacs. I see no reason why azhdarchids would not develop the same behaviours, so we may find some of them colonising urban areas and living off our waste. Perhaps this would mean that some modern azhdarchid species would be fairly resistant to the current global species decline, as the route to evolutionary success nowadays seems to mostly revolve around living off our garbage (well, it is the only resource we’re not running out of). (Image, above, shows said exploitation of waste in action)

If wild azhdarchids did take foot in urban settings, encounters with them may be a little daunting for human residents. As we discussed in the last post, pterosaurs seem to have increased their average body size over time, so later forms were much larger than the earlier. Perhaps we’d feel fairly confident stopping smaller (2.5 m span) animals from spreading rubbish all over our driveways, but would we feel the same about 4, 7 or 10 m span animals? Perhaps not. Plus, did I mention that these pterosaurs may have been gregarious? Several azhdarchid localities have yielded associated azhdarchid skeletons (Lawson 1975; Cai and Wei 1994) or very abundant azhdarchid remains (Nessov 1984; Ösi et al. 2005), suggesting that they were at least tolerant of each other, or perhaps even hanging around in little groups. All told, in this hypothetical world of pterosaurs, we’d probably need to seriously rethink our philosophy on garbage disposal. Probably best to keep the cat in, too.

They can eat my trash, so long as they don’t eat me
Speaking of modern pterosaur diets, an enormous elephant in the room needs to be acknowledged: would we be on the menu? This is a legitimate question, and not because we’re used to Tinseltown pterosaurs having a taste for human meat. Some azhdarchids were so enormous that they could consume people-sized prey (by which, I mean small adults, not just children). We don’t have particularly extensive fossils of giant azhdarchids to test this with, but we do have a key component for answering this question: a giant pterosaur skull fragment comprising the jaw joint and some bones from the roof of the mouth (shown on the left, in ventral view, in the image below). This belongs to the 10 m span Hatzegopteryx, one of the largest azhdarchids known, and is notable for its unusually robust construction of stout bony struts and enormous jaw condyles. By doubling its width we can attain minimum estimate of the complete jaw width, revealing a staggering maw 500 mm across (Buffetaut et al. 2002, 2003). (Image, below, shows the mirrored Hatzegopteryx jaw skull element. The ventral braincase and posterior jaw region of Thalassodromeus is shown for comparison and to scale. Thalassodromeus, by the way, has a jaw of 160 mm width and 700 - 800 mm long. Hatzegopteryx was mucking huge).

We should remind ourselves at this point that we’re a) talking about the minimum width here, so there's possibly room for a little more expansion; and b) these are, so far as we can tell, animals capable of flight, and yet had skull widths that many large dinosaurs would be jealous of. As with many pterosaurs, the asymmetrical nature of the jaw condyle would deflect the lower jaw laterally when opened so that much of the 500 mm jaw width could be used for swallowing food. The posterior palatal region is also highly vaulted, so there is additional swallowing space in the dorsal region oral cavity, too. Combine this with the likelihood of a large gulf between the mandibular rami occupied by distensible gular pouch (known from several exceptionally-preserved pterosaur specimens), and it seems more than likely that Hatzegopteryx could fit a person into its throat.
After that, of course, you’d need to be moved down the long neck, a length up to 3 m if we assume that the giants had necks of comparable proportions to those of smaller azhdarchids. Unfortunately for us, we have good evidence that pterosaur throat tissues were highly elastic and capable of encompassing large prey, so we may slip through an azhdarchid oesophagus without issue. The preservation of a recently-devoured fish in a complete juvenile Rhamphorhynchus specimen reveals just how large some pterosaur prey items were, and how stretchy their throats must have been to accommodate it (see detail of the trunk region of this specimen, below. After Wellnhofer 1975). The specimen in question was preserved in the process of digesting a fish that – as preserved – occupies 60 per cent of its trunk length, but may have been even larger as the anterior end had already been partially digested (Wellnhofer 1975). Pterosaurs, then, may have had small bodies, but they weren't afraid of packing their meals in. Our previous discussions on how giant pterosaurs could support our weight in flight have obvious connotations here, too: if one could support our weight externally, there seems little reason to suggest they couldn’t internally. We may fill their bellies, but we wouldn't impede their locomotion in doing so.

The outlook isn’t looking promising for us, then. Larger members of the populace may be a bit too massive to comfortably digest, but leaner or smaller folks may well be at risk. In any case, giant azhdarchids would be best avoided. If we did encounter one, would our chances of being eaten be high? Perhaps it would depend on context of engagement. On open ground, the 2.5 m long limbs and powerful muscles of giant azhdarchids would almost certainly chase us down and, hey, let’s not forget: they can fly. It's hard to outrun an animal that can fly fast enough to get a speeding ticket on most roads. We may be safe if we could get to cover or a cluttered setting, as the giant azhdarchid bauplan is hardly suited to moving through narrow confines or probing crevices. Without that, though, I don’t fancy our chances. Azhdarchids of this sort may be quite difficult to deal with too, short of simply killing them. Troublesome bears or cats can be moved far enough away from populous areas that they won’t bother people again, but we’d be hard pressed to stop relocated azhdarchids from simply flying back to wherever we caught them. The more I think about it, the more it seems that large azhdarchids would actually be quite a dilemma for us, and one that would probably see most of them being shot. All told, maybe it’s best for us all that they're extinct.

