A mural for Dippy: restoring a celebrity Diplodocus in art

My mural of a Diplodocus carnegii herd, currently keeping Dippy, the Natural History Museum's Diplodocus cast, company in Dorset County Museum. At 4 x 2 m, it's the third biggest picture I've ever done, and - as positioned at the museum - the most visible.

If you head to Dorset County Museum at some point before May 9th 2018 you'll be able to see a genuine dinosaur celebrity: the Natural History Museum's 'Dippy' Diplodocus skeleton, on the first stint of its 'Dippy On Tour' campaign of UK museums. The trip is well worth the visit even if you're familiar with the specimen from the NHM's Hintze Hall. A mezzanine around the skeleton, and the smaller size of the exhibition space, allows visitors to get closer to Dippy than ever before, and you can see the specimen from elevated positions unavailable at the NHM. If you're a sauropod fan in the UK, this might be your best chance to see this specimen up close and personal. It's free to see the skeleton, but you do need to book in advance - the tickets are flying off the shelves, so don't expect to just walk in.

A discerning audience checks out my prints at Naturally Curious. Say, some of those images look a little Life-through-the-Ages II-y...

Alongside Dippy is a collection of art entitled Naturally Curious, works by four different artists inspired by fossils and the natural world. My work is among them (above) and includes a 4 m wide mural based on the Dippy specimen and its palaeoenvironment - the same image that welcomed you to the post. It's not placed with the rest of my work but hanging right next to the Dippy skeleton itself - the first time a detailed artistic restoration has been associated with the specimen since the 1980s when a scale model stood next to its tail. This mural, commissioned by the Dorset County Council, was a great opportunity to bring Dippy's visitors up to speed on the latest ideas on sauropod dinosaur life appearance (as well as very flattering for me - it's not every day you're asked to display art next to one of the most famous dinosaurs in the world). The process involved learning a lot about the Dippy specimen, applying some new ideas about dinosaur anatomy to Diplodocus, and looking into the specifics of Dippy's palaeoenvironment. If that's not fodder for a blog post, I don't know what is.

Because production time on the mural was short, we decided to augment an existing picture rather than start from scratch. The image in question is below, and was created in 2009 to publicise work by Mike Taylor, Mathew Wedel and Darren Naish on sauropod neck posture (Taylor et al. 2009). The Dorset team liked the image and, though quite dated now, it gave an anatomical and compositional framework that had been approved by several sauropod experts, shaving a lot of time off the production schedule. The final artwork is different to the original in many respects but much of the 2009 DNA remains obvious, including our nod to Rudolph Zallinger's Age of Reptiles mural.

PR art for Taylor et al. (2009), showing D. carnegii with its neck held aloft rather than - as was fashionable at the time - held horizontally. 2009 was a long time ago for me, artistically speaking.

Working with Dippy, and establishing the scene

It's important to any palaeoartwork to know the nature of the actual fossil material behind a reconstruction, and it might come as a surprise to know that 'Dippy the NHM Diplodocus'* is a different entity to the specimen it's cast from. The 'real' Dippy is Carnegie Museum specimen 84 (CM 84 for short), the holotype of Diplodocus carnegii, unearthed from Jurassic sediments of Wyoming in 1899. It's a mostly-complete skeleton missing elements of the limbs, the end of the tail and the skull, and these elements were sculpted or casted from other animals to create the mounted Dippy skeletons in museums around the world. This makes Dippy mostly representative of a single individual, but still a composite of several Diplodocus. CM 84 has been extensively documented - especially in Hatcher's 1901 monograph - and this makes it an excellent specimen to base a palaeoartwork on. Scott 'Master of Dinosaur Bones' Hartman's 2013 Diplodocus skeletal restoration was used to fill in the proportional gaps, and Tschopp et. al (2015) provided some very useful data on diplodocid osteology, often up close and in clear detail.

*The NHM's CM 84 cast is not the only Diplodocus to bear this nickname: the actual CM 84 specimen was also christened 'Dippy' when discovered in 1899, and several museums around the world use this name for their casts. In this article, my use of 'Dippy' consistently refers to the NHM cast.

Where the Diplodocus roam: depositional settings of the Morrison Formation at the time when Dippy lived. The Dippy site itself is in southeast Wyoming, among the series of wetlands that line the eastern side of the Morrison basin. From Turner and Peterson (2004).

CM 84 stems from the centre of the Morrison Formation, a famous Late Jurassic unit that yields, in addition to Diplodocus, many famous dinosaurs: Allosaurus, Stegosaurus, Brontosaurus, Ceratosaurus and Camarasaurus, among others. The Morrison Formation is geographically extensive with major outcrops in Colorado and Wyoming, and additional exposures in 11 other states (above). Palaeoenvironmental studies show variation in climate and habitats across that range. We know that southern regions were drier, that a number of water bodies existed across the basin, and that water and sediment influxes were received from highlands to the west and, possibly, the east (Turner and Peterson 2004). The Wyoming quarry where CM 84 was recovered represents an ancient lake, part of a broader series of wetlands in the east of the Morrison depositional basin (Turner and Peterson 2004; Brezinski and Kollar 2008). It's been suggested that these relatively well-watered settings may have been important habitats for dinosaurs of all kinds, offering abundant plant material compared to the surrounding arid environments (Turner and Peterson 2004). I took these details on board for the mural, changing the backdrop of the 2009 image from a sparse lake margin to a well-vegetated, westward-facing gateway with distant hills. The result is hopefully something not too far off the environment that CM 84 was buried in, and maybe lived in.

