Thursday, 26 September 2013

The solution to everything: under the (Jurassic) sea, part 2

In the last post, I mentioned that I was currently working on a Oxford Clay Formation and ichthyosaur display for the University of Portsmouth. Most of that post was dedicated to the various graphics and text generated for the ichthyosaur end of things (specifically, Ophthalmosaurus), so we'll now turn attention to the other half of the display: the Oxford Clay Formation itself, its palaeoenvironment and fauna. The words below are a very brief introduction to one of Britain's most stellar fossil units, complete with some of the artwork and graphics which will soon be adorning the walls of UoP. If you want to know more about the Oxford Clay, you may also want to check out Mark Wildman's Saurian, which has discussed the Oxford Clay and its fossils at length across many posts. Baring a quick nod to Dave Martill for his help with shaping the words here, I'll hand you over to the display text.

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One-hundred and sixty million years ago, most of Europe - including the British Isles – was underwater, flooded by a warm, shallow sea populated by astonishing marine reptiles, gigantic fish and a diverse invertebrate fauna. The Oxford Clay Formation, one of the UK's most famous fossil-bearing rock units, provides an extensively researched window into this Jurassic marine ecosystem.
Extent of the Oxford Clay across the UK, with major localities. Whittlesey, the source of the marine reptile skeleton behind this and the preceding blog post, is highlighted in red. 
The Oxford Clay: geology, geography, economic geology
The Oxford Clay Formation is an extensive succession of dark mudrocks with intermittent limestones which crop out  almost continuously from Dorset to Yorkshire. Further exposures are found on the seabed of the English Channel and in Normandy, France. The entire Oxford Clay sequence is of late Middle Jurassic to lower Upper Jurassic age (164-159 Ma) and fossils occur throughout, although most vertebrate fossils occur in the Peterborough Member, a unit of organic-rich rocks which represent the lowest part of the formation. Considerable commercial interests in the Peterborough Member date to the 1870s when excavation of its clays began for brick making. The high organic content of these clays meant that they fired quickly at low temperatures, allowing for production of high-quality bricks at low cost. The Oxford Clay brick pits are now mostly closed, but the tremendous economic interest in the Oxford Clay has ensured that multitudes of fossils were continually excavated from quarries on an industrial scale for nearly 100 years, permitting a detailed view of the Oxford Clay palaeobiota.

Palaeoenvironment and palaeoecology
The Oxford Clay sea was a warm (water column temperatures of 20°C) and shallow (tens of metres) marine environment, with a rich supply of nutrients from local land sources. The abundance of light and nutrients supported a rich and complex ecosystem (below). Planktonic organisms, including numerous types of algae and zooplankton, were abundant in the Oxford Clay sea and likely formed the basis of its food web. Plankton was the food source for small invertebrates and juvenile fish, which in turn were preyed on by the larger fish, ammonites, belemnites, squid and reptiles that comprise the majority of Oxford Clay fossils. Ammonites are particularly common components of the Oxford Clay, being represented by some 78 species. The community of bony fishes and sharks was almost as rich as that of the ammonites, with 32 species adapted to exist in a variety of ecological niches. The Oxford Clay fauna contains one of the most spectacular bony fish to ever evolve, the 12-15 m long pachycormid Leedichthys problematicus. This animal was not a predator however, but instead filtered plankton from the water column using enormous gill apparatus.
Schematic reconstruction of the Peterborough Member fauna, palaeoenvironment and nutrient cycling. Animals are not to scale, unless you wish to invoke the Father Dougal sense of size. Based on data from Martill and Hudson (1991) and Martill et al. (1994).
The most famous Oxford Clay animals are the marine reptiles (below), which including ichthyosaurs (the 'fish lizards'), plesiosaurs (four-flippered reptiles with variably sized heads and necks, some of which – the pliosaurs - were the dominant predators of Jurassic seas) and thalassosuchians (marine crocodiles). Dinosaurs are also known from the Oxford Clay, likely representing animals washed in from the hinterland or individuals that died swimming between islands. Small flying reptiles, pterosaurs, were also present, but are very rare fossils.

Composition and abundances of the Peterborough Member reptile fauna. Based on Martill and Hudson 1991.
The sea floor was not as vibrant with life as the water column. Because the sea floor sediments and bottom waters had relatively low oxygen levels, the diversity of benthic species was restricted compared to the waters above. Bivalves, gastropods, arthropods and foraminifera comprise the majority of fossils from these communities, as well as the burrows of organisms which lived within the soft sea floor sediments. Sediment stability was an issue for some benthic organisms, leading to colonisation of decaying animal skeletons as substitutes for firm substrates by some species..

Micro- and macroconchs (male and female, respectively) of the ammonite Erymnoceras coronatum, hanging around the Oxford Clay seaway. The macroconch is 40-50 cm across, while the microconch, as is typical of ammonites, is about 20-25% of that size.
Ammonites: floating clocks and palaeontological enigmas
Ammonites, nektonic cephalopods with chambered external shells, form the backbone of biostratigraphy for Mesozoic rocks. Ammonite faunas evolved rapidly enough to permit identification of one million year intervals of Mesozoic time, allowing for very precise dating of ammonite-bearing rocks. The Erymnoceras coronatum ammonites shown above are one of the index fossils for the Peterborough Member, placing it firmly in the middle Callovian stage of the Jurassic.

Oxford Clay ammonites provide key data on the evolution of ammonites, and were integral in identifying male (small, elaborately ornamented ‘microconchs’) and female (much larger, less ornamented ‘macroconchs’) morphs. Despite the abundance and familiarity of ammonite fossils however, many aspects of their anatomy and lifestyles remain mysterious. Questions such as what they ate, where they lived in the water column, their floating orientation, as well as the exact nature of the squid-like creature living within the shell, remain unanswered.

Bonus fun: the assembled board
As a way of signing off these two linked posts, I thought it might be fun to show off the entire display board itself, just so anyone interested can see how all the text and images here will hang together. The entire thing is well over 3 m long, so should look fairly imposing when it's finally printed.
UoP's Oxford Clay and Ophthalmosaurus display text, coming soon to a display cabinet near me.
And that's our time in the Oxford Clay seaway done for the time being, folks. I'm hoping to get back to fairly regular posting over the next few weeks, because things have been a bit quiet about here of late thanks to a particularly busy conference season. Coming soon, hopefully: some comments on the All Yesterday's sequel, All Your Yesterdays.

