Gallery and print store

Friday, 20 February 2015

Deinonychus, Parasaurolophus, Dreadnoughtus and Carnotaurus welcome in the MarkWitton.com print store

Since launching a limited print buying service at the close of last year I've had enough interest to warrant investing more resources into print sales. The result is an online print store over at the new slightly revamped MarkWitton.com where you can buy prints at a range of sizes and prices with just a few mouse clicks. Payment goes through Paypal, and delivery should be within a week or so for UK customers, and 2-3 weeks for international orders. There's a catalogue of recent artworks to choose from, which I'll expand over time, but I'm also happy to take orders for artwork not hosted there yet. If you would like a print of an older, unhosted piece, let me know.

To celebrate the launch of the store, I thought it would be cool to show four of my favourite new pieces of art generated within the last few months. These all represent private commissions which I have permission to post and sell as prints. If you want your own copy, you know where to go...

Dreadnoughtus dwarfs Talenkauen, is happy

"Oh, you say you're a medium-sized dinosaur? Sorry, it's hard to hear you with my head all the way above the trees here." Experts predict Dreadnoughtus schrani was jerk it was to other, smaller species like the iguanodont Talenkauen santacruensis. Print.

First up is Chris Wummer's commission of giant, latest Cretaceous titanosaur Dreadnoughtus schrani, an animal which needs little introduction after the publicity of its discovery last year. Dreadnoughtus was publicised as the most massive terrestrial animal of all time at 59 tonnes, but regular readers of the palaeoblogosphere may know that sauropod guru Matt Wedel questioned this over at SVPOW! through rough volumetric estimates of mass and, later, when considering the restored Dreadnoughtus trunk as too long. Palaeoartist Greg Paul has also provided contrary comment on the 59 tonne estimates and restored proportions (although I'm not really sure what context that article is presented in - it looks like an unpublished MS). Estimating the mass of any extinct animal is difficult and especially so at the extreme sizes represented by giant titanosaurs, but there seems good reason to think the Dreadnoughtus holotype individual achieved a mass of 30-40 tonnes. That's still very big of course, but within fairly 'typical' ranges for giant titanosaurs.

There are two versions of the Dreadnoughtus image shown here. Chris wanted the picture to have personal relevance and so asked for his house to be included. That choice was inspired by his residence in Philadelphia, the city were Dreadnoughtus was studied and unveiled to the world. Switching between the version with familiar modern objects and a completely 'natural' scene reinforced how difficult it is to show absolute prehistoric animal size without a frame of reference: Dreadnoughtus looks a lot smaller when its head isn't clearing a rooftop. Two ornithopods - the 4 m long iguanodont Talenkauen santacrucensis - were added to this version to help stress the size of the sauropod. It's still difficult to appreciate a precise size of the sauropod in this image, but hopefully it at least looks very big, which might be the best we can hope for in images without obvious scale references.

Deinonychus pair in the swamps

Two Deinonychus antirrhopus either taking a moment to drink, or looking at something really interesting at the bottom of that pool. Print.

Next up is Patrick Murphy's pair of Deinonychus antirrhopus. The Early Cretaceous dromaeosaur Deinonychus has been restored so many times that it's difficult to come at it from a fresh angle. I thought one way to do that was to not show it on open plains, but in a backswamp. Deinonychus is known from two geological units, the Cloverly and Antlers formations, both of which represent sediments deposited by ancient, subtropical rivers and their floods. Some sediments in the Antlers Formation represent large (10 m wide or more) abandoned river channels, complete with evidence of soils, low velocity or still water, and ancient vegetation (Hobday et al. 1981). The depicted animals are meant to have recently eaten something - their muzzles are still read with blood - and popped down to their local swamp for a drink and some shade. I imagine that these guys are set to sit down and digest after this, waiting until they get hungry enough to chase prey again.

The arms of the foreground animal are pressed tight to the body in the manner proposed by palaeoartistic Queen of the maniraptorans, Emily Willoughby, rather than held half-folded as we're more used to seeing them. As Emily explains, there is good reason to think the 'arms out' postures we're used to is nonsensical - animals just don't carry themselves like that (including ourselves: our arms don't just hang limp - we fold, stow and hold them when they're not in use).

These guys were a lot of fun to paint: Deinonychus has an appealing character - a sort of mash up of a wolf and a raptorial bird - which is fun to try to capture. My thought is that Deinonychus should always look like an animal which we would admire and revere, but would purposely avoid close proximity with.

Parasaurolophus, alone with other dinosaurs

Parasaurolophus walkeri, wondering where his friends are. Print.
Delano DuGarm's Parasaurolophus walkeri brings us back to the Late Cretaceous, specifically the Campanian. Delano's brief was for a fairly minimalist scene, which I think matches one part of the 'Campanian story' quite well. By this time some of the fauna and flora we think of as epitomising the Mesozoic were already gone or showing clear evidence of decline, including ichthyosaurs, some dinosaurs, pterosaurs and ammonites. Although some taxa were doing fine in this interval, and even radiating, seeds of change were already being sown for Cretaceous biospheres. We have to wonder how long many 'classic' Mesozoic groups would have lasted even without the global catastrophes occurring at 66 million years ago: even without them, the post-Mesozoic world might have been quite different.