Proportions, poses and pedes

Although some tweaks were made to the proportions of the animals from my 2009 image, the basic poses of each was maintained. Readers may question why the necks of the animals have remained aloft when some researchers and artists still use the horizontal neck poses popularised in the late 1990s. The primary basis for horizontal sauropod necks are the famous Dinomorph digital models (Stevens and Parish 1999 and subsequent works) and, though debates on these matters continue, a number of papers have found issues with these models, to the extent that I'm not sure they're reliable at present. Rather than summarise these issues here, I suggest you simply read Mike Taylor and Matt Wedel's blog series on sauropod neck posture over at SV:POW! - all the citations and discussion you need are there, and in much greater detail than I could cram into one paragraph.

This means that the postures used in my mural are still, almost 10 years on, based on the conclusions of Taylor et al. (2009). If you missed this paper (which you need miss no more, seeing as it's open access), it used x-ray data to show that all extant terrestrial amniotes habitually hold their necks with an elevated base during idle but alert behaviour. As summarised by Mike and colleagues in their abstract:

"Unless sauropods behaved differently from all extant amniote groups, they must have habitually held their necks extended and their heads flexed."

In other words, if sauropods didn't carry their necks at an upward angle, they would differ from all terrestrial tetrapods alive today, and there's really no compelling reason to think that was the case. I like this argument because it's based on a broad dataset of real, live animals, not a series of assumptions about how we think they work - when reconstructing animal poses, that's an important distinction. Articulated sauropod fossils show that such poses were attainable, and biomechanical studies suggest that strung-out, horizontal poses would be energetically demanding compared to more vertical poses, and that the necks of sauropods are frankly maladaptive if the neck was not capable of reaching up to gather food (e.g. Taylor et al. 2009; Christian 2010). More work needs to be done here, and it remains difficult to say exactly how sauropods carried their necks for a number of reasons, but data arguing for elevated neck postures seems more compelling than the alternative for the time being. With all this in mind, I am still happy with the neck poses from 2009, and only added some slight curvature to give a sense of motion.

Of course, no-one is saying that sauropods could only carry their necks aloft: we're talking about their default, habitual pose, not those employed during other behaviours like foraging or drinking. Here's artistic proof.

But while my sauropod necks remained mostly unchanged, tweaks were made to other anatomies. I missed papers regarding sauropod foot posture in my original work and gave my Diplodocus elephant-like feet, as if they were walking on the tips of their toes. It turns out that this was wrong: their feet were semi-plantigrade and we need to be restoring all sauropods with longer, flatter feet (Bonnan 2005). With sauropod hands having an unusual horseshoe-shaped profile (Paul 1987), it's long past time to bin elephant hands and feet as a model for sauropod appendages: any artists out there still using elephant legs as a model for sauropod limbs, take note. The overall proportions of the animals were modified too, with more muscle added to the neck base, torso and tail base; the cranial proportions corrected, and the torsos given more bulk. I didn't add too much, though: diplodocids were relatively slender as sauropods go, with deep, but not especially wide bodies. They're a world away from the likes of titanosaurs, which were much heftier throughout the trunk (below)

My PR art for the description of the titanosaur Shingopana songwensis, with another titanosaur - Rukwatitan bisepultus - in the distance. Notice the bulk in their torsos - the chests of diplodocids were a world away from these chunkers.

A very Dippy face-lift

Ideas about the facial anatomy of sauropods have been undergoing something of a quiet revolution in recent years (as explored in blog posts by Matt Wedel and Darren Naish), and good skull material of Diplodocus allows for artists to consider their craniofacial tissues in detail. Many readers will know that the long-held notion of sauropod nostrils being placed at the top of their skulls has been challenged through careful analysis of their bony nasal anatomy (Witmer 2001). It seems that the obvious nasal openings atop sauropod skulls are only the 'internal' apertures of a larger nasal complex which covered most of their snouts. These are especially obvious in some taxa, like Giraffatitan (below), but are also evident in diplodocids. Knowing this, we can move the position of the nostrils to the front of the snout, at the anterior limit of the nasal region. This isn't an arbitrary decision: virtually all reptile nostrils are located at the front of their nasal skeleton, so sauropods would be weird if they didn't do this (Witmer 2001).

Giraffatitan brancai shows us how extensive sauropod nasal skeletons really are - they actually extend right the way down the face (Witmer 2001). Illustration from Witton (in press).

But other than probable nostril placement, we don't know much about the soft-tissues inhabiting these expanded nasal regions. Were they relatively slender, only slightly modifying the shape of the skull contours, or where they expanded, drastically altering the shape of the face? We don't know, but the unusual noses of monitor lizards give one model for artists to follow. As with sauropods, monitor nasal cavities are large, complex basins occupying much of the snout. Within them sit bulbous cartilaginous nasal capsules, and it's these, rather than the bones of the skull, which create the swollen, sometimes 'boxy' appearance of monitor snouts. If the same was true for sauropods, their facial contours might have deviated markedly from the underlying skull. I used this model in my Dippy mural, adding a healthy bulge of tissue to the face over the entire nasal region. It changes the shape of the craniuim quite considerably, contrasting with the horse-like face so familiar to us in other Diplodocus restorations, but still - hopefully - being within the realm of scientifically credibility.

A tiny eye, big nose and Jaggeresque lips. This is not the Diplodocus I grew up with, but all three of these anatomies have a grounding in sound science. 

Regular readers will not be shocked to see covered teeth on my Diplodocus. The conversation about dinosaur lips and other extra-oral tissues is ongoing, but the presence of covered teeth in virtually all tetrapods suggests we should assume this condition for dinosaurs too, unless we have good reason to remove them (I've blogged on this a lot - see this, this and this). Sauropods meet most of our current, provisional criteria for having covered teeth: their snouts have low foramina counts, which seems to superficially correlate with lips in living species (Morhardt 2009); they lack evidence of sculpting typical of tight facial tissue around their their jaw margins (or anywhere else on their skulls, for that matter - sauropod skulls in general seem to lack obvious epidermal correlates), and their teeth are small enough that they would be easily covered by lips. New data on Camarasaurus teeth further supports the assertion of generous oral tissues in sauropods (Wiersma and Sander 2017) and, collectively, these lines of evidence suggest a set of (perhaps lizard-like?) lips around the mouth of Diplodocus is a reasonable inference, without providing any supporting evidence for a perpetual toothy grin.