References

  • Martill, D. M. and Hudson, J. D. (1991). Fossils of the Oxford Clay (Field Guides to Fossils) (No. 4). The Palaeontological Association, London.
  • Martill, D. M., Taylor, M. A., Duff, K. L., Riding, J. B., & Bown, P. R. (1994). The trophic structure of the biota of the Peterborough Member, Oxford Clay Formation (Jurassic), UK. Journal of the Geological Society, 151(1), 173-194.

Saturday, 14 September 2013

The solution to everything: under the (Jurassic) sea, part 1

It's been very quiet around these parts of late as my August and September transformed into a minor tour around Western Europe for talks and conferences. SVPCA in Edinburgh, the VIth International Symposium of Dinosaurs and their Environment in Burgos, Spain, a talk about my book in London and - next week - the Jehol/Wealden biotas conference in Southampton. Busy times indeed, leaving little room for blogging, painting or, well, anything at all, really.

In the interests of posting something, I thought I'd share two halves of a project I've was working on before I set off on my travels. Some months ago I was asked by the University of Portsmouth to spruce up a display featuring a partial skeleton of the ichthyosaur Ophthalmosaurus icenicus from the Oxford Clay Formation, a famous unit of Jurassic sediments deposited 162 - 158 Ma. Being the well organised professional that I am, I can't show you any photos of the specimen or display here*, but I can share some of the artwork and text which will, in the coming weeks, be plastered all up in our geology department. The display is divided into two broad components, one part being about the rich palaeontology of the Oxford Clay Formation itself - depositional setting, palaeobiota and the like - and the other dedicated to Ophthalmosaurus. It's worked out that the ichthyosaur section is far more complete than the other, so we'll start with that today, and have the sister portion following shortly. Maybe I'll even get my act together and show photographs of the specimen itself, because it's pretty neat.

*Is this the result of another batch of sticky palaeontological politics? Heck no: I just haven't taken any photos yet.

Ophthalmosaurus icenicus skeleton in lateral view. From McGowan and Motani (2003).
The painting at the top of this post is of O. icenicus and, as may be expected, is one component of the new display. It's one of my first efforts at a detailed painting of a marine animal and my first ever real attempt at rendering an ichthyosaur. Both were a lot of fun to do, and I wouldn't be surprised if we don't see more ichthyosaurs around these parts in future. The reconstruction benefited enormously from conversations with University of Bristol PhD student Ben Moon who, among other things, is redescribing O. icenicus for his thesis. Ben not only provided suggestions and comments about an earlier version of the image but also supplied me with a heap of literature concerning Ophthalmosaurus and ichthyosaurs in general. Ben blogs about his work and ichthyosaur science over at Ichthyosaurs: a day in the life…, so be sure to head over there if fish lizards float your boat.

Before I hand you over to the other components of our display, I'll say a few things about the reconstruction which, for reasons of space, couldn't be included in the exhibit. I set the scene in a shallow, coastal setting rather than the infinite blue seas we often see marine reptiles in. I completely understand why such compositions dominate marine reptile art, but I figured it would be nice to try something a little different. Plus, setting the animal closer to the shore meant I could make the water a little stiller, as if this chap had swum into a quiet, shallow lagoon or bay. Having relatively still water was important here because of the point of view. Again, just to be different, I thought a somewhat dorsal view of the animal may be interesting, but choppy waters would mean having to obscure or distort its proportions with waves and ripples, which didn't seem like a sensible thing to do in an educational display piece.

A dorsal view also allows for showcasing the dimensions of this animal. Rather than lithe and slender, as we often imagine aquatic animals are, Ophthalmosaurus was a broad and rotund animal with powerful shoulders, a barrel-shaped body, and a wide posterior skull region (below). Scale is always difficult to convey in images with no familiar objects to relate to (the seagull-sized floating pterosaur is the best I've got for scale here), but I tried to give an impression of the large size of this animal, too. Ichthyosaurs are often depicted resembling small dolphins or porpoises, but even mid-sized, 4-5 m long ichthyosaurs like Ophthalmosaurus were a lot bigger. I wondered if this size, not to mention the jaws brimming with 160 conical teeth (the original Walking with Dinosaurs, which likely introduced many of us to O. icenicus, erred on this front: see below for details), would allow O. icenicus to predate fairly large squid along with smaller fish and cephalopods. Reflecting this, I riddled it's hide with scars from battles with relatively mighty teuthids. Not all these scars may have been made by big squid, however, as ichthyosaurs were not above inflicting serious injury on each other, either. The colours of the animal were, again, an attempt at injecting a little originality into depictions of this animal. Although a lot of oceanic creatures are undeniably shades of grey, black and white, the superb visual acuity of Ophthalmosaurus suggests that visual signalling and recognition of individuals may have been important to these ichthyosaurs (Humphries and Ruxton 2001). I thought a complex pattern of ocean-penetrating reds, browns and whites may reflect this idea nicely.

Ophthalmosaurus icenicus in anterior view. Far from being lithe and slim, O. icenicus was almost as wide as it was tall. This is one of the many adaptations O. icenicus bears to fast swimming, and has also prompted the controversial hypothesis that the Antrhopocene joke 'yo' momma so fat...' had origins in Upper Jurassic marine settings. Image from McGowan and Motani (2003).

I'll stop there - this was meant to be a short, 'picture of the day' type post - and hand you over to the display text about this species. A lot of the information is quite basic, but it may still prove somewhat interesting. We've yet to print any of these images and text out for our display by the way, so be sure to leave any constructive comments you may have in the comment field below. Tune in soon for some details of the Oxford Clay seaway which housed O. icenicus, not to mention a plethora of other fascinating animals. Over to the display text...

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Only one species of ichthyosaur is currently recognised from the Oxford Clay, Ophthalmosaurus icenicus. O. icenicus has a wide distribution across Europe and Asia, a 20 million year stratigraphic range, and is famous for bearing some of the largest eyes of any animal known. Ophthalmosaurus and its opthalmosaurid relatives were a diverse and important group of Jurassic and Cretaceous ichthyosaurs, dominating the Cretaceous chapter of ichthyosaur evolution until the group became extinct at the end of the Cenomanian (Late Cretaceous, 94 Ma).

