Mark P. Witton's Blog

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 thepinnacle 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 has 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 mostlylacks 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.

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.

Head and neck biting sexual behaviour in Tyrannosaurus rex. A novel, brutal and undeniably speculative reconstruction for tyrannosaurs, sure, but is it the result of pure, unbridled palaeoartistic license, or is there something more to it?

It seems that "speculation" is the current word on everyone's lips in palaeoartistic circles. Thanks largely to the enormous success of All Yesterdays, and the recent unveiling of its sequel, All Your Yesterdays, palaeoartists across the internet have buzzing with excitement over the possibilities opened by speculative leaps of logic. This is undoubtedly a Good Thing. I wrote almost a year ago about why I thought All Yesterdays and the ideas it embodied were great, and a must-see for anyone interested in vertebrate palaeontology or palaeoart. I stand by that, and am certain that many of us in the palaeoart community have be positively influenced by this project in the way we recreate extinct species. All Yesterdays revelled in speculation about prehistory, arguing that we were not being open-minded enough about our depictions of animal appearance and behaviour. The crux, as anyone reading this probably knows, is that many 'traditional' palaeoart concepts are likely erroneous by being overly conservative, and thus 'fail' at both restoring ancient life and producing convincing looking animals. In addition, All Yesterdays highlighted a number of conventions which had become tropes within palaeoart, and argued palaeoartists produce far more accurate studies of extinct life when these clichés are broken, not to mention more interesting ones. What gave All Yesterdays such a strong message was that it, for the most part, was scientifically sound, cleverly turning conventions on their head or showing us logical, plausible ancient phenomena that we'd not imagined before.

For the All Yesterdays sequel, All Your Yesterdays, we see a minority of palaeoartists reaching further than it's predecessor dared, showing some very elaborate anatomies and lifestyles which may, in my opinion, go further than reasonable inference, even enhanced with speculation, may allow. Before we get any further, I want to stress that this post is not a review of All Your Yesterdays. I enjoyed the book, and think it's well worth seeking out for a look at for some excellent and thought provoking imagery. But yes, it does contain a few images which made me question this newfound speculative approach to palaeoart. We have to bear in mind that All Your Yesterdays was crowdsourced, the result of a contest for "original, creative concepts that are at least partially in-line with our current understanding of extinct animals" from Irregular Books. This is naturally going to draw a range of knowledge bases, some of which may be more comprehensive than others, and it may be that some of the more eyebrow-raising images therein are simple mistakes. I'm not going to name names here, because I gather the artists behind All Your Yesterdays were not aware that their work was going to be showcased as a 'significant' addition to the All Yesterdays canon, but I'll hint that molluscan salinity tolerances, the nesting habits in pterosaurs, the soft-tissues of spinosaurids, hadrosaurs and thyreophorans, and the evolution of viviparity were just some things which prompted this post. It's important to stress that problematic 'overspeculations' are not confined to a few pieces in All Your Yesterdays, but a small but noticeable chunk of post-All Yesterdays palaeoartworks which, arguably, jump the palaeoart shark. It's these artworks I want to focus on here.

Getting introspective with speculation
Chiefly, some artwork inspired by All Yesterdays seems to take license for increased palaeoartistic speculation as a sign that 'anything is possible in nature', without any real consideration for how likely some possibilities are. Other pieces showcase strange anatomies for the sole purpose of contrasting with more traditional standard depictions, without considering why such reconstructions are common in the first place. These works, presented as part of a movement that I think I understand and agree with, have gone beyond the science which has to underpin any recreation of an extinct being. The question is, how much speculation we can use before our work stops being palaeoart and starts being fantasy images starring extinct species?

Detail of neck biting Tyrannosaurus. I'm sure he's got a great personality.

Of course, I'm not the first person to ponder this. Indeed, the inspiration for this post, All Your Yesterdays, muses on this same issue:

"In short, speculation in palaeoart should be seen as a sliding scale. At which point does a speculation render itself too extreme? And is it even possible to reach said extreme given the ridiculous soft tissue structures and absurd behaviours present in the modern world? It is, in fact, surprisingly difficult to come up with a speculative piece of palaeoart that is unconditionally ridiculous (at least, so long as the basic rules of anatomy, biology and physics are applied, as they are in science-based reconstructions)."

All Your Yesterdays, p. 7

These words contrast with a few comments online. Amid the near-universal acclaim for All Yesterdays, one or two (and three, four, five) folks have made about palaeoartistic speculation running away with itself, a far cry from the suggestion that palaeoart can never, so long as basic science is followed, be too ridiculous. It seems there's some need, then, for discussion about the appropriateness of speculation in palaeoart: how it should inform our work, how far we can take it, and whether all speculations are equal. After ruminating on this for a couple of days, it seems that the best way to tackle this is by dividing palaeoartistic speculation into three categories (as with any classification of an organic, creative process, are best perhaps viewed as major points a continuum), which I'll call primary, secondary and tertiary. These distinctions effectively denote how far depicted ideas stray from actual data. We'll outline these types of speculation first, and then discuss their use below.

Primary speculations
Speculations directly based on fossil data, whereby the evidence for a behaviour, event or anatomical feature is reasonable, but details may be murky and require some imagination to restore. Gut content, pathological bones and complex track sites are good examples of evidence which can be used to inspire palaeoart using primary speculation. We may not know the entire truth behind these fossils, but we can whittle it down to a few very likely possibilities. Basic elaboration of predicted integument of an animal - making fluffy integuments long or short, altering distribution and so forth - would be an example of primary speculation on anatomy, as would adding things like wattles, skin-folds and other likely anatomical details to reconstructions. With primary speculations, we can be more-or-less entirely confident that we're displaying a degree of truth in our work.

Secondary speculations
Speculations not directly supported by fossil data, but operate within our spectrum of knowledge to maintain a degree of plausibility. This may include extrapolation of common behaviours and, to a limited extent, elaborate anatomies from closely related animals to reconstructed species. Extrapolating some behaviours from or close ecological, anatomical or biomechanical analogues may fall into this camp too. Ritualised behaviours (below), unusual ways of dying and foraging on unexpected food sources are good examples. Depicted behaviours may serve to show the function of prominent anatomies. Slightly unusual interpretations of integument and other body tissues (perhaps as responses to climate, seasons, sexual selection etc.) probably fall into this category, so long as they are consistent with the integuments known within a 'reasonable' phylogenetic bracket. In short: speculations which adorn fossil species with features so fundamental to animal existence that, even in the absence of fossil data, we can be confident they occurred in deep time.

Ritualised courting chaoyangopterid pterosaurs, Lacusovagus magnificens. Did pterosaurs do this? There's no direct fossil evidence for it, but the abundance of ritualised mating behaviour in modern animals suggests we can be relatively confident that they, and other fossil species, used complex ritualised behaviour. This undoubted speculation gains indirect support from the broad array of sociosexual devices we see on many fossil species, and hints of ancient sexual dimorphism, both of which indicate sexual behaviours were as complex and sophisticated in prehistory as they are today. Image from Witton (2013).

Tertiary speculations
Speculations operating completely outside, and sometimes contradicting, fossil data. May rely entirely on application of very specific modern animal behaviours and anatomies to fossil species, often transferring rare, sometimes highly specialised lifestyles to fossil animals. There is no particular logic or reason behind these applications: they are entirely arbitrary. In other cases, complex biologies and life histories are invented for fossil taxa. Creation of soft-tissue anatomies without, or in spite of, consideration of underlying musculoskeletal system and/or soft-tissue fossil data. Reliant on the absence of data concerning fossil species, because 'anything is possible'. Hypothetical examples of such speculations are things like lactating dinosaurs, notosuchians with trunks, an egg-laying Deinotherium, hadrosaurs with antler-like structures growing atop their crests. Jaime Headden's woolly ankylosaur, his cautionary 'mess of speculation', is a knowing graphic example of tertiary speculations gone mad.

Speculations, what are they good for?
If these are the tools of the speculative palaeoartist, what are their application? Anyone familiar with palaeoartistic practises will recognise that the former two grades of speculation are standard tenets of palaeoart. Such speculations provide our leaps of logic into prehistory and, without them, palaeoart would be an pretty limited endeavour, probably entirely formed of musculoskeletal reconstructions. It's important to recognise that such speculations were not originated by All Yesterdays, as primary and secondary speculations have always been used in palaeoart. The masterstroke of All Yesterdays was to show how primary and secondary speculations could be bolder and more imaginative than most mainstream palaeoart suggested. The result is artwork which is both interesting, unique and supported by actual data.

The image at the top of this post is the result of such an inference. It's well known that many large theropods engaged in head-biting behaviour, and some specimens of Tyrannosaurus (including BHI 3033, better known as the common T. rex museum mount 'Stan') bear particularly extensive damage to their posterior skulls. The inference made here is that Tyrannosaurus engaged in aggressive head and neck biting during copulation, a widely seen behaviour among vertebrates that can often involve substantial damage to the head and neck of the female, sometimes leading to death. I'm not the first to envision this behaviour for tyrannosaurids. Tanke and Currie (1998) suggested nuptial biting as a cause of tyrannosaurid head pathologies but suggested it was refuted by the apparent small size (50% of full size) of many tyrannosaurids with head wounds. Of course, it now seems that dinosaurs became sexually mature when only half grown (Erickson et al. 2007), so this hypothesis may be back on the table. The resultant image is a radical and speculative depiction of Tyrannosaurus behaviour, but one that has a foot firmly set in science.

Cast of the skull of Tyrannosaurus 'Stan', BHI 3033, at in the Oxford University Museum. Stan's skeleton is particularly damaged around the posterior head and neck region, with a probable tooth wound penetrating it's braincase, a smashed postorbital bar (a dorsal projection of tyrannosaur skulls which anchored neck muscles) and broken neck vertebrae. Photograph by Marc Vincent, from Love in the Time of Chasmosaurs.

The same cannot be said for tertiary speculations. Some inferences made at this level are so far removed from actual data that they have little or no evidence to support them, and thus abandon the scientific basis which should underpin any palaeoart. Others may disagree, but I think good palaeoart, like good science, is led primarily by evidence, not speculation. This most obviously impacts tertiary speculations which arise, it seems, for the sole purpose of overturning convention. "This animal is always shown like/doing this... what if it looked like/did THIS SHOCKING THING?!??" While there's nothing wrong with trying to keep palaeoart fresh, we should remind ourselves that not everything common in palaeoart is a trope or meme, or the product of unimaginative artists. Sometimes, that's just how animals were, and conventions are based in very sound evidence. Deviating from these conventions is a move away from data, which is the exact opposite of what we want to be doing here.

Other tertiary speculations apply highly unusual behaviours borrowed from modern animals, or those which are entirely made up, to fossil species for no clear reason. This can be effective on occasion, presenting a fossil species in a radical light which may make us reconsider our preconceived notions of that species, but I'm generally not a fan. Why, of all the behaviours that we can imagine or observe in in the modern day, should we chose that specific animal as a model? And do we really expect the rarest, most elaborate and weirdest behaviours to be present in specific fossil animals? Are we actually predicting that extinct animals behaved (often adorned with the same colour schemes and patterns) exactly like these aberrant modern animals? We'll score far more science points if we apply more widespread behavioural phenomena to our palaeoart. This doesn't mean we have to confine ourselves to dull behaviours like travelling and foraging, because we can also rely on primary and secondary-level speculations to give us behaviours like resting, taking care of personal hygiene, reproducing, interacting with one another and so on. Likewise, lots of interesting anatomies can be extrapolated from the fossil record itself. In sum, while we should take inspiration from modern taxa, arbitrarily 'transforming' fossil animals into ancient versions of modern species stretches credibility quite far, and is perhaps a rather unscientific approach to our work (this point echoes one made earlier, also in response to some art in All Your Yesterdays, at Laelaps).

A counterargument could be made that tertiary speculations allow us to imagine how sophisticated and complex ancient worlds were but, again, I question this. Like any guesswork, they're of questionable significance. Unknowns are unknowns. Tertiary-grade restorations are as likely to be incorrect as accurate. These depictions may fire the imagination briefly, but the flames are tiny compared to those fuelled by cool ancient behaviour derived from actual evidence. It's one thing to see a shocking piece of palaeoart, but quite another to realise that there's actually tangible evidence behind it. Rather than pondering the great unknowns of deep time when confronted with a tertiary speculation, I frequently react with the opposite approach, thinking about what we can actually deduce about a given issue, and what a more likely interpretation may be.

Why I find tertiary speculations frustrating. The fossil record is full of interesting animals with known interesting behaviours, like these burrowing Oryctodromeus, and yet they are frequently overlooked in palaeoart for entirely speculative renditions of familiar taxa. Check out this post for more on this animal and it's need for a PR campaign.

This brings us to a more pragmatic bugbear about tertiary speculations. Extremely speculative palaeoartworks are actually fairly common, at least online, while innumerable cool palaeontological topics with a significant factual basis are completely ignored. Why use art to make rather hollow points about unknown topics when there's plenty of art to be made concerning subjects we do know about? Even familiar animals have unusual, rarely-depicted behaviours which we can infer from fossils with minimal amounts of speculation (such as the tyrannosaurs above), not to mention the shedloads of fossil species which are wholly unrepresented in art (and yes, I'm well aware of the hypocrisy of saying this in a post featuring Tyrannosaurus), many of which are also known to have interesting and unusual behaviours. Heck, it's common knowledge that palaeoart is heavily biased towards a few taxa, so just showing some of these rarely seen animals would be a thought-provoking, cliché-busting achievement in itself. Is it not better, as scientific illustrators, to base our work on what we know rather than what we don't?

Which leads to...
So, yes, despite being an advocate of using speculation in palaeoart, I'm not a huge fan of the extreme and uncontrolled speculation we're seeing creeping into modern portfolios. This may sound like I'm jumping off the All Yesterdays bandwagon, but I don't think I am. Most of our best palaeoartists - including those behind All Yesterdays - use speculation of primary or secondary grade, and are more notable for avoiding clichés and artistic conventions than they are for presenting highly speculative lifestyles and anatomies in fossil species. They elaborate existing knowledge to create more convincing depictions of fossil animals, and apply detailed research of the fossil record to show us sights we've never seen before. Some of their work may seem outlandish and brash, but it's actually far more measured than it looks.

I'm sum my point up as this. While we should be using speculation to push palaeoart to its limits, we need to know both which bits we can push, and when to stop before our speculations get the better of our work. This doesn't deny us licence to make our reconstructed ancient worlds amazing and interesting and, in fact, it may make our work more striking. It's one thing to see an outlandish reconstruction of the past, but all the more poignant when we realise the weird, strange or even shocking visage before us is based on truths, and not just imagination.

References

Erickson, G. M., Rogers, K. C., Varricchio, D. J., Norell, M. A., & Xu, X. (2007). Growth patterns in brooding dinosaurs reveals the timing of sexual maturity in non-avian dinosaurs and genesis of the avian condition. Biology Letters, 3(5), 558-561.
Tanke, D. H., & Currie, P. J. (1998). Head-biting behavior in theropod dinosaurs: paleopathological evidence. Gaia, 15, 167-184.
Witton, M. P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press.

Mother and calf Leptocleidus superstes, a freshwater leptocleidid plesiosaur, explore a swampy river inlet in Lower Cretaeceous Sussex. Of course, a real swampy scene should probably be drawn showing an impenetrable amount of suspended sediment and goo with, possibly, some plesiosaur-shaped silhouettes, but that would make for a lousy image.

For various reasons, I've recently taken an interest in the plesiosaurs of the Wealden Supergroup. The latter will need no introduction to many readers here, being a very famous succession of Lower Cretaceous sediments which provide one of the best known dinosaur faunas in Europe, along with a diverse array of pterosaurs, crocodilians, amphibians, fish and, well, all sorts of things. The big deal about Wealden plesiosaurs is that they represent - gasp! - freshwater and brackish species rather than the marine variants we're more familiar with. Reading into these animals has been pretty fascinating and resulted in the generation of the following text and images presented here. My hope is that these will one day have a 'proper' home, but they'll have to sit here and wait for the meanwhile. The text below has been targeted at a fairly general audience and may not contain anything new for some readers, and doesn't contain citations. If, however, you're after more Wealden plesiosaurs (and who isn't?) with an authoritative twist, you'll want to be sure to check out this Tetrapod Zoology post and, of course, Adam Stuart Smith's Golden Trilobite Web Award winning-Plesiosaur Directory. If Mesozoic marine animals are your thing, you may also want to check out these posts on Ophthalmosaurusand the Oxford Clay fauna.

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Plesiosaurs are well-known aquatic Mesozoic reptiles characterised by their four large flippers and variably developed necks and heads. Their anatomy is completely unlike that of any other swimming animal, with barrel-shaped bodies tightly locked together by large, plate-like limb girdles which bore robust, powerfully muscled paddles. These flippers, highly modified limbs which are of no use on land, were entirely responsible for propelling plesiosaurs through water, their tails being relatively short and of apparent little assistance in underwater propulsion. This group, more correctly termed 'Plesiosauria’, has long been recognised as falling into two lineages: the pliosauroids and plesiosauroids. Some pliosauroids were super-predators like Liopleurodon and Pliosaurus, animals with likely stretched between 7 - 10 m in length with enormous skulls and jaws. These animals were likely top predators of many marine settings, hunting other large swimming vertebrates. Most pliosauroids bore relatively short necks but, in contrast, several plesiosauroid lineages – including famous species like Elasmosaurus, Cryptoclidus, and Plesiosaurus– developed long necks and small heads, ideal for foraging on relatively small fish and squid. Neck and skull proportions were once taken as a clear indicator of which group a given plesiosaur would belong to, but this idea has fallen from favour as the complexity of plesiosaur evolution has become apparent.

We mostly imagine these reptiles as sea- and ocean-going animals, making their occurrence in freshwater and brackish facies like those of the Wealden seem unexpected. Plesiosauria was a successful and adaptable group however, with a complex evolution that ran for 135 million years from the Late Triassic (c. 200 Ma) to the end Cretaceous (66 Ma) and included acclimatising to waters across the entire planet. Although plesiosaurs are undoubtedly mostly marine, they can be found in freshwater and brackish habitats throughout much of their history. Indeed, it seems that plesiosaurs invaded near-shore and freshwater habits on multiple occasions, although the catalyst of these invasions remains unknown. Did they thrive in environments free of large aquatic predators? Were they exploiting untapped niches and food sources? More data is required to answer these questions.

Skull reconstruction of Leptocleidus capensis, an Early Cretaceous leptocleidid from South Africa. The skull of L. superstes was probably pretty similar to this. Based on illustrations in Cruickshank (1997).

Wealden plesiosaur fossils are not particularly common. Most are isolated vertebrae, fragmentary limb bones and teeth, with only a handful of partial articulated skeletons and skulls known. These remains are important to palaeontologists because the Lower Cretaceous record of plesiosaurs is rather sparse, so Wealden plesiosaurs – rare as they are - provide an important window into this phase of plesiosaur evolution. Plesiosaur remains are span the entire Wealden stratigraphy and occur in both sub-basins, suggesting that they were long-term denizens of Wealden ecosystems. Three species of Wealden plesiosaur are currently recognised, each known by incomplete skeletons: Leptocleidus superstes (Upper Weald Clay Formation, East Sussex; also see the image above), Vectocleidus pastorum (Vectis Formation, Isle of Wight) and Hastanectes valdensis (Wadhurst Clay Formation, Hastings). Some fragmentary Wealden plesiosaur fossils clearly differ from these animals and likely represent additional, poorly known species.

Leptocleidus and Vectocleidus belong to a plesiosaur group known as Leptocleididae, an unusual lineage of Late Jurassic – Early Cretaceous plesiosaurs with necks of short or moderate length and relatively small skulls. This anatomy represents an ‘intermediate’ grade between the short-necked pliosauroids and long-necked plesiosauroids, which has caused some confusion about their relationships to other plesiosaurs. Some suggest they are a ‘relict’ lineage of early, generalised pliosauroids, but other proposal consider them derived plesiosaurids which abandoned long-necked morphologies in favour of a more generalised body plan. Whatever they are, it is noteworthy that all known leptocleidid fossils are known from freshwater, brackish or near-shore environments, suggesting they abandoned the more typical plesiosaur existence of life in open waters and spent much of their time in lakes, rivers and coastlines. This would make leptocleidids comparable to some modern seals (including Baikal seals, several types of ringed seal and harbour seals) and dolphins (such as the Irrawaddydolphins; Baiji, Chinese river dolphin, and Tucuxi, Amazonian river dolphins) which have abandoned pelagic lifestyles or, at least, make considerable incursions up estuaries and rivers in search of food. Indeed, seals and river dolphins may be the best modern ecological analogues to Wealden leptocleidids. The skulls and jaws of these plesiosaurs were equipped with large jaw muscles and conical, partially serrated teeth, ideally suited to feeding on a small bodied prey. Their diet probably mostly comprised fish, supplemented by opportunistic taking of other, small swimming animals. The four-flippered propulsion system of plesiosaurs may have been ideally suited to navigating complex and tight underwater habits in pursuit of cryptic prey, permitting for excellent manoeuvrability as well as bursts of speed.

Skeletal reconstructions of mother and foetal Polycotylus latippinus, polycotylid plesiosaurs which are not a million miles away, phylogenetically speaking, from leptocleidids. Was this strategy of birthing solitary, large calves found in leptocleidids - and other plesiosaurs for that matter - as well? From O'Keefe and Chiappe 2011; image from here.

