Book review: The Paleoart of Julius Csotonyi, Csotonyi and White 2014

From Titan Books.

The Paleoart of Julius Csotonyi: Dinosaurs, Sabretooths and Beyond (Csotonyi and White 2014) is another palaeoart-focused book from Titan Books, who brought us the acclaimed Dinosaur Art: the World’s Greatest Paleoart two years ago (White 2012). Anyone familiar with this book will immediately note the very similar format and high production quality in this recent Titan release. Although slightly smaller than Dinosaur Art, this will - again - leave readers wondering how the extremely affordable price (£25) covers production costs. Csotonyi was, of course, one of the artists featured in Dinosaur Art but, this time, is entirely running the show. Fans of his work will have little doubt that he can carry an entire book by himself. For the last decade Csotonyi has been establishing himself as one of the world’s premier palaeoartists, illustrating countless press releases, books, articles and museum walls with intricate paintings or digitally-manipulated photograph composites. His work is in such demand that he is one of the few individuals globally who can make a living out of palaeoart, a status which is testament to the quality of his work.

Before we get into the review itself, I want to stress how much of a milestone this book is. Palaeoart and palaeoartists suffer a PR problem where artists are considered unimportant and interchangeable: individuals who are secondary to the scientists pushing palaeontology forward and the audience who – often superficially – experience their work. Titan Books showed that palaeoart could be tackled more seriously and respectfully with Dinosaur Art and are cementing this idea in dedicating a whole book to a leading palaeoartists. Csotonyi's position as a working palaeoartist with major publisher support is rather exclusive, but exactly the sort of treatment palaeoart needs. I hope that Csotonyi’s solo album sells well enough to kickstart a series of books featuring other artists. Intentionally or not, Julius’ artwork is a good place to start this hypothetical series: aesthetically pleasing, extremely high quality, and blending traditional palaeoart approaches with some more complex and radical compositions. As a means to test the market for these sort of books, Julius is one of the strongest candidates currently available.

As an industy, palaeoart needs all the help it can get, starting with this logo.

Right, big-picture stuff out of the way now: what of the book itself? At its most basic level, The Paleoart of Julius Csotonyi is effectively an expanded version of his chapter from Dinosaur Art, juxtaposing imagery alongside an interview about Csotonyi’s art, influences and background. The interview, confined to the first 23 of the 156 pages, features intelligent questions and the interesting responses from the artist. Csotonyi’s passion for art and science are clear even before his images are displayed in earnest, as is the amount of work required to produce the large, ultra-high-quality imagery he is famous for. He leaves no doubt that many personal sacrifices are required to work as one of the world’s leading palaeoartists. This section also contains rarely-seen early works and non-palaeontological artwork, including some dedicated to astronomy. Some of the interview responses and other text features words which may be unfamiliar to lay audiences, but a glossary is provided to help readers navigate these terms.

The real meat of the book is relatively text-light so as to provide maximum space for Csotonyi’s art – large format is the only way to appreciate the detail it contains. The art is roughly arranged in chronostratigraphic order, with Palaeoazoic, Mesozoic and Cainozoic subjects separated into different chapters. As usual within palaeoart, the bulk of the artworks depict Mesozoic dinosaurs, and theropods are particularly well represented. Each piece is accompanied by brief details of the composition and commissioners, and some featuring additional comments from scientists about the subject animals. These comments mostly complement Csotonyi’s talents or spin yarns about research associated with the depicted species and, I guess, are designed to boost the scientific content of the book. I do feel a trick has been missed here because none pass particular comment on the decisions made when reconstructing the animals. Seeing as a lot of Csotonyi's art is produced alongside consulting scientists, I’d like to know what input they had. Even the most tightly constrained reconstructions of a fossil animal requires a lot educated guesswork and speculation about palaeobiology and life appearance and - in my own experience at least - not all of this is left to the artist. After all, this is a primarily a book about scientific art, and it seems that these comments could be more insightful than discussions about fossil localities, chance discoveries, or another complement for Julius' artwork (meant with all due respect, of course, but we know he's good. That's why we bought the book!).

A busy day in Permian Texas. Photo composite by Julius Csotonyi, from The Palaeoart of Julius Csotonyi. Image from here.

