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and restored proportions (although I'm not really sure what context that article is presented in - it looks like an unpublished MS).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.

Does Deinonychus really have one of the most powerful bites of all dinosaurs?

Quick sketch of Deinonychus antirrhopus with expanded, bone-puncturing jaw muscles, a requirement of having a bite as strong as a modern alligator. Say what? Read on...

There's a part in Michael Crichton's Jurassic Park novel where Velociraptor attempt to bite through bars to reach a people-shaped lunch. Presumably, they're meant to give readers something to rally behind seeing as one person in the line of fire is Ian Sodding Malcolm - I'd be chewing through steel too if it meant we could enjoy a few moments without another preachy monologue. Crichton describes them as hyena-like in their ability to bite through steel, delivering thousands of pounds of pressure per square inch and gnawing their way through thick metal bars in 15 minutes.

Dromaeosaurids biting through steel bars - heck, any animal biting through steel bars, including hyenas - intuitively sounds like crazy talk*. But was Crichton at least right about the strong bites of dromaeosaurids? I've been doing some investigating on dromaeosaur jaw muscles for a new palaeoart commission, but I've come unstuck. Here's why.

*Is there any substance to claims about modern animals biting through steel? Given that tooth enamel is only very slightly harder than straight steel, I wonder how long teeth would last when gnawing through anything but the thinnest metal sheet.

Recently, Gignac et al. (2010) presented a suite of bite marks on Tenontosaurus bones argued to show Deinonychus as capable of deeply puncturing bone with powerful bites. The tooth gouges match those of large Deinonychus in many aspects (bite mark size, shape, correspondence with dental arcade) and broken teeth associated with the same Tenontosaurus corroborate suggestions that Deinonychus fed from the carcass. Other teeth, not from Deinonychus, were also at the site, but their owner does not seem to have left any other obvious traces. Experiments with modern cow bones suggest Deinonychus needed a whopping 8200 N to puncture Tenontosaurus bones to the degree seen in the fossil remains. This value puts Deinonychus bites on par with those of adult alligators and leaves hyenas in the biomechanical dust. It also grants Deinonychus one of the highest estimated bite forces of any dinosaur, even greater than animals of much larger size. The tooth marks only match the largest known Deinonychus individuals, possibly indicating that juveniles were incapable of delivering such bite forces. Because Deinonychus puncture wounds are rare, Gignac et al. argue that puncturing bones was not common in Deinonychus, and that their powerful bites were primarily used for aggressive behaviours instead.

Bitemarks in the radius of Tenontosaurus specimen FMNH PR 2261, below, compared to the dental arcade of Deinonychus antirrhopus, above. This is one of many pathologies on FMNH PR 2261, almost all of which have been attributed to Deinonychus feeding behaviour. From Gignac et al. 2010.

For artists, Gignac et al.'s paper has important implications. Generating 8000 N of bite force requires a lot of muscle, so we might predict that Deinonychus jaws had the same swollen jaw muscles of modern crocodiles to generate all those bone-smashing newtons. This is at odds with other reconstructions of Deinonychus, where the jaw muscles do not atypically alter the contours of the face. I don't know how visible expanded, crocodile-like jaw muscles would be on deeply feathered maniraptorans, but reconstructions with sparse or naked faces would certainly need to take this on board. I've had a quick play about with this concept in the conservatively feathered Deinonychus above.

Problem is, Gignac et al.'s conclusions are not uncontested. Biomechanical assessments of Deinonychus jaws have found they were mechanically weak and ill-suited to delivering powerful bites (Therrien et al. 2005; Sakamoto 2010; Fowler et al. 2011). Therrien et al. (2005) estimated Deinonychus bite force at a relatively wimpy 15.7% of alligator jaw power, which Gignac et al. translate into 1450 N. This isn't unimpressive - as strong as that of a 30 kg wolf - but a far cry from an alligator-like bite, and certainly deflates our reconstructed jaw muscles to their traditional size. On the face of it, I certainly find the arguments for weak jaws more convincing. Hyenas and alligators have robust, wide and solidly-built skulls with generous room for jaw muscle placement, whereas the skull of Deinonychus is full of holes, is relatively narrow and slender, and with comparatively little room spaces jaw for muscles.

So, what to do? Jaws with relatively small muscles have been the norm in Deinonychus palaeoart since its discovery, but is it time we changed that? Were their jaws actually visibly and powerfully muscled as inferred by their trace feeding evidence, or is there something missing here? Is it significant that lower estimates of their bite forces match those of animals which can also puncture bone (wolves - see Haynes 1982)? If anyone has anything to add, please let me know...

References

• Fowler, D. W., Freedman, E. A., Scannella, J. B., & Kambic, R. E. (2011). The predatory ecology of Deinonychus and the origin of flapping in birds. PLoS One, 6(12), e28964.
• Gignac, P. M., Makovicky, P. J., Erickson, G. M., & Walsh, R. P. (2010). A description of Deinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations. Journal of Vertebrate Paleontology, 30(4), 1169-1177.
• Haynes, G. (1982). Utilization and skeletal disturbances of North American prey carcasses. Arctic, 266-281.
• Sakamoto, M. (2010). Jaw biomechanics and the evolution of biting performance in theropod dinosaurs. Proceedings of the Royal Society B: Biological Sciences, 277(1698), 3327-3333.
• Therrien, F., Henderson, D. M., & Ruff, C. B. (2005). Bite me: biomechanical models of theropod mandibles and implications for feeding behavior. The carnivorous dinosaurs, 179-237.