At least Leptocleiduswas a fairly large animal for the Wealden waterways, attaining body lengths of around 3 m. This size may have dissuaded attacks from even the largest Wealden aquatic and semiaquatic predators, but the same cannot be said for their calves. ‘Calves’ is an appropriate word here: fossils of Late Cretaceous plesiosaurs (which happen to be closely related to leptocleidids) show that at least some plesiosaurs did not lay eggs like many other reptiles, but instead gave birth to a solitary, large and very well developed baby. This reproductive strategy is extremely similar to that of large mammals but is virtually unheard of in reptiles. Although live births are known in many modern lizards and snakes, only a few modern reptiles (various types of skinks) are known to produce a single, large and highly developed offspring. The development of such reproductive strategies in plesiosaurs is therefore rather remarkable (though we must be mindful that we do not know how common this strategy was across Plesiosauria). Both mammals and reptiles that invest heavily in a single offspring are highly social and engage in maternal care, which may indicate that adult plesiosaurs did the same. Perhaps Wealden leptocleidids protected their young from predators, warding off attacks from marauding goniopholidids crocodilians and other plesiosaurs until they were large enough to look after themselves.

Hastanectes valdensis: a possible pliosaur which, even at only 2 m long, is good reason not to paddle in Wealden waterways. Especially if you're a small crocodile.

Such predatory attempts may have been attempted by our third Wealden plesiosaur, Hastanectes (above). Some have suggested that Hastanectes is a pliosaurid rather than a leptocleidid, and closely related to the large, powerful members of this lineage with short-necks and large skulls armed with tusk-like teeth. If so, Hastanectes may represent a small (2 m long) version of these predators. Interestingly, no Hastanectes specimens currently known represent fully-grown animals, suggesting it may have grown somewhat larger. Even at 2 m in length, such a pliosaur would be keen predator of small and medium-sized swimming creatures in Wealden waters, perhaps taking not only fish but also regularly hunting other reptiles. This interpretation of Hastanectes has not gone unchallenged, however: some very recent studies have suggested it represents another Wealden leptocleidid.

A fourth, and largely mysterious type of Wealden plesiosaur is represented by very scant remains indeed. A solitary vertebra from the Hastings Group hints at the presence of a long-necked plesiosauroid within the Wealden. Exactly what sort of plesiosaur this represents however, and how it may have functioned within the Wealden palaeoecosystem, is unknown at present.

References

Cruickshank, A. R. I. (1997). A lower Cretaceous pliosauroid from South Africa. Annals of the South African Museum 105, 207–226.
O’Keefe, F. R. & Chiappe, L. M. (2011). Viviparity and K-selected life history in a Mesozoic marine plesiosaur (Reptilia, Sauropterygia). Science 333, 870-873.

This week saw the pre-publication of a new paper by myself and Darren Naish on one of our favourite topics, azhdarchid pterosaur* feeding habits. The article is now available in proof format in the Open Access journal Acta Palaeontologica Polonica, with the final, fully typeset version following sometime next year. Darren and I are no strangers to the long-necked, frequently gigantic azhdarchids of course, having discussed azhdarchid foraging habits at length in a 2008 paper and concluding that previously proposed lifestyles - skim-feeding, sediment probing, obligate scavenging - were inconsistent with azhdarchid functional anatomy. Instead, we proposed a novel hypothesis, that azhdarchids were 'terrestrial stalkers', basically just a sexy way of saying 'they wandered around on the ground and ate whatever they could find'. Hey, half of selling an idea is a snappy name, baby.

*Surely no-one here needs to be told what an azhdarchid is? You do? Then check out this article for a primer.

Why do we think azhdarchids were 'terrestrial stalkers'? A handy infographic explaining our reasoning, from Witton and Naish (2013). The greyed cervical vertebrae indicate the range of azhdarchid neck motion according to Averianov (2013), which we are pleased to see meeting our expectations of ground-reaching ability (see Witton and Naish 2008; Fig. 8 and caption).

We're not the only folks with opinions on azhdarchid palaeoecology of course. Although I think the terrestrial stalker idea has been generally well received, Alexander Averianov (2013) disagreed with the idea. Earlier this year, he proposed that the terrestrial stalker hypothesis is flawed for three major reasons, which can be summarised as:

Azhdarchid remains are always found in ancient lake and river deposits, which indicates they were feeding there as well.
Grounded azhdarchids were vulnerable to predation from theropod dinosaurs, being ill-suited to rapid takeoff or other means of quick escape.
We overlooked the helical jaw joint of azhdarchids in our 2008 paper. Azhdarchids possess a skewed jaw joint which laterally displaces the mandibular rami when the jaw is opened, expanding the throat region marginally. According to Averianov (2013), this is a sign of expanding, pelican-like jaws, which permitted fish to be scooped from water in flight, which is a superior hypothesis to terrestrial stalking.

After some discussion between ourselves, Darren and I decided that we should respond formally to these points - Witton and Naish (2013) is the result. In doing so, we were able to explore some aspects of azhdarchid palaeobiology a little more, as well as put some comments into print on the way we interpret the lifestyles of fossil animals. Hopefully, a lot of the things we have to say on this will be of interest to readers here, so I thought I'd provide a quick summary.

Taphonomy is not destiny
Averanov's (2013) first 'flaw' is problematic for pretty elementary reasons. It's common knowledge that all manner of fossil terrestrial animals occur in aquatic environments because that's where the majority of continental sediments accumulate. Azhdarchids routinely occur in aquatic deposits with the likes of dinosaurs, reptiles, birds and so on, but we don't assume the latter are tied to water simply because their fossils are found in ancient rivers and lakes. Ergo, we shouldn't assume this for azhdarchids either. Taphonomy does not necessarily correlate with palaeobiology. Moreover, it's not true that all azhdarchids are found in remnants of aquatic settings: some occur in ancient deserts and ash beds. There's not much else to say on this fairly basic point (check out the paper if you want to read our full response), so we'll get onto the more interesting stuff.

Killer storks, giant pterosaurs, and the Age of MurderDeathReptiles
A number of folks have asked us about the vulnerability of grounded pterosaurs to predators, and Averianov (2013) specifically mentions the problems azhdarchids would have taking off when faced with attackers ("It is hardly probable that huge azhdarchids could take wing in one go and running for acceleration is difficult in marshland conditions” - Averianov 2013, p. 207). As we note in our new paper, palaeobehaviour is hard to discuss in a truly scientific manner and we are wary of just making bold, arm-wavy comments about ancient predator-prey interactions. There are some comments we can make, however, which do not rely on crass speculation.

Firstly, modern ideas of pterosaur takeoff (which regular pterosaurophiles will know means quadrupedal launching) suggest these animals could become airborne in seconds from a standing start (contra Averianov 2013). Thus, there is little reason to think that azhdarchids - or any other pterosaurs - would have to engage in panicked running to escape predators. Quad launches also permit greater acceleration and power than bipedal launches. This may make pterosaurs actually more adept at turning tail from predators than large modern birds, which do have to engage in a little taxiing before becoming airborne. We therefore do not envisage that grounded pterosaurs - even giant azhdarchids - would struggle to escape predators when startled.

According to some, this is pretty much what the Mesozoic looked like all the time. Background borrowed from here.

We also note that while terrestrial stalking is considered an unusual lifestyle for pterosaurs, comparable ecologies are actually pretty common among modern birds. Indeed, a lifestyle of walking around and eating stuff found on the ground seems to be the 'default' foraging strategy for many bird groups, and there's no indication that this makes them atypically vulnerable to predation. This even applies to large birds which live in predator-rich environments, where big cats, dogs, hyenas and other predatory species are real dangers. We have to ask why Mesozoic ecosystems would be any different? Is it because ancient reptiles are generally portrayed as aggressive monsters who're constantly pitched in battle (above)? Maybe, but this is almost certainly wrong. Darren communicates this very clearly in our new paper:

"...the idea of azhdarchids may have been highly vulnerable to terrestrial predation labours under several probably erroneous assumptions, including viewing theropods as unstoppable killing machines, immediately pouncing on and devouring any grounded pterosaur. In point of fact, the behaviour of living predators indicates that theropods large and small likely exploited easy prey (Hone and Rauhut 2010), ignored or avoided large or awkward prey, and were not a perpetual, 24-hour menace across all environments, worldwide." Witton and Naish 2013 (In Press)

I've discussed the over-statement of aggressive behaviour of Mesozoic animals several times before, and I'm sure I'm not alone in finding portrayal of dinosaurs as angry murder/death/kill machines irritating. It's frustrating enough when seen in popular media, but particularly irksome when it seemingly influences scientific discussions. I don't want to understate predation risks, but modern animals demonstrate that behaviours like extended bouts of foraging, resting and socialising can be performed without being ripped to pieces by passing predators. Assuming the Mesozoic operated under the same basic principles, it almost certainly wasn't the 190 million year bloodbath it's often made out to be.

A giant pterosaur compared to top theropod carnivores of giant azhdarchid-bearing Late Cretaceous ecosystems. A, Tyrannosaurus rex, representing the largest known predator in Maastrichtian North America; B, Balaur bondoc, largest predatory theropod of Maastrichtian Romania; C, Arambourgiania philadelphiae, standing in for the similarly-sized azhdarchids which lived alongside A and B, respectively; D, human sleuth for scale. From Witton and Naish (2013).

The composition of azhdarchid-bearing faunas is also of interest here (above). In some parts of time and space, enormous, 10 m wingspan azhdarchids lived alongside large predators like tyrannosaurids and spinosaurids. In others, the biggest theropods were turkey-sized. In fact, in latest Cretaceous European deposits, azhdarchids are the biggest predatory animals by a huge margin, and unlikely to be bothered by any theropods once they grew beyond a certain size. In these settings, azhdarchids weren't in perpetual trouble from theropods: they were perpetual trouble for theropods. Heck, the sheer size of an adult giant azhdarchid is impressive even alongside the very largest carnivores, and we wonder if this alone would dissuade less ambitious predators. Of course, there are plenty of small azhdarchid species which may be somewhat more easily subdued by theropods, and there are plenty of faunas were azhdarchids are not large, dominant species, but it's worth stressing that some azhdarchids lived in settings devoid of serious predator risk.

Of course, there were likely some occasions when azhdarchids were caught out by predators: would this spell instant doom for the pterosaur? Not necessarily. Again, this is hard to say with confidence, but we note that large modern storks - which resemble azhdarchids more than any other modern species - can be far more dangerous than most folks realise. These birds can inflict severe, sometimes fatal injuries with their beaks when panicked and cornered. Children are seriously wounded or even killed by marabou storks when trying to harvest soft white contour feathers from these usually calm birds (Mackay 1950). Zoo staff routinely arm themselves against attack from captive jabiru storks because attacks are so frequent and vicious (Shannon 1987). Indeed, even relatively large animals like tapirs are no match for angry jabirus. These storks are not armed with razor-sharp, hooked beaks: they deliver this damage with their simple, long, pointed bills. Whether this means azhdarchids used their jaws as similarly formidable weapons is anyone's guess, but it demonstrates that azhdarchid-like bills can be used as fearsome predator deterrents if wielded properly. Remember, of course, that some azhdarchids probably had beaks over 2 m long, which 6-8 times longer than those of even the largest modern storks. An giant azhdarchid in a bad mood may be well worth avoiding.

We have some additional discussion on this point in our MS, but I think you get the gist of what we're saying. Our bottom line is not that azhdarchids could wander about Cretaceous plains without a care in the world, just that there is no reason to assume they were overtly vulnerable to predation risks. Indeed, there is evidence to quite the opposite in several cases, and there is no reason to think this is a flaw in the terrestrial stalker hypothesis.

The scoop-feeding pelican-mimic thing
This does not mean, of course, that azhdarchids had to be terrestrial stalkers just because they could walk around without being eaten immediately: water-trawling 'scoop feeding' could still be a viable alternative to terrestrial stalking. Citing the helical jaw joint of azhdarchids as evidence for a pelican-like expanding throat region, Averianov (2013)'s summation of his azhdarchid feeding hypothesis reads:

"...azhdarchids flied [sic] slowly above the water surface of large inland water bodies… looking out for fish or small fish shoals. As prey is detected, they opened the mouth, expanding the throat sac due to the spiral jaw joint, and captured fish in this scoop net, formed by the jaw rami and throat sac. Then, the head was thrown abruptly back by extension of the neck in the posterior region and prey was swallowed.” Averianov 2013, p. 209

Although far from the first author to compare pterosaur and pelican jaws favourably, this is the first time (to my knowledge) that specifically pelican-like throat expansion has been proposed for pterosaurs and linked to a certain foraging strategy. The exact method of foraging suggested here - a mix of 'scoop' and skim-feeding - does not have a modern representative but is clearly an 'extreme' lifestyle, likely to incur considerable loading on azhdarchid skulls, jaws and neck. As with some other proposed 'extreme' azhdarchid lifestyles, like skim-feeding, we'd expect to see considerable specialisation in azhdarchid anatomy to reflect this but, unfortunately, we don't. Indeed, our assessment of this feeding mechanism suggests it is fraught with biomechanical and functional problems, in addition to failing tests offered by comparative anatomy.

Extending jaw area measurements of the brown pelican and select azhdarchid pterosaurs. Note the pelican is being rather lazy with it's jaw bowing, and yet still achieves much greater area increase than the azhdarchids. From Witton and Naish (2013).

We investigated the plausibility of 'scoop-feeding' in several ways. Firstly, we measured flexed and unflexed jaw areas of azhdarchids and pelicans to compare their range of jaw expansion (above). It turns out that azhdarchid jaws achieve pretty negligible amounts of jaw area increase even when an unrealistic amount of jaw flexion is permitted. By contrast, a bowed pelican jaw achieves an enormous area increase even when not trying very hard: we could only measure a partially bowed pelican jaw, but even this left pterosaur jaw expansion looking pretty pathetic. We utilised the same area measurements of azhdarchid jaws to calculate drag forces incurred on an azhdarchid neck during the 'scoop' phase of foraging, when the entire mandible has to be ploughed through the water. Unsurprisingly, the resultant drag forces were pretty huge, and are several hundreds times higher than the strain permissible by an azhdarchid fifth neck vertebra (hat tip to Mike Habib for suggesting using our jaw area data in this way). An azhdarchid that lowered its jaw into the water to try 'scoop feeding' would die a horrible, horrible death. This, of course, has further negative implications on the idea that azhdarchids were skim-feeders: even partial submersion of their mandibles was likely to snap their necks.

Brown pelican jaws in action. From Schreiber et al. (1975)

As if it didn't look bleak enough for 'scoop feeding', things took a turn for the worse when we compared azhdarchid and pelican jaw anatomy. Pelican mandibles and throats are amazingly freaky and specialised, and these adaptations directly relate to their manner of grabbing prey (above). Their foraging adaptations include differentially mineralised jaw bones which create distinct 'hinges' at points along the jaw; short mandibular symphyses; loosely-jointed posterior jaw bones; super-elastic throat tissues; reduction of the tongue, and skin-like beak tissues which permit jaw flexion. At least some of these features should be detectable in jaw fossils, but no indication of similar adaptations are found in azhdarchid jaws. In fact, directly opposing anatomies are seen in most instances. But what of the helical jaw joint? Isn't that functionally significant? Probably not, because helical jaw joints are far from unique to azhdarchids, being seen across all manner of archosaurs. Given the range of ecologies encapsulated by archosaurs with helical jaw joints, they're clearly of questionable, if any, significance to foraging strategies. It seems that the potential for azhdarchid jaws to perform expanding actions are limited at best, and we should stop referring to their gently-bowing mandibular rami as being 'pelican-like': they're really nothing of the sort. Indeed, the only animals we know of with even remotely pelican-like jaws are rorqual whales. I could go on (and we do in the paper), but I guess it's already clear that we don't consider 'scoop feeding' a viable alternative to terrestrial stalking at all.

Extreme lifestyles require extreme anatomies. Here's a summary of what you need to be a skim-feeding species, according to the modern skimming bird, Rynchops. From this post.

A closing point
In sum, we more-or-less go full circle in our new study, coming back to terrestrial stalking as the most likely current interpretation of azhdarchid palaeecology. Reflecting on this study, and the other studies into pterosaur palaeoecology I've been involved with (Humphries et al. 2007; Witton and Naish 2008, 2013; Witton 2012), it strikes me that proposed 'extreme' foraging methods are almost always inferred from a few anatomical characteristics rather than entire bauplans. This is certainly the case for 'scoop feeding' and skim-feeding (e.g. Kellner and Langston 1996; Martill 1997; Averianov 2013). Why do we keep doing this? It almost seems that our default assumption for pterosaurs is that they lived crazy, outlandish lives which we select evidence to verify. This is a completely backwards and unscientific way of assessing ancient animal habits. Modern animals with 'extreme' lifestyles wear their adaptations across their bodies, suggesting that we need to look at the entire picture of extinct species before we propose our palaeoecological interpretations (see details on skim-feeding adaptations, above). Folks like myself and Darren currently champion the terrestrial stalker hypothesis not because it's our 'pet idea', but because it's currently the only hypothesis which considers the entire azhdarchid bauplan (see our infographic at the top of the post), is consistent with biomechanical or functional parameters of azhdarchid anatomy and matches lifestyle predictions made through comparative anatomy. It may well not be the last word on this topic, but at least there's a foundation of science to it, which is more than can be said for a lot of proposed pterosaur lifestyles (see Witton 2013 for a review). If we're expecting to understand the palaeoecology of these animals in detail, we really have to move away from our rather basic, selective interpretations of their anatomy and provide more detailed, dedicated assessments.

I'll have to stop there for now. Be sure to check out the rest of Witton and Naish (2013) for further details on this study and, for more on pterosaur palaeoecology and azhdarchids in general, you may want to check my book (Witton 2013).

References

Averianov, A. O. (2013). Reconstruction of the neck of Azhdarcho lancicollis and lifestyle of azhdarchids (Pterosauria, Azhdarchidae). Paleontological Journal, 47(2), 203-209.
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.
Kellner, A. W., & Langston Jr, W. (1996). Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from Late Cretaceous sediments of Big Bend National Park, Texas. Journal of Vertebrate Paleontology, 16, 222-231.
Mackay, H. (1950). The quaint Marabou stork. Zoo Life 5, 91-92.
Martill, D. M. (1997). From hypothesis to fact in a flight of fancy: The responsibility of the popular scientific media. Geology Today, 13, 71-73.
Schreiber, R. W., Woolfenden, G. E. & Curtsinger, W. E. (1975). Prey capture by the Brown Pelican. The Auk, 92(4), 649-654.
Shannon, P. W. (1987) The Jabiru Stork (Jabiru mycteria) in zoo collections in the United States. Colonial Waterbirds 10, 242-250.
Witton, M. P. (2012). New insights into the skull of Istiodactylus latidens (Ornithocheiroidea, Pterodactyloidea). PloS One, 7(3), e33170.
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(5), e2271.
Witton, M. P. & Naish, D. (2013) Azhdarchid pterosaurs: water-trawling pelican mimics or "terrestrial stalkers? Acta Palaeontologica Polonica (in press)

An old, old sight, and yet somehow so young.

Finding time to blog has been more-or-less impossible of late. In the effort to keep things ticking over, I thought I'd post this quick painting as a prelude to a post I hope to have together soon. The image is, technically speaking, a piece of palaeoart, but shows a very, very dated interpretation of a fossil species. Retropalaeoart, if you will.

Question is, what is the main animal in this image? I'm not aware of any similar depictions of this taxon (which doesn't mean they don't exist, but they're probably rare) and several colleagues have already struggled to work out what this is meant to be. I'm not going to reveal the answer just yet, but feel free to leave guesses below in the comment feed. Note that the literature used to inform this reconstruction is rather vague on many anatomical details, so a fair bit of interpretation and imagination were used to put this together. That said, the identity of this animal is not that obscure, and I'm sure many readers will quickly grasp what I'm attempting to do here. The first person to guess correctly wins the satisfaction of being the first person to guess correctly.

Hopefully, the answer will be revealed in the next couple of days. Good luck!

A couple of days ago, I played for time in my posting schedule by asking readers to identify the deliberately outdated reconstruction of a fossil species shown above. I'm relieved to say the event was not a complete washout, with several dozen suggestions made in the blog comment feed and on Facebook - thanks to those who made suggestions. Most proposed that this animal is an archaic view of a marine reptile, perhaps a placodont, mosasaur, pliosaur or, best of all, Edward Cope's famous backwards Elasmosaurus. Others thought it may be an early interpretation of Basilosaurus or a Megalosaurus in its lizard-like 1820s guide.

None of these are quite on the money. I did try to leave a few hints in the image and article. The post title and keywords hinted at a reptilian identity; I mentioned that the interpretation is very, very old, and that the literature describing this animal was rather vague and open to a lot of interpretation. The marine reptiles in the top left are deliberate nods to the article describing the habits of the mystery animal, which proposed it 'might keep in check the Crocodilians and Plesiosauri'. Perhaps the biggest giveaway was the illustration caption, which read "An old, old sight, and yet somehow so young.", a quote from Moby Dick. I'm sure a lot of you have already put these hints together but, in case it's not obvious, the image above shows my rendition of Cetiosaurus as a gargantuan reptilian superpredator of Mesozoic seas, as described by Richard Owen in 1841. Of course, we also know Ceitiosaurus, the 'whale lizard', as (pretty much) the first sauropod ever named, so another way to view this is as retropalaeoart of a sauropod. Congrats to Mike Traynor, Myungkeun Ryu and Tim Morris for guessing correctly. Please treat yourselves to an extra spoonful of peas for dinner.

How is that a sauropod?
It's widely known that sauropods were once thought to be marine animals, but I'm sure some of you are wondering just how I came to reconstruct this animal in this guise, perhaps even if you are familiar with Owen's (1841) description (you can download this, for free, here). There's a lot of points to consider here, the most important of which is that this is entirely based on the very first report of a sauropod, not any later considerations. My Cetiosaurus is how it may have been imagined in 1841, perhaps after hearing the first public discussion on them (Owen's 1841 paper is actually a summary of this talk by an anonymous author, not a manuscript penned by the man himself). The illustration attempts to showcase the basic thrust of Owen's hypothetical animal along with a few nods to specific details he mentions in his description, along with some palaeoart trends of the mid-1800s.

How much of the world first met what would become sauropod dinosaurs: the title of Owen's 1841 lecture memoir. Seven pages of text, no specific names, no specimen numbers, no holotype, and no illustrations, and the beginning of a monstrously complex taxonomy which has only recently been revised into a useful format.