Although a complete skeleton of O. icenicus has never been found in the Oxford Clay, a full knowledge of its skeletal anatomy has been assembled from multiple incomplete skeletons. Unlike many other ichthyosaur specimens, Oxford Clay O. icenicus material is frequently preserved in three dimensions, making it an important species for understanding the anatomical complexities and functional anatomy of these reptiles. Since its recognition in 1874, O. icenicus has become one of the most completely known of all ichthyosaurs and a common component of studies into ichthyosaur taxonomy and functionality. Ophthalmosaurus perhaps attained the pinnacle of its fame in 1999 when it featured prominently in the classic BBC documentary Walking with Dinosaurs.

Anatomy
Like all ichthyosaurs, O. icenicus is supremely adapted to life in the marine realm. It possesses a full complement of ‘thunniform’ (Greek, ‘tuna-like’) features common to Jurassic and Cretaceous ichthyosaurs including reduced hindlimbs, a well-developed caudal (tail) fin, and a short, inflexible trunk region. O. icenicus was a moderately sized ichthyosaur, attaining body lengths of 4-5 m when fully grown.

Not so toothless after all: the fierce jaws of Ophthalmosaurus icenicus. From Kirton (1983).
The skull of O. icenicus has attracted much research interest because of its peculiar anatomy. The bones supporting the eyeball, the sclerotic rings, are enormous at 220 mm across. Among living animals, only giant squids have larger eyes but, for its body size, O. icenicus has the largest eyes known of any animal, alive or extinct. These eyes sit above a long set of jaws which have long been considered entirely, or almost entirely toothless. This interpretation is erroneous, however, as well-preserved O. icenicus and closely related ophthalmosaurid species clearly show small, slender and pointed teeth in each jaw. It seems that these teeth were weakly anchored into their dental grooves (like many ichthyosaurs, O. icenicus mostly lacks individual tooth sockets), and fell away readily once their owners began decomposing.

Lifestyle
The enormous eyes of O. icenicus have prompted much discussion among palaeontologists. It is generally considered that these eyes allowed O. icenicus to dive to great depths to find food, with their 90 mm wide pupils able to gather light beyond the perception of most other marine animals. Despite their size however, the eyes of Ophthalmosaurus would only permit vision at 40 m greater depth than those of marine animals with 'typically-sized' eyes, and only 50 m more than our own. The giant eyes of O. icenicus were considerably more capable of detecting shape and other visual details in low light conditions however. In environments where we could only see grainy outlines of other animals, Ophthalmosaurus could see in high definition. Possible confirmation that O. icenicus dived to great depth stems from evidence of decompression trauma (‘the bends’) in several specimens, a harmful condition caused by development of gas bubbles in the bloodstream of animals rapidly ascending from deep water.

The slender jaws and tightly packed, simple teeth of O. icenicus suggest it primarily ate squid and small fish, a diet confirmed in part by preserved stomach content of closely related, North American ophthalmosaurids. Propulsion for swimming was generated by the large, lunate caudal fin. Like other advanced ichthyosaurs, O. icenicus swam like a modern shark or whale, with a largely immobile trunk skeleton minimising undulations along the body when swimming, maximising the propulsive effects of the tail fin. This made O. icenicus one of the fastest reptiles, for its body size, in the Oxford Clay palaeoenvironment. The large, powerfully muscled shoulder girdle and forelimb paddle of O. icenicus betray an ability to rapidly steer and manoeuvre during pursuit of its prey. It is likely that O. icenicus used its powerful swimming ability to roam across several Jurassic seas, a habit which may explain its occurrence in numerous, geographically distant locations.

References
  • Humphries, S., & Ruxton, G. D. (2002). Why did some ichthyosaurs have such large eyes?  Journal of Experimental Biology, 205, 439-441.
  • Kirton, A. M. (1983). A review of British Upper Jurassic ichthyosaurs. Unpublished PhD Thesis, University of Newcastle-upon-Tyne. 239 pp.
  • McGowan, C. & Motani, R. (2003). Part 8 Ichthyopterygia. Sues H–D (ed.) Handbook of Paleoherpetology. Munchen: Verlag Dr. Friedrich Pfeil. 175 p.

Wednesday, 21 August 2013

9 things you may not know about giant azhdarchid pterosaurs

The 2015 version of the giraffe vs. azhdarchid vs. person image, now in it's fifth iteration (see the general history of these images through the years: 200620072009). The giraffe is a big bull Masai individual, standing a healthy 5.6 m tall, close to the maximum known Masai giraffe height. The pterosaur is a 10 m wingspan Arambourgiania philadelphiae (for reasons I cannot go into now, it is not wise to consider the appearance of giant azhdarchid taxa interchangeable any more: this should not be considered Hatzegopteryx thambema or Quetzalcoatlus northropi). The Disaknowlegement provides the human touch. These characters will receive some additional company soon.
The splendid beasts that are giant azhdarchid pterosaurs have occupied my thoughts a lot of late, mostly thanks to three upcoming talks I'll be delivering about them at upcoming conferences and society meetings. Preparing that number of talks in a short space of time has given me a whole new interpretation of the term 'death by PowerPoint' so, to take a break from animating slides and producing diagrams, here's a quick run down of 10 factoids you may not know about giant azhdarchid pterosaurs (the likes of Quetzalcoatlus northropi, Hatzegopteryx thambema and Arambourgiania philadelphiae - as if they need introduction) and their smaller relatives. Even if these facts are familiar, please feel free to enjoy the new bits of artwork accompanying the post. Those of you really into the ever evolving depiction of these pterosaurs really should also pay a visit to this recent Tetrapod Zoology post: I'm clearly not the only one with giant pterosaurs on the brain.

They nearly weren't called 'azhdarchids'
'Azhdarchidae' is a terrific name. It's short but mysterious, relatively easy to spell, and PR friendly enough that even the British tabloid The Sun has used the term on at least two (I think) occasions. The name 'Azhdarchinae' was coined by the late Lev Alexandrovich Nesov in 1984 from the Uzbek word 'azhdarkho', a name for a mythical dragon, and also the nomenclatural basis for the medium-sized Uzbek azhdarchid Azhdarcho lancicollis. Nesov's name encompassed all three azhdarchid genera known at that time: Azhdarcho, Titanopteryx (now known as Armabourgiania) and Quetzalcoatlus. Almost simultaneously, however, the exact same set of taxa was being roped into another group by Kevin Padian, which he termed Titanopterygiidae after, obviously, Titanopteryx. Nesov's 'Azhdarchinae' pipped the far-less elegant Titanopterygiidae to the publishing punch by a matter of months, and took nomenclatural priority for the group. Padian elevated Azhdarchinae to 'family' level in a short note in 1986, giving us our now familiar term, 'Azhdarchidae'.