Diplodocus sp. skull CM 11161 - note the well-preserved sclerotic ring in the orbit. It's quite large, but the internal aperture - which the eye peeps though - is pretty small. From Tschopp et al. (2015).

I was happy to find that we have some good data on eye size in Diplodocus. Many readers will know that sclerotic rings - small bony plates arranged in a ring that line the front of the eyes of many tetrapods - are great indicators of eye size in fossils. The diameter of the ring itself gives a minimum size for the eyeball, and the internal opening approximates the extent of the visible eye tissue. Tschopp et al. (2015) figure a terrific, only slightly distorted sclerotic ring in a Diplodocus skull which suggests a reasonably large eye considering the size of the animal, but the ring plates are quite thick, creating a relatively small internal opening. Thus, while the eyeball was large (perhaps indicating good eyesight?), the visible eye area was not huge. No giant eyes for my Diplodocus in the mural, then, and especially with the additional nasal and oral tissue on the face, they ended up looking quite beady-eyed.

Spines, skin and colour

We don't have any data on the skin for Diplodocus, but skin impressions from other sauropods - including other diplodocids - suggest non-overlapping scales are their most likely covering. I used the extensive skin impressions from the Howe Quarry diplodocid (possibly Kaatedocus?) as my main reference point for the mural: these show not only details of diplodocid scales (polygonal, each about 3 cm across) but also that a line of subconical spines was present along the top of the tail (Czerkas 1992). Some of these were relatively large - up to 18 cm tall - so would be conspicuous even from a distance. These structures were included in the 2009 work and I saw little reason to remove them for the mural, as they remain based on best insight into Diplodocus skin. We don't know how extensive the spine row was in the Howe Quarry animal, so I arbitrarily extended it along almost the entire animal, creating a look consistent the spiny backs of many lizards. The skin was topped of with a number of deep folds: these seem prominent in many living reptiles, but we don't often include them in dinosaur art.

Colour scheme for my Diplodocus. If you're a carnivorous dinosaur, the body says 'all you can eat', but the tail says 'you can't afford it'.

Colour and patterning remains a complete unknown for sauropods, so our only mechanism for restoring colour their colour involves looking for modern analogues and considering their likely pigmentation mechanisms. Very generally speaking, larger tetrapods show less striking patterning and duller colouration than smaller ones, and this trend seems common enough to assume it might have been true in fossil tetrapods too (and yes, I know there are plenty of exceptions, but we're looking for the wood here, not the trees). This may reflect, at least in part, the availability of carotenoids - pigments which create bright colours - in terrestrial settings. Animals cannot create carotenoids directly so must ingest them, and the bigger they are, the more they need to generate large patches of brilliant colouration. We know that many birds struggle to attain their maximum degree of pigmentation because terrestrial habitats offer variable, often limited carotenoid availability. If many of these relatively tiny animals struggle to find enough of pigment to colour themselves, it's hard to imagine the biggest terrestrial animals of all time faring any better. If so, sauropods would be reliant on melanin, which animals can synthesise, but only produces dull shades of grey, red, brown and black, and layers of structural colour on their scales. Reptiles employ structural colour frequently to create vivid colours, but mostly in concert with other pigments - green lizards, for instance, have scales with yellow pigment overlain by blue structural colour.

Pigmentation mechanics is not our only consideration, of course: we must also consider colour function. Colour has important roles in animal homeostasis and behaviour, and we have to give our reconstructions colour schemes which are appropriate to their lifestyle and biology. At such large size we might assume that camouflage was not important for Diplodocus, and we might also infer that too much dark pigment would be detrimental to its heat exchange. Dark pigments attract heat, and given that sauropods almost needed to lose heat more than gain it, darker skin have been disadvantageous in hot climates like those of the ancient Morrison. Putting all this together, I chose a fairly dull mottled pattern of browns, creams and greys, with some lighter ornamental scales and spines to break up the monotony. One area that I did elaborate was the tail: if, as long suspected, Diplodocus employed its whip-like tail defensively, it could have drawn attention to its weaponry with colouration and patterning. Eagle-eyed viewers might also note that the smaller Diplodocus has some more vivid patterning, echoing a common condition of reptiles where juveniles are more brilliantly coloured than their parents. I toyed with adding a strikingly coloured juvenile, but decided not to on grounds that tiny, precocial baby sauropods probably didn't hang out with adults, and because less can be more when it comes to composing paintings. Hopefully, the colour scheme is believable and consistent with our understanding of animal colouration, which - 99.9% of the time - is the best we can hope for in the palaeoart game.

The mural in situ, mere metres from Dippy's tail. This photo was taken at the opening night of the exhibition, hence the funky lighting. The museum is also entirely horizontal, not at a slight angle as shown here, but I'd been at the opening night wine by this point. Note the small panels next to the mural - they explain the science that went into it, effectively being a condensed version of this article.

That covers the majority of the major decisions that went into the mural, so I'll leave our discussion here. Remember that you have until May 9th to see the mural and other artworks in Dorset. They aren't an 'official' part of Dippy on Tour show so, when Dippy leaves Dorset, the mural and other art won't be following - book those tickets now if you want to see them. I'll be talking about palaeoart at the museum on March 14th - book tickets for that here and, if you're reading this and come along, please say hello.

Finally, if you'd like a copy of this mural for yourself, you can grab a good quality print from my online store, where it's available in a range of sizes. Alternatively, you can access a high quality printable file of the mural if you sponsor my work at Patreon - details below.