The first sauropods, as with many dinosaurs, were not recovered from anything like complete remains. Cetiosaurus was mostly described from caudal vertebrae and a few other bones, including limb elements and a partial shoulder girdle, and that was about all. These bones were mostly collected from Jurassic rocks of Oxfordshire, but others came from similarly-aged deposits from other locations in south east England. Owen's Cetiosaurus was subsequently represented multiple individuals without overlapping components, hampering any hope of attaining a sense its relative proportions. As such, virtually none of the iconic aspects of sauropod appearance were apparent in 1841, save for one: Cetiosaurus was clearly huge. Owen stressed how the fossils he had were much larger than those of an elephant or even Megalosaurus, and that only Iguanodon and 'full-sized whales' had bones of comparable size. Remember that many still considered Iguanodon as a lizard-like animal of tremendous length in 1841, not the more sensibly proportioned, rhinoceros-like animal we think of as the 'Victorian Iguanodon'. No size estimates for Cetiosaurus were provided in the 1841 lecture, but it's clear that Owen thought it was seriously big.

It was not only the appearance of this animal which remained enigmatic: it's affinities among Reptilia were not immediately clear. It is often reported that Owen initially considered Cetiosaurus to be a giant marine crocodile, but this is not apparent from his 1841 lecture (Taylor 2010). Cetiosaurus was compared with a number of other animals, including whales, marine reptiles, crocodiles, lizards and several genera which would later be recognised as dinosaurs. The nature of the vertebrae and the presence of a claw were sure fire signs that Cetiosaurus was of saurian origin and not, despite its size, an ancient cetacean. Owen did note that several aspects of its bone structure were reminiscent of whale bone however. We should recall here that Owen was primarily working from caudal vertebrae, which are far more whale-like in their guise than the complex, hollowed cervical vertebrae we may think of when we imagine sauropod vertebrae (below). Several favourable comparisons were made between Cetiosaurus, dinosaurs and crocodiles, but Owen refrained from allocating Cetiosaurus to a specific reptile group until 1842, when he referred it to Crocodilia (Owen 1842).

A caudal vertebra referred to Cetiosaurus by Owen in 1853, now referred to Pelorosaurus. It's not difficult to see why Owen considered vertebrae like this to be whale-like. From Wikipedia.

What of its habits? Again, there's precious little to go on here from Owen's lecture. Owen suggested the animal had to be aquatic because its bones had a cancellous texture reminiscent of cetacean bones. The size of the animal suggested it was not likely to populate small rivers and streams and probably lived in larger aquatic settings - the marine realm. On diet, it's reported that "the surpassing bulk and strength of the Cetiosaurus were probably assigned to it with carnivorous habit, that it might keep in check the Crocodilians and Plesiosauri" (Owen 1841, p. 462). Little other evidence for this predatory existence is provided, although fossils of "large conical teeth" were mentioned as possibly belonging to Cetiosaurus.

The lost world of Cetiosaurs, superpredator
By now, we're starting to emerge with a picture - vague as it is - of Owen's Cetiosaurus, c. 1841. A nondescript, gigantic, whale-like marine saurian which predated other marine reptiles is about as far as we can go but, hey, that's still pretty neat. Sadly, it seems no-one thought Owen's Cetiosaurus was worth illustrating and we can't really be sure what Owen, or any of his contemporaries, thought about its life appearance. This is a weird fact in itself, because reconstructing extinct animals was becoming quite fashionable around 1840. Maybe Cetiosaurus was just too poorly known to be professionally illustrated, or perhaps its relatively quick ushering into Crocodilia meant that, despite its size, it just wasn't exciting compared to the then newfangled dinosaurs and other more 'exotic' fossil species. But still, people must have pondered the life appearance of Cetiosaurus in 1841. It's not like a giant, whale-like killer reptile isn't sufficient fuel for the imagination. What must have Owen's lecture audience been thinking as they left his talk? The learned folks of the 1800s must have speculated and imagined ancient worlds as much as we do, and who knows what bizarre anatomies and behaviours they envisaged? Perhaps their speculations were even more elaborate than ours, their knowledge being far less constrained by data than our own.

My quick illustration here is an attempt to recapture some of this lost imaginary wonder, showing how someone in the 1840s may have imagined Owen's whale-lizard without any concept of what sauropods were actually like. Of course, given how little information we have to work with from the 1841 lecture, there's a lot of room for artistic manoeuvring here. I'll bet you could change almost every detail of this illustration and still call it Cetiosaurus c. 1841. In fact, it'd be very interesting to see what others might come up with based on the same information - I'd gladly compile a compendium of superpredator Cetiosaurus works for a blog post here if people send them in. In the meantime, I'll explain how my 1841 Cetiosaurus ended up as it did.

Material of Cetiosaurus oxonensis described by Philips (1871), the single species we now recognise within Cetiosaurus. These were the first sauropod remains which offered a significant glimpse into sauropod biology, and changed perceptions of Cetiosaurus forever. Image from Wikipedia.

Overall, my Cetiosaurus looks more like an oversized lizard than anything else, because many of the earliest renditions of fossil animals are very lizard-inspired. I guess the concept of 'reptiles' was quite restricted in the early 1800s. The tail is not shown in a crocodile-like guise because Owen noticed some differences in the cross-sectional structure of croc and Cetiosaurus caudals, but it is rather long because the caudal vertebrae of Cetiosaurus were reported as proportionally longer than those of Megalosaurus. Reflecting the fact that the tail was one part of the body we had some knowledge of in 1841, I thought this should at least look a bit sauropod-like. I tried to emphasise the 'whale' aspect of the 'whale-lizard', making the body rather bulky but keeping the limbs rather reduced, a bit like early cetaceans. In keeping with the nods towards dinosaurs and crocodiles, I decided not to make the limbs into flippers, and maintained a healthy set of claws on the end of the digits. The integument is a mix of smooth, whale-like skin and crocodilian-like scales and scutes. As is typical of early prehistoric reptile restorations, the head is generically reptilian, looking a bit like those of lizards or short-faced crocodylomorphs. Making the head small was an attempt to emphasise the bulk of the body and lean towards 'generic' reptile proportions. The prey animals are, as mentioned above, a deliberate nod towards Owen's lecture and serve to show how enormous this Cetiosaurusis meant to be.

What became of Owen's Cetiosaurus?
Unlike other early, erroneous reconstructions of dinosaurs, the idea of Cetiosaurus as a marine superpredator is barely more than a footnote in stories of dinosaur discovery, despite this interpretation remaining unquestioned for several year. Perhaps history has largely forgotten this animal because it was not widely reconstructed. With retrospect, we might argue that Gideon Mantell (1850) first put forward an argument against this reconstruction when he proposed a terrestrial existence for his then new Pelorosaurus - an animal based on the holotype for Owen's Cetiosaurus brevis*. However, Mantell also argues that Pelorosaurus is distinct from Cetiosaurus because it was a terrestrial creature: he didn't outright refute the concept of a reptilian superpredator itself. Perhaps John Phillips (1871) was the man who truly put Owen's aquatic superpredator to rest. He described much more complete Cetiosaurus remains (above) which provided a new understanding of its anatomy and relationships. Although the long neck was still not known, Phillips (1871) was able to rationalise a semi-aquatic creature with well-developed limbs, a parasagittal gait and large body size. He was also the first to propose that Cetiosaurus may have been a dinosaur. This represented a large stride towards the reality of sauropod dinosaurs, although these revelations were quickly superseded: the Bone Wars, and the American sauropod bounty they represent, were only a few short years away. The sauropod discoveries they brought rendered Owen's superpredatory marine Cetiosaurus a completely obsolete, erroneous interpretation of sauropod palaeobiology, and one that Owen was probably very happy to forget about.

*Cetiosaurus has a hella confused taxonomic history which has only recently been sorted. Over a dozen Cetiosaurus species were named for fossils across Britain by Owen and other workers, spreading Cetiosaurus across time, space and sauropod phylogeny. We now only recognise one species of Cetiosaurus, C. oxoniensis. See Upchurch and Martin (2003) for a review of this taxonomic debacle.

And that's all I've got time to say for now. I'll leave you with another image of some waterlogged sauropods, this time of a more conventional variety. The animals here are Pelorosaurus conybeari, a somphospondyl from Lower Cretaceous Britain. P. conybeari, of course, is another aspect of the Cetiosaurus story, being one species to come out of the Cetiosaurus taxonomic complex. That's a whole other article however - check out Taylor and Naish 2007 if you want to know more. Thanks again for contributing to the 'guess the retrosaur' game if you commented!

Pelorosaurus conybeari, the nomenclatural destiny of some Cetiosaurus material, in what a great Alabamian philosopher once referred to as 'big ol' fat rain'.

References

Owen, R. (1841). A description of a portion of the skeleton of the Cetiosaurus, a gigantic extinct saurian reptile occurring in the oolitic formations of different portions of England. Proceedings of the Geological Society of London 3, 2: 457-462.
Mantell, G. A. (1850). On the Pelorosaurus; An Undescribed Gigantic Terrestrial Reptile Whose Remains are Associated with Those of the Iguanodon and Other Saurians in the Strata of Tilgate Forest, in Sussex. Philosophical Transactions of the Royal Society of London, 140, 379-390.
Owen, R. (1842). Report on British Fossil reptiles, Pt. II. Reports of the British Association for the Advancement of Science 11: 60–204.
Phillips, J. (1871). Geology of Oxford and the valley of the Thames. Clarendon Press, Oxford, 529 pp.
Taylor, M. P. (2010). Sauropod dinosaur research: a historical review. Geological Society, London, Special Publications, 343(1), 361-386.
Taylor, M. P., & Naish, D. (2007). An unusual new neosauropod dinosaur from the lower cretaceous hastings beds group of East Sussex, England. Palaeontology, 50(6), 1547-1564.
Upchurch, P., & Martin, J. (2003). The anatomy and taxonomy of Cetiosaurus (Saurischia, Sauropoda) from the Middle Jurassic of England. Journal of Vertebrate Paleontology, 23(1), 208-231.

Some parts of Lower Cretaceous Britain was subject to regular, short-lived wildfires caused by lightning strikes after long dry seasons, phenomena which played an integral role in forming the fossil-rich plant debris beds of the Wessex Formation. Here, the early tyrannosauroid Eotyrannus lengi stalks the edge of such a wildfire. Note that this Eotyrannus is based on new skeletal reconstructions presented in recent papers (e.g. Naish 2011), not the better known, original reconstruction presented by Hutt et al. (2001).

If you're into Mesozoic reptiles, you could find yourself in much worse places than southern England. Much of the exposed geology in the southern part of the UK belongs to a unit known as the Wealden Supergroup, a series of Lower Cretaceous rocks representing ancient alluvial fans, river channels and floodplains. Many of Britain's Cretaceous dinosaurs and pterosaurs stem from Wealden deposits, along with numerous other types of fossils including armoured dinosaurs, plesiosaurs, famous sauropods and weird, burrowing amphibians.

A slumped plant debris bed in the Wessex Formation, Brighstone Bay, Isle of Wight. Image borrowed from the UK Fossil Network forums, by one only known as 'Alan'.

Fossils occur found throughout Wealden rocks but, as is often the case in palaeontology, the majority are concentrated into narrow horizons. One type of Wealden fossil bed deserves special praise and attention: the plant debris beds of the Wessex Formation. Plant debris beds are narrow, green-grey bands of pebbles, mud and plant debris which comprise only a fraction of the Wessex strata, but represent a tremendous source of its fossils. Indeed, these beds provide the majority of Britain’s Cretaceous dinosaur species as well as many other fossil species, including many rare microvertebrates. Debris bed fossils range from small, badly preserved portions of plant and isolated, broken bones, teeth and scales, to substantial chunks of very large organisms - partial or near-complete animal skeletons and 3 m long logs (below). With continental deposits relatively rare in the Lower Cretaceous, the plant debris beds represent an important window into European faunas of this time, and studies into their palaeontology are ongoing (see below).

Enormous, pyrite-riddled chunks of fossil tree trunks, like these bits of the conifer Pseudofrenelopsis, litter the beaches beneath the Wessex Formation after weathering out of plant debris horizons. The ruler in this image is 150 mm long.

The story behind the plant debris beds has intrigued scientists for decades, leading to detailed research into their formation. Because the Wessex Formation represents a complex environment - an arid floodplain dominated by enormous, meandering rivers which were bordered by wooded highlands, and subjected to long summer months with temperatures well over 30°C but short, cool and rather wet winters - several different ideas about debris bed genesis have been proposed (best summarised and explored in Sweetman and Insole 2010). Plant debris bed sediments bear characteristics of debris flows; powerful, water-saturated sediment surges which ooze across landscapes to create poorly organised pools of mud and detritus. Such flows were clearly not regular events in the Wessex palaeoenvironment. Although many plant debris beds are known, they are relatively minor components of the Wessex Formation and are randomly distributed within Wessex strata. They were not, therefore, seasonal events and must reflect particularly unusual or extreme environmental conditions. Some have suggested that intense river flooding events and bank breaches account for these deposits, but plant debris beds are not associated with river sediments in a manner predicted for breached riverbanks deposits. Because the plant remains they contain are similar to leaf-litter found in modern forests, it is likely that they originated external to the Wessex floodplain, perhaps starting on nearby upland, wooded areas, not within the river channels. Indeed, debris flows generally start on slopes when water saturated soils and sediments become too heavy and unstable to resist gravity. The slopes required to begin plastic sediment flows are not large, and the relatively low upland areas surrounding the Wessex floodplain were likely sufficiently inclined to catalyse debris flows. Topographic highs on the floodplain itself may also have done the job. Presumably, the heavy rainfalls incurred during winter seasons was the water source which saturated Wessex soils to a critically unstable level.

The secret ingredient
This is only half the story, however. Sediment flows do not start after most heavy rainfalls because precipitation is mostly absorbed by leaf litter, intercepted by plant canopies, and soils are bound by vegetation. We know that the Wessex palaeoenvironment was fairly well-vegetated, and it is likely that its plants prevented Wessex slopes from collapsing. The secret ingredient required to make a debris flow, it seems, was fire (above). A common component of all plant debris beds is the abundance (about 50%) of burnt plant material, suggesting they were only formed after fires - likely caused by lightning strikes after long, dry summers- had swept through surrounding areas. An absence of burnt tree trunks suggests Wessex wildfires were not particularly intense, their main effect being removal of canopy cover, low-level vegetation and leaf-litter. This left the environment denuded enough for rainwaters to directly interact with soils and underlying sediments. Modern wildfires raise soil temperatures to hundreds of degrees and alter their physical properties, reducing water capacity and increasing erodibility. The result is a perfect recipe for debris flows: unprotected, easily transportable soils and sediments are left exposed to heavy precipitation, which likely arrived in earnest during winter storms.

Model of plant debris bed deposition on the Wessex Formation floodplain. Based on Sweetman and Insole (2010).

The range of sediment and fossil sizes within the plant debris beds indicate that they did not travel far, maybe a few kilometres at most, but they hoovered up any organic and sedimentary material they encountered. Large sediment flows can travel relatively quickly – up to 16 kph – and carry objects weighing many tonnes. Large dinosaur carcasses and tree trunks would be carried without hesitation by flowing oozes of debris moving across the Wessex floodplain. The surges finally lost momentum when they reached depressions such as ponds, oxbow lakes, abandoned river channels or simply topographic lows, creating the thin bands of sediment we can see today in Wessex Formation cliffs. The rarity of complete animal remains suggests that few animals were killed in the transportation process, and most vertebrate fossils probably represent bones or carcasses collected en route by the debris flow. This model for plant debris bed formation is, of course, rather generalised and may not apply to all beds. Each plant debris horizon is unique and, although this model likely accounts for at least some aspects of each, each has its own characteristic depositional history. Interestingly, no other fossil horizons match the sedimentological properties of the plant debris beds, making them important to not only palaeontologists, but also sedimentologists.

It is, of course, palaeontology which benefits most from these deposits however. Ongoing examination of the debris beds fossils, largely by renowned Wealden expert Steve Sweetman, continues to reveal new discoveries. Scientists now recognise the plant debris beds as key sources of Cretaceous microfossils as well as larger, macro-scale remains. These are extracted by sieving large quantities (literally tonnes) of plant debris bed sediment, followed by many hours hunched over microscopes to analyse and identify the new finds. This hard work has certainly paid off, adding significant detail to our understanding of the Wealden palaeobiota (below). We now know that dinosaurs were only a fraction of the tetrapod fauna in these environments, with lizards, amphibians and other small animals comprising the bulk of Wessex diversity. New discoveries are still being made, and it's an exciting time to work on Wealden fossils.

How plant debris beds changed the world. A, Wessex Formation tetrapod assemblage prior to bulk sampling and detailed study of plant debris bed fossils; B, the same assemblage after. Data from Sweetman and Insole (2010).

Plant debris beds conservation
The exciting fossil content and accessible nature of many plant debris beds has made them a favourite source of fossils to hobbyists, private collectors and professionals for centuries. This interest has undoubtedly contributed to our detailed understanding of the Wealden fossil assemblage and will continue to do so in future. It is essential, however, that plant debris beds and other Wealden exposures are treated with care and responsibility. All too often, a walk along Wessex Formation exposures reveals depressing signs of geological vandalism: holes bulldozed into slumped cliffs in vain efforts to seek fossil-bearing horizons; messages carved into soft sandstones; dinosaur footprint casts with smashed toes, and even trackways with individual prints removed using power tools. Plant debris beds are often more conspicuous by the smashed rocks surrounding them than their lithological features. While some geological vandalism clearly reflects activities of bored, idle individuals, other types - and particularly that associated with debris beds – reflects the desires of eager individuals to discover and excavate fossil remains. We have to keep this in check. Over-enthusiasm not only risks damaging important specimens but also the surrounding sediments and other, less desirable fossils, both of which offer essential details on the depositional context of a fossil specimen. Remember that hammer blows do not only remove overburden, but also smash whatever lies beneath the surface.

The point here is not, of course, that Wealden fossils should be the sole remit of trained collectors, but that we should all be conscientious about our geological heritage. It is often far wiser, for instance, to alert local museum or university staff about an exciting find before collecting it, rather than risking damaging the specimen and it’s geological context by taking it immediately. If nothing else, contacting local professionals can provide sound advice on an appropriate manner to collect and preserve fossils. As with any fossil discoveries, accurate records must be made about the location and horizon of a new find and, if the specimen looks like it may be important, collectors should strongly consider accessioning their finds to a museum. Collectors who work with museums and scientists are frequently involved in the science that can follow a new discovery, helping to analyse and document the find in scientific papers and books. I can vouch from personal experience that this can happen relatively quickly. A new Wealden fossil accessioned to Dinosaur Isle (the Museum of Isle of Wight Geology under any other name) or the Natural History Museum seems to always get local palaeontologists buzzing, and several Wealden experts are well known for analysing new specimens within weeks of their arrival. If they are important, they end up being written up into technical papers, may be further featured in other palaeontological books and media, and may even end up on public view in museums.

What you'll want to understand fossils from plant debris beds, or any other part of the Wealden, for that matter.

How do you know if a fossil is 'important' enough to bring it to the attention of expert? Fossil identification guides, such as the excellent and highly comprehensive English Wealden fossils (Batten 2011) and Dinosaurs of the Isle of Wight (Martill and Naish 2001) are a useful means to gauge not only the identification of a Wealden fossil find, but also how ‘significant’ it may be. Many Wealden vertebrates are especially poorly known and new data on them is highly sought after, so it may be worth getting any well-preserved vertebrate material checked out. Doing so ensures that the window into Lower Cretaceous Britain offered by these remarkable beds remains widely open to all, which seems only right considering the importance of of these beds to British palaeontology.

References

Batten, D. J. (ed.) (2011). English Wealden Fossils. The Palaeontological Association, London.
Hutt, S., Naish, D., Martill, D. M., Barker, M. J. & Newbery, P. (2001). A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22, 227-242.
Martill, D. M. & Naish, D. (2001). Dinosaurs of the Isle of Wight. The Palaeontological Association, London.
Naish, D. (2011). Theropod dinosaurs. In: Batten, D. J. (ed.) English Wealden fossils. The Palaeontological Association (London), pp. 526-559.
Sweetman, S. C., & Insole, A. N. (2010). The plant debris beds of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England: their genesis and palaeontological significance. Palaeogeography, Palaeoclimatology, Palaeoecology, 292(3), 409-424.

The carcharodontosaurian Neovenator salerii stalks a pair of rebbachisaurid sauropods in Lower Cretaceous Britain, using darkness as cover. (If this image is impossibly dim, a brighter, albeit less atmospheric version can be seen at the end of the post.)

Finding time for Blogging has recently become quite difficult despite no shortage of topics to cover or new paintings to post. In the interest of keeping things alive, here's a quick painting I recently finished which tackles that most traditional subject of dinosaur palaeoart: predation. This is a rare topic for my work because the ferocity, speed and armaments of theropods and their prey are subjects of so many depictions that I almost find them artistically off-putting. For all their dynamism - gaping maws, slashing claws, wrestling limbs - they've become so common that they've become (whisper it quietly) a bit boring. Even the most exciting experiences become dulled if overexposed, and we may have hit that mark with dinosaur predation scenes. Not to mention that a lot of the overly-done operatics associated with dinosaur predation art really start to grate after a fashion. Theropods roaring at their prey; 'slasher poses', animals wrestling in long, drawn out battles; completely mismatched combatant species which bear little resemblance to predator/prey interactions in modern times (seriously chaps: stop drawing a dromaeosaurs attacking animals hundreds of times their size - they're not freakin' superheroes!), and so forth. So yes, for the most part, I switch off when I see depictions of dinosaur predation in favour of things which I find more conceptually interesting. Like, er... animals standing around doing nothing, lying down, walking about or perhaps, if I'm feeling adventurous, chewing a leaf.*

*Bear in mind that, in being British, I'm allergic to excitement.