Delano's lone Parasaurolophus painting gave a good opportunity to hint at this changing world. The left of the painting features a few (speculative) wading birds and two bird flocks leaving the trees - these, of course, are the 'new dinosaurs' that will live on through the late Cretaceous troubles. The Parasaurolophus on the right looks a bit big and cumbersome by contrast, sort of like an old design which can't compete with new technologies. Aiding this comparison is the relative chunkiness of the Parasaurolophus skeleton: hadrosaurs are hardly a svelte bunch, but the bones of Parasaurolophus are especially big and robust, with expanded areas for muscle attachment. As far as I'm aware, the significance of this is unknown (but let me know otherwise in a comment below!).

Carnotaurus with a difference

Azhdarchids > theropods, as demonstrated by this lousy predation attempt by Carnotaurus sasteri. Print.

Finally, we're popping back to Maastrichtian South America for Chris Tait's Carnotaurus sasteri vs. azhdarchids image. An obvious artistic departure from the rest, this is an attempt to achieve a comic-book style in line with Chris' intention to give this to his son as a present. I've tampered with minimalist, comic-book styles before and quite enjoy it. Comic-book palaeoart - especially Ricardo Delgado's Age of Reptiles graphic novels - has influenced my work since the age of nine because of the energy, character and personality infused into the animals. Of course, you have to try hard not to find character in animals like Carnotaurus which, with its strange proportions and anatomy, looks almost like work of comic book fiction already (must... resist comment... about fictional theropod design and Jurassic World...). Carnotaurus, like other abelisaurs, was adapted for speed more than manoeuvrability, and this attempt to grab a passing pterosaur snack is an example of how nimble, agile prey might easily evade one. The pterosaurs shown here are quite small, which might seem odd for very late Cretaceous azhdarchids - aren't the small pterosaurs meant to be gone by then? Fragments of pterosaur jaw from Late Cretaceous Hungary indicate that some azhdarchid species retained small absolute body sizes even when most of the group represented medium-giant species (Prondvai et al. 2014). The discovery of these smaller Late Cretaceous pterosaurs does not buck the overall trend of average pterosaur size increase throughout the Mesozoic of course, but it does show that there were some exceptions to this wider trend.

Yes yes yes... but how are the bees doing?


Regular readers will know that I'm donating all funds from February sales of one print to the Bumblebee Conservation Trust. The good news is that I'm now up to a donation of £130, and there's still eight days left to get your order in. I'm really happy to have sold enough of these to break £100 - huge thanks to everyone who's bought one - and exceeding £150 is my new goal. 

It's now easier than ever to buy a copy of the bee-charity print, so you can get yourself a copy and help our struggling wildlife with just a few mouse clicks. Prices start at £20 (+shipping), and I'm giving as much as I can from each sale to the trust. 

References

  • Hobday, D. K., Woodruff, CM, Jr., McBride, MW. (1981), Paleotopographic and structural controls on non-marine sedimentation of the Lower Cretaceous Antlers Formation and correlatives, north Texas and southeastern Oklahoma. Recent and ancient nonmarine depositional environments, 71-87.
  • Prondvai, E., Bodor, E. R., & Ősi, A. (2014). Does morphology reflect osteohistology-based ontogeny? A case study of Late Cretaceous pterosaur jaw symphyses from Hungary reveals hidden taxonomic diversity. Paleobiology, 40(2), 288-321.

Sunday, 8 February 2015

Controversial ceratopsids revisited: woolly Pachyrhinosaurus and scavenging Styracosaurus

Spurned on by a print request, I've spent free time this week revising two images of ceratopsids which may be familiar to long-term readers: my woolly Pachyrhinosaurus perotorum and scavenging Styracosaurus albertensis. The former is now just over two years old, and the latter a whopping eight years old - wow, have I really been messing about with internet palaeoart for that long?

Maastrichtian Alaska was quite chilly, but woolly Pachyrhinosaurus perotorum doesn't care. See this post for the original image and exploration of the concept shown here. Prints are available.
Because I appreciate some folks are fond of my original paintings, I haven't deviated too far from the original compositions and instead just added more detail, tweaked colour values and tidied up some sketchy areas. I'm very conscious of not 'pulling a Lucas' on my old work. Most importantly, the science has been improved/corrected: the cranial morphology of Pachyrhinosaurus perotorum is now correct to that species (like a doofus, I based the morphology in the original image on a different Pachyrhinosaurus species) and the tyrannosaur in the scavenging scene is appropriately filamentous. Thanks to Darren Naish, Zachary Miller and Christian Kammerer for discussions of Styracosaurus horn shape.