Enjoy monthly insights into palaeoart and fossil animal biology? Support this blog for $1 a month and get free stuff!

This blog is sponsored through Patreon, the site where you can help online content creators make a living. If you enjoy my content, please consider donating $1 a month to help fund my work. $1 might seem a meaningless amount, but if every reader pitched that amount I could work on these articles and their artwork full time. In return, you'll get access to my exclusive Patreon content: regular updates on research papers, books and paintings, including numerous advance previews of two palaeoart-heavy books (one of which is the first ever comprehensive guide to palaeoart processes). Plus, you get free stuff - prints, high quality images for printing, books, competitions - as my way of thanking you for your support. As always, huge thanks to everyone who already sponsors my work!

References

• Bonnan, M. F. (2005). Pes anatomy in sauropod dinosaurs: implications for functional morphology, evolution, and phylogeny. In: Tidwell, V. & Carpenter, K (eds) Thunder-Lizards: The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington, 346-380.
• Brezinski, D. K., & Kollar, A. D. (2008). Geology of the Carnegie Museum dinosaur quarry site of Diplodocus carnegii, Sheep Creek, Wyoming. Annals of Carnegie Museum, 77(2), 243-252.
• Christian, A. (2010). Some sauropods raised their necks—evidence for high browsing in Euhelopus zdanskyi. Biology Letters, 6(6), 823-825.
• Czerkas, S. A. (1992). Discovery of dermal spines reveals a new look for sauropod dinosaurs. Geology, 20(12), 1068-1070.
• Hatcher, J. B. (1901). Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton (Vol. 1, No. 1-4). Carnegie institute.
• Morhardt, A. C. (2009). Dinosaur smiles: Do the texture and morphology of the premaxilla, maxilla, and dentary bones of sauropsids provide osteological correlates for inferring extra-oral structures reliably in dinosaurs? Western Illinois University.
• Paul, G. S. 1987. The science and art of restoring the life appearance of dinosaurs and their relatives - a rigorous how-to guide. In Czerkas, S. J. & Olson, E. C. (eds) Dinosaurs Past and Present Vol. II. Natural History Museum of Los Angeles County/University of Washington Press (Seattle and London), pp. 4-49.
• Stevens, K. A., & Parrish, J. M. (1999). Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science, 284(5415), 798-800.
• Taylor, M. P., Wedel, M. J., & Naish, D. (2009). Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica, 54(2), 213-220.
• Tschopp, E., Mateus, O., & Benson, R. B. (2015). A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ, 3, e857.
• Turner, C. E., & Peterson, F. (2004). Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis. Sedimentary Geology, 167(3-4), 309-355.
• Wiersma, K., & Sander, P. M. (2017). The dentition of a well-preserved specimen of Camarasaurus sp.: implications for function, tooth replacement, soft part reconstruction, and food intake. PalZ, 91(1), 145-161.
• Witmer, L. M. (2001). Nostril position in dinosaurs and other vertebrates and its significance for nasal function. Science, 293(5531), 850-853.
• Witton, M. P. In Press. The Palaeoartist's Handbook. Crowood Press.

New sauropodoramas: Stormy brachiosaurs! Apatosaurine brontosmash!

Realising that Recreating an Age of Reptiles was a bit light on sauropod art, I've been beavering away on two additional sauropodoramas* to pad things out a bit. I thought I'd share them here.

*Sauropods are such special animals that they deserve their own nomenclature for most things, including artwork. See, for another example, 'shards of excellence'.

The first is a reworking of a 2013 image of the Wealden (probable) brachiosaur Pelorosaurus conybeari in hammering wind and rain. We know that Wealden climates were subject to storms and intense downpours on occasion (lightning and floods being, of course, key elements in the production of fossil-rich plant debris horizons in certain Wealden deposits) and it stands to reason that any sauropods around when those rains arrived would have got quite wet indeed. I don't say that just casually: the prospects of being a wild animal the size of a house mean that you're actually pretty exposed to just about everything weather can throw at you. When unexpected meteorological fit hits the shan, your options as a giant are pretty limited. Running away is out, because your legs are pillar-like structures adapted for supporting immense weight, not nimble escape. Seeking shelter is not an option either, because you're bigger than everything else around you. You're just too darned huge to do anything but stand there and take it. The life of a sauropod must've been spent baking in the sun, being battered by wind, and drenched in rain. I find that idea quite romantic and evocative as an artist. When painting sauropods, I often wonder how cracked, weathered and worn their skin must've been through a lifetime of battles with changing weather.

Like masts in a storm, three Pelorosaurus conybeari brave typically English weather, c. 135 million years ago. They're doing their best to look tough next to a couple of rainbows.

Second is an image inspired by a recent SVPCA talk by sauropod expert Mike Taylor and his colleagues Matt Wedel, Darren Naish and Brian Engh. Regular readers of the palaeoblogosphere will probably already know where this is going, given that Mike's talk (and the upcoming Wedel et al. paper) has been given some hefty coverage at SV:POW!. Those familiar with sauropods will know that apatosaurines (Apatosaurus, Brontosaurus and a few other taxa) have atypically proportioned, large and robust neck vertebrae, with their cervical ribs being especially elongated and reinforced. These structures possess peculiar buttresses on their underside which, it seems, are not products of muscle or ligament attachment (if they are, they have no modern analogue). Instead, they might relate to an epidermal feature like a boss or horn, as such structures sometimes leave peculiar swellings on underlying bones. Exactly what these anatomies indicate has long been puzzling, and all the more so because all apatosaurines show neck vertebrae with these features. Some (like Brontosaurus) were more extreme than others in development of these features, but even modest apatosaurines were doing crazy, mysterious stuff with their neck anatomy. Question is, what?