My interest in dinosaur predation art was piqued recently however thanks to re-watching the excellent BBC series Planet Earth and The Life of Mammals. Both feature copious amounts of footage filmed at night using infra-red lights, revealing how many animal species are as active nocturnally as they are during the day. Many species undertake complex nocturnal activities in spite poor night vision, and it's obvious that this brings clear advantages to species with generally higher visual acuity or those with eyes specifically adapted to work well in dim conditions. Generally speaking, this means advantage: predators.

Did the same apply to Mesozoic ecosystems? Possibly. We can currently only speculate on the day-night activity cycles of ancient animals (and no, using sclerotic rings and orbit shape to infer nocturnality as proposed by Schmitz and Motani [2011] doesn't work: see Hall et al. [2011]), but given what we know of dinosaur physiology and palaeoecology, facultative nocturnal habits for some species doesn't seem out of the question. Theropod dinosaurs, like modern carnivores, often have more acutely developed senses than the herbivores they likely often preyed upon, and it isn't crazy to think that some would use this to their advantage by hunting at night. We may further speculate that - like some modern carnivores - nocturnally active theropods punched above their weight, attacking unusually big or dangerous prey they because their ability to remain undetected is that much greater (see, for a famous modern example, the lions and elephants in the BBC video below).

From here, it's easy to see how I came up with the image above. It shows the carcharodontosaurian Neovenator, one of the largest theropods known from the Lower Cretaceous Wessex Formation, creeping close to a couple of rebbachisaurid sauropods (a relatively recent addition to the Wessex dinosaur fauna, but currently not represented by any name-bearing material). The Neovenator can see the sauropods with much greater clarity than they can see it, although they are not completely oblivious to its presence. I've tried to instil a sense of agitation and nervousness about them, brought on by the proximity of something which sounds and smells like trouble. Despite its ocular advantage, the Neovenator is not charging in with blazing teeth in typical palaeoart fashion, instead biding its time, keeping low and quiet, and waiting for the right moment to launch an attack. The sauropods are, after all, a bit bigger than it is (estimated as 9 m long by Mannion 2009, compared to 7.5 m for Neovenator) and a lot heavier. I don't imagine Neovenator would normally take prey as large as this, and is only taking such a chance because the night has shifted odds slightly in its favour. Still, a clumsy move would not only ruin a successful stalk but also risk injury, so caution is the best policy. Maybe the copse behind the sauropods is part of the plan too, with Neovenator driving the sauropods into a setting where they're likely to encounter unseen obstacles and pitfalls. Hopefully, the dim nature of the painting helps convey some of the uncertainty and dread that the sauropods are experiencing. Like the sauropods, we can't see much, only just enough to be sure that the rebbachisaurids are in trouble, and that the game is currently Neovenator's to lose.

I've not had the time to check thoroughly, but it does seem that images of dinosaurs in near darkness are pretty rare, and maybe that's something worth thinking about changing. Palaeoart is primarily about showing off the anatomy and form of animals but, if we're trying to create mood, we may want to take bold steps away from clearly lit subjects shown in broad daylight. There's a lot of atmosphere to be found in the unseen or the murky and, as with adding atmosphere to any visual medium, less is often more. Using extremes of lighting or visually-limiting weather conditions may obscure some details of the animals we're aiming to show, but it can tell us a lot about the biology and 'character' of a particular species. An 'extreme' environment becomes a character in its own right, and the animals have to respond to their surroundings rather than simply existing within them. I enjoyed painting these Pelorosaurus in a rainstorm (below), for instance, because the picture seems to convey how tough these animals would have to be. There's no shelter large enough for sauropod-sized animals, so they simply must have endured any awful conditions thrown at them. This isn't a great picture for saying 'this is what Pelorosaurus looked like', but we get a good sense of the hardy nature of these animals, as well as the message that their physiology is capable of sustaining them through hard times. Hopefully, the barely-seen postures and positioning of the animals in the predation scene at the top of this post convey a similar sense of character, as well as throwing some new light (or removing it, I guess) from a familiar palaeoart subject. It would be remiss of me to talk about atmospheric palaeoart without mentioning Doug Henderson's new online gallery, a site the internet has sorely needed for some time and a veritable masterclass in using environments to create moody, character-filled palaeoart.

Pelorosaurus conyberi in the rain, looking all tough and moody. For more on this image, head to this post.

So that's my brief take on dinosaur predation then: a barely discernible scene of virtually immobile, quiet animals without a single tooth, claw or roar in sight. Coming next (probably): something more substantial on a boring old ornithopod that's on the lee slope of fame.

UPDATE (almost immediately after posting): Predictably, a couple of people are suggesting the image at the top of the page is a little dim. Here's a slightly brighter version to show what's going on.

References

Hall, M. I., Kirk, E. C., Kamilar, J. M., & Carrano, M. T. (2011). Comment on “Nocturnality in dinosaurs inferred from scleral ring and orbit morphology”. Science, 334(6063), 1641-1641.
Mannion, P. D. (2009). A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England. Cretaceous Research, 30(3), 521-526.
Schmitz, L., & Motani, R. (2011). Nocturnality in dinosaurs inferred from scleral ring and orbit morphology. Science, 332(6030), 705-708.

Retrosaur Iguanodon, c. 1854. Based, of course, on the sublime work of Benjamin Waterhouse Hawkins.

Space year 2014 marks the 189th anniversary of the naming of a dinosaur icon, Iguanodon. The major beats of the discovery and research history of this Lower Cretaceous herbivore are so well-established within palaeontological lore that most readers will need little reminder of it here. We all know that Iguanodonwas first known from large, iguana-like teeth found in southern England in 1822, supposedly by Gideon Mantell's wife, which we all also know is widely considered an embellished tale: the teeth were probably found by Mantell himself or quarrymen. Equally familiar is Mantell's naming of Iguanodon in 1825 with the first specific name given to this genus, anglicus, added by Friedrich Holl in 1829. As the second dinosaur to be named, Iguanodon was part of the trio of dinosaur genera used by Richard Owen to name Dinosauria in 1842 and was reconstructed alongside its cousins, Megalosaurus and Hylaeosaurus, by Richard Owen and Benjamin Waterhouse Hawkins as an awesome dinosaurian rhino in 1854. Discoveries of more complete Iguanodon remains, first in Britain and then in the coal mines of Bernissart, Belgium, led to a reconsideration of this bauplan. The most extensive work on this front was conducted by Louis Dollo in the 1880s, who took the complete Iguanodon skeletons from Bernissart - among the first complete dinosaurs known from anywhere in the world at that time - and created the famous 'kangaroo' posture for Iguanodon, broken tails and all, which dominated reconstructions of this animal for the next century. It was not until the 1980s that Iguanodon adopted the appearance of the facultatively bipedal, horizontally-backed ornithopod we know today. So far, so familiar.

Undoubtedly, Iguanodon is a 'classic' dinosaur, and has been a mainstay of popular dinosaur literature for decades. Other dinosaur species named in the early 1800s have not enjoyed the same treatment (Thecodontosaurus, Ceitiosaurus and Hylaeosaurus for instance, are not household names), so its popularity is not just a result of it being one of the first dinosaurs known. Most of us can probably remember a key Iguanodon depiction from our childhood dinosaur books, magazines or films - or from a Love in the Time of Chasmosaurs vintage palaeoart post if you're not yet through puberty - with it stood upright and, of course, giving an irrepressible thumbs-up with its famous thumb spike. These Mesozoic Fonzies, which diehards always knew came in big (I. bernissartensis) and small (I. atherfieldensis) flavours, wouldn't stop manually approving their surroundings even when being attacked by passing generic 'megalosaurs'. Final revisions to its anatomy - an aloft tail and quadrupedal stance - have been drifting into popular depictions for years now, replacing MesoFonz with a heavyset herbivore often depicted living in herds and browsing at different levels. While its lack or truly bizarre anatomy or ferocity may have prevented Iguanodon from ever being the most famous of dinosaur species, there's little doubt that it's held a long-term place in palaeo-pop culture.

All good things...
At least, until recently. If the internet palaeo scene is anything to go by, Iguanodon seems to be sliding down the popularity pole at the moment. It just doesn't seem to be the topic of much conversation any more, or even artwork. Feathered theropods, weird sauropods, horned dinosaurs and even hadrosaurs - boring old hadrosaurs - seem to have stolen the limelight. Perhaps this is because our taxonomic and palaeobiological perceptions of many prehistoric animals have radically changed in recent years whereas Iguanodon, frankly, has remained rather static. It's a bit too familiar. Dinosaur palaeontology has changed radically in the last few decades, but it's changed around Iguanodon, which has done little more than tip forward a little since the 1980s. Discussions about feathers, postures, weird soft-tissue details and whatnot have passed it by entirely, and even a relatively recent shake-up of its taxonomy, where the Cretaceous-straddling, globe-spanning monster-Iguanodon genus was carved up into multiple genera spread across time and space (see Darren Naish's Scientific American articles here, here and here for details) did little to revive public interest in one of our longest serving and best-known dinosaurs. Iguanodon seems to be a dinosaurian washed-up Golden Age movie star: once great, now rarely mentioned, and only wheeled for nostalgia.

The gossip magazines would have a field day.

Behind the scenes, however, Iguanodon or, more correctly, 'iguanodonts' are becoming more and more interesting. Far from large, bland and overly-familiar ornithopods, the modern concept of iguanodonts comprises several distinct Lower Cretaceous species with markedly different bauplans which created complex herbivore communities. Their anatomy varied in many aspects other than simply size - even their famous thumb spikes are actually quite disparate - and functionality must have been equally diverse. The very evolution of iguanodonts is also more complex than we thought: rather than forming a clear group of ornithopods, iguanodont taxa seemingly comprise a messy, not-fully-understood bush of species on the ornithopod branch trunk leading to true hadrosaurs (e.g. McDonald 2012a). Thus, there is no truly correct term for a group comprising Iguanodon and its close relatives: 'iguanodont' here is used in a vernacular sense. In short, it seems that iguanodonts have fallen off the popular radar just as they're getting more interesting and worthy of attention

Iguanodonts: the undiscovered country
At the heart of this newfound complexity is the aforementioned reappraisal of iguanodont diversity. It's worth stressing that the charge to slay the waste basket monstergenus Iguanodon, started by Norman and Barrett (2002) and followed by the likes of Paul (2008), Norman (2010), Carpenter and Ishida (2010), McDonald et al. (2010), McDonald (2012a, b) and others, was not a case of splitting minor taxonomic hairs. Unlike the differences which separate many fossil animals, most taxa pulled from Iguanodon are characterised by radically different morphology which would be obvious even in life. In Britain alone, the handful of species recognised as various members of Iguanodon may now comprise as many as nine genera (not counting objective synonyms). It's well known that Iguanodon is now monospecific, containing only the giant species I. bernissartensis. In the UK at least, this is principally known from the Wessex Sub-basin of the Wealden Supergroup of the Isle of Wight, although it also occurs in the Weald Sub-basin of Surrey, Sussex and Kent (below). It was joined in both basins by Mantellisaurus, the smaller iguanodont once called Iguanodon atherfieldensis and, in the Wessex, by two other possible taxa: Proplanicoxa galtoni and Dollodon bampingi. All but Proplanicoxa galtoni are known from elsewhere in Europe, which cannot be said for other British iguanodonts Barilium dawsoni*, Hypselospinus fittoni, Sellacoxa pauli and Kukufeldia tilgatensis from the Weald Sub-basin, also of the Wealden Supergroup of Sussex and Surrey. These animals are geologically older than the more familiar Iguanodon and Mantellisaurus and, for now at least, do not seem to overlap stratigraphically. A further genus, Owenodon hoggi, has been named for "Iguanodon" material from the British Purbeck Group. A number of other Asian and North American genera have also been pulled from Iguanodon, but the British record seems unusually diverse and implies that multiple iguanodonts existed in the same basins. Admittedly, exactly how many European iguanodont taxa are valid remains uncertain - there are arguments for it being over-split and overly-conservative - but even a relatively cautious assessment suggests several iguanodont faunas evolved in ancient Britain.

*Fascinating aside: according to Norman (2011a, b) there's a good chance that the original Iguanodon teeth belong to Barilium. There's not much we can do about this now - after years of confusion over what Iguanodon is, the name has been irreversibly transferred to I. bernissartensis. While most agree this was one appropriate cause of action to take - most of us have always thought of this species as the 'classic'Iguanodon - there are lots of niggles and issues with the choice of bernissartensis as the surrogate type species of Iguanodon. The similarity of the original 'I. anglicus' teeth to Barilium is just another hangover from the excessive lumping that Iguanodon experienced in its first 180 years of recognition.

Simplified overview of British iguanodont distribution. The taxa listed here do not include recently named objective synonyms and includes several genera which some authors (e.g. Norman 2011a; McDonald 2012) would happily remove. I. anglicus, the original Iguanodon and nomen dubium, is included for interest only. Silhouettes provide very rough proxies for maximum taxon size to show the possible nature of iguanodont faunas, borrowed from Paul (2008).

Quite how these contemporary animals did not trip over each others ecological toes remains to be established. Some truth to the 'classic' view of Iguanodon species occurring in different size classes remains, with most newly recognised species equating to large- or medium-size dinosaurian herbivores. What is now very apparent, however, is that size is only one way in which these animals differ. The large iguanodont Barilium, for instance (below), is about the same length as I. bernissartensis (10-12 m) but is much more heavily built, with proportionally heavyset hips, shoulders, limb bones, a chunky anterior tail region and very tall neural spines along much of its back. While it's difficult to call I. bernissartensis a gracile creature, its bones are certainly more svelte than those of Barilium: its limbs are longer, its vertebrae lower, and its limb girdles less stocky. A similar story is echoed in the smaller iguanodonts which lived alongside the giants: Hypselospinus, contemporary of Barilium, was a relatively small (about 6 m long) but stocky species, with chunky limb bones and a thick shoulder girdle. By contrast, other 'small' iguanodonts - such as the 6- 7 m long Mantellisaurus and Dollodon - were rather gracile, with slender limbs and relatively delicate hands. Despite its robust body, Hypselospinus shared a relatively gracile jaw construction with other smaller iguanodonts. With many further differences in their fine anatomy, a clear message can be seen: iguanodonts were not merely resized variants of the same bauplan rolled out over the Lower Cretaceous. Quite how their different anatomies plugged into their palaeoecology and niche differentiation remains to be established, but its possible - maybe probable - that their anatomical differences reflect different foraging strategies, habitat preferences and routine predation responses. Perhaps the geologically younger, slender variants were quicker on their feet than their rotund forebears? Did the more robust species spent more time locomoting quadrupedally? No-one really knows at the moment, but there's clearly a lot of interesting things going on here and a lot of interesting research to be done.

Barilium dawsoni, a large and very robust iguanodont from the Valanginian of Sussex, caked in dried mud. This stunted pollex of this animal, which was probably quadrupedal most of the time, means it'd be hard-pressed to give a thumbs up even if it wanted to. A flock of 'Ashdown maniraptorans', tiny, poorly known theropods no larger than an Eurasian magpie, add scale (see Naish and Sweetman 2011 for details).

It would be remiss of us to not mention that the most famous iguanodont feature - their thumb spikes - are also far from uniform in size or construction. The function of the iguanodont pollex has long proved controversial, but a role in stabbing generic theropods in the neck is a common assumption. This long-held assumption is questioned by the range of morphologies associated with the pollex however. Most of us are familiar with the general construction of the iguanodont pollex thanks to oft-reproduced images of the Iguanodon hand, such as...

Left Iguanodon bernissartensis manus. Image from here.

Here, the pollex is conical and fairly large, but remains detached from the carpal block (iguanodont wrist bones fuse into a single unit with age). Thus, the pollex retains an ability to move somewhat. The pollex of Mantellisaurus is generally similar to that of Iguanodon, except that it is much, much smaller - probably far too small to be used as an effective predator deterrent. By contrast, the pollex of another small iguanodont, Hypselospinus, was proportionally large and robust, being about 40% as long as the forearm. Rather than being truly conical, the pollex of Hypselospinus was laterally compressed and tightly attached to the carpal block so little or no flexion was possible. The thumb of fatso Balirum was actually fused to the block itself, and is of further note for being incredibly short: Barilium would struggle to give a satisfactory 'thumbs up' to anyone. So again, we see evidence of diversity in these unassuming dinosaurs: pollex size, shape, flexion and reinforcement all vary across iguanodont taxa. We may take this as a sign that thumb spike function was also variable across iguanodonts, so there may not be one single explanation for their existence. The tight pollex articulations of some species seemingly make the pollex part of the antebrachial functional unit than the hand, and are strangely reminiscent of the carpometacarpal knobs and spurs of many birds (see - again - a TetZoo series on this topic, starting here). Alas, the function of many bird hand spurs are not well researched, but the general consensus - supported by direct evidence in many cases - is that they're primarily used in combat and aggressive behaviours, much of it intraspecific. In some cases, they may even be used to make noise when slapped against the flanks of their owners. Who knows: perhaps iguanodonts with tightly welded, inflexible thumb spikes used their pollices in a similar way. But what of species with flexible thumb spikes? Could they be used as weapons too? If so, how come the large pollex of Iguanodon was not fused to the carpus when the large thumb of Hypselospinus is? Did that make it a less effective weapon? And what was Mantellisaurus using that piddling little thumb spike for, if anything? Questions, questions, questions...

The bit where I stop writing
In sum, while it would be silly to say that iguanodont science is undergoing anything like a revolution or renaissance, there's certainly a lot of tinkering going on and the results are exciting whatever your specific taste in palaeontology - taxonomic, functional, or palaeoecological. Granted, the outcome of these ongoing studies are not going to make newspaper headlines, but if you're interested in dinosaur palaeobiology - and you are if you've read this far - then this should be very cool, interesting stuff. If the apparent decline in public interest for iguanodonts is because many of us consider them overly-familiar, then we need to think about changing that attitude. Far from being 'done to death', after many decades of fairly static interpretation, iguanodont science is becoming more interesting than ever.

For an easy to access, relatively up to date and inexpensive look at a bunch of iguanodonts, you could do a lot worse than checking out Dave Norman's chapter on ornithopods in English Wealden Fossils (Norman, 2011b). Further brief musings on the decline of a dinosaur celebrity are provided in this post on Stegosaurus.

References

Carpenter, K., & Ishida, Y. (2010). Early and “Middle” Cretaceous iguanodonts in time and space. Journal of Iberian Geology, 36(2), 145-164.
Paul, G. S. (2008). A revised taxonomy of the iguanodont dinosaur genera and species. Cretaceous Research, 29(2), 192-216.
McDonald, A. T. (2012a). Phylogeny of basal iguanodonts (Dinosauria: Ornithischia): an update. PloS one, 7(5), e36745.
McDonald, A. T. (2012b). The status of Dollodon and other basal iguanodonts (Dinosauria: Ornithischia) from the Lower Cretaceous of Europe. Cretaceous Research, 33(1), 1-6.
McDonald, A. T., Barrett, P. M., & Chapman, S. D. (2010). A new basal iguanodont (Dinosauria: Ornithischia) from the Wealden (Lower Cretaceous) of England. Zootaxa, 2569, 1-43.
Naish, D., & Sweetman, S. C. (2011). A tiny maniraptoran dinosaur in the Lower Cretaceous Hastings Group: evidence from a new vertebrate-bearing locality in south-east England. Cretaceous Research, 32(4), 464-471.
Norman, D. B. (2010). A taxonomy of iguanodontians (Dinosauria: Ornithopoda) from the lower Wealden Group (Cretaceous: Valanginian) of southern England. Zootaxa, (2489), 47-66.
Norman, D. B. (2011a). On the osteology of the lower Wealden (Valanginian) ornithopod Barilium dawsoni (Iguanodontia: Styracosterna). Special Papers in Palaeontology, 86, 165-194.
Norman, D. B. (2011b). Ornithopod dinosaurs. In: Batten, D. J. (ed.) English Wealden fossils. The Palaeontological Association (London), pp. 407-475.
Norman, D. B., & Barrett, P. M. (2002). Ornithischian dinosaurs from the lower Cretaceous (Berriasian) of England. Special Papers in Palaeontology, 68, 161-190.

Two Wealden dryosaurids Valdosaurus canaliculatus, argued below to be striking and exciting animals that we should all be enthused about, shown here milling about a Lower Cretaceous woodland, not doing very much.

The wide interest palaeontology receives is largely because many fossil animals are spectacularly charismatic, their popularity enhanced by large body size and terrific anatomical features. Not all fossil animals are well adorned with attention-grabbing anatomy, of course. Some animals, even those belonging to particularly famous groups like marine reptiles, pterosaurs or dinosaurs, are devoid of immediately-striking features and proportions, and may be so 'average' that they rarely receive dedicated attention outside of technical literature. Step forward the most middling, most average and downright beigest of all ornithopods, the dryosaurids.

Mounted skeleton of the Jurassic dryosaurid Dysalotosaurus lettowvorbecki in the Humboldt Museum's excellent dinosaur hall. Photo by Masur, from Wikimedia Commons. Beige.

The Jurassic-Cretaceous clade Dryosauridae contains animals which, at first glance, represent the mean of dinosaur extremes. Most of these animals, early offshoots of the ornithopod group Iguanodontia, are small or medium-sized, at 3-4 m long. They have fairly short, unremarkable ornithopod skulls and small grasping hands which are, well, quite a lot like those of other small-ish ornithopods. They possess no horns, claws or even particularly arresting teeth, their jaw tips being entirely toothless and cheek teeth, as with most ornithopods, being leaf-shaped and coarsely serrated. This restricted them to a diet of leaves and other herbage, and there's not even any strong hints of omnviory. In short, they aren't especially cute, aren't really spectacular, and, to look at one, it's hard to find a truly distinctive, memorable feature. Perhaps this is why the only time they're given decent palaeoartistic renditions is when they're being pursued by a more striking theropod, and are relegated to bit-parts and cameo roles in most dinosaur books and palaeodocumentaries.