On that bombshell, then, I think that’s enough of this craziness for the time being. Hopefully, someone, somewhere, will have taken something useful from these posts and, if nothing else, we finally have a picture of a cowboy quad-launching a giant pterosaur. With that, I think my work here, and perhaps the respectable portion of my career, is finished. 

  • Bennett, S. C. 2003b.  New crested specimens of the Late Cretaceous pterosaur Nyctosaurus. Palaeontologische Zeitschrift, 77, 61-75.
  • 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.
  • Buffetaut, E., Grigorescu, D. and Csiki, Z. 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (western Romania). In: Buffetaut, E. and Mazin, J. M. (eds.) Evolution and Palaeobiology of Pterosaurs, Geological Society Special Publication, 217, 91-104.
  • Cai, Z. and Wei, F. 1994. Zhejiangopterus linhaiensis (Pterosauria) from the Upper Cretaceous of Linhai, Zhejiang, China. Vertebrata PalAsiatica, 32, 181-194.
  • Frey, E., Buchy, M. C., Stinnesbeck, W., González, A. G. and Stefano, A. 2006. Muzquizopteryx coahuilensis, n.g., n. sp., a nyctosaurid pterosaur with soft tissue preservation from the Coniacian (Late Cretaceous) of northeast Mexico (Coahuila). Oryctos, 6, 19-40.
  • Habib, M. B. 2010. 10,000 miles: maximum range and soaring efficiency of azhdarchid pterosaurs. Journal of Paleontology, 30, 99A-100A.
  • Kahl, M. P. 1987. An overview of the storks of the world. Colonial Waterbirds, 10, 131-134.
  • Lawson, D. A. 1975. Pterosaur from the Latest Cretaceous of West Texas: discovery of the largest flying creature. Science, 185, 947-948.
  • Nessov, L. A. 1984. Pterosaurs and birds of the Late Cretaceous of Central Asia. Paläontologische Zeitschrift, 1, 47-57.
  • Ősi, A., Weishampel, D. B. and Jianu, C. M. 2005. First evidence of azhdarchid pterosaurs from the Late Cretaceous of Hungary. Acta Palaeontologica Polonica, 50, 777-787.
  • Ősi, A.,Buffetaut, E. and Prondvai, E. 2011. New pterosaurian remains from the Late Cretaceous (Santonian) of Hungary (Iharkút, Csehbánya Formation). Cretaceous Research, 32, 4556-463.
  • Wellnhofer, P. 1975. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Palaeontographica A, 148, 1-33, 132-186, 149, 1-30.
  • 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.
  • Witton, M. P. and Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE, 3, e2271.

Tuesday, April 24, 2012

Our lives with pterosaurs, part 1

Not many mornings ago the lovely Georgia Maclean-Henry and I were discussing the the topic of 21st 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...


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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. 

Tuesday, April 17, 2012

Bacteria and head crests

A new paper is out in Lethaia that mostly concerns taphonomy, but technically involves pterosaurs, as well.  Sadly, it does require a subscription to read, but here is the abstract (thanks to Ben Creisler for bringing this to my attention):

Pinheiro, F.L., Horn, B.L.D., Schultz, C.L., de Andrade, J.A.F.G. and Sucerquia, P.A (2012)
Fossilized bacteria in a Cretaceous pterosaur headcrest.
Lethaia (advance online publication).
DOI: 10.1111/j.1502-3931.2012.00309.x.

We report herein the first evidence of bacterial autolithification in the Crato Formation of Araripe Basin, Brazil. The fossilized bacteria are associated with a tapejarid pterosaur skull, replacing the soft-tissue extension of the headcrest. EDS analyses indicate that the bacteria were replaced by phosphate minerals, probably apatite. The bacterial biofilm was likely part of the prokaryotic mat that decomposed the pterosaur carcass at the bottom of the Araripe lagoon. This work suggests that bacterial autolithification could have played a key-role on soft-tissue preservation of Crato Formation Lagerstätte.

Thursday, April 5, 2012

Aero Evo

Greetings fellow Pterosaurphiles,

Just a quick note that I have just launched a blog called "Aero Evo":

This is a new blogging endeavor of mine, and my first solo run at it.  Those that have worked with me in the past know that I sporadically post to H2VP and the Blog.

This blog will differ substantially from what I have done previously.  First and foremost, I will be specifically discussing animal flight - particularly the evolution of flight - this naturally includes the ins and outs of pterosaur flight.  The format is also going to be different form what I have done in the past. I have designed this blog to be a rapid-fire, regularly updated feed.  I expect to post something almost every day (holidays and such excepted, of course). Posts will typically be quite short - when I have something more lengthy to say, I will link over to H2VP or  In this way, the site is designed for something of a micro-blogging approach (though not as micro as Twitter... maybe it's a milliblog?  centiblog?)  I do anticipate linking in a Twitter account, as well as other social networking tools in the near future (Twitter account should be active within the next week).

I opened with a string of seven posts, so there is already content there to read.  One of them is even about pterosaurs! I may cross-post a longer version of that discussion here when time allows.