Have these depictions have been supported or refuted by any new discoveries? As far as I'm aware, skin impressions still remain elusive for Pachyrhinosaurus, although new data has emerged on the facial integument of juveniles (Fiorillo and Tykoski 2013). The 2014 discovery of Kulinadromeus and its assortment of filament-like scales, true filaments and other integumentary oddities (Godefroit et al. 2014) might indirectly add credence to the idea of shaggy ceratopsids, however. Along with Psittacosaurus and Tianyulong, Kulindadromeus shows that the evolution of ornithischian integument was complex, that single animals can bear a suite of different integument types, and that the assumption of dinosaur skin being ancestrally scaly is uncertain. The weird scales in (unpublished) skin impressions of Triceratops are further evidence that 'one skin fits all' approaches to reconstructing these animals are likely flawed, and that even clades with relatively limited anatomical disparity - like ceratopsids - had diverse integuments. Thus, the idea that some members of Dinosauria may have looked very different to our traditional interpretations is being strengthened by genuine data, and shaggy arctic ceratopsids remain a fun extrapolation of that concept. For further discussion on these points, check out my discussion of version one of the woollysaur painting.

The Campanian centrosaurine Styracosaurus albertensis scavenges the remains of a tyrannosaurid. He was going for warpaint on his face, but he ended up at 'Tonto'. For fun, the original 2007 version can be seen here. Prints are available.
What of scavenging ceratopsids, as in the reworked 2007 image of a tyrannosaurid-eating Styracosaurus? Ceratopsid omnivory has yet to be explored in the technical literature and, to my knowledge, remains best represented by a short paragraph in Paul (1991). More recently, Mallon and Anderson (2013) provided reasoning for why ceratopsids were not predatory animals, although their discussion seems to consider 'carnivory' synonymous with 'predation': opportunistic scavenging or omnivory are not explored. This leaves most discussion of ceratopsid scavenging online, and several famous denizens of the online palaeontological community seem to support it. Back in 2007 I wrote a long essay substantiating the idea. That essay is no longer online*, but the argument is pretty straightforward:

*After eight years, I figured it's time to archive my old Flickr stream. The bulk of the content there is not representative of modern science or a good representation of my work, so it's been taken offline. I won't pretend I'm not a bit sad to do so, but there's obviously reason for bringing internet searches to my best, most recent work, not images I created when first learning how to paint.

  1. As is well-known, a number of modern herbivores eat animal remains on occasion. This may reflect nutrient stress (thought to explain carrion use by hippos, which is not as common as 'common knowledge' might suggest) or else a method of supplementing a mineral-deficient diet (as in deer, cows, giraffes and a host of other hoofed mammals - Hutson et al. 2013). Remarkably, some cases of hippo carnivory involve the hippos killing animals first, and they will also scare other carnivores from kills to obtain carcass access (Dudley 1998). Of further interest is that entire herds of hippos will chew on carcasses when available - these are not the acts of rogue, aggressive or aberrant individuals (Dudley 1998). Note that studies on the carnivorous tendancies of generally herbivorous animals are in their infancy, and it may be that this behaviour is more common and opportunistic than we currently realise.
  2. Other species, such as pigs, ingest animal matter as part of their normal diets. Studies on some pigs suggest 28% of their diet is derived from animals, either being invertebrates or carrion (e.g. Thomson, and Challies 1988). There is no reason to think that large extinct animals were incapable of comparable omnivory, but we restrict most discussion of it to smaller dinosaurs and pterosaurs. We can predict that such animals should have jaws mostly adapted for herbivory (e.g. teeth suited to browsing and grazing, long 'cheek' toothrows, vertically displaced jaw joints etc.) but would also have some means to process animal remains (e.g. crushing teeth to break bones, caniform teeth or sharp beaks for ripping meat etc.).
  3. Ceratopsid jaws certainly belonged to primarily herbivorous species capable of chewing their food, but their approach to herbivory was unusual. Their teeth and jaws, unlike other herbivorous dinosaurs and mammals, were incapable of grinding plant matter. Instead, they sliced food into pieces, their teeth sliding vertically past one other like scissors. Ceratopsid beaks are also unusually deep and narrow compared to other dinosaurian herbivores, and recall the beaks of parrots in many respects. The beaks of these birds are famously powerful, enabling their owners to access a range of nuts, seeds and animal matter (e.g. Greene 1999). The diet of of ceratopsids has been questioned by palaeontologists because chopping plant matter is not common among modern herbivores. To the contrary, most food slicers are carnivores - meat is easier to chop and slice into easily digested chunks than it is to grind into a paste. One sensible suggestion is that ceratopsids ingested particularly fibrous, woody plant matter (see Mallon and Anderson 2013 and references therein). We might imagine them devastating Cretaceous shrubs, removing entire chunks of tree - leaves, branches and bark - with each bite, or overturning plants with their huge heads to access their roots and tubers. However, it is odd that their jaws aren't more convergent with those of other herbivores, as grinding mechanisms have developed so many times in multiple tetrapod lineage and might be considered optimal for breaking down plant matter. So, maybe ceratopsid jaws were used for more than simply eating plants, and their shearing teeth and hooked beaks are the traits of omnivory we mentioned above, equally capable of slicing plants and animal remains. Opening carcasses, snapping smaller bones and slicing meat was almost certainly possible with their jaws and beaks, and we might imagine ceratopids as Mesozoic variants of pigs: largely herbivorous species with opportunistic carnivorous tendencies, and certainly capable of competing with strict carnivores for carcass access. The possibility that they could occasionally kill other animals for food, as demonstrated by the aforementioned hippos, is not unreasonable.
Back in 2007 I mentioned a possible smoking gun for this idea - a rumoured Psittacosaurus specimen with bony gut content. Since then, it's become apparent that that specimen either doesn't exist, has disappeared or has otherwise been forgotten about - it's best to consider that an unsubstantiated rumour for now. Despite this, I still think the concept of ceratopsian omnivory has legs: maybe a technical paper on the topic would be worthwhile.