Csotonyi himself gives some works longer explanations about the processes involved in the reconstruction. These often highlight works with unusual compositions or viewpoints (such as the excellent ‘fish-eye’ sauropod view) and describes the way each piece was executed, often with alongside draft versions. These provide some insights into his process and will doubtlessly be useful to budding artists. My personal take-home message from these is the exhaustive consideration and research required to understand not only fossil animals, but to also reproduce realistic landscapes and lighting, particularly when odd perspectives and water are involved.

On the art itself: Csotonyi’s images are created using a range of media, including traditional and digital painting, sketches and – most commonly – digital photographic manipulation. I’m going to come clean here and admit that I’m not enormously fond of photographic manipulation. Many such works often fall into palaeoart’s own variant of the ‘uncanny valley’ or, all too often, present oddly-proportioned, strangely posed creatures which have little in common with their known anatomy. Julius’ photo composites are easily among the best, if not the best, attempts at photo-realistic 2D palaeoart out there however, and present reasonably reconstructed animals at either photo-realistic quality, or within inches of it. Some images, particularly the more ambitious, crowded scenes (fans of ‘a busy day in deep time’-type images are well served here) do bear niggles which jar the illusion, such as animals appearing too sharply defined against the background. To a certain extent, this is unavoidable: photomanipulation is incredibly difficult to pull off even remotely well, and even Csotonyi’s lesser successes are still amazing efforts. There are no overused photographic elements, no blurred skin textures, no cloning of animals to create herds of the same individual. When the photomanipulation does work well – and it frequently does – the effects are nothing short of stunning (e.g. below). The image of the resting Edaphosaurus on page 33 could easily be mistaken for a genuine, beautifully shot photograph. As with Dinosaur Art, some panoramic scenes unfold to show enormous vistas stuffed with detail. Many of these fold-outs allow those of us with empty pockets our first detailed look at the many murals Julius has created for North American and Australian museums.

Photo composite Acrotholus audeti and Neurankylus lithographicus  by Julius Csotonyi, from The Palaeoart of Julius Csotonyi. Image from here.

My favourite images in the book are digital paintings (below), such as the dancing Guanlong, the mothering polycotylid and the ceratopsid portrait gallery on pages 102-103. Not only do these show the trademark Csotonyi attention to detail but they’re wonderfully lit and composed: they feel more ‘of a scene’ than the photo composites. A neat touch is that alternative versions of well-known paintings are sometimes included. I actually prefer the near greyscale version of the Acheroraptor press release image on page 43 to the original, its dusky palate and the removal of the mammal from the hero animal’s mouth creating an entirely different tone to the more familiar version.

Digitally painted Brachiosaurus by Julius Csotonyi, from The Palaeoart of Julius Csotonyi. Image from here.

Of course, scientific accuracy is also essential for palaeoartworks to be considered successful. In this respect, the book also delivers. Thoroughly modern reconstructions of fossil subjects are presented: extensively feathered maniraptorans, diverse integuments in other dinosaurs, correctly orientated limbs and so on. In light of All Yesterdays (Conway et al. 2013), Csotonyi’s approach to extinct animal reconstruction may be considered conservative - there are no outlandish, speculative audacities here in terms of appearance or behaviour. Most of the depicted animal interactions are predatory, and the soft-tissues of the reconstructed species are not especially elaborate. Perhaps this is because nearly all of the artworks were commissioned by researchers and museums, clients who tend to favour safer, more conservative palaeoartworks. We should not lose sight of how progressive even ‘conservative’ modern palaeoart actually is. Many sights now familiar to us would have been considered heretical just a few years ago: Csotonyi shows several tyrannosaurs with variable amounts of feathering in the book with little fanfare, for instance. For dinosaurs at least, it’s becoming harder to produce wholly shocking palaeoart without unreasonably bending palaeontological science or speculating wildly. While Csotonyi’s book may lack the accessory frills, wattles and elaborate behaviours of some modern palaeoart, it acts as a fantastic milestone for how far palaeontology and palaeoart has moved in recent years. Moreover, I do not want to give the impression that the images are not interesting or novel: fishing Dimetrodon (above), Polycotylus nuzzling its offspring to the water surface to breathe and reptiles swimming between the dredging fronds of rafting crinoids are just some thought-provoking Csotonyian innovations.