Matt, Mike and others have recently been outlining a first principles approach to this conundrum. They note that the reinforced construction of apatosaurine necks, the additional muscle attachment afforded by vertebral expansion, and those strange vertebral buttresses might render their necks effective clubs or wrestling appendages, particularly well suited to rapid, powerful downward motions. Summarised a little more succinctly: there is reason to think Brontosaurus and kin might've smashed the crap out of each other, or other animals...

...with their necks.

Yowsers. But outlandish as the Brontosmash hypothesis seems, it really isn't just idle speculation: a paper is in the works, the Taylor et al. SVPCA talk abstract is a preprint at PeerJ, and you can see the case explained in Mike's talk slides here. I find it pretty convincing myself: I mean, there had to be some reason apatosaurines had those crazy necks. Evolution is a sloppy craftsman at times, but the energy put into growing and maintaining such massive neck anatomy must've been substantial, and that almost certainly reflects a certain adaptive purpose. Combat might well have been that driving force. We also know from living animals - camels, giraffes and some seals - that necks are used for fighting, and that neck-based combat can promote reinforcement and restructuring of neck anatomy. It certainly sounds provisionally convincing to me, and I'm sure we'll hear a lot more about it in the future as the hypothesis is developed.

We're also sure to see this concept frequently in future palaeoart. Mike has been collecting some of the early artwork of this idea over at SV:POW!, including a wealth of coloured sketches and concepts by Brontosmash coauthor and palaeoartist Brian Engh, palaeoartist Bob Nicholls, #MikeTaylorAwesomeDinoArt (the revolution palaeoart deserves, if not the one it needs) and an alternative interpretation of apatosaurine neck data provided by myself (we secretly know I'm on the money with that one). I also decided to attempt a full on painting:

Multiple tonnes of Brontosaurus excelsus in disagreement.

There're two nods to classic palaeoartists here. There's a Knightian influence to the style (not the first time he's infected my work), as well as, via the very upright postures of the wrestling animals, a hat-tip to Robert Bakker's famous 'boxing Brontosaurus' image. The latter had a big impact on me when I first saw it as a teenager, and it's been on my mind for obvious reasons with all this talk of fighting apatosaurines. I thought it also made for a bit of a contrast to Brian's 'official' depictions as well, these showing the animals in quadrupedal or near-quadrupedal poses (I assume at least some of the postures in those artworks mimic neck combat in elephant seals, a favoured modern behavioural analogue of Team Brontosmash). The setting is meant to be in the wetter, northern parts of the Morrison Formation palaeoenvironment, alongside swollen river margins. Initial plans were to record the progression of the wrestling match in muddy footprints, but adding splashes and visual noise to proceedings was too much fun, especially with those tails whirling around everywhere. Sloshing water provided a means showing specific actions, too, the splashes from colliding brontosaur hide signifying each powerful, multi-tonne impact. This was definitely a fun image to put together, and it's certainly a favourite of my recent work. Brontosmash!

That's all for now. Coming soon (probably): The Triassic! And a boring old pterosaur that we just can't leave alone!

These sauropodoramas were brought to you by Patreon

Regular readers will know that this blog and artwork is sponsored by patrons who pledge support at my Patreon page. For as little as $1 a month you can help keep this blog going and, as a reward, you get to see a bunch of exclusive content, and I'm really grateful to everyone who contributes. I'm especially thankful at the moment because, around a week ago, my art PC almost flatlined. My patrons have taken the sting out of repair costs, as well as given an incentive for futureproofing my hardware. Thanks chaps - you're awesome (if, sorry, not quite as awesome as neck smashing brontosaurs. But what is?).

Humps, lumps and fatty tissues in dinosaurs, starring Camarasaurus

I like to see fossil animals restored as if they belong in the world they're depicted in. That is, not just as basic, conservative reconstructions of ancient species in an certain landscape, but instead with colours, integument and soft-tissue adaptations suited for their possible lifestyles and the environments they frequented. To this end, last year I published an illustration of the Late Jurassic, North American sauropod Camarasaurus supremus as an species well adapted for life in arid settings. As a common part of the famous Morrison Formation dinosaur fauna, dry conditions would be familiar to Camarasaurus, and especially because it occupied the drier, desert-like southern extent of the Morrison palaeoenvironment. I rendered Camarasaurus as a dinosaurian camel, complete with several common cranial adaptations to resisting dry conditions and, most obviously, a fat hump on its back.

2014 restoration of Camarasaurus supremus, published in Witton (2014). Painted to make a point about palaeoart (as well as plugging the awesomeness of All Yesterdays), here's what the caption read. "Reasoned speculation in palaeoart. The sauropod Camarasaurus supremus depicted with adaptations for living in a very dry environment: enlarged nasal cavities to aid resorption of moisture, sealable nostrils to reduce evaporation, wrinkled skin to enhance heat dissipation, white and tan colouring to resist heat soaking, and a fat hump to store energy. Such features are speculative, but do not contradict any data we have for this taxon, and are consistent with the adaptations of modern desert-dwellers."

I decided to revisit this image this week to boost the sauropod content of Recreating an Age of Reptiles (coming soon, I swear!). In doing so, I decided to conduct some more research into the likely nature of non-avian dinosaur fatty tissues. I wanted to keep the fat store on Camarasaurus, as equivalent structures provide energy and water reserves for many modern desert species, and there's no reason to think that extinct dinosaurs would not have developed fat stores for similar purposes. However, is a camel-like hump really likely in a dinosaur? Can we credibly restore any details of dinosaur fats? These were questions I sought to investigate more thoroughly before jumping into my revisions.