Lev Alexandrovich Nesov holds the fossil cervical vertebra, notarium and jaw tip of the azhdarchid Azhdarcho. Image from Unwin (2005).
Tiny bodies
Despite their giraffian proportions, giant azhdarchid torso were relatively tiny. Witton and Habib (2010) noted that, like many pterodactyloid pterosaurs, their torsos were probably only a third or so longer than their humeri, suggesting a shoulder-hip length of about 65-75 cm for an animal with a 10 m wingspan. That's a torso length not much larger than your own, although they were considerably more stocky and swamped with muscle. Azhdarchid shoulders, in particular, are well endowed with attachment sites for flight muscles, as are (for pterosaurs) their pelves and hindquarters.

Giant azhdarchids did not suffer from flight power shortages
Many internet commenters often roll out the idea that giant azhdarchids would struggle to take off from the ground, even allowing for new ideas like quadrupedal launching. These folks need to get out of their armchairs, however, and check out some classic work on animal flight and giant pterosaur takeoff. James Marden's 1994 work on animal takeoff found some surprisingly consistent scaling trends among animal flight power and takeoff ability, allowing us to predict the muscle power of even long extinct fliers like Meganeura, Archaeopteryx and a 10 m span azhdarchid. The resulting aerobic power output of azhdarchid flight muscles - all 60 kg of them (a fairly safe bet for a 250 kg azhdarchid given what we know of animal flight muscle fractions among modern fliers) - is a bit rubbish, only 4.52 N/kg of body weight. Animals need to be generating 9.8 N/kg to fight gravity, so this would seemingly ground our giants. Bear in mind, however, that swans, albatross, vultures and turkeys also have aerobic power outputs of around 4.5 N/kg from their flight muscles, and they can fly just fine. The secret to their takeoff lies in the great power of anaerobic muscle contraction, which provides twice the power achieved under aerobic regimes. Using anaerobic power, giant azhdarchid power outputs are 10.098 N/kg of body weight, a value surpassing the 9.8 N/kg and matching the anaerobic power outputs of a 10 kg swan or 1 kg vulture (see graph, below). In terms of power availability, then, giant azhdarchids would not have struggled to launch any more than a large bird, so all these suggestions about poor takeoff ability and whatnot can be put to bed.

Scaling of flight performance with body size under anaerobic power output. The dashed line is the minimum lift needed to overcome gravity. Anaerobic power is 225W/kg, the upper limit of avian anaerobic output. From Marden (1994).
An unsurpassed 80 million years of evolutionary history, and growing
Azhdarchids are undeniably best known from Upper Cretaceous rocks, but they also have a patchy and sometimes controversial Lower Cretaceous record. Recently, Gareth Dyke and colleagues (2011) demonstrated that the group were probably present at the very base of the Cretaceous, in Berriasian (c. 140-145 Ma) deposits of Romania. Given that azhdarchids are definitely present at the final stage of the Cretaceous, this gives the group a stratigraphic record spanning the entire Cretaceous: 80 million years in total. This is longer than any other pterosaur group. Two cervical vertebrae from the Late Jurassic of Africa may extend their temporal range another 5 million years, although the affinity of these specimens remains controversial.

A much improved skeletal reconstruction of the small azhdarchid Zhejiangotperus linhaeiensis over my oft-reproduced effort from Witton and Naish 2008. Note the use of pacing strides, a gait indicated by pterosaur trackways but seldom seen in pterosaur palaeoart.
More than just long necks
When we describe azhdarchids, we often use two qualifiers: 'toothless' and 'long-necked'. In fact, these pterosaurs are brimming with characterising features (above). Their rostra are particularly elongate compared to all other pterosaurs, their orbits are depressed well into the lower half of their skulls, their wing metacarpals and femora are atypically long, and their extremities are short and robust. Their mid-series cervical vertebrae are famously simplified into almost tube-like structures, and their humeri are deceptively derived from the pterodactyloid norm. The wing fingers of azhdarchids occupy a relatively small 47% of their wing lengths, a value only approximated by one other pterosaur group, the closely related thalassodromids. Artists, take note: grounded azhdarchids should not be reconstructed with their folded wing fingers stretching skywards over their backs: they couldn't reach that far.

But no, seriously, the long necks
The cervical vertebrae of giant azhdarchids are poorly known, with only a few specimens (and even fewer good ones) being recovered to date. These rare fossils do, however, clearly indicate substantial neck proportions in at least animals like Arambourgiania. The holotype cervical V of this animal is around 660 mm long, and is missing an estimated 100 mm from its posterior end. Steel et al. (1997) scaled this vertebra isometrically with relatively complete neck skeleton material from the 4.7 m wingspan azhdarchid Quetzalcoatlus sp. to predict a whopping 3071 mm length for cervicals III-IX in Arambourgiania. The use of isometry here is questionable (Witton and Habib 2010), but is defensible given the amount of azhdarchid neck material available to these authors in the mid-nineties. Ongoing work I'm involved with (which will hopefully be published before we're too much older) has attempted to apply allometry to calculations of giant azhdarchid neck lengths. The results are a little more conservative than the 3 m offered here, but we're still landing in the "seriously long neck" camp. Whether azhdarchids will retain the title of absolutely longest necks outside of Sauropoda (Taylor and Wedel 2013) remains to be seen however: I suspect they may ultimately just be pipped by the weirdo protorosaur Tanystropheus. Dammit.
The 'Big Necks Which Don't Belong to Sauropods Competition', won by the giant azhdarchid Arambourgiania. From Taylor and Wedel (2013).
Finally, some data on neck arthrology
The necks of azhdarchids are not just famous for their size, but are also renowned for their rather inflexible joints. These widely discussed features have been the bane of many azhdarchid lifestyle interpretations (see Witton and Naish 2008 for a review), but actual quantification of their arthrological range has been lacking until recently. This is, in part, because a complete 3D azhdarchid cervical series has been elusive for many years, but Alex Averianov (2013) recently produced a composite digital neck skeleton for Azhdarcho to figure out their range of motion. The results were more-or-less what we all expected: very limited range in the mid-series, with most of the mobility limited to the extremes. A surprising amount (but still fairly restricted) range of motion was afforded at the neck base, however. As may be expected, this study is very welcome to those of us interested in the biomechanics and functional anatomy of these animals, and I'm glad to see it.