Bumblebee Conservation Trust charity prints: an update

In my last post I mentioned you can buy a print of my Tyrannosaurus vs. bees painting and donate money to the Bumblebee Conservation Trust. I'm happy to say £55 has been raised in the last week for this cause, and thanks to those who've bought in. It would be great to make even more money however: if you'd like to contribute, find out more here.

Of course, prints are available for all my other work too, including the ceratopsid pieces above. Contact me at wittonprints@gmail.com to order one, and check out this page for prices and other details.


References


  • Dudley, J. P. (1998). Reports of carnivory by the common hippo Hippopotamus amphibius: short communication. South African Journal of Wildlife Research, 28(2), 58-59.
  • Fiorillo, A. R., & Tykoski, R. S. (2013). An immature Pachyrhinosaurus perotorum (Dinosauria: Ceratopsidae) nasal reveals unexpected complexity of craniofacial ontogeny and integument in Pachyrhinosaurus. PloS one, 8(6), e65802.
  • Godefroit, P., Sinitsa, S. M., Dhouailly, D., Bolotsky, Y. L., Sizov, A. V., McNamara, M. E. & Spagna, P. (2014). A Jurassic ornithischian dinosaur from Siberia with both feathers and scales. Science, 345(6195), 451-455.
  • Greene, T. C. (1995). Aspects of the ecology of Antipodes Island Parakeet (Cyanoramphus unicolor) and Reischek's Parakeet (C. novaezelandiae hochstetten) on Antipodes Island, October-November 1995. Notornis 46: 301-31
  • Hutson, J. M., Burke, C. C., & Haynes, G. (2013). Osteophagia and bone modifications by giraffe and other large ungulates. Journal of Archaeological Science, 40(12), 4139-4149.
  • Mallon, J. C., & Anderson, J. S. (2014). The functional and palaeoecological implications of tooth morphology and wear for the megaherbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada. PloS one, 9(6), e98605.
  • Paul, G.S. (1991). The many myths, some old, some new, of dinosaurology. Modern Geology, 16: 69-99
  • Thomson, C., & Challies, C. N. (1988). Diet of feral pigs in the podocarp-tawa forests of the Urewera Ranges. New Zealand journal of ecology, 11, 73-78.

Monday, 2 February 2015

Tyrannosaurus, Mesozoic bees, and bee-friendly palaeoart!

The stem-birds and the bees - two juvenile Tyrannosaurus rex investigate a Cretaceous honey bee nest. Prints are available, and you'll be contributing to bee conservation if you buy one in February 2015. See below for details.
Here's something you don't see every day - a depiction of a beehive in the Mesozoic. Bees rarely make it into Mesozoic palaeoart, but genuine bees were certainly contemporaneous with non-avian dinosaurs. The oldest bees have been found in Early Cretaceous amber inclusions (Poinar and Danforth 2006) and their fossils show that many traits of modern bees - including those related to collecting pollen - were already present by this time. Indeed, one of the oldest known bees is preserved with bits of pollen stuck to its hair. Trace fossils also suggest that many modern bee behaviours - nest building, burrowing etc. - were also taking place in the Mesozoic (e.g. Genise et al. 2002).

Calibrating the Mesozoic diversification of bees is difficult because their fossils are exceedingly rare. However, the likelihood that early bees were pollinating early flowering plants means that their diversification is of interest to not only palaeoentomologists but also those trying to understand the establishment of modern ecosystems. The Mesozoic can seem like a time of weird and wonderful plants and animals, but this view is skewed by our interest in unusual Mesozoic megafauna. A lot of our modern biota and ecologies have their origins around these animals, so much so that time-travelling humans would probably find many Mesozoic settings quite familiar. It seems that Mesozoic bee diversity fits this idea, as studies of bee DNA suggests crown-group bees evolved in the Early Cretaceous and quickly diversified into groups we would recognise from the modern day (Cardinal and Danforth 2011, 2013). This radiation likely included the adoption of at least ancestral variants of complex social behaviour we associate with modern bees (Cardinal and Danforth 2011).