The unkillable skim-feeding hypothesis lives on. Art by Julius Csotonyi, from The Palaeoart of Julius Csotonyi. Image from here.

I do have a few issues with some science behind the artwork. I’m told that an unfortunate misunderstanding resulted in the extensive discussion of Rhamphorhynchus skim-feeding on pages 136-139 (Hone, pers. comm. 2014; above. See the comment from Julius below for the sull story). This was, in fact, meant to reflect dip-feeding or surface-gleaning. Folks who keep up with pterosaur research will know that skim-feeding habits in flying reptiles has been looked into several times, consistently found problematic (e.g. Chatterjee and Templin 2004; Humphries et al. 2007; Witton and Naish 2008, 2013), and widely publicised. It’s a surprise and a shame, then, that this idea made it into the book without someone noticing, and particularly so because the science elsewhere is pretty tight. I also wonder if some of the photo composite crocodyliforms are shown with entirely accurate scute patterns, as most seem to have been taken from modern crocodylians – many Mesozoic crocs had very different, often simpler scute morphologies. And while we’re moaning, I do wonder if some more complex images would have benefited from small ‘key’ illustrations demonstrating the position of each animal. This is not only because the animals can be hard to spot in the complex, detailed scenes on offer (this is not meant as a slight – remember that many of the more complex images are intended to be hundreds of times larger on museum walls), but because linking a list of unfamiliar names to specific creatures can be difficult. Individuals intimately familiar with genera of all major vertebrate groups should be OK (they exist, honest), but I suspect they will only make up a fraction of this books audience.

These are only minor issues in the grand scheme of things, however. The intelligence and quality of The Paleoart of Julius Csotonyi makes it essential for anyone interested in palaeoart, as well as more general aficionados of palaeontology, natural history, or natural history art. I have no doubt that palaeoartists will be keeping a close eye on its success, and hoping that it presents the first of a wave of similar tomes from Titan Books. That’s all to come, though: for the time being, The Paleoart of Julius Csotonyi cements Csotonyi’s status as a world leader among the current crop of palaeoartists, and this book will only further his success.

References

• Chatterjee, S., & Templin, R. J. (2004). Posture, locomotion, and paleoecology of pterosaurs (Vol. 376). Geological Society of America.
• Csotonyi, J. & White, S. (2014). The Paleoart of Julius Csotonyi: Dinosaurs, Sabre Tooths and Beyond. Titan Books, London.
• Humphries, S., Bonser, R. H., Witton, M. P., & Martill, D. M. (2007). Did pterosaurs feed by skimming? Physical modelling and anatomical evaluation of an unusual feeding method. PLoS biology, 5(8), e204.
• White, S. (2012). Dinosaur Art: the World’s Greatest Paleoart. Titan Books, London.
• Witton, M. P., & Naish, D. (2008). A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS One, 3(5), e2271.
• Witton, M. P., & Naish, D. 2013. Azhdarchid pterosaurs: water-trawling pelican mimics or" terrestrial stalkers"? Acta Palaeontologica Polonica. (In press).

Rhamphomummies and zombie skim-feeders

A 'mummified' Rhamphorhynchus muensteri entangled with the spear-like rostrum of Aspidorhynchus acutirostris, presumably reflecting a failed predation effort by the latter. Painting of a privately-held specimen, used with permission.

A few months ago, Frédéric Weber asked me to render two images of a spectacular, unpublished specimen from the famous Jurassic Solnhofen deposits of Germany. It showed a rare association between two animals: the non-pterodactyloid pterosaur Rhamphorhynchus muenesteri and a ganoid fish, Aspidorhynchus acutirostris. Associated fossils are not uncommon in some deposits, but they are extremely rare in the Solnhofen Limestone. Fred wanted images of this Rhamphorhynchus/Aspidorhynchus association to illustrate a recent article in Fossiles magazine devoted to pterosaur specimens from Solnhofen (Weber 2013), with this particular specimen being all the more important because the pterosaur's body outline has been preserved by growths of calcite crystals rather than decaying away. 'Mummified' pterosaurs like this aren't entirely unheard of, but they remain rare and are exciting for what they tell us about soft-tissue distribution. Making this specimen even more spectacular is the preserved wing tissues of the pterosaur and the perfect state of the neighbouring Aspidorhynchus. Fred wanted to show the exquisite preservation of the specimen but was asked not to reproduce photos by its owner, so he asked me to do my best at reproducing it in a few images. The article containing this image is only the latest in a series on pterosaurs produced by Fred and, even if you cannot read French, they're well worth tracking down for their awesome imagery.