You knew there was a 'but' coming
As usual, appearances can be deceiving. There's actually a lot more going on with these dinosaurian plain Janes than casual glances may suggest. If you stare at a skeleton of a dryosaurid long enough, the pronounced difference in their fore and aft proportions becomes inescapable. The head, neck, forelimbs and torso belong to much smaller dinosaurs than their legs and tail, which are proportionally much longer and more robust than we'd expect from their anterior skeleton. This enlarged posterior region does not seem to reflect expansion of the gut either, as it does in some other herbivorous dinosaur species. Rather, the pelvic bones betraying the depth of the belly are fairly shallow, suggesting the legs and tail are long for the sake of being long, not to accommodate increased body size or torso girth. Of further note are dryosaurid feet, which are not only surprisingly long and gracile but also possess a mere three toes, a contrast to the primitive ornithopod condition of four. Their femora have a very long, finger-like fourth trochanter (the variably shaped process on the posterior surface of dinosaur femora which anchored posterior hindlimb muscles) and a very large and prominent scar occurs where the famous caudofemoralis musculature anchored to the thigh. As in all dinosaurs, this muscle ran to the anterior portion of the tail (discussion here), the elongation and deepening of which permitted a great deal of room for its attachment.

Put together, these femoral and caudal features are clear indicators of large hindlimb retractor muscles and, along with the svelte body and long legs, betray the habit of very rapid running. Indeed, the cursorial features of dryosaurids are so marked that they were probably among the swiftest of all ornithischians, a trait which may explain their conspicuous lack of ornament, armour and weaponry compared to other dinosaurs. Such elaborations are not without use of course, but they are just extra weight for a running animal. Thus, rather than thinking of dryosaurid skeletons as boring, we should view them as the bones of lithe, streamlined, athletes. I wonder if we'd consider these animals dinosaurian Mr. Averages if we could see them in life, their running abilities likely making them very striking and conspicuous animals in many Jurassic and Cretaceous ecoystems.

Britain's Cretaceous dryosauid: Valdosaurus
Dryosauridae was a widespread group with fossils occurring in Africa, Europe, North America and New Zealand. One British dryosaurid, the Wealden Supergroup taxon Valdosaurus, has become particularly interesting in recent years. Bones ultimately referable to this genus were described from the Wessex Formation, Isle of Wight, as early as 1888 by Richard Lydekker. They were not recognised as being Dryosaurus-like until the 1970s however, the decade which also Valdosaurus canaliculatus receive its name (Galton 1977). A second Valdosaurus species was erected for Nigerian material by Galton and Taquet (1977), but has since been moved to its own genus, Elrhazosaurus. It took a while to appreciate that dryosaurids were a unique radiation of ornithopods rather than merely oversized versions of Hypsilophodon, with the first inclinations of this idea only appearing in the 1980s. Somewhat surprisingly, the monophyly of Dryosauridae was untested for many decades, but has recently been borne out under phylogenetic analysis (e.g. McDonald et al. 2010; Barrett et al. 2011). Alleged Valdosaurus material from Spain and Romania seemed to extend the range of this animal across Europe, but these referrals have not withstood scrutiny: Valdosaurus remains UK-only for the time-being.

Holotype femur of Valdosaurus compared to those of other small ornithopods. Note the size of the scar for M. caudofemoralis, 'p', in Valdosaurus. Figure and caption from Galton and Taquet 1977.

As usual for a Wealden dinosaur, Valdosaurus isn't known from a huge amount of material. Various bits and pieces have been referred to this taxon for decades but, like many other British dinosaurs, recent work has tightened up what can and cannot be referred to it (Barrett et al. 2011). We now consider Valdosaurus known primarily from hindlimb and pelvic remains, along with some vertebrae and portions of the pectoral girdle. These remains suggest Valdosaurus was a large dryosaurid with a body length of about 4 m, and a particularly well-distinguished, large caudofemoralis muscle scar on its femur (Barrett et al. 2011). Does this mean it had a particularly big set of hindlimb protractors and was especially fleet-footed? Maybe, but it's hard to say in the absence of more complete specimens. Still, assuming the rest of its proportions were like those of other dryosaurids, it was probably the fastest ground animal in the Wealden Supergroup and capable of outrunning any contemporary predator.

Valdosaurus: apocalypse survivor?
What makes Valdosaurus especially interesting and unique among Wealden dinosaurs is its longevity. The Wealden dinosaur fauna is essentially divided into two groups: a 'lower' and 'upper' assemblage. The 'upper' contains the most widely known taxa, animals such as Iguanodon, Polacanthus, Baryonyx, Hypsilophodon, Neovenator and the like. These animals occur in rocks dating to the Hauterivian and Barremian, about 133-125 Ma. The 'lower' fauna features slightly lesser known taxa: Barilium, Hylaeosaurus, Pelorosaurusand so on, all of which are of slightly older, late Berriasian-Valangian vintage (138-133 Ma). The transition between these faunas is not continuous, with a series of poorly-fossiliferous Hauterivian-aged strata - representing about 4 million years - occurring between more productive Wealden rocks. William Blows has proposed across several papers that this gap may not merely be an artefact of sampling (although this remains possible), but a low-level extinction event that wiped out the 'lower' fauna and allowed the 'upper' assemblage to repopulate (e.g. Blows 1998). Not all agree that this apocolyptic interpretation is the most likely explanation of the Hauterivian Wealden dinosaur gap - some argue that we just need to look harder for more bones. Whatever, something clearly caused a lot of upset for the Wealden dinosaur fauna in the Hauterivian, resulting in significant reorganisation of dinosaur faunas by late Hauterivian-Barremian stages: old taxa disappeared, and new ones - sometimes entirely different clades - replaced them.

How does Valdosaurus fit into this? Although classically part of the 'upper' Wealden assemblage, Valdosaurus is now known to occur in the 'lower' fauna (e.g. Blows 1998; Barrett et al. 2011). This makes it the only dinosaur to span the Hauterivian gap, suggesting it lived through whatever turned out the older Wealden dinosaurs and brought in the new. It must be stressed that the older Valdosaurus remains are not terribly complete and may not be V. canaliculatus proper, but they are extremely similar to Valdosaurus remains from the 'upper' Wealden and at worst, they represent a very close relative, perhaps a direct ancestor. Of further interest here are recent reconsiderations of Valdosaurus/dryosaurid abundance within the Wealden. Dryosaurs were once considered rare in these deposits, but ongoing appraisals of British Lower Cretaceous dinosaurs suggest they were far more abundant than once realised, and populous enough to question the dominance of iguanodonts in Wealden herbivore palaeoecology (Barrett et al. 2011). Given that Valdosaurus represents a good chunk of the Wealden dryosaur material, we may take this as a sign that it was not only a long-lived taxon, but also one that had a strong foothold in Wealden habitats.

The longevity and abundance of Valdosaurus may see it being considered one of the greatest 'success stories' of Britain's Lower Cretaceous dinosaurs, and the implications of its success to Wealden palaeoecology undoubtedly make it one of the more interesting members of the assemblage. A key question - why did it persevere when all other species didn't? - now hangs over this unassuming animal's head. With work on the Wealden fauna constantly ongoing, it seems like a case of 'watch this space' to see just how our new perception of Wealden dryosaurids will influence broader interpretations of Britain's Lower Cretaceous dinosaurs. Exciting times indeed, then, and a far cry from the perception of Valdosaurus and dryosaurids as easily-forgotten, 'average' dinosaurs: at least one of them is, from a certain perspective, one of the most interesting dinosaurs in the UK.

References

Barrett, P. M., Butler, R. J., Twitchett, R. J., & Hutt, S. (2011). New material of Valdosaurus canaliculatus (Ornithischia: Ornithopoda) from the Lower Cretaceous of southern England. Special Papers in Palaeontology, 86: 131–163.
Blows, W. T. (1998). A review of Lower and Middle Cretaceous dinosaurs of England. New Mexico Museum of Natural History and Science Bulletin, 14, 29-38.
Galton, P. M., (1977). The Upper Jurassic dinosaur Dryosaurus and a Laurasia-Gondwana connection in the Upper Jurassic. Nature, 268(5617): 230-232
Galton, P. M., & Taquet, P. (1982). Valdosaurus, a hypsilophodontid dinosaur from the Lower Cretaceous of Europe and Africa. Geobios, 15(2), 147-159.
McDonald, A. T., Kirkland, J. I., DeBlieux, D. D., Madsen, S. K., Cavin, J., Milner, A. R., & Panzarin, L. (2010). New basal iguanodonts from the Cedar Mountain Formation of Utah and the evolution of thumb-spiked dinosaurs. PloS one, 5(11), e14075.

Baryonyx walkeri, the famous, much discussed spinosaur from Lower Cretaceous Britain. A number of goniopholidids skulk in the foreground.

I assume that most people want to read new stuff when they're browsing online, and I try to take the same attitude to my own blogging. I'd much rather offer fresh perspectives or cover rarely-discussed issues than simply rehashing the same tried and tested material that we've all picked up from elsewhere. This explains why the image above, showing the famous Lower Cretaceous British spinosaurid Baryonyx walkeri, has sat on my hard-drive since November. Drafted for a project which needed a picture of a theropod, it's been collecting dust for ages while I've been wondering what to say about it here. Problem is, we all know too much about Baryonyx. It's well known that the 1986 description of Baryonyx provided the first real look anyone had ever had into spinosaur anatomy; that spinosaurids have kinda weird, superficially-crocodile like skulls which permitted feeding on a variety of prey which included fish and other dinosaurs; that the forelimb anatomy of this group, formed of robust arms and large claws, is particularly interesting... The list of things we all know about Baryonyx goes on. Is there anything left to say about this animal which hasn't been poured over dozens of times before?

Hopefully, this
There may be one component of Baryonyx palaeontology which, while hardly unknown, at least doesn't get mentioned too often. When considering the discovery of Baryonyx, we imagine the story starting in 1986 or perhaps, in 1983, when the holotype specimen was found. Eric Buffetaut's (2010) research into early spinosaurid discoveries suggested this tale warrants a prequel however, one which started a whopping 160 years before Baryonyx was found. As with other British dinosaurs such as Iguanodon and Cetiosaurus, Baryonyx also has a long history which dates back to the first dinosaur discoveries, and it even stars A-list 19th century palaeontologist celebrities.

Our story begins around 1820, when Gideon Mantell recovered, or was given, a series of conical, sharp teeth from the same Tilgate Forest quarries which would later yield the first bones of Iguanodon. These teeth came in three flavours, all variations on a conical shape with differing degrees of slenderness and curvature. They all clearly belonged to carnivorous animals. Of interest here are teeth that Mantell characterised as being paritcularly slender, laterally compressed, with carinae on the anterior and posterior margins and distinct grooves on the lingual and labial surface. To Mantell, the teeth resembled those of long-snouted crocodiles or perhaps, at the suggestion of his mentor in comparative anatomy, William Clift, monitor lizards. Mantell first put these throughts into print in 1822 and in several other publications throughout the 1820s, favouring their crocodilian identification and making repeated positive comparisons to long-snouted Crocodyliformes such as gharials and the extinct teleosaurs.

Cuvier's (1824) illustration of Mantell's Wealden 'crocodile' tooth, left, compared to the actual specimen. From Buffetaut (2010). Image borrowed from here.

Mantell was not the first to illustrate these strange Wealden teeth however. This accolade belongs to Baron Georges Cuvier who, having been sent teeth for analysis by Mantell, proceeded to illustrate them in 1824 (above). Cuvier was not above illustrating unusual fossil specimens even when his peers had more claim to the prestige of publishing them first, having also done this with Iguanodon material. Cuvier's 1824 illustration and discussion of Mantell’s alleged crocodyliform teeth agreed with Mantell’s identification, also positively comparing them with the teeth of animals we would ultimately call teleosaurs. Far from being miffed with Cuvier partially scooping his discovery, Mantell seemed chuffed that he and Cuvier were in agreement in documents published in the late 1820s. Perhaps this came as a relief after Mantell's Iguanodon teeth were identified those of a rhinoceros by Cuvier: having one of the leading comparative anatomists in the world shoot your ideas down - even if he's wrong - can't do much for one's self esteem.

A few years later saw entry of Sir Richard Owen into discussions of Mantell’s alleged crocodyliform Wealden teeth. In Owen’s seminal Odontography, a major overview of animal teeth published from 1840-1845, he named them Crocodilius (Suchosaurus) cultridens. Like Cuvier and Mantell, Owen also made several favourable comparisons between the Wealden teeth and other fossil Crocodyliformes, including teleosaurs*. In a contemporary work, Report on British Fossil Reptiles (1842), Owen noted some subtle differences between the cross-sectional shape and carinae position of the Wealden teeth and those of crocodiles, although he maintained a crocodyliform referral for the teeth at this time. Later, Owen seemed less certain about this identification, noting in an 1878 publication that his subgenus Suchosaurus had a ‘nearer affinity or transition to the Dinosaurian order than does any of the Mesozoic Crocodilia’. This was the first clear indication that all was not as seemed with Mantell's early Wealden discovery. However, an 1884 Owen manuscript which basically rehashed his 1878 discussion of Suchosaurus,contained none of the doubt he expressed in 1878. Clearly, Owen had changed his mind about the similarity of the Mantell's 'crocodile' teeth to those of dinosaurs.

*The story becomes somewhat complicated here by the referral of a vertebra to Suchosaurus, which was suggested as early as 1888 to represent an iguanodont and remains that way today. However, this was not immediately accepted by 19th century naturalists and it is not is not always clear if they are discussing the vertebra or teeth when considering the affinities of Suchosaurus.

Most 19th century palaeontologists followed Owen’s lead in considering Suchosaurus a crocodile-like animal, but others were not convinced. Felix Plieninger (1846) and John Hulke (1979) both suggested that Suchosaurus had greater affinity with Dinosauria than other reptiles. Plieninger was definitely basing his discussion on the Suchosaurus teeth, although it's not clear whether Hulke is considering these or the vertebra also referred to this taxon. Other authors, such as Heinrich Georg Bronn (1849) considered Suchosaurus a reptile of uncertain identity, at least for a while (he later agreed with Owen). The mystery surrounding Suchosaurus was more-or-less left there however, as these were among the last discussions Suchosaurus was to receive in palaeontological literature. Although a second Suchosaurus species was named in 1897-1898 for a Portuguese tooth, the taxon fell out of regular use in discussions of Wealden animals – even its Crocodyliformes – in the 20th century.

Back to the future
Fast forward to the 1980s and, to everyone’s delight, Baryonyx walkeri was discovered and described from a fairly complete skeleton found in Surrey. Among the many surprises associated with its discovery were its slender, laterally compressed and grooved teeth, a distinctive dentition that saw any similar isolated tooth from the Wealden being allocated to Baryonyx (e.g. Martill and Hutt 1996 - see below). It didn’t take long the penny to drop: by 2003 it was realised that the teeth of Baryonyx were very, very similar to those of Suchosaurus (Milner 2003). After nearly 200 years, the real identity of Suchosaurus was revealed: a spinosaurid theropod. This meant that, far from being relatively new discoveries for the Wealden, spinosaurs were actually among the very first animals to be documented from the British Lower Cretaceous. Hats must be tipped to the likes of Plieninger and Hulke and, to a lesser extent, Owen and Bronn, for their insightful taxonomic comments on the very fragmentary material they had to work with. Each of them saw, to greater and lesser extents, past the crocodile-like appearance of the Suchosaurus teeth to suggest they may be crocodile-like dinosaurian reptiles. That's pretty good going considering what they had to work with.

Isolated teeth attributed to baryonychine theropods from the Wessex Formation, Isle of Wight. From Martill and Hutt (1996).

Unsurprisingly, several authors have mentioned the likelihood that Suchosaurus and Baryonyx are one and the same (e.g. Buffetaut 2010; Mateus et al. 2011). Although their teeth do differ in subtleties of carinae and groove development, it has long been noted (even by Mantell way back in the 1820s) that such particulars of dentition are readily worn away in life or taphonomy. It is therefore possible, maybe probable, that Suchosaurus and Baryonyx are synonyms, the teeth of the former simply being worn versions of the latter. If so, the animal we know as Baryonyx was actually one of the first dinosaurs ever found. But if it's likely that Baryonyx and Suchosaurus are the same animal, why are we still talking about Baryonyx instead of resurrecting Suchosaurus as the Wealden spinosaurid genus? There are several reasons. Firstly, the dentition of Baryonyx is not unique among baryonychines, creating the (admittedly unlikely) possibility of Suchosaurus being synonymous with another baryonynchine taxon. A second possibility, that Suchosaurus is a second Wealden baryonychine, prevents another problem. But most important is our third reason: the type material of Suchosaurus possesses no real defining features, giving us nothing to diagnose this genus with. This echoes the situation of many ‘classic’ dinosaur species of course, and palaeontologists sometimes work taxonomic magic to transfer their name to other, diagnostic specimens. There seems little reason to do this for Suchosaurus however, it being a fairly obscure and under-discussed animal for much of the 20th century. Unlike Iguanodon or Allosaurus, which have received name transfer treatment in the past, Suchosaurus is not a familiar animal with a poor type specimen, so it isn’t too criminal to refer the type specimen to Spinosauridae indet. and let the name Suchosaurus slip into the nomen dubium realm of obscurity.

So there we have it, then: Baryonyx and Wealden spinosaurids have, from a certain point of view, been known for as long as any other dinosaur you care to mention, and some folks had an inkling of spinosaurid's superficially crocodile-like morphology even when they were only known from teeth. For more on this story and the early discoveries of spinosaurids, be sure to check out Buffetaut (2010), Mateus et al. (2011). To find out happened to the rest of the 'crocodile' teeth handled by Mantell in the 1820s, read Salisbury and Naish (2011). Further, exciting news on the developing science of Wealden spinosaurs can be found in this near-recent blog post over at Mark Wildman's Saurian.

References

Bronn, H. G. (1849). Index Palaeontologicus, 2. Abetheilung. Schweizerbart, Stuttgart.
Cuvier, G. (1824). Recherche sur les ossemens fossiles, tome V, 2ème partie. Dufour et E. d'Ocagne, Paris.
Hulke, J. W. (1879). Vectisaurus valdensis, a new Wealden dinosaur. Quarterly Journal of the Geological Society, 35(1-4), 421-424.
Mantell, G. A., & Mantell, M. A. (1822). The fossils of the South Downs; or illustrations of the geology of Sussex. Lupton Relfe, London.
Martill, D. M., & Hutt, S. (1996). Possible baryonychid dinosaur teeth from the Wessex Formation (Lower Cretaceous, Barremian) of the isle of Wight, England. Proceedings of the Geologists' Association, 107(2), 81-84.
Mateus, O., Araújo, R., Natário, C., & Castanhinha, R. (2011). A new specimen of the theropod dinosaur Baryonyx from the early Cretaceous of Portugal and taxonomic validity of Suchosaurus. Zootaxa, 2827, 54-68.
Milner, A. C. (2003). Fish-eating theropods: a short review of the systematics, biology and palaeobiology of spinosaurs. Journadas Internacionales sobre paleontologiá de Dinosaurios y su Entoro, 2, 129-138.
Owen, R. (1840–1845). Odontography. Hippolyte Bailliere, London.
Owen, R. (1842). Report on British fossil reptiles. Part II. Reports of the meetings of the British Association for the Advancement of Science, 11, 61-204.
Plieninger, T. (1846). Über ein neues Sauriergenus und die Einreihung der Saurier mit flachen, schneidenden Zähnen in eine Familie. Jahreshefte des Vereins für vaterländische Naturkunde in Württemberg, 2(1), 148-154.
Salisbury, S. W. & Naish, D. (2011). Crocodilians. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 305-369.

There's only one rule in successful advertising: if you can't use sex, use Star Wars. Background borrowed from NASA, text generated by Fontmeme.

Welcome to The Wealden Crocodyliformes Trilogy! As in, three whole posts dedicated to the major types of Wealden Crocodyliformes! Yeah! Woot! Let's all have a pear!

Right, let's back up a bit. Hopefully, it’s well known that modern crocodilians represent only a tiny fraction of crocodile-line archosaur diversity. Crocodyliformes, the major group of crocodile-like archosaurs which ultimately begat our modern crocodile fauna, was ancestrally much more morphologically and ecologically diverse than its modern representatives. This is true to the point that the common labelling of crocodilians as ‘living fossils’ is only true in a very loose sense. Superficially crocodile-like Crocodyliformes have certainly been around for well over 100 million years, but even some of their close relatives were very different beasts. Despite this - hopefully – widely known fact, reconstructions of ancient Crocodyliformes, or even articles about them, are not exactly commonplace. Running through the major types of crocodyliform once found in Lower Cretaceous Britain, specifically those from the Wealden Supergroup, gives an opportunity to at least scratch the surface of Mesozoic crocodyliform diversity. Wealden Crocodyliformes are diverse, with 11 species identified in a recent review (Salisbury and Naish 2011). As with many Wealden groups, the long research history of these animals (Wealden crocodyliform teeth were first found in the 1820s) does not mean they have been 'done' by palaeontologists - there remains much to learn about Wealden crocodylomorph palaeobiology. Indeed, at some point in this trilogy, we'll cover a cool, new and in-press discovery - more on that later, as I've already said too much.

A key point to note in each of these articles is the major anatomical differences these animals have from modern crocodiles, meaning that not only their lifestyle but also appearance would contrast from anything we associate with Crocodyliformes today. This is despite the Wealden Crocodyliformes not, by any stretch of the imagination, representing the most 'extreme' bauplans offered up by the croc-line archosaurs. This message should ring particularly loudly for artists who simply place modern crocs in the Mesozoic (a crime I'm as guilty of as anyone). All right, enough preamble already – let’s meet our first subject, the resourceful, tiny atoposaurid crocodyliform, Theriosuchus.