Averianov's (2013) reconstructed neck arthrology of Azhdarcho lancicollis. That's one stiff neck.
Incidentally, some folks have asked me what I think of Averianov's suggestion that azhdarchids weren't what Darren Naish and I termed 'terrestrial stalkers' in our 2008 paper (generalised terrestrial foragers which spent much of their time wandering over Cretaceous plains in search of small animals and rich plant material like modern storks and ground hornbills). I won't say much now, but Darren and I don't agree with the alleged 'flaws' put forward against our hypothesis, and especially do not agree with the proposed 'aerial scoop feeding' counter hypothesis. Our formal reply has just been through peer review, and we hope to complete the minor tweaks needed to get it ready for publication very soon.

Swimming piscivores and aerial hawking: genuinely suggested azhdarchid lifestyles
It's well known that most recent 'serious' proposals of azhdarchid lifestyles are things like skim-feeding, terrestrial stalking and wading, but many other, frankly outlandish palaeoecological hypotheses have been thrown at azhdarchids over the years. Lev Nesov perhaps takes home the prize for the most bizarre ideas, proposing in his 1984 paper that azhdarchids could swim to find food (both along the surface and by diving) and pursue 'poorly flying' vertebrates through the air. In the same paper, he also advocates skim-feeding as a probably azhdarchid lifestyle. I remain unsure which part of azhdarchid anatomy indicated to Nesov that these animals had superhero-like abilities to acquire food.
Sauropods give a giant azhdarchid the evils. Seems they don't like being buzzed at close range
The awesomopower of giant pterosaur flight
Although azhdarchids are frequently discussed for their natty terrestrial capability nowadays, it's important to remember than any substantial travelling they had to do was probably performed in the air. Computations of the flight abilities of giant azhdarchids have returned seriously impressive results (Witton and Habib 2010). As mentioned above, azhdarchids likely employed anaerobic power for strenuous flight activities like takeoff and perhaps flapping bursts, and likely relied mostly on thermal soaring and flap-gliding like modern raptors to remain airborne for long periods. Their minimum sink and best glide speeds are steady cruises at 16.3 - 24.9 m/s (58.7 - 89.4 kph) but, if they were in a hurry (such as looking for a source of uplift), speeds of up to 48.3m/s (173 kph) were possible for short durations. We estimated that azhdarchids had about 90 - 120 seconds of anaerobic burst power before tiring, meaning these animals could go from a standing start to - literally - several kilometres away in the space of a few minutes. Yowsers. What's more, the size and bodily resources available to such large creatures permitted tremendous flight times: up to 16,000 km of travelling without resting or foraging were likely possible. That's the equivalent of an animal flying from London to Vegas non-stop, realising it forgot its passport, and then flying home again without touching the ground.

And that's your lot for now, folks. If you want to know more about azhdarchids, be sure to check out my book for a whole chapter about them, which is something like the second biggest entry in the entire thing. Things may go quiet over the next few weeks while I'm away at various conferences, but posting will resume when I get back.

References

  • Averianov, A. O. (2013). Reconstruction of the neck of Azhdarcho lancicollis and lifestyle of azhdarchids (Pterosauria, Azhdarchidae). Paleontological Journal, 47(2), 203-209.
  • Dyke, G. J., Benton, M. J., Posmosanu, E., & Naish, D. (2011). Early Cretaceous (Berriasian) birds and pterosaurs from the Cornet bauxite mine, Romania. Palaeontology, 54(1), 79-95.
  • Marden, J. H. (1994). From damselflies to pterosaurs: how burst and sustainable flight performance scale with size. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 266(4), R1077-R1084.
  • Nesov, L. A. (1984). Pterosaurs and birds of the Late Cretaceous of Central Asia. Paläontologische Zeitschrift, 1, 47-57.
  • Padian, K. (1984). A large pterodactyloid pterosaur from the Two Medicine Formation (Campanian) of Montana. Journal of Vertebrate Paleontology, 4(4), 516-524.
  • Padian, K. (1986). A taxonomic note on two pterodactyloid families. Journal of Vertebrate Paleontology, 6(3), 289-289.
  • Steel, L., Martill, D. M., Kirk, J. R. J., Anders, A., Loveridge, R. F., Frey, E. & Martin, J. G. (1997). Arambourgiania philidelphiae: giant wings in small halls. The Geological Curator, 6, 305-313.
  • Taylor, M. P., & Wedel, M. J. (2013). Why sauropods had long necks; and why giraffes have short necks. PeerJ, 1, e36.
  • Unwin, D. M. (2005). The pterosaurs from deep time. Pi Press, New York.
  • Witton, M. P., & 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(11), e13982.
  • Witton, M. P., & Naish, D. (2008). A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS One, 3(5), e2271.

Friday, 9 August 2013

Pterosaurs invades the newpapers, this weekend!

Good news, everyone! If you've not already made the plunge and bought Pterosaurs, you can enjoy a teaser article in this Sunday's (11/08/13) Observer to sample it's flavour, available both online and in dead-tree format. The piece covers mostly familiar ground for those with an ear for the jungle drums of pterosaur research, but may serve as a useful taster for current pterosaur science for anyone else. Perhaps of wider interest will be the showcasing of artwork taken straight from the book itself, including several pieces which are yet to be seen elsewhere. If this is the final impetus you need to buy the book, there's promise of a discounted price and free shipping from The Guardian Bookshop. I'll pop a link to the article into this post when it becomes available. (UPDATE: The article has now been posted: find it here).

While I'm stroking my PR cat, of further note is that Pterosaurs was reviewed in New Scientist by Jeff Hecht earlier this week, concluding that "[the] explanations and diagrams shed vivid light on the most intriguing creatures that ever flew, and in richer detail than even [Wellnhofer's 1991 pterosaur encyclopedia] could have managed just two decades ago." The article also features images from the University of Portsmouth Southbank pterosaur display, including our late, 10 m wingspan model of a flying azhdarchid. RIP, BigQuetz.