Yo extant diapsids so fat

If we're thinking about how to restore dinosaur fats, we need to investigate what the reptile lineage is capable of when it comes to producing and storing fatty tissues. The composition of diapsid fats is a little different to our mammalian ones, although we share functionally comparable approaches to fatty tissue makeup in many respects, including responses to endothermic demands (Goff and Stenson 1988; Saarela et al. 1991; Azeez et al. 2014). Amniotes, as a whole, have fairly similar approaches and uses for fatty tissues, which is great, because that allows us to make some reasonable inferences about fossil species.

Modern reptiles generally have lower fatty tissue fractions than mammals because of their lower energy requirements (Birsoy et al. 2013; Azeez et al. 2014). However, this is not to say that they are incapable of storing large quantities of fat, or even putting on weight rapidly. Some reptiles are indeed lean species, but some - most famously certain geckos, but also some iguanas, skinks and snakes - periodically or permanently hold large stores of fat in case of hard times, or to prepare themselves for energy-intensive feats (e.g. reproduction or long distance travel). Reptiles generally sequester fatty deposits within their torsos or in their tails, but some species also store them in their armpits and in fat pockets located at the back of the head. Individuals of many lizard species are considered healthy when these regions are literally bulging with fatty mass. To my knowledge, these masses are not directly supported by the skeleton or other tissues: it is simply the cohesive nature of fatty tissues and dermis which keeps them in place. It is known that some lizards can pack their tissues with fat rapidly when necessary, some experiments finding geckos can increase their body mass by 50% in four days (enough fuel to sustain them for over half a year!) (Mayhew 2013). Indeed, reptiles are so good at packing on fat, and maintaining it, that owners pet reptiles will know that obesity can be a real issue for captive lizards.

What about living dinosaurs? As with other diapsids, birds can rapidly generate fatty tissues in anticipation of stressful periods, and frequently do so before, for instance, migrating (Lindström and Piersma 1993). 10-15% body fat is considered low for a migrating bird, with the bodies of some species comprising 50% fatty tissues before embarking on their travels - seasoned ornithologists recognise birds as positively emaciated when they finish their journeys (Alerstam and Christie 1993). However, birds are not fully reliant on fatty tissues as energy stores, some species routinely using their muscles and organs as fuel sources during long migrations. It seems only their lungs and brains are safeguarded against being turned into energy (Battley et al. 2000): everything is fair game for fuel or other components needed to maintain a functioning body. Avian fatty tissues are, like those of lizards and crocs, deposited within their torsos but, in lieu of large tails, they also store them across the surface of the chest and abdomen. Bird skin has some transparency, and field ornithologists interested in avian fat tissue fractions can determine their extent by simply checking the amount of yellowish fat tissue visible underneath bird feathers (e.g. Rogers 1991).

The dinosaur hump controversy

Is there any direct indication of fatty tissues in Mesozoic dinosaurs? The answer is probably 'no', except for the controversial idea that the elongate dorsal neural spines if some dinosaurs are indicative of a camel-like 'hump' morphology. Spinosaurus, Ouranosaurus and Deinocheirus are key species here, these animals being depicted sometimes as humpbacked creatures. These interpretations are not the sole remit of artists, either: Bailey (1997) proposed that the tall neural spines of certain dinosaurs supported masses of tissue acting as energy stores or heat buffers - in other words, a heap of fat.

I must admit to being very sceptical that neural spine anatomy is linked to fat humps. For one,it seemingly violates what we see in the extant phylogenetic bracket for dinosaurs, where no species (to my knowledge) have substantial fat deposits on their backs. Of course, it might be queried how meaningful phylogenetic bracketing is for this issue. Fatty tissues seem quite pliable in an evolutionary sense, being chucked around animal bodies with ease as lineages adapt to new conditions (Birsoy et al. 2013). It isn't crazy to think that dinosaur bodies are different enough from those of modern diapsids that they could not have their own take on fat distribution, and there are certainly functional constraints on extant diapsid fatty tissues which are unlikely to apply to non-avian dinosaurs. However, that's only speculation, and one which conflicts with a big pool of direct data on this issue.

Another approach might be to look at animals which do have fatty humps on their backs - several types of mammal - to see if their composition is analogous to anything we see in non-avian dinosaurs. What do their humps look like internally?

A collection of animals with humpbacks and sails. Fatty humps are not directly supported by skeletons in modern species including (B) lowland gorillas (Gorilla gorilla), (C) dromedaries (Camelus dromedaries) and (D) white rhinoceros (Ceratotherium simum). Vertebral spines anchor sails in some modern lizards, such as crested chameleons (Trioceros cristatus; E), and withers anchor powerful neck muscles as in American bison (Bison bison; F). Cropped figure from Witton (2014); B–D and F from Goldfinger (2004); E historic x-ray (1896) by Josef Maria Eder.

Turns out that most mammalian humps are akin to those bulging reptile fat masses mentioned above: they tend to exist without internal support or even osteological correlates. Where humps do correlate with bone, they are comprised of powerful musculature, not fat: the shoulder humps of rhinos and bison show this well. These structures might have subcutaneous fat on them, but this is not their primary composition, nor does fat storage seem to be a principle adaptive purpose. In several species, like camels and rhinos, the longest neural spines do not align with soft-tissue humps at all, these actually being located over dorsal vertebrae with smaller neural spines (camels) or short-spined cervical vertebrae (rhinos). Taking our attention away from mammals, and turning to reptiles, we see that elongate neural spines anchor laterally compressed sail-like structures, not masses of fat. It thus seems that we have no modern correlation between fatty humps and skeletons at all, and that there is no link between elongate neural spines and fatty deposits - quite the opposite actually seems true. It was this suite of observations which led to my 2014 humped Camarasaurus image: bizarrely, it is more consistent with modern data (though still extremely speculative) to put a camel-like hump on something without long neural spines, like Camarasaurus, than it is to put one on Spinosaurus, Ouranosaurus or Deinocheirus. Sail-like structures or (at least for the lower regions of the spines) muscle attachment seem more parsimonious interpretations of their strange vertebrae - if we're being scientific (as we should be in palaeoart), we really shouldn't be looking at those tall neural spines and thinking 'fat hump correlate'.