Neat things come in small packages
Our fist Wealden crocodyliform is a far cry from the role of large, voracious apex predator we often think of when crocodiles are mentioned. At only 550 mm long, Theriosuchus was tiny compared to most Wealden Crocodyliformes and likely risked predation from even moderately-sized contemporary predators. Theriosuchus is a long lived genus known across Europe and Asia from Late Jurassic – Late Cretaceous deposits and several species are known. Wealden fossils of this animal – a partial skull from the Wessex Formation and isolated teeth from the Ashdown and Wadhurst Clay Formations of East Sussex – are too fragmentary to refer to any existing species, or permit identification of a Wealden-specific one. For the time being then, the Wealden Theriosuchus is simply referred to as Theriosuchus sp.

The Lower Cretaceous, Wealden atoposaurid, Theriosuchus sp., prancing about in pursuit of locusts.

Theriosuchus belongs to Atoposauridae, a group of neosuchian Crocodyliformes which are seem closely related to the group containing modern crocs, Eusuchia. Atoposaurids possess several 'derived' eusuchian features in their nasal and vertebral regions, hinting at a possible close relationship with this group (fun fact: classic 'eusuchian' features actually evolve repeatedly in ancient Crocodyliformes, which can confound taxonomic assessments of fragmentary fossil crocodyliform material - more on this later). The most distinguishing feature of atoposaurids is their size. Even when fully grown, no atoposaur exceeds one metre in length. They are correspondingly sometimes labelled as 'dwarf’ species, but this label is not an entirely accurate. So-called ‘dwarf’ species are not uncommon (elephants, deer, many lizards and crocodilians are just some lineages containing 'famous' dwarfs) but - by definition - they must be descended from closely related, larger relatives. All currently known atoposaurs are small, so they cannot be said to have reduced their size from their ancestral condition. Thus, they are not true ‘dwarf’ Crocodyliformes, just small ones.

Although unquestionably crocodile-like, the life appearance of Theriosuchus probably wasn't strongly comparable with any modern animal. Broadly, atoposaurids recall attributes of crocodiles and long-legged lizards, but their relatively svelte skeletons and long limbs are also vaguely reminiscent of some small mammals. Their skulls are rather low and short, thanks to an unusually abbreviated and broad snout which tapers into a rounded muzzle. Unlike many Crocodyliformes, atoposaur nasal openings remain separated and placed on the lateral margins of the snout tip, rather than being combined into a single opening on the upper snout surface. Their eye sockets are proportionally large but an opening in the skull above and behind the eye, the upper temporal fenestra, is rather reduced. This suggests that at least some of their jaw muscles were not as large as the famously enormous jaw muscles of modern crocodiles. Atoposaurid body proportions are rather typical of Crocodyliformes with short necks, tubular trunks and a tail of moderate length, but the limbs of Theriosuchus and most other atoposaurids are rather longer and more gracile than we've come to expect from croc-line archosaurs (this is not universal across the group: other atoposaurids have rather squatter limb proportions). Two rows of square or rectangular, keeled osteoderms extended along the neck, back and tail, becoming slightly more prominent on the tail. Most are pretty flat, so atoposaurid backs would look considerably less ornate than those of modern crocodilians. In Theriosuchus at least, the dorsal osteoderms possess ‘peg and groove’ joints which locked each osteoderm into its neighbour, forming a relatively immobile bony sheet along the back. This feature is not common to all atoposaurids, but is found in some other Crocodyliformes - albeit not modern ones. It's thought that this locking mechanism provided more than just reinforcement of the armour along the animals back, also helping to resist bending and twisting movements in the torso when the animal walked or ran. Additional osteoderms occur beneath the tail and neck.

Theriosuchus pusillus, one of the best known members of this genus, from the lower Cretaceous Lulworth Formation, UK. Image from Owen (1878), borrowed from Wikimedia Commons.

Like many Crocodyliformes, the teeth of Theriosuchus are deceptively complex. The teeth lining the jaw tip are rather conical with slight striations and carinae, while those behind become rather lance-shaped - longer than wide, with a pointed apex. The carinae of these teeth are rather coarser than those at the jaw tip. In some Theriosuchus species, the teeth at the back of the mouth are compressed into blade-like structures with particularly coarse serrations. Two peaks in tooth size can be seen in atoposaurid jaws, the first occurring with a large conical tooth which forms a ‘psuedocanine’, and the second (smaller) peak among the anterior lance-like dentition. A notch in the side of the upper jaw means that the ‘pseudocanines’ were probably visible even when the mouth was closed. Put together, the dentition of Theriosuchus was multifunctional and ideally suited to processing soft prey items: the anterior teeth could pierce and stab; the lance-shaped teeth could crush and cut, and the blade-like teeth (if present) could shear and rip into soft-food.

Raccoon-crocs?
The dentition of Theriosuchus suggest that, like other atoposaurids, it may have been primarily carnivorous, likely foraging for small vertebrates, arthropods and carrion. As in modern crocodiles, their diverse teeth may have also permitted ingestion of nutritious plant matter. Unlike modern crocodiles however, several features of atoposaurid anatomy suggest they found much of their prey away from aquatic settings. Relatively long limbs increased their stride distances, allowing for potentially rapid locomotion, while their interlocked osteoderms likely reduced the strain of walking and running on the trunk skeleton. The latter is likely true of all Crocodyliformes with interlocking osteoderms, but Theriosuchus was also a small, lightweight creature, thus reducing strain on its trunk even further when walking. Put together, the combination of small body size and a reinforced back may have allowed Theriosuchus to sustain long periods of walking and running compared to other Crocodyliformes. The general rarity of atoposaurid fossils compared to those of other Crocodyliformes - both in the Wealden and elsewhere - lends some support to this idea: animals which spend a lot of time in water generally have a higher preservation potential than those which don’t, simply because their remains are that much closer to environments where sediments are likely to accumulate and bury them.

Aquatic behaviour for Theriosuchus cannot ruled out, however. While the osteoderm bracing system likely limited their torso flexibility - thus somewhat impeding the ability for rapid and manoeuvrable swimming - the retention of a powerful, flexible tail and low body shape probably still permitted fair swimming performance. Thus, it is quite possible that terrestrial food sources were supplemented with diminutive fish and other small aquatic prey from time to time. Atoposaurids like Theriosuchus may be best regarded as very adaptable, generalised species which, if we were forced to crowbar them into a modern niche, may be most equivalent to small, semiaquatic mammalian carnivorans – raccoons, otters and so forth. Their generalised diet means that Theriosuchus probably competed for food with lizards and amphibians more than their fellow Crocodyliformes, and perhaps their ability to forage on land and in water, in concert with low body sizes, gave Theriosuchus an edge in a crowded Wealden ecosystem filled with many aquatic and terrestrial predators. Thus, while many Wealden animals were probably relatively restricted to specific foraging habitats and prey types, Theriosuchus could forage freely in both settings, resourcefully enjoying whatever morsels it could wrap its tiny jaws around.

The crocodyliformes we'll meet in the next instalment of The Wealden Crocodyliformes Trilogy are not quite as ecologically generalised as Theriosuchus - aspects of their size, dentition or proportions dictate that they had to commit to at least some lifestyle specifics. To see what they are, and how they fit more broadly into Wealden palaeoecology, you'll have to come back for Episode 2...

References

Owen, R. (1879). Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement IX, Crocodilia (Goniopholis, Brachydectes, Nannosuchus, Theriosuchus, and Nuthetes)". Palaeontographical Society of London Monograph 33: 1–19.
Salisbury, S. W. & Naish, D. (2011). Crocodilians. In: Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 305-369.

Insert your own whoops, hollers,cheers, or discharging firearms here.

Welcome to Episode 2 of the snappily-titled Wealden Crocodyliformes Trilogy!* We'll waste no time with introduction - read this if you haven't already - and dive straight into our second group, the goniopholidids. Much of the information herein is derived from Salisbury and Naish (2011) so, if in doubt, consult this tome for further details.

*Snappily titled? And it's about crocodiles...? Man, I'm so wasted on you guys.

Without question, the Wealden waterways were lorded over by a group of Crocodyliformes known as Goniopholididae. The namesake of this group, Goniopholis, is one of the more familiar Mesozoic crocodyliforms after famous taxa like Sarcosuchus and Deinosuchus, and is well known as a relatively ‘conventional’ crocodyliform compared to some of the other weirdo crocs doing the rounds in the Mesozoic. Goniopholidids are found throughout Jurassic and Cretaceous rocks in the Northern Hemisphere and are part of several famous fossil faunas, including being the best known crocodyliforms of the Wealden fauna. Miscellaneous goniopholidid teeth and scutes occur throughout the Wealden, and their existence has been known for a long time. Teeth ultimately attributed to indeterminate goniopholidids were found in Sussex during the 1820s by Gideon Mantell as part of the same collections of crocodile’ material which was later found to contain unappreciated early records of Wealden baryonychines.

Despite this long history, work on Wealden goniopoholids is still developing (Salisbury and Naish 2011). At one time, most Wealden goniopholid taxa were considered members of Goniopholis proper, the famous Owen-named genus of great historic significance. As with many 'classic' genera, Goniopholis is now appreciated to be a bit of a taxonomic mess and claims of 19 species are being scrutinised (e.g. Salisbury and Naish 2011; Andrade et al. 2012). Recent reviews have suggested that the Wealden goniopholidid assemblage contains a sole Goniopholis species from the Weald Sub-basin and two other genera from the Wessex Sub-basin, all known from good skull material and, in the latter instances, a series of articulated postcranial remains (Salisbury and Naish 2011). These named species include Goniopholis willetti from the Grinstead Clay Formation, Sussex; Anteophthalmosuchus hooleyi (below), from the Wessex and Vectis Formations of the Isle of Wight, and Vectisuchus leptognathus, also of the Wessex Formation (why Vectisuchus when it’s not found in the Vectis Formation? ‘Vectis’ is the Roman word for the Isle of Wight, so ‘Vectis’ frequently pops up in animal names from this part of the world). The latter was almost known from a complete skeleton, but a cliff fall during its collection rendered much of the hindlimb, pelvis and tail inaccessible. In spite of this incident, it’s still fair to say that this group has one of the better records among Wealden reptiles, and it might get even better. Fragmentary goniopholidid jaw fossils hint at further, unnamed species, but they are currently too poorly represented to warrant naming.

The Wealden goniopholidid Anteophthalmosuchus hooleyi takes advantage of a flooding river to hunt two stranded Hypsilophodon foxii. The big one is Using the Ballet to escape.

Goniopholidids vs. modern crocodilians, round 1: anatomy

What kind of Crocodyliformes were goniopholidids? Because these animals appear to resemble modern crocodiles in size, shape and probably lifestyle moreso than any other well-known Mesozoic Crocodyliformes, they are often reconstructed as ancient copies of large modern species like Nile or saltwater crocodiles (e.g. Karl et al. 2006 - see reconstruction here). This isn’t really the case, however: goniopholidids may look a little similar to modern crocodilians at first glance, but much of their anatomy is unconventional and their possible habits were likely rather different. If we compare these aspects directly, their differences will soon become apparent.

We’ll start with size. Here, it must be said, goniopholids are undoubtedly pretty similar to modern crocodilians. The largest Wealden goniopholidids – Anteophthalmosuchus and G. willetti - were large animals each attaining at least 3.5 m long. This is a pretty comparable size for many modern crocodiles, and may even seem a little on the small side compared to the 5 m+ lengths attained by some extant crocodilians. Don’t be fooled into thinking this makes Wealden goniopholids diminutive creatures, however: a 3.5 m long crocodyliform would somewhere around 200 kg in weight and stretch longer than your 3-seater sofa. These were undoubtedly big, bulky animals. Vectisuchus, by contrast, was a much smaller species, only attaining 1.2 m in length.

In fine anatomy, we start to see obvious differences between the ancient goniopholids and modern crocodilians. Goniopholidid backs were covered with two rows of rectangular osteoderms with interlocking pegs at their distal margins – they are much like the atoposaurids we met last time in this respect (Salisbury and Frey 2000). These are largely devoid of ornamentation with only slight keels along their dorsal surfaces. This configuration is rather different to the more complex and ornate osteoderm arrangements seen in modern crocodyliforms, and goniopholidid osteoderm shields would probably seem rather simple and inelegant by contrast. Also unlike modern crocs, goniopholid osteoderms do not extend far up the neck, perhaps because doing so would impair neck mobility (see below), and further osteoderms were found along their bellies. These were formed of hexagonal plates rather than long, rectangular ones however. Another key distinction between goniopholidids and modern crocodilians is found in their forelimbs. Most goniopholids have arms which are at least as long as their legs and many species - including Anteophthalmosuchus and Vectisuchus– have forelimbs which surpass the length of the hindlimb. This increased length is provided by relatively elongate humeri and wrist bones, and would give goniopholidids taller statures than those of all modern crocs, which are always shorter up front than behind. If we extending this comparison further, we’ll see that goniopholidid forelimb length is almost unique among all Crocdyliformes, being longer than virtually all of their relatives.

Like many modern crocodilians, goniopholidids possess the well-built, powerful skulls of formidable predators. There is also overlap in general skull shape with modern crocs too, with G. willetti and Vectisuchus having rather long, slender snouts which are narrower than the posterior regions of their jaws. By contrast, the skull of Anteophthalmosuchus belongs to a real bruiser; its jaws only gently converge from the enormous posterior region to form a chunky, roughly triangular skull with a rounded muzzle. Both skull types are equipped with goodly-sized, slightly recurved conical teeth which would not look out of place on modern crocodilians. Again however, there are differences in detailed anatomy. Of particular interest is the orbits of Anteophthalmosuchus, which only permitted forward vision rather than anterolateral as is usual for Crocodyliformes (its name, roughly meaning ‘forward-eye-crocodile’, reflects this - see Salisbury and Naish 2011). A similar condition is also seen in Vectisuchus, but it is not quite as well developed and seems to have arisen independently. Goniopholid skulls are also rather flatter than those of modern crocs, and have distinctly over-biting upper jaws. An unusual hollow in the cheek region, known as the maxillary depression, was also present, apparently representing an unusually large pressure-sensitive region of the goniopholidid face (Andrade 2009).

A house-proud Goniopholis willetti stands at the entrance to his burrow. Note his long arms, narrow jaws, and lack of a doormat.

Goniopholidids vs. modern crocodilians, round 2: habits

It may be expected that these similarities and differences between modern crocodilians and goniopholididis may translate to overlapping, but also slightly different lifestyles. Happily, because the anatomy of Wealden goniopholidids is well-documented, we can make some informed speculation as to how these animals may have lived and, indeed, this seems to be the case. The size and robust skeletons of G. willetti and Anteophthalmosuchus suggests that the ecological bucks of Wealden waterways stopped with them: occasional visits from spinosaurids aside, they were the largest predators in Wealden lakes and rivers and clearly well suited for tackling large prey items. We might imagine each as the apex predators of their respective waterways, taking small or medium-sized terrestrial animals, large fish and other aquatic reptiles as prey. This gives these animals a role much like those filled by several species of large crocodilians today. Smaller Vectisuchus, by contrast, probably ranked it in the mid-league of ancient Wealden ecosystems, probably capable of holding its own against most aquatic Wealden species but wanting to be wary of its larger cousins. Applying trends of snout shape and prey preference of modern crocodiles to Wealden goniopholidids suggests they likely differed in general prey preference: slender-snouted Vectisuchus and G. willietti probably took relatively smaller prey than the massively-jawed Anteophthalmosuchus. Through overall body size and jaw shape, these animals probably avoided stepping on each other’s ecological toes – at least Anteophthalmosuchus and Vectisuchus were contemporaries which probably practised niche partitioning (Salisbury and Naish 2011).

We might expect goniopholidids to exploit their large size in a similar way to modern crocodilians. Large modern crocodiles often focus their predation efforts to certain times of year when environmental conditions are favourable, such as times when rivers and lakes are in flood, when prey is particularly abundant, or at least the climate is more forgiving. Given how extreme the Wealden climate was - summer temperatures in some parts of the Wealden reached 36–40°C and experienced annual droughts (Sweetman and Insole 2010) – goniopholidids may have used similar strategies. As with big modern crocodilians, their large bodies hold ample reserves to wait out leaner or stressful times, and it’s possible that some goniopholidids waited out the long, hot Wealden summer in cooling pools or burrows (see image, above), while smaller crocs had fewer resources to fall back on and continued to exert themselves throughout hard times.

Beyond these generally favourable comparisons however, many aspects of goniopholidid anatomy hint at different habits to modern crocodilians. For instance, the development of goniopholidid maxillary depressions likely represent enlargements of sensory organs present in modern crocodilians used to detect prey at the water/air interface (Andrade 2009). All else being equal, does this indicate that goniopholids were more routinely grabbing prey at the water surface rather than diving for food or living generalist lifestyles? In other instances, it’s not clear what significance goniopholidid anatomical quirks may have. It’s difficult not to wonder why some Wealden goniopholidids possess entirely forward-facing eyes, for instance, and if this was related to feeding. Ordinarily, increased amounts of forward vision are associated with development of binocular vision and heightened abilities to judge distances. Might that mean predation techniques were unusual in some goniopholidids, involving chases, or carefully judged lunges and strikes at prey?

The preferred habitats and locomotory methods of goniopholidids are also worth pondering. There is some evidence that larger Wealden goniopholidids were mostly confined to a semi-aquatic existence, as their interlocking osteoderms likely strengthened their backs and improved terrestrial competency (as it does for atoposaurids and several other type of ancient crocodyliform), but their sheer weight likely impeded terrestrial locomotion over sustained periods (Salisbury and Frey 2000). The same is true of large modern crocodiles: here, reinforced vertebral joints perform a similar job to osteoderm bracing but still fail to facilitate effective, fast terrestrial locomotion for long periods. Larger crocodilians therefore spend much of their time in water, and certainly find most of their food there. If so, this makes the atypically long forelimbs of goniopholidids all the more interesting. Often, development of relatively equate limb lengths in quadrupeds is considered a sign of good terrestrial proficiency, betraying a well-balanced animal with effective carriage and equal gait efficiency in both limb sets. But how can this apply to large, heavy goniopholidids if they weren’t walking very much? Doubtless, an increased forelimb stride length was useful on occasions when large goniopholidids did leave the water, but why develop these features if much of their lives were spent in deep water? Did these animals ‘walk’ along river beds more than other Crocodyliformes? Was this trait even important for big adults? Perhaps smaller or juvenile goniopholidids took advantage of long forelimbs before they outgrew real terrestrial proficiency, spending more time on land before becoming more thoroughly aquatic at larger sizes. We could speculate all night about the intriguing possibilities here: Crocodyliformes are sophisticated creatures which do a lot more than eat, sleep and wander about: they also dig burrows, construct nests, climb onto trees and rocks, and are very sociable. Could their long forelimbs be related to these behaviours? Vertical size is seemingly more intimidating to modern Crocodyliformes than girth (Farlow and Dodson 1975) - might long arms and a tall stature have incurred social significance for goniopholidids? It’s not inconceivable that the long arms of goniopholidids were influenced by these activities rather than just locomotion, and I suspect an investigation into the evolution and functionality of their forelimbs would yield some very interesting results.

The outcome

In sum, then, it seems that we need to be cautious when thinking of goniopholidids as 'conventional' Crocodyliformes or simply forebears of modern crocodiles. Many aspects of their anatomy are not only different from those of modern crocodiles, but actually downright odd, and likely impacted on their habits and lifestyles significantly. Palaeoartists - bear all this in mind the next time you set out to draw your goniopholidids skulking in the background of your dinosaur artwork.

For the concluding post in the Wealden Crocodyliformes Trilogy, we're going out with a bang and an exciting new discovery - and it's not very far off now. Stay tuned!

References

Andrade, M. B. (2009). Solving a century-old mystery: the structure and function of the maxillary depressions of Goniopholis (Crocodylomorpha, Neosuchia). In Journal of Vertebrate Paleontology (Vol. 29, pp. 54A-55A).
Andrade, M. B. de, Edmonds, R., Benton, M. J., & Schouten, R. (2011). A new Berriasian species of Goniopholis (Mesoeucrocodylia, Neosuchia) from England, and a review of the genus. Zoological Journal of the Linnean Society, 163(s1), S66-S108.
Farlow, J. O., & Dodson, P. (1975). The behavioral significance of frill and horn morphology in ceratopsian dinosaurs. Evolution, 353-361.
Karl, H. V., Gröning, E., Brauckmann, C., Schwarz, D, & Knötschke, N. (2006). The Late Jurassic crocodiles of the Langenberg near Oker, Lower Saxony (Germany), and description of related materials (with remarks on the history of quarrying the “Langenberg Limestone” and “Obernkirchen Sandstone”). Clausthaler Geowissenschaften, 5, 59-77.
Salisbury, S. W. & Frey, E. 2000. A biomechanical transformation model for the evolution of semi-spheroidal articulations between adjoining vertebral bodies in crocodilians. In Grigg, G. C., Seebacher, F. & Franklin, C. E. (eds) Crocodilian Biology and Evolution. Surry Beatty & Sons (Chipping Norton, Aus.), pp. 85-134.
Salisbury, S. W. & Naish, D. (2011). Crocodilians. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 305-369.
Sweetman, S. C., & Insole, A. N. (2010). The plant debris beds of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England: their genesis and palaeontological significance. Palaeogeography, Palaeoclimatology, Palaeoecology, 292(3), 409-424.

3/3 - this, ladies and gentlemen, is the end. At least, until the inevitable prequels where I'll ignore the canon of the expanded universe and do my best to tarnish everything you liked about the original trilogy.

Here we are then, the last instalment of the Wealden Crocodyliformes Trilogy. Following the posts on atoposaurids and goniopholidids, today we're going out with a bang by covering a newly described Wealden crocodyliform unleashed on the world this morning. The study was written up by my University of Portsmouth chums and colleagues Steve Sweetman, Ulysse Pedreira-Segade and Steven Vidovic (Sweetman et al. 2014), and Steve V. has covered some aspects of his involvement at his blog. The paper is open-access so, for the full skinny on the discovery, you should head here.