One of my favourite implications of this work is the suggestion that the Apini were present in the Late Cretaceous (Cardinal and Danforth 2011, 2013). Apini are better known as honey bees, and, assuming their ability to make and store honey in nests was ancestral to the entire group, we may have seen Late Cretaceous reptiles raiding their colonies like modern animal rob their nests today. I find concepts like this really 'ground' the behaviour of fossil animals - the idea that a theropod or small ornithopod might partake in sting-filled nest vandalism to obtain energy-filled honeycomb seems like a very real, likely concept, and far more grounded than the gladiator matches we often see associated with dinosaur foraging. I've tried to capture some of that reality in the image above, showing dog-sized juvenile Tyrannosaurus rex taking on a colony of increasingly angry honey bees. Getting past the bee defenses is not proving easy, and the smaller Tyrannosaurus is close to adopting a full-on duck-and-cover defensive response to his aggressors. Videos of bears failing nest raids often show them hunkering down and covering their faces with their paws - I thought it would be fun to have Tyrannosaurus try that with it's proportionally small arms.

Bee-friendly palaeoart. Yes, it's a thing now.

My sudden interest in Mesozoic bees was catalysed by a donation request for an auction at Cumberland House, Portsmouth's Natural History Museum. The auction is raising money for a new beehive at the museum and, rather than just printing off some old work, I thought it would be fun to produce something new and relevant to the event. I'll be providing a framed version of the above work as a lot for sale - check out the Cumberland House Natural History Museum Friends Facebook page for the latest on the auction.


The Cumberland House auction is not the only way to get a piece of palaeoart while helping bee-related causes - for the next month, any copy of this print I sell will directly help a leading UK bee charity. Yes, bees need charities now, being in trouble globally thanks to habitat loss, climate change and the wide use of insecticides (see, for instance, this, this, and this for a taster of this issue). Several national populations and species have gone extinct in recent years, and more are set to follow. This is not just a problem for the 'natural' world: we rely on bees to pollinate many of our crops. Food prices and availability are set to change for the worse as bee populations and diversity dwindle so, whether you consider conservation an issue or not, we need to do something about their decline. For this reason, all February 2015 sale proceeds of my Tyrannosaurus and bees print will be donated to the Bumblebee Conservation Trust, a UK charity devoted to restoring bee habitats, encouraging bee-friendly policies at local, national and European governmental level, and raising awareness of the bee conservation crisis. Prices for my prints start at £20 (+£5 shipping) - most of that will go straight to the bees, and you get a print out of the deal. Contact me at wittonprints@gmail.com if your want to know more.

References

  • Cardinal, S., & Danforth, B. N. (2011). The antiquity and evolutionary history of social behavior in bees. PLoS One, 6(6), e21086.
  • Cardinal, S., & Danforth, B. N. (2013). Bees diversified in the age of eudicots. Proceedings of the Royal Society of London B: Biological Sciences, 280(1755), 20122686.
  • Genise, J. F., Sciutto, J. C., Laza, J. H., González, M. G., & Bellosi, E. S. (2002). Fossil bee nests, coleopteran pupal chambers and tuffaceous paleosols from the Late Cretaceous Laguna Palacios Formation, Central Patagonia (Argentina). Palaeogeography, Palaeoclimatology, Palaeoecology, 177(3), 215-235.
  • Poinar, G. O., & Danforth, B. N. (2006). A fossil bee from Early Cretaceous Burmese amber. Science, 314(5799), 614-614.

Wednesday, 28 January 2015

Bonus pterosaur (anurognathid) art you've never seen before! (sort of)

Anurognathus ammoni makes itself like a tree, but doesn't leave. Prints are available.
Last week I unceremoniously dumped several revamped pterosaur images on the blog after they were prepared for a talk on one of my favourite topics - pterosaur functional morphology and biomechanics. Turned out that I wasn't quite done tinkering with old images however, because another piece - above - was set for 11th hour reworking. It shows one of the subject taxa of my talk - an anurognathid pterosaur - hunched up and perched in a tree, its cryptic colouration helping it to blend in somewhat with the underlying branch. The original version can be found in my book, with this newer variant merely adding more detail, depth and a bit of background.