If this isn't quite enough of a pterosaurian fix for you, don't forget about the Pterosaurs talk being held at the Natural History Museum, London, this September.

Thursday, 8 August 2013

Childhood dinomania: the greatest of all palaeontological mysteries?

Sinornithoides youngi, a long-legged, gracile troodontid from China. But why are he and his contemporaries so darned popular, and particularly with children?
Perhaps the greatest question that surrounds prehistoric animals is nothing to do with their palaeobiology or evolution at all. An enormous question, and one that perhaps continues to defy satisfactory answer, concerns their endless cultural appeal. Why are these long-dead animals so darned fascinating to us? Internationally, vast sums of money are spent on research into them, the care of their fossils and the educating of others about them. We put their remains on display in vast, elaborate museums, write no-end of books and articles on them. But why? Why are we do dedicated and passionate about these animals, to the point of near obsession in some individuals? I can understand that a few components of palaeontology have clear rewards. Palaeontologists specialising in invertebrates and microfossils are essential components of any team hoping to find hydrocarbon reserves, giving their research obvious application and financial implications. Such studies may also shed light on rates and mechanisms of evolution, which has bearing for the conservation and preservation of our modern biota. Most fossil vertebrate lineages, however, are of little use for, well anything. They may be interesting, but the scant nature of their fossil record doesn't allow their use in any applied studies. Our interest in them is purely academic. Knowledge for the sake of knowledge, I guess we could say.

Minor interests
Of course, interest in fossil vertebrates is not confined to academics and, in fact, the largest audiences for prehistorically-themed topics is under 10 years old. Of all fossil animals, the appeal of Mesozoic reptiles to young individuals is particularly well known, and encouraged by adults for good reason. Mesozoic reptiles introduce children to important concepts of science and the natural world, provide wonderful material to teach mathematics, literary and drawing skills, and, unlike many other things kids are interested in, they represent reality. Learned information about Mesozoic reptiles are learned facts about things that actually happened, not some silliness about Pokémon, ThunderCats, or... blast, who the devil do children like?... Or Morgan Freeman.

Young interests in palaeontology aren't really questioned, they're just accepted and ran with. Discussions as to why young people are so interested in Mesozoic reptiles aren't uncommon, but they're of secondary concern to nurturing childhood interests in the topic. As Dave Hone wrote about this topic at his Lost Worlds, " I won't pretend to know why, but kids really do love dinosaurs and the important thing is that they do." There's certainly nothing wrong with this attitude, but the why of this question has been on my mind of late. My second cousin is as dinosaur-obsessed as any young boy should be and I'll be spending the day with him next week. I'll also be gaining a nephew before too long. Between these two small members of my family clan, I'm expecting to have to play the cool, 'dinosaur'-researching relative for a while yet. All of which makes me wonder why, why why are small people so interested in these animals?

Proof that I liked 'safe monsters' as much as anyone when I was small. What's a 'safe monster'? Read on! (image by me, age 7[ish]. My younger self bore amazing powers of prediction for my own future with the pterosaur attacking dinosaur).
Standard responses
The most common explanation I've heard to this question is stressed in this article and others like it. Mesozoic reptiles are monstrous, and kids like monsters. They like these even more however, because they're long dead, and therefore 'safe'. Unlike real monsters, like the bogeyman, things that live under the bed and recent Discovery Communications documentaries, Mesozoic reptiles can't hurt us any more. Under this logic, extinction is the key agent here. Kids like the security that extinction offers between themselves and the monsters they're reading about.

Jurassic Park author Michael Crichton offered a completely different explanation, linking dinosaurs with authority figures, like parents. He wrote in his 1993 novel:
"...he mused on what it was about Dinosaurs that appealed to kids. He decided that dinosaurs represented a sort of symbolic authority to kids, a sort of surrogate parent. Just like a parent, they were simultaneously frightening yet accessible, and they presented an authority figure they could love. He also thought that children found satisfaction in saying the names of the animals, as that represented a sort of power of the vanished giants, showing a form of control."
Here, it would seem, it's not extinction at all that's key: it's the perception of authority and accessibility that Mesozoic animals seemingly offer children, and their own desire to master and control their expression. Other common explanations include an escapist quality to learning about the distant past, being able to express our childhood selves through acting out dinosaur fantasies, and because dinosaurs are strange, and yet real beings.

I've got to admit that I cannot really reconcile any of these explanations with what I know about being interested in Mesozoic animals, either as an adult or a child. They - particularly the first two suggestions - seem to complicated, too 'psychological'. I cannot ever remember associating Tyrannosaurus with my parents, or disliking other monstrous creatures because they weren't long extinct. I don't think the 'distance' between myself and dinosaurs, or any other monsters, really mattered. The fact that Mesozoic animals once existed was kinda cool I guess, but clearly not a deal-clincher: I was interested in plenty of make-believe things when I was small. And while kids are undoubtedly irrational sometimes, I don't think their grasp of what is a tangible, 'real' threat and slightly scary but fantastic beast isn't as blurred as the above explanations suggest. I note that many of the suggested points are rather anthropocentric, explaining that our childhood selves are interested in these animals because they reflect our own lives somehow, but that also doesn't seem right. My childhood interest in dinosaurs and the like seemed more innocent than that: I just wanted to know more about them and play within their universe. These ideas don't even seem like explanations which, in hindsight, chime with a deeply buried feeling associated with my childhood obsession with all things Mesozoic. Conversations with friends and colleagues suggest these explanations are similarly unfamiliar to them.

This makes me wonder if we're thinking about this the wrong way. We seem to expect that the appeal of Mesozoic reptiles to children is a unique trait, an X-factor, something inherently mystical about these animals which mean most children will be under their spell at some point. There may be, but I wonder if we're over-thinking this. Perhaps there is no unique factor behind the popularity of Mesozoic reptiles with young humans, and they're popular with kids for the same reasons that a lot of things are. Maybe the reason children like Mesozoic reptiles is very simple: they're just really cool.