Those of you with ears to the ground of pterosaur research will know that this specimen is not one of a kind. Another, WDC CSG 255, was described by Eberhard 'Dino' Frey and Helmut 'King of UV' Tischlinger back in 2010, and at least three others are known. Given how rare such associations are in Solnhofen desposits, the repeated association of these animals implies some common explanation for their co-preservation. The rationale provided by Frey and Tischlinger (2010) sounds pretty convincing to me. They suggest that Aspidorhynchus frequently predated Rhamphorhynchus but, because the pterosaur was a little too big and gangly for its mouth, it's wing membranes became entangled on the fish's rostral spar or teeth and could not be swallowed. In efforts to shake the pterosaur loose, some Aspidorhynchus accidentally entered the anoxic bottom waters of the Solnhofen lagoon and, well, the rest is pretty self explanatory. It's quite probable that these predatory events were accidental, which may explain why many Aspidorhynchus specimens preserve fishy gut content, but none show successfully ingested pterosaur bones.

The Rhamphomummy and it's attacker in full. Line drawing of a privately-held specimen, used with permission.

But that's not all
Remarkably, one of these associations provides some insight into what brought the Rhamphorhynchus into striking range of Aspidorhynchus. The throat region of the WDC CSG 255 Rhamphorhynchus is full of undigested fish bones (probably Leptolepides) which suggest it was foraging for food just before it was grabbed by an Aspidorhynchus(Frey and Tischlinger 2010). The fact that at least some Rhamphorhynchus were likely foraging in the immediate interim before being attacked has, of course, raised interest in the foraging method utilised by Rhamphorhynchus because it may be linked to the attacks from Aspidorhynchus. Frey and Tischlinger (2010) suggest two options here. Firstly, Rhamphorhynchus may have grabbed fish from the water surface by dip-feeding, and was then grabbed. Unlikely, they say, because this wouldn't give the Aspidorhynchus enough time to grab the pterosaur once it disturbed the water. So a more likely idea, they suggest, is skim-feeding.

"Skimming... took time and resulted in a significant signal of turbulence, when the mandibular rostrum ploughed through the silent water surface. Such turbulences attract all kinds of fishes and are also were easily detectable for an Aspidorhynchus. Furthermore, the vane at the terminus of the long tail of the pterosaur could have contacted the water surface too due to the extremely low surface approach with a flight altitude of no more than 50 mm. Large Aspidorhynchus thus could grab a skimming Rhamphorhynchus by just raising the head through the water surface. The specimen presented here strongly suggests that Aspidorhynchus actually did exactly this." Frey and Tischlinger 2010, p. 4. (my emphasis)

Skim-feeding, we meet again
Yes, skim-bloody-feeding. A number of pterosaur workers - myself included - view the skim-feeding pterosaur hypothesis as highly problematic, based on very superficial science, and a complete non-starter based on simple comparative anatomy. Despite this, this idea is incredibly tenacious within pterosaur literature. Skim-feeding was widely considered a viable forging method for pterosaurs up until the mid-2000s (e.g. Wellnhofer 1991; Hazlehurst and Rayner 1992, Kellner and Campos 2002; Unwin 2005) when, under a hail of scientific bullets, several authors suggested it was implausible for numerous reasons (Chatterjee and Templin 2004; Ősi et al. 2005; Humphries et al. 2007; Witton and Naish 2008). Humphries et al., the first (and only) dedicated study of skim-feeding in pterosaurs inflicted the deepest wounds, using biomechanical testing and comparative anatomy to conclude:

"Both modelling the energy requirements of skimming pterosaurs and analysing their osteology casts serious doubt on the ability of pterosaurs to habitually skim-feed. Although our physical modelling suggests that small pterosaurs may have been energetically capable of skimming, there is no anatomical evidence to assume that Rhamphorhynchus or any other small pterosaurs were skimmers." Humphries et al. (2007), p. 5

I was part of that study (my first publication, nonetheless) and thought that, with other authors suggesting similar misgivings about the idea, that skim-feeding had been stopped dead. Like the foraging hypothesis equivalent of a freakin' zombie, it has since risen again with more questionable science to prop it up (Stecher 2008; Frey and Tischlinger 2010; Averianov 2013). Even attempts to subtly downplay the likelihood of pterosaur skim-feeding in blogs ("Die you skim-feeding bastard, die!") haven't got the message through. What will it take to down this thing? Here's another go, then, at explaining why I, and others, think this hypothesis is a complete non-starter and should be abandoned.