This depiction of anurognathid palaeobiology isn't merely idle speculation on my part. In 2007, pterosaurologist Chris Bennett described a famously spectacular, tiny specimen of Anurognathus from the Jurassic of Germany preserved with its limbs and wing fingers folded around its body. Chris noted that this posture is common in anurognathid fossils but largely unseen in other pterosaurs, and suggested it reflected a common in vivo limb configuration specific to this group. He further speculated that the purpose of this pose was to make the animals compact and inconspicuous, for which cryptic colouring would also be beneficial. There are obvious parallels to make here with insect-chasing birds like nightjars and potoos, which also rely on specific postures and colouration to blend into their surroundings. This is not merely to avoid detection by predators, but also gives an advantage for ambushing prey. Given that anurognathids are widely considered insect-chasers, the surprising difficulty associated with catching some insect prey and the explosive flight ability of these little pterosaurs (stay tuned!), Bennett's speculations about their appearance and habits fit neatly into current models of anurognathid palaeobiology, and can be considered a reasonable way to depict these animals in palaeoart.

Coming soon - hopefully - a host of theropods, more pterosaurs, and the most exciting dinosaur art of all... a solitary hadrosaur!

Reference


  • Bennett, S. C. (2007). A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift, 81(4), 376-398.

Tuesday, 20 January 2015

Pterosaur art you've never seen before! (sort of)

Later this week I’m travelling to the Netherlands to give a talk on pterosaurs at the Museon, The Hague. I’ll be part of a series of public talks on Mesozoic reptile lifestyles celebrating the opening of the Museon's new Dino Jaws exhibition, and it should be a blast. I’ve revisited some of my older pterosaur paintings to add more detail and depth when featuring them in my talk, and thought I’d share the results here. Some of these images aren’t that old really, but, thanks to beefing up my painting rig before Christmas, I find some of my work from even a few months ago can look a lot nicer with just a few hours work. As usual, prints are available of all images shown below.

Arambourgiania: remaining huge in artwork since 2013. See this page for the original.
First up is a tweaked version of my 2013 Arambourgiania, a giraffe, and a standard wife-unit scale bar. There’s not much to say here – I just wanted to put more detail into the pterosaur so it looks better in a close-up panning presentation animation. At some point, hopefully soon, a version of this image featuring two azhdarchids will be published.

An azhdarchid in high-altitude, long distance flight. Original here.
Second, the flying azhdarchid which made a debut at TetZooCon last year. I felt the initial image was a bit flat, so this has more depth added to the background. The depicted animal is a ‘generic’ azhdarchid, although obviously similar to the smaller Quetzalcoatlus species. It’s shown flying rather high – many thousands of feet in the air – on a long-distance flight. Mike Habib and I have droned on about the awesome flight capability of giant azhdarchids for years, and we expect the range and flight speed of smaller azhdarchids – with, say, 5 m wingspans – to be relatively impressive too. They may not have been capable of booming around the planet with the same gusto as their giant cousins, but continent hopping was certainly not beyond them.

The anurognathid Anurognathus ammoni, brought to you by evolutionary processes which wanted Muppets to rule the skies. 
The third reworking shows a species at the other end of the pterosaur size spectrum, the diminutive Anurognathus ammoni. Some readers may recognise this painting from my book. Anurognathids haven’t been covered in much detail at this blog, but that will likely change soon when Mike Habib and I publish a new study on their functional morphology in the near future. This painting alludes to something which we attempt to quantify in that study – prey size. Anurognathids are frequently depicted as hawking relatively large insects like dragonflies, but – based on prey proportions in modern avian insect hawkers, and the delicate build of anurognathid skulls – much smaller insects were probably pursued instead. Catching aerial insects is already difficult enough, so why chase relatively rare, enormous and feisty prey when abundant small midges can be scooped out of the sky with relatively little effort? Because anurognathids aren't big beasts - wingspans of less than 0.5 m are common - their likely prey was probably best measured in millimetres, as shown by the Target Midge in this picture. Other features to note in this painting include the tufted wing tips and completely fuzzy face, both of which are known from fossils and, for the time being at least, unique to anurognathids. The ‘cryptic’ colouration and nocturnality are nods to recent work on these pterosaurs suggesting these pterosaurs were shy, well-hidden creatures which were primarily active at dawn and dusk. More on these neat pterosaurs as time – and manuscript progress – permits.

To finish – because I can’t not post this – here’s a poster for the superhero movie the world deserves, but not the one it needs right now. Image by Jon Davies (@SovanJedi on Twitter – you may recall his equally excellent lampooning of in-your-face dinosaur art from last year).

That logo needs a T-shirt. Image manipulation by Jon Davies.