The Anatomy of Cool
Let's run with this idea for just a moment. Mesozoic reptiles certainly tick all the boxes for Cool Things That Kids Like. Starting with the most obvious: they look awesome. Innumerable cartoons and comics featuring appealing characters and creatures are testament to the power awesome-looking beings have over children. The muscular bodies, dynamic postures, horns, frills, teeth and claws of many Mesozoic reptiles are clear signs of badassery, and kids of all ages respond positively to that. Perhaps the consistent choice of favourite dinosaurs in youngsters reflects this. Although most children's dinosaur books introduce a wide selection of species, it's the most anatomically extreme and charismatic species that are picked out by generation after generation as Top Dino. Triceratops, TyrannosaurusBaryonyx, VelociraptorAnkylosaurus, Brachiosaurus and so forth are consistent favourites. Some kids - especially cootie-ridden girls, because they're rubbish and smelly - might like prefer cuter, baby versions of dinosaurs,  but they still pick babies of the most immediately interesting taxa. By contrast, no kid has ever said that their favourite dinosaur is Iguanodon or Hypsilophodon, because they're freakin' boring to a sub-10 year old. This is despite them being among the 'safest' dinosaurs, bearing no real offensive equipment and having no interest in eating children. Kids dig awesome, even if it's a little scary, and their favourite dinosaurs are full of it.

Do kids like Sinornithoides? I don't know that they do, but it would definitely score Cute Points when they realised that the holotype was found in a Mei-like sleeping posture. Of course, Sinornithoides was described by Russell and Dong way back in 1993, including discussion of its sleeping posture, meaning it pre-dates the announcement of sleepy Mei by over a decade. This fact seems mostly overlooked nowadays, however.
Mesozoic animals are also immediately characterisable. A cursory glance at a menagerie of Mesozoic animals reveals which ones are 'good' - the plant and fish eaters - and which are 'bad' - the carnivores. Universes designed with young people in mind go to great lengths to give their characters similarly recognisable traits of good and bad. They also, as with Mesozoic reptiles, make their characters wear their lifestyles on their sleeves. It's immediately clear that they spend their time doing interesting things because their appearance (clothing, physical characteristics, objects they carry) consistently reflects their habits. When do we see warrior characters in children's shows put their weapons down, or adventurers leave their backpacks and hats behind? Never, because it's part of who they are. The same is true of Mesozoic reptiles: their lifestyles are clear from their anatomy, and their habits are obviously interesting. As with invented universes, this allows even young children to have a fairly immediate, if very basic understanding of the dynamics of the Mesozoic world, and that makes it fun to play with and think about. I've written before about how some Mesozoic creatures even come with pre-conceived ideas of 'character': the frills and horns of some dinosaurs recall the armaments of knights, the powerful jaws and teeth of tyrannosaurs make them obvious threats, and so on. These perceived anthropomorphisms may tie into the choice of favourite species among children, perhaps reflecting elements of wish-fulfilment and reflection of individual  personalities, but the same applies to their selection of a favourite Transformer or mutated ninja turtle.

What about complicated Latin and Greek names? Surely they must have some unique appeal? It's perhaps no coincidence that many favourite Mesozoic animals are also those with the coolest names. Animals with undoubtedly disastrous (Futalognkosaurus) or boring (the infinite numbers of Placename-osaurus we now have) names are unlikely candidates for being any child's favourite. The strong, weighty names of DeinonynchusPteranodonPlesiosaurus and Diplodocus are where it's at. Really, they aren't actually too different or more difficult to say than invented names of child-approved fantasy universes. A of extinct animal names are no trickier or less familiar to children than the names of Star Wars or Lord of the Rings characters, for instance. There may be no more psychological significance to a child saying the word 'Gallimimus' than there is them saying 'Legolas' or 'Dagobah'.

The stats and factoids associated with Mesozoic reptiles are perhaps also factors in childhood palaeo cool. Any juvenile palaeo nut worth their salt knows the size, mass, biogeography, geological period, lineage, and diet of a hundred extinct species. Our brains are sponges for that kind of stuff when we're small, but not only for Mesozoic animals. Kids get obsessive about all manner of data, hence the success of all these newfangled Japanese card playing games with weird animals and, before them, things like Top Trumps, complex board and video games and RPGs. It seems that, if children like a topic, and the information is there to be learned, they'll take it in whether it has a dinosaur stamped on it or not.

Sinornithoides again, acting as end-of-post wallpaper
We've now also created a rich array of Mesozoic reptile merchandise for children to enjoy - toys, games, books, films and TV shows and so on - which, again, mirrors the development of universes invented for child consumption. These are food in the purest form for the imaginations of small children, enhancing their ability to play out their own interpretations of the Mesozoic in the same way that the merchandise of invented franchises allows kids to play within other universes. Unlike many franchises aimed at children, however, Mesozoic reptiles rarely disappear from fashion, and their merchandise is always easy to obtain. Indeed, I wonder if the perpetual availability of Mesozoic reptile merchandise and media has made it almost certain that child interests in these animals will never go away. Given the ripeness of childhood minds for the awesomeness of Mesozoic reptiles and the associated financial gain from making Mesozoic merchandise, we may be creating a self-fulfilling prophecy that children will always be introduced to and inspired to learn more about these animals.

The discussion at the end
With all these things considered, I really wonder if Mesozoic reptiles have, or indeed need a mysterious 'X-factor' to explain their appeal. I don't think it's been an intended goal of palaeontologists or merchandisers, but these two contrasting industries have created a window into the Mesozoic that children can enjoy on many levels, developing a world which couldn't be more child-friendly if someone designed it. The many parallels we see between childhood palaeo culture and industries designing universes to interest children are surely a reflection of this. Cool, identifiable creatures with interesting lives, awesome names and stats, and a wealth of merchandise. That description could describe how children will interpret palaeontology, or it could describe the way they'll interpret Doctor Who.

As a final point to chew on, I think it's interesting that we don't really feel a need to explain the childhood appeal of superheroes, spaceships and giant robots by means of an X-factor', but we do for Mesozoic reptiles. Adults just accept that kids find these more anthropocentric topics inherently awesome and interesting, and that's good enough. Why doesn't that work for palaeontological topics? Is it a little worrying that we think like this? That the raw appeal of the natural world, which kids seem to intuitively grasp as interesting and awesome, isn't a strong enough draw on it's own, and requires rationalising into a more a anthropocentric model to explain it's childhood appeal? Maybe there's something to be learned from that. General knowledge and understanding of the natural world is critically poor, biological education is consistently being attacked by anti-scientific groups, and media groups increasingly think that the natural world needs sexing up with human interaction and made-up science. Maybe if we just remembered that it's OK to find the natural world fascinating and awesome because it is, and that we don't need to make ourselves the centre of everything, these issues wouldn't be anywhere near as big and worrying as they are.