Where's the beef?
Firstly, there's never been an in-depth, detailed study suggesting skim-feeding was likely in any pterosaurs. So far as I can tell, the link between skim-feeding and pterosaurs started with throwaway comments by Marsh (1876), who suggested the mandible of Pteranodon was reminiscent of the lower jaw of modern skimming birds. Since Marsh, nearly 20 articles have suggested pterosaurs may have skim fed, but none have really added much to his idea. Most simply suggest, with varying degrees of certainty that pterosaurs of all kinds (rhamphorhynchids, 'campylognathoidids', ornithocheirids, dsungaripterids, thalassodromids, azhdarchids are candidates) were skim-feeders based on very superficial anatomical comparisons with modern animals. Kellner and Campos (2002) did the most thorough job with Thalassodromeus, but even that was a fairly brief comparison between their new taxon and modern skimmers that was very restricted by it's publication in the short-piece journal, Science. There's certainly never been anything published with sufficient quantified or even illustrative evidence to support skim-feeding in pterosaurs. It really seems that  pterosaur skim-feeding has become an established concept not because of its scientific credibility, but because of its longevity and popularity. Similar comments could be made about many established, 'common knowledge' ideas about fossil animals.

The skull and mandible of Rynchops niger in lateral view (A) and mandible in dorsal view (B). Note the extremely derived anatomy on every facet of this thing, all of which reflect skim-feeding habits. From Witton (2013).

The rather superficial science behind skim-feeding could almost be excused if it weren't for the extensive documentation of the lifestyle and functional anatomy of modern skimming birds. The exhaustive work (essentially a whole book) produced by Richard Zusi (1962) is a key reference here. It's widely known that, in the modern day, skim-feeding is only practised by a couple of bird species, all of which belong to the genus Rynchops. Thanks to several generations of ornithologists researching this animal, we know that Rynchops is specialised six-ways-from-Sunday for it's unusual habits. Check out the Rynchops skull and mandible, above, for instance. Virtually every facet, every joint and feature reflects it's lifestyle. This specialisation extends to its neck and flight style. Zusi (1962) noted a whopping 26 obvious morphological adaptations to skim-feeding, which are detailed in a handy cut-out-n'-keep guide below.

The result of these is that when handling a skimmer skull, even if you'd never seen one foraging, there's no doubt whatsoever about it's preferred habits. These birds need to be so specialised because, frankly, skim-feeding is a ridiculous way to feed. Dragging your lower jaw through a relatively viscous, obstacle-filled fluid at 16-32 kph and hoping to hit something you can eat isn't a particularly sensible approach to foraging. Skimmers can't even see what they're trawling into (Martin et al. 2007), and they regularly run aground in shallow mud or blunder into vegetation. On occasion, these impacts are severe enough to cause crashes or snap off the tip of the mandibular rhamphotheca (Potter 1931). Of course, evolution has a wonderful disregard for sense and logic, and skim-feeding behaviour simply promoted the development of impact resistant necks and skulls, with reinforced jaw joints and powerful jaw muscles. These include enlargement of their secondary jaw joints (a common avian feature; labelled as 'medial processes' on the diagram above), considerable reinforcement of the mandible and a broad neck base to anchor powerful, impact resisting neck muscles. Because the forces acting on Rynchops jaws during skimming are so high, skim-feeding birds have to pull their jaw muscles tight when foraging: the upper jaw is 'opened' via kinetic hinges at the mid-length of the skull. Biomechanical modelling of skimmer flight suggests skim-feeding flight is energetically demanding (Humphries et al. 2007), necessitating extremely streamlined lower jaw tissues along with abradable, rapidly-growing beak tissues to replace those worn away in accidents. Because skim-feeding impacts - desired or otherwise - pull the head into the water, skimmer necks are also unusually long and flexible. We could go on: these birds are fascinating case studies of adaptation.