Monday, 5 January 2015

Babified Allosaurus and prehistoric sphenodontians

A curious juvenile Allosaurus is told to get off the lawn owned by a grumpy Opisthias. Prints are available. 
With Christmas 2014 fading into memory, I can start sharing pieces of artwork commissioned for presents by various clients without fear of spoiling any surprises. I have several of these to reveal, and the first of which is above, showing an alsatian-sized Allosaurus and a feisty Jurassic sphenodontian, Opisthias. The Allosaurus in this image is based on one of the smallest Allosaurus specimens known, the partial skeleton SDSM 30510. This specimen, described by John Foster and Daniel Chure in 2006. is notable for not only its small size but also its proportions: it seems that very young Allosaurus had relatively longer legs than their parents, which is interpreted as them being more sprightly and cursorial than larger Allosaurus individuals (Foster and Chure 2006). I tried to capture these proportions accurately in the image, not the least because it was commissioned as a Christmas present for John Foster, the chap who discovered and assessed the significance of the specimen (I hear from my commissioner, ReBecca Hunt-Foster (@paleochick), that it's got the seal of approval). It must be stressed, however, that much of the reconstruction is speculative because many details of tiny Allosaurus anatomy remain unknown. Thus, a lot of the anatomy here reflects 'babification' of larger Allosaurus specimens. 

Allosaurus is joined in this image by the small sphenodontian Opisthias rarus. As with many small Mesozoic herps, Opisthias is not well known and much of what you see here as goes appearance and anatomy is based on the modern tuatara. It would be nice to know what Mesozoic sphenodonts really looked like rather than just trotting out variants of the Sphenodon bauplan again and again. Until better fossils are known, I guess this remains the most sensible option, however, as tired as it is. At least have good skull material for Opisthias and, from this, we can see it wasn't a straight replicate of the Sphenodon condition: the snout is longer, the temporal region rather shorter, and the teeth are generally more bulbous without pronounced anterior fangs. I attempted to further differentiate my Opisthias from Sphenodon with a green and red colour scheme, although its behaviour - an open mouth 'push up' pose - is a classic sphenodon threat display, a nod to the aggressive nature of modern male tuataras.

As is becoming tradition around these parts, I tweeted some in-progress images of this painting.




Coming soon: Deinonychus! The pterosaur formally known as 'Phobetor'! Comic-style Carnotaurus!

Reference


  • Foster, J. R., & Chure, D. J. (2006). Hindlimb allometry in the Late Jurassic theropod dinosaur Allosaurus, with comments on its abundance and distribution. New Mexico Museum of Natural History and Science Bulletin, 36, 119-122.

Sunday, 21 December 2014

Taking in the festive air with an azhdarchid pterosaur

An azhdarchid pterosaur takes off in a festively-coloured woodland, because it's Christmas. Prints are available
I was recently thrilled to have the above image featured on the front cover of The Anatomical Record, its depiction of a freshly launched azhdarchid pterosaur tying in with the first paper of the issue. And yes, the colours are deliberately festive, because the Anatomical Record adopts a Christmas theme for its December issues, hence the deep reds and greens of my image. There's two stories I briefly want to tell about this: one about the paper it accompanies, and the other about the art itself.

The paper

My art accompanies the work of Nick Geist and his team on the respiratory mechanism of large pterodactyloid pterosaurs (Geist et al. 2014). Lung ventilation in pterosaurs is an interesting topic. The torso skeleton of many pterodactyloids is locked up pretty tightly thanks to their vertebrae fusing together, their scapulocoracoids being tightly braced between their sterna and backbones and a series of robust, mostly immobile ribs. How were their lungs or air sacs inflated within such a rigid skeleton? Because this configuration isn't a million miles from the torso skeletons of some birds, some authors (Claessens et al. 2009) have suggested that pterosaurs may have breathed in basically avian manner: muscles anchoring to small ribs set between the sternum and larger thoracic ribs move the sternum up and down, pumping air around the body in the process.

This has been accepted fairly widely for the last five years, but now Geist et al. (2014) have presented an alternative argument. They suggest that pterosaur sternal ribs are ill suited for anchoring such muscles because they are very slender - we might even call them fragile - and often entirely cartilaginous, the latter observation borne out by their poor representation in fossil record. Indeed, large portions of the pterosaur chest seem cartilaginous and rarely preserved - the bony sterna of many species (Dorygnathus and Scaphognathus spring to mind) are tiny, and cannot possibly have supported the flight musculature indicated by their powerful shoulders and forelimbs. There must have been large cartilage extensions to these in life. Moreover, in many respects pterosaur torso construction resembles those of crocodilians more than birds, such as the manner with which the thoracic ribs articulate with the vertebrae and the essentially vertical orientation of the ribs themselves. This configuration does not permit the rib rotation required to move the sternum in respiration, and actually adds further rigidity to the anterior pterosaur torso. A bird-like respiratory mechanic may be unlikely for pterosaurs then.

So how were pterosaurs breathing, then? Perhaps the only part of their bodies which wasn't locked up tight and permitted the expansion and contraction required for breathing was their bellies. Behind the sternum sits a suite mobile bones: the belly ribs (gastralia) and the prepubes, a pair of paddle-shaped bones articulated with the pelvis, along with a few 'floating' sternal ribs. Perhaps, like crocodiles, but unlike birds, pterosaurs used this region of their body to control the pressure in their lungs. Crocodiles use contraction of their abdominal muscles to move a large, body-spanning liver forward to compress their lungs, while relaxation of their abdominal wall then allows the liver to retract and the lungs to expand, bringing in their next breath. It seems this action accounts for about 65% of air moved in and out of their lungs, with the rest coming from costal - rib - movements. Given that it seems only pterosaur bellies were flexible enough to inflict substantial changes on body volume, it is not inconceivable to think they used a similar 'belly-pump' (or extracostal pump) as their principle means of controlling air flow into their lungs.