Reference

  • Russell, D. A., and Dong, Z. M. 1993. A nearly complete skeleton of a new troodontid dinosaur from the Early Cretaceous of the Ordos Basin, Inner Mongolia, People's Republic of China. Canadian Journal of Earth Sciences, 30, 2163-2173.

Wednesday, 31 July 2013

Pterosaurs: The Natural History Museum Talk, September 2013

HyPtA D does the NHM logo. What's a HyPtA D? You need to buy Pterosaurs to find out, or attend the Pterosaurs NHM event in September. HyPta D image from Witton (2013); NHM logo borrowed from here.
Those of you with long-term memories may recall that, this September 10th (2013), the critically-acclaimed tome Pterosaurs: Natural History, Evolution, Anatomy is being celebrated with a public lecture at none other than the Natural History Museum, London. Details of the event have now crystalised and been made public over at the NHM's website. The talk will take place at 19:00-20:00 in the Neil Chalmers Seminar Room and cover all things pterosaurian: our changing understanding of these animals since their discovery, current ideas on many aspects of their palaeobiology, lots of palaeoart and photographs of specimens and, no doubt, some over-the-top PowerPoint animations which I'll spend hours tweaking for no obvious benefit. I'll do my best to keep to time (I have an excellent track record for punchy, concise talks, honest) so I can field questions at the end of the talk.

Note that the event is for NHM Members Only, will cost £5.50 per ticket, and booking is required. Details about membership with the NHM can be found here, and further information on the event and NHM memberships are available from your telephone, at +44(0)20 7942 5792.

I'm already looking forward to this, and hope to see many of you there.

UPDATE: I've just realised that the NHM's Lorna Steel, a pterosaur worker herself, is giving a behind the scenes tour of the NHM's extensive pterosaur collections on the same day as this talk (10/09/13) for NHM members, also for a mere £5.50. It seems that, if pterosaurs are your thing and you're an NHM member, you'll really want to be in London on the 10th of September.

Reference

  • Witton, M. P. 2013. Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.

Tuesday, 30 July 2013

Engaging my Disacknowledgement

Tupandactylus imperator, a rat, and the Disacknowledgement. Not in that order. From Witton (2013).
Weirdest thing happened today: I finished two planned bits of work ahead of time (I know. I'm scared too!). That doesn't mean I'm off the hook work-wise. I was away last week (hence the lack of a fresh post) and catching up is making for a very hectic few days, but the fact that two bits of work were finished bang on time for an afternoon tea break means I've got time to slip in a quick bit of blogging without the usual guilt trip. We'll have to keep it brief, though, and discuss the rather straightforward image shown above.

Rather obviously, this image is a play on those most standard of palaeontological artworks, the extinct-creature-human-scale diagram, in this case showing the flamboyantly crested tapejarid pterosaur Tupandactylus imperator and a fully-fleshed Homo sapiens instead of a silhouette. Those who've read my book, Pterosaurs, may recognise this image from page 221. Note that the Tupandactylus soft-tissue crest is convex along its posterior margin instead of concave, as it's often been depicted. New fossils, such as those mentioned in Pinheiro et al. (2011), suggest that this 'fuller' crest is more likely than the concave crest indicated by the T. imperator holotype (Campos and Kellner 1997). The mandible shape also follows the specimen described by Pinheiro et al. (2011) rather than, as in most depictions of this animal, a generalised tapejarid mandible based on closely related species. Believe it or don't, virtually all that's known for certain of T. imperator is skulls, with only two specimens preserving mandible remains. Tapejarid skeletons without skulls are known from the Tupandactylus-bearing Crato Formation, and some of them likely represent bits of T. imperator itself, but we can't be certain of this until skeletons with associated cranial remains are recovered. Until then, we'll have to be satisfied with the revelation that T. imperator has chin big enough to scare even Kurt Russell, and wait for further discoveries. Be sure to check out this image of Tupandactylus navigans, another Crato pterosaur with a penchant for elaborate headgear, for more information on this genus.

But enough about that
What makes this picture more unusual than many like it is that it depicts an actual, real-life person who I happen to know very well, and anyone who's read Pterosaurs will also be familiar with. Here's where she's mentioned at length, from the 'Acknowledgements' page. She got her own section and everything.
Disacknowledgement
Finally, although customary in book acknowledgements to honor those who help steer projects to completion, it seems unfair to not mention the tremendous negative impact on this project made by Georgia Maclean-Henry. As the single most destructive force against this work, she took my attention from this project so frequently that we ended up moving in with each other halfway through the writing process and have ended up making some sort of home together. She continues to distract me from all kinds of work to this very day and, frankly, I could not be happier about it.
So yes, here she is. The Disacknowledgement herself. The 'single most destructive force against this work', and many others. I chose this picture to post now because today is the 2nd anniversary of the aforementioned moving in with my Disacknowledgement. I'm not normally one for noting or making a big deal of such things (as the Disacknowledgement knows all too well), this ties in with a more important recent event: the Disacknowledgement agreed to marry me when I asked her last week, which is all very exciting and I'm rather over the Moon about (before anyone asks, there were no knees involved, but there was a breccia, not to mention a kick-ass grey seal sighting moments before. He was huge!). Seeing as this image puts me in a good (and probably fairly unique) position to broadcast this happy fact while clinging to some sort of palaeontological relevancy, there seemed no better way to spend this brief teabreak. Speaking of which, said break ended quite a few minutes ago: best get on with other things, including hoping that the Disacknowledgement doesn't mind being referred to as 'the Disacknowledgement' all the time. Sorry dear. 

References
  • Campos, D. A. and Kellner, A. W. A. 1997. Short note on the first occurrence of Tapejaridae in the Crato Member (Aptian), Santana Formation, Araripe Basin, Northeast Brazil. Anais-Academia Brasileira de Ciencias, 69, 83-88.
  • Pinheiro, F. L., Fortier, D. C., Schultz, C. L., De Andrade, J. A. F. and Bantim, R. A. 2011. New information on the pterosaur Tupandactylus imperator, with comments on the relationships of Tapejaridae. Acta Palaeontologica Polonica, 56, 567-580.
  • Witton, M. P. 2013. Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.