Rhamphorhynchus mummy skull detail. A dorsoventrally slender mandible and a mouthful of teeth probably aren't the best way to approach skim-feeding.

With the mechanics of skim-feeding so well understood and its adaptations so obvious on animal skeletons, there's really no excuse for skim-feeding in pterosaurs to be so superficially considered. There's only so many ways for a flying tetrapod to trawl a mandible into things it hopes are food after all, so we should expect common adaptations between pterosaurs and Rynchops. Compare the skull of Rhamphorhynchus in the painting above, with that of Rynchops. Even in that crude approximation of its anatomy we can see the lack of of cranial reinforcement, the wimpy areas for jaw muscle attachment, and the bloody-great teeth where a knife-like skimming jaw should be. And yes, there are specimens of Rhamphorhynchus that show the jaw tip was extended with soft-tissue, but nothing like that seen in Rynchops (see image, above). The same arguments can be levelled at all other proposed pterosaur skim-feeders, even the animal named after it's alleged skim-feeding habits, Thalassodromeus (Kellner and Campos 2002). There are no convincing anatomical correlates for skim-feeding habits in any known pterosaur (Humphries et al. 2007; Witton and Naish 2008). This is almost certainly why pterosaurs with wingspans over 2 m (which, of course, is about the size of large Rhamphrohynchus) lack sufficient power output for skim-feeding (Humphries et al. 2007): their jaw shapes were never adapted for efficiently cutting through water. Smaller pterosaurs may be able to plough a short length of toothless jaw tip through water, but they'll be aching with the muscular exertion on their jaws, and in huge pain if they hit anything. I feel it would be remiss here to ignore the story behind testing streamlining in the Thalassodromeus jaw tip, which was so violently stressful that it broke the testing rig of the Humprhries et al. (2007) study. Back in 2007, I shared my recollection of what became known as the 'Thalassodromeus Flume of Doom':

Rather old and silly presentation slide. Based on real events.

In all the press accompanying the publication of Thalassodromeus, one worker is recorded as saying it must’ve looked like a ‘vision of hell’. Well, hats off to him: he was right. There was something unerringly terrifying about the massive jaw tip of this thing hurtling towards you at great speed. Maybe it’s because there was water everywhere. The moment Thalassodromeus began to skim, the whole rig started shaking manically, throwing water about like a possessed jetski and drawing worried glances from the crew. Notching the speed higher, the rig became more unstable and, to everyone’s surprise, the aluminium bar was even bent on one run. This was replaced and, eventually, the time came to set max speed: 25 kmph. The catcher, a nervous looking PhD student, was braced and ready. At the other end of the flume, the pterosaur-cyborg beast glared at him, the water eerily calm before the violence that would follow. “You ready?” asked Stu, and I gulped my affirmative. The winch was pulled. Suddenly, the beast was roaring down the runway. The room echoed with the inhuman screaming of its wheels on the track. The jaw was convulsing madly. Water crashed over the tank walls. Then the screaming stopped with a loud bang: the Thalassodromeus was airborne; the whole rig arcing through the air and spiralling forward - only milliseconds separated it from a watery grave. My clothes ripping against the metal tank and the waves pounding my body like Achilles in the River Scamander, I leapt forward and grabbed the plummeting contraption moments before it hit the water. We rushed the wounded rig from the flume to check its health: the aluminium bar was totally twisted, the electronics shot. The little blinking lights on the mechoreceptor faded to black. The rig lay dead in Richard’s arms. Stu called to the Heavens in anger. Dave cried. I was soaking wet. It was about then that we started wondering if ‘ocean runner’ was a name slightly too optimistic about the skimming capabilities of its owner. With testing brought to a dramatic but premature end for the day, we retired for back massages and herbal treatments from attractive Scandinavians to recover from the ordeal. Such is the life of courageous university researchers. (link to original)

Put together, these three reasons - the lack of a good studies in favour of pterosaur skim-feeding, the fact we know so much about modern skim-feeders, and the overwhelming evidence against skim-feeding in pterosaurs - are why I find it a tiny bit irritating that this idea is still being discussed as plausible. It just seems, I dunno, that our ideas should be moving on or something.

Night of the living skim feeders
If skim-feeding in pterosaurs is so objectionably flawed, why won't the idea be politely resigned to history? I predict four causes.