What does this mean for pterosaur lung structure overall? It's well known that pterosaur skeletons and bodies were pneumatised to the same extent, if not more, than avian dinosaurs, prompting suggestions that pterosaurs also had solid avian-like lungs and similar unidirectional flow-through pulmonary mechanics (Claessens et al. 2009). Do the observations of Geist et al. (2014) refute this? Well, not really, but they don't support them, either. As Geist et al. point out: we really don't know anything concrete about pterosaur lung structure, and it's actually pretty hard to tell anything about them from bones alone. A bird-like lung may have been present in pterosaurs and would certainly be consistent with extensive skeletal pneumaticity. However, we need to be careful about exclusively linking extensive pneumaticity with bird-like respiratory organs: flying fish, which of course have no lungs at all, also have pneumatised skeletons thanks to outgrowths of their swim bladders (Geist et al. 2014). Moreover, our uncertainty is not helped by a general lack of knowledge about reptile lungs. This year has seen several revelations about the lungs of extant reptiles being more complex, and sometimes more avian-like, than previously thought. We might need a better handle on reptile lung diversity, and the phylogenetic distribution of different lung structures within Sauropsida, before we start making inferences about the lungs of long extinct reptile lineages. In sum, while the avian-like pterosaur lung remains a viable hypothesis, it's not the only option on the table. We might be able to gain insights into how the body cavity of pterosaurs was manipulated to move air in and out, but their precise lung anatomy remains largely mysterious (Geist et al. 2014). There's a lot more we could say about this, but you'll have to track down the full paper for further details.

The cover image

Festivodactylus in situ.

There's a bit of a story behind the cover artwork for this paper too. It's hardly the stuff of novels but, given that 2014 has been another year in which palaeoart plagiarism and working practices have been a hot topic, it's nice to share a happier, positive story about a palaeoartwork for a change.

This cover has been a long time coming, with Nick asking me for potential cover art for the paper at the end of last year. I duly obliged by lending the flying Anhanguera from my book. Nothing much happened while the paper was crunched through the publication mill, until in November the cover art arrived. Looked like I was due for the December issue, which, as noted above, Anatomical Record always jazzes up with festive colours - green, red and white. This involved tweaking the colours of my original art to meet these, as well as some stretching and cropping to fit the AR cover format. Without going into details, I wasn't really happy with the results. Uh oh. Pessimist I am, I foresaw the worst. I stress that these expectations weren't because of previous experience of working with Nick or AR, but my experiences with other clients and agencies. Protesting about art use normally leads to Bad Things: unhappily forced compromises, loss of commissions, or having to fix 'problems' without pay. When writing back to Nick and AR with my concerns, I pretty much expected the whole cover project to fall apart. I pitched, without optimism, the idea of doing another image, for a fee, to replace the modified one. Despite linking to the 'State of the Palaeoart' article I helped pen this year to substantiate my request for payment, I was expecting the same old response: lack of money, thanks but no-thanks.

To my complete surprise, Nick, his colleagues and AR were on board with everything. The 'palaeoart situation' was new to them all, but I - we, the palaeoart community - had their sympathy. Within a day, AR had been able to put things on hold for a week while I drafted a new image to their specifications and size, Nick and his team rapidly found a generous payment for the work at short notice, and we all ended up with a product we were happy with.

I mention all this for two reasons. Firstly, Nick, his team and AR deserve accolade for being so refreshingly cool and respectful of palaeoartistry. Secondly, independent palaeoartistry can seem a most hopeless industry at times: we get ripped off by everyone from toy companies and movie makers to museums and publishers; our marketplace is mainly structured around exploitation of individuals, and sympathy or assistance from those in the position to change this can be hard to find. But, as this case shows, it's not all hopeless. Increasing awareness of the issues facing palaeoartistry does help rectify them, change can happen, and we have more supporters than we know. I'm optimistic that eventually we'll all have more stories like this one than the negative situations currently reported so frequently.

Best to you all for the festive period, see you all in 2015!

References


  • Claessens, L. P., O'Connor, P. M., & Unwin, D. M. (2009). Respiratory evolution facilitated the origin of pterosaur flight and aerial gigantism. PloS one, 4(2), e4497.
  • Geist, N. R., Hillenius, W. J., Frey, E., Jones, T. D., & Elgin, R. A. (2013). Breathing in a box: Constraints on lung ventilation in giant pterosaurs. The Anatomical Record, 297, 2233-2253.