This most recently identified Wealden crocodyliform is among the most sophisticated and unusual of all Wealden crocs. Named Koumpiodontosuchus aprosdokitii, it is known from a well-preserved skull which was recovered in circumstances owing much to chance and good fortune (Sweetman et al. 2014). This animal is currently only known for certain from the Wessex Formation of the Isle of Wight, specifically from fossil-rich cliffs next to the seaside village of Yaverland, and the only known skull of it is broken in half. The posterior half was discovered in March 2011 by holidaying fossil hunters, who took it to the local dinosaur museum (Dinosaur Isle, of Sandown) to have it identified. Another family, on a fossil-hunting holiday three months later, then found the front half of the skull. They took this to the same museum where, by chance, the same museum staff who’d handled the first piece were on hand. It was realised that each piece belonged to the same specimen, and the first half was rapidly brought back to the museum to check the degree of articulation. Remarkably, the join between the broken pieces was near perfect – clearly neither chunk had been exposed to weathering effects very long before being discovered – and the entire skull could be seen. Each piece was then donated to the museum to allow its study. Given the chain of events and people involved in the discovery of Koumpiodontosuchus, it’s easy to imagine how only single halves of the skull might be known to science, or even neither. This is clearly yet another story which stresses the importance of amateur fossil hunters to Wealden fossil discoveries, and the benefits of responsible collecting.

Holotype skull and mandible of the button-toothed crocodyliform, Koumpiodontosuchus aprosdokitii. From Sweetman et al. 2014.

Button-toothed crocodiles in context

Koumpiodontosuchus is a member of Bernissartidae, a group named by Sweetman et al. (2014) which only contains two species: Koumpiodontosuchus and Bernissartia fagesii. The latter is a famous, small Jurassic and Cretaceous crocodyliform known from France, Denmark, Spain, Portugal and particularly Belgium, where a spectacular complete skeleton has been unearthed. Indeterminate species of Bernissartia also seem to occur in the Ashdown Formation of Hastings (Salisbury and Naish 2011), but this identification may eventually warrant reappraisal now that Koumpiodontosuchus has been discovered. Bernissartid remains are not new, some of the first material of these animals being documented in the 1850s and Bernissartia itself being named from Belgian fossils in the 1880s. Isolated teeth, likely referable to Koumpiodontosuchus, have been found in Wealden deposits since at least the 1970s (Buffetaut and Ford 1979), so were clearly present across the entire geographic and stratigraphic range of the Wealden Supergroup.

Bernissartia has long been a bit of an oddball among Crocodyliformes, possessing some unusual anatomy and being of uncertain placement in crocodyliform systematics. The discovery of Koumpiodontosuchus provided a bit of light on this front, suggesting that Bernissartia was part of a group containing at least one other similar species, and that they occupy an evolutionary place between atoposaurids and the goniopholidid + Eusuchia radiation. This position isn’t too surprising, as there are a number of features in bernissartids which link them to Eusuchia – see below. Bernissartidae is primarily defined by dental characteristics, with the most obvious one also being the namesake of Koumpiodontosuchus: “button-toothed crocodile” (if anyone wants a common name for these Crocodyliformes, this is the one to use). The posterior teeth of bernissartids are rather globose – wide, short and blunt – and distinctive compared to the dentitions of most other Crocodyliformes. It’s these teeth which, even in isolation, betrayed the presence of bernissartids in the Wealden well before the more substantial Koumpiodontosuchus fossil was discovered. Their other teeth are quite different to this, however. The mid-region dentition is rather conical in shape; ‘pseudocanines’ erupt about 25 % of the jaw length from the jaw tip, and conical teeth emerge procumbently from the jaw tips themselves. Koumpiodontosuchus has two large pseudocanines on its lower jaw, which erupt so close to each other that they share a single, enlarged tooth socket. Bernissartia, by contrast, only possesses one.

The new Wealden bernissartid Koumpiodontosuchus aprosdokitii foraging for molluscs. It's eating a mud snail, Viviparus cariniferus, while tiny (6 mm long) physid gastropods Prophysa crawl over pond scum in the lower left of the image. Dragonflies provide scale, while unnamed tetanurans (based on findings of Benson et al. 2009) prowl around the background. This reconstruction is featured in Sweetman et al. (2014).

Bernissartids packed this sophisticated dentition into relatively tiny jaws: these were not big crocodyliforms. Indeed, with body lengths of approximately 600 mm, bernissartids were probably the smallest crocodyliform species in the entire Wealden succession. Like goniopholidids, bernissartids bore osteoderm shields on their backs and bellies, but the dorsal series was rather more complex than those of other Wealden crocodyliforms. Rather than possessing two rows of interlocking osteoderms as we saw in goniopholidids and atoposaurids, bernissartids possess four rows of osteoderms along their backs. These comprise two sets of rectangular, double-keeled scutes along the midline, and laterally bordering square osteoderms with single keels (Salisbury and Frey 2001). None of these interlocked, and – based on what we’ve discussed for other Wealden Crocodyliformes – it’s worth considering what impact this had on bernissartid locomotion. Rather than supporting their trunks with scutes, it seems that bernissartids developed procoelus trunk vertebrae (that is, vertebrae with centra extending into the corpus of the vertebra behind) to support their bodies when walking (Salisbury and Frey 2001). This feature, along with their relatively complex osteoderms, is shared with eusuchians and are some of the reasons why these animals have classically been allied to these Crocodyliformes. Of further interest here is the biconvex nature of the first bernissartid tail vertebra – this has further implications for their locomotion, which we’ll get to below.

The bit on palaeoecology

Ecologically, it seems that bernissartids had a preference for hard shelled prey. Their blunt posterior dentition has been labelled as ‘tribodont’ – literally meaning ‘crushing teeth’ – and, like slamming a couple of anvils together, are ideally shaped to crunch hard shells. Some confirmation of this idea is seen in the wear facets often seen on tribodont bernissartid teeth. Classically, their prey was largely considered to comprise molluscs such as the freshwater snails and clams populating Wealden streams and lakes (Buffetaut and Ford 1979). Recently, a broader diet has been postulated for bernissartids however, the logic being that hard shells are hardly restricted to molluscs even in freshwater settings (Sweetman et al. 2014). Insects and crayfish probably formed as much of their diet as molluscs, all of which were likely procured or extracted from soft-substrates with the procumbent anterior teeth. We should not forget the savage-looking pseudocanines of these animals however: these would be of little use against hard prey items, but may have allowed for spearing relatively soft-animals. Perhaps bernissartids are best viewed as rather opportunistic feeders, primarily taking hard-shelled prey but not turning their noses to other types of food when the opportunity arose.

If gastropods like this Wealden mud snail, Viviparus cariniferus, had nightmares, they contained bernissartids.

Where was most of this prey caught? There is evidence that bernissartids were equally at home in water and on land. Their biconvex first tail vertebra suggests their tails were capable of considerable movement for providing burst propulsion through water and, unlike most other Wealden Crocodyliformes, their lack of interlocking osteoderms facilitated lateral trunk motion (Salisbury and Frey 2001). While compromising overall speed, this may have permitted greater amounts of manoeuvrability – ideal for pursing nimble, if relatively slow, aquatic arthropods. We’ve already mentioned that the reinforced trunk vertebrae of bernissartids would provide ample reinforcement for terrestrial locomotion, and their small size is relevant here as well. Like the small-bodied atoposaurids, and unlike the big goniopholidids, bernissartids had relatively small amounts of weight to lug around on land and could likely sustain long periods of terrestrial locomotion without tiring. It’s possible, therefore, that they found much of their prey on land as well as in water, perhaps enjoying the beetles, cockroaches and other tough-shelled terrestrial insects known to occur in Wealden deposits.

It’s worth pointing out that bernissartids may not be the only Wealden Crocodyliformes adapted for hard-shelled prey. The poorly known, 1.5 m long Wealden eusuchian Hylaeochampsa vectiana also has large posterior teeth ideal for smashing shelled prey (Clark and Norell 1992), although the dentitions of other hylaeochampsids are complex and it’s possible Hylaeochampsa had a very varied diet. As discussed for other Wealden Crocodyliformes, it’s likely that the size difference between the bernissartids and Hylaeochampsa would prevent too much overlap in prey preference: the latter may have been capable of eating large molluscs or even small armoured vertebrates, which were probably unavailable to bernissartids. There's lots more we could say here, but I'd best not - maybe Hylaeochampsa will warrant dedicated discussion at a later date.

The end

And I guess that's where we'll leave the Wealden Crocodyliformes for now. As alluded to above, there are other crocodyliform species and groups we could discuss, but they're generally less well known than the taxa we've covered across these posts and it would be difficult to discuss them in comparative depth. I hope you've enjoyed this series of themed posts and, if artwork of ancient Wealden animals is your thing, come back soon for a big announcement about an event related to just that.

References

Benson, R. B., Brusatte, S. L., Hutt, S., & Naish, D. (2009). A new large basal tetanuran (Dinosauria: Theropoda) from the Wessex Formation (Barremian) of the Isle of Wight, England. Journal of vertebrate Paleontology, 29(2), 612-615.
Buffetaut, E., & Ford, R. L. E. (1979). The crocodilian Bernissartia in the Wealden of the Isle of Wight. Palaeontology, 22(4), 905-912.
Clark, J. M., & Norell, M. (1992). The Early Cretaceous crocodylomorph Hylaeochampsa vectiana from the wealden of the Isle of Wight. American Museum novitates; no. 3032.
Salisbury, S. W. & Naish, D. (2011). Crocodilians. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 305-369.
Salisbury, S. W. & Frey, E. 2000. A biomechanical transformation model for the evolution of semi-spheroidal articulations between adjoining vertebral bodies in crocodilians. In Grigg, G. C., Seebacher, F. & Franklin, C. E. (eds) Crocodilian Biology and Evolution. Surry Beatty & Sons (Chipping Norton, Aus.), pp. 85-134.
Sweetman, S.C., Pedreira-Segade, U., & Vidovic, S. (2014) A new bernissartiid crocodyliform from the Lower Cretaceous Wessex Formation (Wealden Group, Barremian) of the Isle of Wight, southern England. Acta Palaeontologica Polonica (in press)

If money was no object, would you buy a sauropod skeleton, or artwork of them? A question to ponder while these Lower Cretaceous rebbachisaurids and 'Angloposeidon' look for water in this desiccating Wealden lake.

The greatest threat to 21st century palaeontology is the inflating commercialisation of fossils. At least, this the view put forward by Kenshu Shimada and colleagues (2014) in a recent article. I don't disagree that this is a growing problem. While the commercialisation of fossils is not inherently wrong, the explosion in auctioning spectacular fossil specimens, often at prices which are well beyond the reach of the scientific institutions, presents many concerns for palaeontological science. This is more than just jealousy from poor palaeontological institutions: we're talking illegal plundering of fossil specimens, locality vandalism and loss of locality data which robs fossils of almost all scientific worth. At auction, buyers are often mislead by scientific over-advertisement to increase auction appeal. Some legitimate scientists are involved in this game, either selling, lending their interpretation to auction lots, or publishing details of privately-owned fossils in peer reviewed literature. The latter, even when done with the best intentions (e.g. Sereno et al. 2009; Tischlinger and Frey 2013) panders to the private fossil market, sending a signal that scientists will accept and make-do with this new status quo. Even museums are getting in on the act, toying with the idea of selling off historically-valuable specimens for funding. The results are legal, economic, ethical and scientific debates which we, as a community, have to work through to find balance between those wanting to profit from and privatise fossils, and those who want them publicly preserved, studied and shared.

Desperate times call for desperate measures, and maybe a radical approach is needed to help settle these debates. Such an idea was pushed forward by Shimada et al. (2014), who proposed that commercialising palaeoart may be a viable alternative to selling spectacular fossils. This is not quite the first time this idea has been mentioned, although I think it's the first time it's been mentioned in print. Admittedly, Shimada et al. do not dwell on the point too long, merely stating that:

"...suggestions have also been made that, similar to the annual meetings of the SVP, our paleontological community can perhaps promote the sales of fossil replicas and 'paleo arts' (e.g., paintings and 3-D models of extinct organisms) as acceptable alternatives [to real fossil specimens]." Shimada et al. 2014, p. 3

Intuitively, this seems like a good idea. Combining the lucrative art market with palaeontology should allow collectors to own fossil-related wares without loss of scientifically-important specimens. Artists would make money, more specimens would end up in academic institutions, and collectors would obtain rare and valuable items - everyone seems to win in this arrangement. As someone with some experience of working within the palaeoart industry however, I'm not convinced that this plan could be executed in the foreseeable future. There are three problems I foresee: 1) original palaeoart and fossil specimens are not as readily interchanged as some may think; 2) our art is not seen as particularly interesting or varied to wider audiences, and 3) the palaeoart community is simply not in shape to offer the high-value, sought-after art required for this bid, and will not be until it receives a lot more support from the scientific community at large.

A Tarbosaurus specimen made famous - or more rightly infamous - when put up for auction in 2012. It was ultimately repatriated to Mongolia after palaeontologists pointed out the illegal nature of its exportation from its native country. Image from (shudder) the Daily Mail.

1. Palaeoart cannot compete with genuine fossils for aesthetic appeal or as a status symbol

As with any material item, the ownership of fossils is pursued because of academic interest, the collector mindset of owning unique objects, admiration of the natural beauty and the attainment of status. Fossil specimens, particularly large and spectacular ones, not only meet these criteria but exceed them tremendously. They're extremely rare. They cost lots of money to buy and maintain. And they're amazing. Looking at a fossil reminds us of unfathomable depths of time and evolution, and the very limits of our human experience. You don't have to know anything about fossils or palaeontology to be awed by them: their mystery, impressiveness, rarity and worth is obvious to anyone. It's little wonder that fossils can be sold at auction for large sums of money: they're immensely charismatic objects, and make major statements about the taste and wealth of their buyers.

If we intend on replacing fossils with palaeoartworks at auction, the latter will need to replace this appeal. Unfortunately, even the best-executed, most accurate or famous palaeoartworks can't inspire the same interest and awe as fossils themselves. That's not because palaeoartists are bad at their jobs, but because they're completely different things. Fossils are natural objects obtained by chance and perseverance, and palaeoart is a human-derived statement about palaeontological science. They're so different that we should probably abandon any hope of palaeoart being fossil substitutes, and realise that we need to sell palaeoart on its own merits. It seems naive to expect rich buyers to turn from fossils to fossil-related artwork when the two have such different cultural statuses, and I think we are misunderstanding the people buying these fossils if we think we can simply swap one for the other.

Like any art, selling palaeoart is dependent on it being a fashionable commodity, culturally significant enough that it seems worth spending money on. Working against palaeoart in this regard is its real lack of status outside of the (largely online) palaeontology community. Palaeoart processes and credibility are poorly understood among the public and its most famous practitioners are entirely unheard of. It seems mostly considered a branch of dry scientific illustration, visual manifestation of what scientists are thinking at a given time. Other times, it's mostly seen as art for children, or pseudo-fantasy work with a similar target demographic to science fiction and fantasy media. I cannot see such art readily appealing to the rich companies and celebrities who buy spectacular fossils at auction. The fact that master palaeoartists frequently find it difficult to auction their work at worthwhile prices lends credence to this idea. Sales of high-value palaeoart will not happen until we can demonstrate its cultural significance to people outside of palaeontology, and that's going to be an uphill struggle.

2. Palaeoart is probably too stylistically and compositionally homogenous to appeal to wider audiences

Because some art is sold on the strength of its style or composition, palaeoart may make some headway in the high-stakes open market so long as it offers a range of styles and subjects, with varied compositions and themes. Currently, palaeoartworks offer quite the opposite however, as it's compositionally and stylistically rather homogenous. Only rarely do palaeoartists deviate from realistic-ish portraits of animals, or animals in landscapes, to more stylistic or abstract waters. To my knowledge, this has never been done for significant financial gain. And yes, while palaeoartists do differ stylistically, it's a marginal difference compared to the spectrum elsewhere. It's little surprise that palaeoart has entered a deconstructionist phase in recent years because its practitioners have noticed how samey and trope-filled a lot of palaeoart is (best exemplified by Conway et al. 2013). From a marketing point of view, this is dangerous territory. It's easy to imagine that many will take the attitude that 'once you've seen one piece of palaeoart, you've seen it all', and if its general style or compositions are not to taste, there's little chance of it being bought. We must remember that our objective here is to make palaeoart appeal as widely as possible, and not only to palaeontologists and dinosaur fans.

Those of us who know palaeoart may argue that it is continually changing and developing, and subject to fashions and trends as much as other artworks. These are mostly related to the methods of reconstruction and changes in science however, and will be rather subtle to lay audiences. We all think All Yesterdays was a big deal, but for the uninitiated, it's just an excuse to draw extinct animals in different postures or with slightly tweaked anatomy. In short, unless potential buyers are up on palaeontological and palaeoart history - and most aren't - this significance of palaeoartworks will be missed. Our current lack of artistic diversity may be a real problem for those wanting to make palaeoart a valuable commodity.

Misty the Diplodocus, auctioned last year in the UK for £400,000. Image by Luke MacGregor/Reuters, from here.

3. Palaeoart needs support to develop the culture required for commercialisation

The points made above highlight palaeoart's biggest problem: it basically lacks context and culture outside of a tiny community. There's no way we can take this little industry to auction and expect it to compete with awesome fossils. There may be ways we can alter this, but it might require a significant overhaul of the way palaeoartists work with scientists, educators and the media. To be honest, palaeoartists are presently treated quite awfully with little public promotion, a resulting lack of public identity and an infamously poor and unreliable economy. This condition describes the 'major players' or 'masters' of palaeoart as well as its lesser-known or new, fledgling artists. We need to change this if we want palaeoart to step into the world of high-value auctions.

How might we go about this? Firstly, it is time that artists were obviously and publicly credited for their work. In other industries, artist names are essentially brands. Artwork is frequently valued because of who produced it rather than the art itself. In most off-line activities, palaeoartist accreditations are difficult to spot or, worse, allocated to faceless institutions or companies. This is even so in richly illustrated palaeontology books, where artists are treated as secondary importance to authors. This may be why palaeoart is often only seen as an extension of science: funny as it sounds, we rarely acknowledge palaeoartist roles in producing palaeoart. As long as we largely deny exposure and name-recognition to palaeoartists, no-one will pay top dollar for their work. Perhaps we should start prominently naming artists who make significant contributions to palaeontological projects - galleries, articles and books - to start building their reputations. With time, artist association may pay off commercially, lending 'brand recognition', credence or quality to the projects they work on. People could start to follow palaeoartist careers in the way we can musicians and actors and, when their original work comes up for sale, potential buyers will have some concept of its significance to the artist as well as wider scientific culture.

We also need to stamp out the idea that all palaeoart, and palaeoartists, are interchangeable. Not only is it highly detimental to palaeoartworks, but it cripples the industry as a whole. Book publishers, outreach coordinators and even major museums regularly have in-house artists directly copy palaeoartworks rather than using original work. Sometimes, the shamelessness of these acts is unbelievable. The reasons for this are normally to do with money and desire for 'in house' styling. This is a disaster for multiple reasons. From an outreach perspective, plagiarising artists often misunderstand their subjects and make mistakes: we fail in our goal of conveying palaeontology accurately. More broadly, these acts are questionable ethically and legally, they dilute the importance and impact of original work, are insulting to the original artists, and ultimately reduce the market value of palaeoartworks. I can't think of another artistic medium which allows this. Radio stations didn't play cover versions of Beatles songs because they don't want to pay royalties. Book publishers do not force artists to re-draw the Mona Lisa so it matches their house styles. They herald the art for what it is, its significance, and the hard work of the people behind it. By allowing palaeoart to be copied so liberally, we send the message that the artists are unimportant, which means their work is also worthless and undesirable.

The sort of crap palaeoartists have to put up with all the time. One is an original image considered shocking and thought provoking when first published, the other is a direct knock-off, produced for profit by a renowned palaeoart plagiarist. The institution hiring the latter has since taken the offending image, and others of similar derivation, out of circulation.

This has to change if palaeoart is to develop any real sense of culture. After all, if the palaeontological community does not respect its artists, how can we expect wider audiences to? We need to stop employing individuals who repeatedly rip off other people's work and, if asked, palaeoartists themselves should refuse outright to rip-off the art of their colleagues. Authors, exhibition developers, publishers, and educators should employ genuine palaeoartists rather than knock-off illustrators, and obtain the education to know when 'historically important' images are more appropriate than new ones. We cannot have culture without a sense of history, after all. Some folks within the palaeontological community already strive to do this, often against the tide of publisher might. Palaeoartists do also sometimes get treated well by publishers, even being featured in well publicised, high quality books celebrating their art (e.g. White 2012). Unfortunately, these are exceptional instances in the palaeontological community, when they should be normal. I don't doubt this proposal will require more money to obtain original artwork for projects rather than second-rate copies, but the investment might pay off: better treatment and more business for palaeoartists; higher quality work for the products concerned; and more marketability for both. This would be a major step towards offering palaeoart as a replacement for fossil specimens.

Longer term, granting palaeoartists more fame, income and success can only have a positive outcome. Financially comfortable artists have more time to make art, which gives us more art to sell instead of fossils. Moreover, it allows time for experimentation. Palaeoart really needs this if we want it to float economically outside of the immediate palaeontological community. We need more stylised and abstract art in addition to more conventional scientific illustrations, or service to dinosaur fanboys. We can look to the popularity of modern animal artwork as a guide here: it's very popular, but also mostly stylised. Palaeoartists have little to offer in this area at the moment, and, if palaeoart is to really help push against over-commercialisation of fossils, we need fossil-based art which is as interesting and striking as the fossils themselves.

But will any of this ever happen?