Tying all this together

Although we may lack direct evidence of them from fossils, data from extant animals suggests it is sensible to restore dinosaurs with noticeable, prominent fatty tissues, especially if we're reconstructing animals associated with extremes of behaviour, climate or environment. Animals about to undertake migration should look well fed and bulky, and those at the other end might look leaner and less nourished. We certainly have good precedent for restoring desert-dwelling Mesozoic dinosaurs - of which there are many - with energy and water reserves, given that even energy-limited ectothermic diapsids take such precautions, as do some endotherms. We should probably not limit fatty tissues to bulky energy stores, either: as in modern lizards, some extinct reptiles may have housed pockets of fat in prominent places to serve as advertisements of health and virility.

Where should we locate those big energy stores? With no direct indication from fossils, I suggest we err on the side of caution and follow the diapsid condition, principally locating them around the tail base and abdomen. Most Mesozoic dinosaurs had well-developed, powerfully muscled tails, and were thus likely capable of supporting a wad of adipose tissue at the tail base. We could start restoring humps in other places, but it seems sensible to keep speculative anatomy grounded somewhere. Besides, it's not like a fat-tailed dinosaur is boring concept!

Combining all this together, I'll leave you with the completed, revised version of my desert-adapted Camarasaurus image, now with fatty tissues fully consistent to those of modern diapsids. This meant chopping off the back hump (I'm not going to pretend I wasn't disappointed to do that), but it's worth it for a more defensible image. Note that the adult is sporting not only a fat tail, which is meant to represent sustenance for wandering through harsh desert settings, but also a pair of natty fat pockets behind the skull. It looks fairly happy with them.

Camarsaurus supremus, queen of the desert, not a member of Weight Watchers.

This post was brought to you by Patreon

Production of this image and article was sponsored by my awesome Patrons, who back me at Patreon. As a bonus, they were privy to production of this image and ongoing commentary on the changes made to it. If that sounds like something you're interested in, you can get involved for as little as $1 a month. You'll also get access to other exclusive content, discount print prices and other rewards for your troubles. A huge thanks to those who have signed on already!

References

• Alerstam, T., & Christie, D. A. (1993). Bird migration. Cambridge University Press.
• Azeez, O. I., Meintjes, R., & Chamunorwa, J. P. (2014). Fat body, fat pad and adipose tissues in invertebrates and vertebrates: the nexus. Lipids Health Dis, 13, 71.
• Bailey, J. B. (1997). Neural spine elongation in dinosaurs: Sailbacks or buffalo-backs?. Journal of Paleontology, 1124-1146.
• Battley, P. F., Piersma, T., Dietz, M. W., Tang, S., Dekinga, A., & Hulsman, K. (2000). Empirical evidence for differential organ reductions during trans–oceanic bird flight. Proceedings of the Royal Society of London B: Biological Sciences, 267(1439), 191-195.
• Birsoy, K., Festuccia, W. T., & Laplante, M. (2013). A comparative perspective on lipid storage in animals. Journal of cell science, 126(7), 1541-1552.
• Goldfinger, E. (2004). Animal Anatomy for Artists: The Elements of Form: The Elements of Form. Oxford University Press.
• Goff, G. P., & Stenson, G. B. (1988). Brown adipose tissue in leatherback sea turtles: a thermogenic organ in an endothermic reptile?. Copeia, 1071-1075.
• Lindström, Å., & Piersma, T. (1993). Mass changes in migrating birds: the evidence for fat and protein storage re-examined. Ibis, 135(1), 70-78.
• Mayhew, W. W. (2013). Biology of desert amphibians and reptiles. In: Brown, G. W. (Ed.). Desert biology: special topics on the physical and biological aspects of arid regions (Vol. 1). Elsevier.
• Rogers, C. M. (1991). An Evaluation of the Method of Estimating Body Fat in Birds by Quantifying Visible Subcutaneous Fat. Journal of Field Ornithology, 349-356.
• Saarela, S., Keith, J. S., Hohtola, E., & Trayhurn, P. (1991). Is the “mammalian” brown fat-specific mitochondrial uncoupling protein present in adipose tissues of birds?. Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 100(1), 45-49.
• Witton, M. P. (2014). Patterns in Palaeontology: Palaeoart-fossil fantasies or recreating lost reality. Palaeontology Online, 4, 1-14.

New takes on the Wealden Supergroup palaeobiota, part 1: Iguanodon, Neovenator, Eotyrannus and others

Regular readers will know that I'm prone to dabbling in palaeoart depicting the environments and animals of the Wealden Supergroup, the 18 million year stretch of Early Cretaceous time represented by mud-and sandstone deposits across the southern UK. Recently, I've been updating some existing Wealden work as well as producing some new stuff of other Wealden species. With no time to produce a new post of substance, here's a bumper 'picture of the day'-type post. Initially, I was going to chuck something like ten images on here, but time has run short and I'll have to split it in two.

If you like anything here, remember that you can buy prints of them all from my shop (there's now a Wealden section, too), which is now also browsable from the comfort of Facebook. OK, enough preamble: into the Wealden once again...

Iguanodon bernissartensis: thumb wars

Two Iguanodon bernissartensis, the quintessential Wealden iguanodont, decide to settle their differences, while members of their herd watch on.