1. It's an established idea, even if it's not based on any particularly rigorous science. Established ideas take a long time to overturn even if evidence to the contrary is strong. 
2. Pterosaurs were flying animals. For some palaeontologists, this equates to them doing everything in flight.
3. There may be unawareness concerning how specialised Rynchops is for skim-feeding, and how unique its morphology is, even among birds. Anyone thinking of proposing skim-feeding habits for pterosaurs really should familiarise themselves with the work on Rynchops lifestyle first, and particularly Zusi's 1962 treatment.
4. Life of the past is frequently considered to be outlandish and overly dynamic (also see discussion of animal poses in palaeoart, here and here). This is perhaps why, when Frey and Tischlinger (2010) considered how a pterosaur may have been attacked by a marine predator, boring ideas like the pterosaur swimming or floating weren't considered*.

*Before anyone asks, there is at least trackway evidence suggesting pterosaurs can swim (Lockley and Wright 2003) and new take off models suggesting water launches weren't difficult (Habib and Cunningham 2010), so let's not hear anything about waterlogging of wing membranes or whatever.

Of course, none of these are particularly defensible. We simply need to stop trotting skim-feeding pterosaurs out at what almost seems like any given opportunity. There's never really been anything to it, and until sufficient evidence - like a pterosaur fossil bristling with skim-feeding adaptions - comes to light, the idea's as dead in the water as the Aspidorhynchus and Rhamphorhynchus we discussed on the way in. I'll take that arriving at conversational full circle as a good place to stop.

Next time (possibly): Space Year 2013: The Golden Age of Palaeoart?

References

• Averianov, A. O. 2013. Reconstruction of the neck of Azhdarcho lancicollis and lifestyle of azhdarchids (Pterosauria, Azhdarchidae). Paleontological Journal, 47, 203-209.
• Chatterjee, S. and Templin, R. J. 2004.  Posture, Locomotion and Palaeoecology of Pterosaurs. Geological Society of America Special Publication, 376, 1-64.
• Frey, E. and Tischlinger, H. 2012. The Late Jurassic pterosaur Rhamphorhynchus, a frequent victim of the ganoid fish Aspidorhynchus? PLoS ONE, 7, e31945.
• Habib, M. B. and Cunningham, J. 2010. Capacity for water launch in Anhanguera and Quetzalcoatlus. Acta Geoscientica Sinica, 31, 24-25.
• Hazlehurst, G. A. and Rayner, J. M. 1992. Flight characteristics of Triassic and Jurassic Pterosauria: an appraisal based on wing shape. Paleobiology, 447-463.
• Humphries, S., Bonser, R. H. C., Witton, M. P. and Martill, D. M. 2007. Did pterosaurs feed by skimming? Physical modelling and anatomical evaluation of an unusual feeding method. PLoS Biology 5, No. 8, e204.
• Kellner, A. W. A. and Campos, D. A. 2002. The function of the cranial crest and jaws of a unique pterosaur from the Early Cretaceous of Brazil. Science, 297, 389-392.
• Martin, G. R., McNeil, R. and Rojas, L. M. 2007. Vision and the foraging technique of skimmers. (Rynchopidae). Ibis, 149, 750-757. 
• 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.
• Potter, J. K. 1932. Fishing ability of the black skimmer (Rynchops nigra nigra). The Auk, 49, 477.
• Stecher, R. 2008. A new Triassic pterosaur from Switzerland (Central Austroalpine, Grisons), Raeticodactylus filisurensis gen. et sp. nov. Swiss Journal of Geosciences, 101, 185-201.
• Unwin, D. M. 2005. The Pterosaurs from Deep Time. Pi Press, New York.
• Weber, F. 2013. Paléoécologie des ptérosaures 3. Les reptiles volants de Solnhofen, Allemagne. Fossiles. 14. 50-59.
• Wellnhofer, P. 1991. The Illustrated Encyclopaedia of Pterosaurs. Salamander Books Ltd., London.
• Witton, M. P. 2013. Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.
• Witton, M. P., & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS One, 3, e2271.
• Zusi, R. 1962. Structural adaptations of the head and neck in the black skimmer Rynchops nigra Linneaus. Publications of the Nuttall Ornithological Club 3, 1-101.