The palaeoart industry has always been a bit of a slum to work in. Even Charles Knight, arguably the most famous palaeoartist ever, spent much of his career on sporadic contracts which made relatively little money (Milner 2012). There's no obvious sign that this is going to change either, or - from a strictly functional perspective - that it even has to. Palaeoart will probably always be around, its practitioners making the best they can from the opportunities that come their way. But this is not to say that perseverance alone makes it fit for high profile auctions as an antidote to over-commercialisation of fossils. There's very little palaeoart can do to develop itself, let alone take the brunt for another cause, until it is properly supported and respected by scientific and media communities, and we stop treating it as a near-worthless addendum to palaeontological science.

References

Conway, J., Kosemen, C. M. & Naish, D. (2012). All Yesterdays: Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals. Irregular Books.
Milner, R. (2012). Charles R. Knight: The Artist who Saw Through Time. Abrams.
Sereno, P. C., Tan, L., Brusatte, S. L., Kriegstein, H. J., Zhao, X., & Cloward, K. (2009). Tyrannosaurid skeletal design first evolved at small body size. Science, 326(5951), 418-422.
Shimada, K; Currie, P. J., Scott, E., & Sumida, S. S. (2014). The greatest challenge to 21st century paleontology: When commercialization of fossils threatens the science. Palaeontologia Electronica Vol. 17, Issue 1; 1E: 4 p;
Tischlinger, H. & Frey, E. (2014). A new pterosaur with mosaic characters of basal and pterodactyloid pterosauria from the Upper Kimmeridgian of Painten (Upper Palatinate, Germany). Archaeopteryx, 31: 1-13.
White, S. (2012). Dinosaur Art: the World’s Greatest Paleoart. Titan Books, London.

As folks who follow me on Facebook and Twitter will have gathered, recent weeks have been spent not-so-secretly gearing up for my very own palaeoart gallery in the UK's spiritual home of palaeontology, Lyme Regis. Today, we're finally ready to go public: Palaeoartworks, as it's ended up being known, is now open.

Panoramic view of Palaeoartworks in near entirety. Image courtesy Georgia Maclean-Henry.

Palaeoartworks can be found in the Town Mill Malthouse, part of the Town Mill complex in the heart of Lyme Regis (map) and, from today (April 7th), is open every day until May 4th (including the Easter holidays). Admission is free, from 10.30am to 4.30pm daily.

The gallery is part of the famous Lyme Regis Fossil Festival, an annual event celebrating palaeontology and natural history with fossil stalls, outreach events, and public lectures by leading palaeontologists. The festival, now in its 9th year, will be running across the Early May Bank Holiday (Friday - Sunday, 3rd-4th May). I'll be present at the gallery for its final weekend, and it would be great to meet some readers if you find yourself in Lyme Regis for the festival. There may even - for the first time ever - be prints available to buy.

So, what can you expect from the gallery? Hopefully, there's a wide enough range of restorations to keep most tastes happy: dinosaurs, pterosaurs, Crocodyliformes, invertebrates, marine reptiles, even some fish. These are organised into are three collections. The first is dedicated to palaeoart of the Wealden Supergroup, a sequence of Lower Cretaceous sediments found throughout south-east England with an intensely studied palaeobiota and palaeoenvironment. Regular readers will know that I've been publishing a lot of Wealden artwork recently - enough, it seems, to fill the wall of a gallery - and my favourites are now on display.

Ever see a man make a gallery out of Wealden palaeoart? Yes, once.

The second set comprises - big surprise here - pterosaurs, the Mesozoic flying reptiles which need no introduction to anyone reading this (but if you need an introduction, consider this). A lot of the pterosaur imagery is reproduced from my book, but there's also some rarely seen or entirely new stuff here too. Efforts were made to show pterosaurs at their most diverse and interesting: you'll see them swimming, climbing, assaulting little dinosaurs, imitating famous film posters, and all sorts of stuff.

Partial shot of the 'Pterosaur' collection. There's a lot more to see in the gallery itself.

The last collection doesn't really have a theme, instead just being a suite of pieces I especially like: mating tyrannosaurs, fuzzy pachyrhinosaurs, noir-inspired palaeoart and so on. This section also features a video of art for which there was no space, including several brand new pieces and modified versions of older artwork. All of the art in the collection was produced in the last three years.

Miscellaneous palaeoart things: paintings, a discussion of ammonite palaeoart, and a scrolling movie of artwork.

If pictures say 1000 words, there's at least 40,000 words on display at my Palaeoartworks. That, however, wasn't quite verbose enough for me, so you'll also find general introductions to the principle art subjects and several 'Palaeoart Case Studies': plinths showcasing fossil specimens behind select reconstructions and some explanation of how palaeoartists use these in their work. There's six of these in total, detailing the different approaches palaeoartists can take to fossil reconstruction, how sometimes we have to look beyond fossils of one particular species to obtain data, and how confident we can be about the resultant restorations. I'll share some of these brief bits of text online over the next few weeks.

So that's Palaeoartworks, then. Coming off the back of a post where the status of the palaeoart industry was not shown in a particularly good light (head here for the full article), it's nice to be writing about an event which pushes palaeoart to the fore. We need more events like this. Overall, I'm really happy with the gallery and hope you enjoy it too - remember to sign my guest book so I know you've visited!

A few acknowledgements

Naturally, there are a lot of people to thank here. Hats off to Kimberly Clarke for inviting my work down to Lyme Regis and organising the gallery space; Philip Clayton for helping organise and install the gallery; University of Portsmouth for sponsoring my printing costs and supplying in-house printing services; Gary Blackwell of Dinosaur Isle and Steve Sweetman for supplying a cast of Koumpiodontosuchus. A huge thanks to palaeoartist and Maximum cassowary-wrangler Gareth 'GaffaMondo' Monger, who provided top-quality printing and framing under tight deadlines (is there any other type?) - Granthams prints come highly recommended. Southsea Gallery virtually saved the show at the last moment. Finally, as usual, thanks to Georgia Maclean-Henry for help and support throughout the entire organisation and installation process. It's totally her fault if the pictures are wonky, though.

If you're heading to Lyme Regis this weekend, or indeed at any point until May 4th, you should stop by the Town Mill: a dedicated gallery of palaeoart lies within. It contains more than just a bunch of pictures however, as it also endeavours to explain how palaeoart is done. A good palaeoartist restores long vanished skeletomuscular systems; knows how to fill anatomical gaps; gives a sense of size to alien-looking creatures, and constantly adapts to changing science to render their subjects more accurately. If they do their job well, viewers won't see how much (often considerable!) paper palaeoartists pull across the patchy, cracked fossil record. But how, specifically, are these illusions pulled off? And can we really be that confident about the results?

Some of the answers lie at my Lyme Regis gallery. Along with the paintings you'll find 'Palaeoart Case Studies', short explanations outlining the path from fossil to reconstruction. In each case, relevant fossil material is also provided to demonstrate how much - or little - artists have to work with. There's six of these in total, and I'll be sharing them here over the next few weeks. First up are the crowd-pleasing giant azhdarchid pterosaurs, animals which are so commonly reconstructed that we must know buttloads about their anatomy and proportions. Or do we? Read on to find out how confident, or not, pterosaur palaeoartists really are about reconstructions of giants like Arambourgiania philadelphiae, below.

Giant azhdarchid pterosaurs: iconic, famous, mysterious

Reconstruction of the giraffe-sized monster pterosaur Arambourgiania philadelphiae. The dirty secret is that 95% of what you see here is extrapolated from other animals.

Restorations of giant azhdarchid pterosaurs like Arambourgiania, Quetzalcoatlus and Hatzegopteryx are understandably common. What captures the imagination more than a giraffe-sized animal with wings spanning 10 m and a 2 m long head? All pterosaurs have an unusual air about them, but giant azhdarchids also have a majesty which is hard for artists to resist. Despite the common nature of their reconstructions however, giant azhdarchid fossils are not only very rare but also extremely fragmentary. No complete, or even near complete, fossils of giant azhdarchid skeletons are known, and a standard family kitchen table could hold the entire inventory of giant azhdarchid bones from around the world. Arambourgiania, for instance, is known from little else than the giant, tubular neck vertebra shown below. It stands to reason that these reconstructions are based largely on inference and educated guesswork, but are they simply products of imagination, or is there more to it?

Arambourgiania philadelphiae holotype vertebra, UJA VF1. From Martill et al. 1998. Scale bar represents 100 mm.

When attempting to restore the appearance of a poorly known fossil species, the first port of call is the anatomy of more completely known, close relatives - the closer the better. The best known azhdarchid species have 3 and 5 m wingspans, so were only a fraction of the size of their bigger cousins. With such a size difference, it is not sensible to assume that the larger animals were perfectly scaled-up versions of these smaller ones. Organisms rarely evolve different sizes without changing proportion somewhere. Bones of larger animals are often more robustly built than those of smaller ones, for instance, because bigger animals have greater masses to support. This is certainly true for giant azhdarchids, as is an disproportionate increase their neck lengths which correlates with size. Paying attention to seemingly trivial scaling details like this can make a tremendous difference to the accuracy of a reconstruction, especially when a lot of extrapolation is involved.

However, this is only half of the story about restoring giant azhdarchids, because deciding which animals are closely related among this group can be difficult. Not all azhdarchids were alike, and the interrelationships between them is unclear. In these muddy taxonomic waters, palaeoartists have to make some educated guesses. Whereas palaeontologists can admit that their data has limitations or that the relevant studies have not been done, palaeoartists have to stretch current data to finish their work. Artists restoring animals with poorly determined taxonomy like giant azhdarchids have to decide which other animals serve as the best models for their reconstructions, and this often involves some degree of intuition and opinion. Such palaeoartworks are especially vulnerable to being proved inaccurate when new data becomes available. Until then, the best reconstructions of these animals are simply those which use the most careful extrapolations and guesswork, and this should be borne in mind when looking at any reconstruction of a giant azhdarchid or other, poorly known fossil species.

Come back soon for the next case study!

Reference

Martill, D. M., Frey, E., Sadaqah, R. M., & Khoury, H. N. (1998). Discovery of the holotype of the giant pterosaur Titanopteryx philadelphiae ARAMBOURG 1959, and the status of Arambourgiania and Quetzalcoatlas. Neues Jahrbuch fur Geologie und Palaontologie Abhandlungen, 207, 57-76.

It's time for part 2 of our 'Palaeoart Case Studies' series, this time featuring two subjects: the tiny Cretaceous crocodyliform Koumpiodontosuchus and the probable Lower Cretaceous troodontid Yaverlandia bitholus. Unlike our last subject in this series, giant pterosaurs, neither of these animals is huge. Koumpiodontosuchus is particularly diminutive with an estimated adult length of 600 mm long. Presenting the scale of an animal accurate is important for good palaeoart, as it's not only an important factor in the animal's biology and ecology, but also an integral part of it's character. Small animals present palaeoartists with a particular challenge because many folks hold the preconception that all extinct animals were large. For diagrammatic images, simply adding a person, modern animal or familiar object next to our creature shows its size, but this cannot work when rendering scenes that took place millions before familiar entities appeared. How do palaeoartists get around this? Read on to find out.

Yaverlandia represents the result of a recent palaeoart success story. After many years of trying, it seems palaeoartists have finally got the hang of recreating convincing-looking feathered dinosaurs. How did they do this? In short, by abandoning the need to show all dinosaurs as scaly reptiles and embracing the birdiness inherent to many species (or, to flip this around, realising that many traits unique to modern birds were common to many of their dinosaur ancestors). But what does this mean for the way we reconstruct troodontids and other feathered dinosaurs? Again, the answers are below.

This series of case studies is in aid of my art gallery in Lyme Regis, running until May 4th, at the Town Mill. Full details here.

Koumpiodontosuchus: a tiny, button-toothed crocodyliform

Reconstruction of the tiny Wealden bernissartid Koumpiodontosuchus aprosdokitii. Hopefully, you can see that it's not a large animal without having to think about it too much, but why is that?

The size of extinct animals a favourite topic of palaeontology aficionados, and presenting it accurately is an important goal for palaoartists. Although we often think of extinct species as very large animals, most were not giants. The skull of the tiny Cretaceous crocodyliform Koumpiodontosuchus show below, for instance, belonged to an adult individual that, in life, was about 600 mm long. But how can palaeoartists express a sense of animal size - big or small - without the use of modern objects, animals or people for reference?

Some general trends of animal appearance can be useful in conveying size in extinct species. These probably aren’t features that most of us think about when observing animals, but they provide palaoartistists with some tricks to give a sense of scale to their subject matter without using other objects or animals for scale. Generally speaking, facial features - particularly the eyes - of larger creatures are relatively smaller than those of more diminutive animals. The limb bones of larger animals are more robust and, as they approach the extremities, are proportionally shorter. Smaller animals often have less conspicuous muscle contours than larger animals, particularly if they have a fluffy covering and, in being lighter, smaller creatures are frequently more sprightly and ‘weightless’ than larger ones.

Animal proportions only give a very general sense of scale, however. To give a more precise measure, palaeoartists often juxtapose relatively familiar species alongside their subjects. The use of ‘background’ animals, or different varieties of plants, are useful in this respect. Even if the audience is not very familiar with these background entities, their proportions in relation to the subject gives an impression of scale. This can work in inverse, too: bigger animals or plants, shown in low contrast at a distance, can help reinforce the size of smaller subjects. Crafty consideration of point of view can also help: does the subject need a very low, tight point of view to be seen, or does a wider frame capture it more adequately? Again, these are not necessarily factors that we consider when viewing animals or artwork of them, but they are essential considerations for palaeoartists attempting to reconstruct not only the anatomy and lifestyle of their subject, but also their size and physical presence.

Yaverlandia: Britain's most bird-like dinosaur

Two Yaverlandia investigate a termite-riddent tree stump in Lower Cretaceous Britain. As with many other dinosaurs, their depiction here as very bird-like creatures is the result of palaeoartists having to completely overhaul the way feathered dinosaurs are rendered.

Known only from skull caps, Yaverlandia bitholus is one of Britain’s lesser known dinosaurs. Found in Lower Cretaceous Wessex Formation cliffs close to its namesake, the Isle of Wight coastal village of Yaverland, it was thought for a long time to represent a member of the bone-headed dinosaur group Pachycephalosauridae. Recently, it has been reinterpreted as Britain’s first troodontid, an omnivorous theropod dinosaur closely related to birds and familiar carnivores like Troodon, Velociraptor and Deinonychus. Troodontids were big brained, nimble animals and most were rather small. Yaverlandia was no exception, with a tentative length estimate of about 2 m.

Any restoration of Yaverlandia and its kin has to incorporate data on dinosaur feathering, details of which have only been available in earnest for the last 20 years or so. The uptake of feathered dinosaurs among palaeoartists has been variable. Some restrict them to specific regions of the body, while others provide smatterings of feathers across primarily scaly skin. Increasing numbers of artists restore these animals as very bird-like however, with feathers across their entire bodies including their heads, tails and legs. Fossil evidence is clearly in line with this latter approach. Bird-like dinosaurs, including troodontids, have been discovered with extensive feathering that covers their not only their torsos necks, heads and tails, but even sometimes their legs and toes.

These discoveries have given palaeoartists a lot to think about when restoring the appearance of bird-like dinosaur species. Feathers are complex, three-dimensional structures which alter the body profile of their owners. They plump the appearance of the body and smooth contours of the animal’s profile. Thus, if a dinosaur has complex feathers, we can no longer simply restore their musculoskeletal system and wrap skin over it, as often done in the past. What’s more, palaeoartists have to think carefully about the way feathered dinosaur arms and hands are rendered, because their feather configuration is similarly complex modern bird wings: feathers erupt from the tip of the second finger to the elbow, with feathers of the shoulders covering the ‘gap’ between forelimb and body feathering.

These ‘new look’ dinosaurs are more bird-like than ever, and evidence is mounting that feathers appeared much earlier in dinosaur evolution than classically realised. It is even quite probable that Tyrannosaurus was feathered. This is disheartening to some who ‘prefer’ the appearance of scaly dinosaurs, and many still erroneously render troodontids and their kin with scaly hides. Wholly feathered restorations of such dinosaurs are without doubt factually accurate renditions however, and entirely uncontroversial among scientists.

For the the final set of Palaeoart Case Studies produced for my Lyme Regis palaeoart gallery (running up until May 4th - catch it now before it's too late! Details here.), we're going to focus on molluscs. Yeah, that's right: palaeoart of squidy things, snails, clams and allies. Given that most palaeoart focuses on charismatic reptiles and mammals, this might be a hard sell. Let's see how the blog hits go with this one...

The general rarity of molluscan palaeoart occurs in spite of this group having a much better fossil record than virtually any vertebrate, as well as being fossils with uses beyond keeping socially awkward vertebrate palaeontologists off the streets. Molluscs do occur in palaeoart of course, but mostly as secondary or background animals, adding flavour to scenes dominated by larger, more charismatic species. This is a shame because molluscs are extremely interesting creatures in their own right, and especially so when we look at the bizarre forms that existed before our Recent molluscan fauna. Conchology is fun in the modern day, but becomes downright mind-bending when multiplied with deep time.

How confident can we be about the life appearance of these ancient shellfish? Because many molluscs have a fossil record quality which is basically opposite that of many palaeoart favourites (i.e. mountains of complete specimens), you might expect that we know a lot about their soft-tissues and life appearance. Do we? Read on to find out.

Erymnoceras: Ammonites - common fossils, artistic enigmas

Are there any more creatures more frustrating to palaeoartists than ammonites? These ancient cephalopods (the group of molluscs that comprising the shelled Nautilus, and the coeloids - squid, octopuses and cuttlefish) are superabundant in many Mesozoic marine deposits and, given this, we would expect at least a few extremely well-preserved specimens which reveal details of their soft-part anatomy and life appearance. This has certainly happened for fossil squid and belemnites, which are known from specimens showing their tentacle counts, ink sacs, body shapes and - sometimes - even the sizes of their eyes. Ammonite fossils are nearly as common as belemnites and certainly far more abundant than fossil squid, so there must be some fossils which inform palaeontologists and palaeoartists about their life appearance... right?

Male and female (respectively) Jurassic ammonites, Erymnoceras coronatum. The size difference between these genders is well constrained by fossil data, but the appearance of the actual animals is not.

Amazingly, no. The basic details of ammonite life appearance are far from clear, and exceptional preservation in the group is almost unheard of. Even the mineralised components of their radulae (rasping organs bearing numerous ‘teeth’, common to most molluscs) are incredibly rare, and good soft-tissue outlines of their bodies are unknown. While we can be certain that a squid-like organism lived in the last chamber of their shells (the ‘body chamber’) and was anchored in by muscles which left distinctive scars on the internal body chamber wall, little else can be said with certainty about their appearance. For instance, how many tentacles did they have? They very likely had some because they represent a grade of cephalopod evolution between Nautilus and coeloids, both of which bear tentacles. However, Nautilus has 90 small tentacles, and most coeloids have 10 large ones (octopuses, of course, have only eight). So how many did ammonites have? 10? 90? Another number entirely? And what of their eyes? Coeloids have large eyes and excellent vision on par with that of vertebrates, while Nautilus eyes are little more than organic pin-hole cameras. Which sorts, if either, did ammonites have?

And these are only immediate, cosmetic quandaries: much remains to be learned about ammonite floating postures, swimming abilities, and lifestyles. Given how elaborate some of their shell shapes are, and the unusual proportions of their body chambers, some ammonites must have had very unexpected appearances and floating mechanics indeed.

Despite being creatures which occur so commonly as fossils that it seems like we should know everything about them, ammonites are creatures fraught with uncertainty for artists and palaeontologists alike. Until new data comes to light, all life reconstructions of ammonites should be taken as extremely tentative, almost speculative renditions of their actual appearance.

Viviparus: a modern glimpse of the past

At first consideration, it may seem that accurately restoring ancient snails may be as hopeless as precisely restoring an ammonite. Like ammonites, their soft-parts are virtually unknown in the fossil record, the slug-like organisms inhabiting their coiled shells only represented by muscle scars left inside the shell.

The Creaceous Wealden mud snail, Viviparus cariniferus; probably the most accurately reconstructed extinct animal on this blog.

This is only sometimes the case, however. Unlike ammonites, snails - known formally as gastropods - are still alive in the modern day, and some types have extraordinarily long evolutionary histories. In some cases, members of modern genera evolved hundreds of millions of years ago, and remain largely unchanged in the present. This is so for members of the gastropod genus Viviparus, which first appear in the Middle Jurassic (c. 168 million years ago) and are still around today. For palaeoartists, these modern animals provide direct insights into the probable life appearance of their older cousins. For instance, modern Viviparus often have variably developed brown and ochre colour banding swirling around shells, so we may infer that their extinct relatives had the same patterning. The head and muscular foot (the name of the creeping gastropod propulsive organ) of modern Viviparus are also rather short and relatively broad, with two long tentacles emerging from the head and prominent eyes situated at their bases. We can’t know for certain that this is exactly what ancient Viviparus looked like, but it’s more parsimonious to assume that they resembled their modern counterparts than looking drastically different. The Early Cretaceous species shown here, Viviparus cariniferus, has been reconstructed with this logic in mind.

Modelling extinct animals on modern variants of the same species does not only apply to gastropods. The closer a fossil assemblage is to the present, the more likely it is to contain animals which have extremely close modern relatives, if not the exact same species. These instances provide palaeoartists with many models to essentially copy and paste into extinct scenes. If the biology of the modern variants is also well understood, they can also lend some compositional input to a palaeoartwork. A painting with Viviparus, for instance, would be most sensibly set around a relatively still or slowly moving water body, as this is where species of these gastropods occur in the modern day. Likewise, the salinity tolerances of modern Viviparus are low, so they only occur in freshwater: a reconstruction of these animals in this domain would therefore be logical. As with lots of palaeoartistic tricks, this technique is directly adapted from palaeontological science, where the biology of modern animals with fossil counterparts is frequently used to shed light on the depositional conditions and palaeoenvironmental settings of the rocks they occur in.