Poor old Iguanodon doesn't get the attention it used to, and a lot palaeoart we do see of it tends to focus on tried and tested behaviours: lots of standing about and eating, but not much else. In this new painting, I've attempted to show two big Iguanodon individuals settling an intra-specific dispute via use of thumb spikes. Long-term readers may recall that we've covered iguanodont thumb spikes before, and that I. bernissartensis has especially big ones. Here, they've been swinging their thumbs at each other's soft bits, causing deep, bloody wounds. This might seem extreme, but there are plenty of modern animals which take intraspecific fights to similarly gory levels - elephant seals were a key inspiration here. I imagine battling Iguanodon would look like an armed sumo-wrestling match, albeit with longer tails and less rice. Note that you can see the breath of several animals here: Wealden winters are not meant to be especially warm.

Rebbachisaurids vs. Neovenator salerii redux

Carcharodontosaurian Neovenator salerii stalks a pair of rebbachisaurid sauropods, using darkness as cover.

A while back I posted about dinosaur predation, noting that modern animal predator acts are often far less gladiatorial and epic than we might imagine. It's this slow, considered approach to predation which I'm attempting to show here, as the carcharodontosaur Neovenator stalks two rebbachisaurid sauropods in the dead of night. The idea is that the Neovenator has much better eyesight than the sauropods, who know they're in trouble, but can't really respond adequately. Note the rain: some recent models of Wealden palaeoclimates suggest it was wetter than previously modelled (albeit with very high evaporation rates for much of the year).

Anteophthalmosuchus hooleyi vs. Hypsilophodon foxii, redux

Large goniopholidid Anteophthalmosuchus hooleyi takes advantage of a flooding river to hunt two stranded Hypsilophodon foxii.

Speaking of rain, we know that some parts of the Wealden were prone to flooding following particularly intense downpours. That's good news for animals adapted for powerful swimming, but less welcome to species which prefer dry land. Here, in this reworked painting, the large Wealden goniopholidid Anteophthalmosuchus hooleyi has found a stranded pair of adult and juvenile Hypsilophodon foxii, and is taking full advantage of the situation. Goniopholodids are a group of almost-crocodiles characterised by long forelimbs, interlocking scutes and overbitten jaws - you can read more about them here.

Eotyrannus lengi: firestarter, redux 

Early tyrannosauroid Eotyrannus lengi stalks the edge of such a wildfire. 

What else does rain bring? Sometimes, lightning. When introduced to a parched Wealden landscape, lightning strikes caused short-lived canopy fires which, ultimately, created conditions ideal for fossil preservation. In this reworked painting, a fully-feathered tyrannosauroid Eotyrannus lengi is prowling the periphery of a Wealden canopy fire to grab any animals flushed out by the flames.

The tiny wars of Wesserpeton evansae, redux 

Two Wesserpeton evansae get in each other's faces, because some animals are just jerks.

OK, enough about Wealden weather. Here's a reworked version of two of the Wealden's tiniest tetrapods - indeed, some of the smallest fossil tetrapods of all - facing off in leaf litter. Recently named Wesserpeton evansae, these are albanerpetontids, very small amphibians which only died out a few million years ago. The 35 mm snout-vent length of these animals did nothing to temper their ferocity, and numerous jaws of Wesserpeton have healed fractures and breaks from intraspecific tussles. The animals in this picture are speaking the aggressive body language of modern salamanders as a prelude to their conflict. Two sauropods hang around in the background because, hey, it's called the Age of Dinosaurs for a reason. Some people have suggested this image borders on the trippy and surreal. Stay off the shrooms, kids. 

Rebbachisaurids and chums

Lower Cretaceous rebbachisaurids and giant sauropod 'Angloposeidon' look for water in this desiccating Wealden lake.

I do like rebbachisaurids, that group of sauropods who didn't get the memo about long necks. They're only represented by scrappy remains in the Wealden (a scapula) which is enough to tell us they were there, but not substantial enough to carry a name. Here, a few individuals are digging around a rapidly drying lake-bed to find a substantial source of water: digging elephants were the inspiration for this scene. In the background, probable brachiosaurid 'Angloposeidon' struts its stuff. It's meant to be walking particularly tall - I like the idea that fossil animals would carry themselves in different, characteristic ways, just as modern animals do. A pink gnathosaurine pterosaur has snuck into the foreground, just because. 

A lesser-seen Wealden scene: the Hastings Beds palaeobiota

Finally for now, here's one more new painting. This is a reconstruction of a swollen river representing part of the Hastings Beds, the oldest deposits of the Wealden, complete with local reptile fauna. The animals shown here are really poorly known: titanosaur 'Pelorosaurus' becklesii (bits of forelimb), possible carcharodontosaurian Becklespinax altispinax (three dorsal vertebrae), eucryptodiran turtle Hylaeochelys belli (a shell), and the possible azhdarchoid previously known as 'Palaeornis cliftii' (humerus). So yes, take the 'restorations' of these animals with an evaporite mine of salt: they're really just better known, fairly 'generic' representatives of groups represented by these Wealden taxa, air-dropped into a Wealden setting. Becklespinax is obviously modelled closely on Concavenator, as they seem to be pretty closely related and have a similar taste in dorsal ornamentation. I gave Becklespinax a more vertical anterior sail margin however, as indicated by the fossil. There's an article waiting to be written on palaeoart like this - should we even bother 'reconstructing' poorly known scenes and species? I clearly think we should, but we'll have to discuss the reasons why another time. 

I'm just now realising that there's a lot of confrontation in these images. Come back soon for a more placid, relaxed set of pictures in part 2...

Mamenchisaurus youngi presents a money-off print offer and other links of interest

Jurassic sauropod Mamenchisaurus youngi was a pretty freaky looking thing: a weird, upturned tail base; some sort of 'sail' along the hip/tail junction; a hugely oversize neck and massive shoulders. Here, one is shown engaging in a bird-like threat display: head and neck down, vocalising, and elevating its tail. The other is engaging in bird-like can't-be-botheredness.   Prints of this image are available here.

With apologies for a post entirely devoted entirely to loosening money from your pockets, there are three items of newsworthiness I want to share here. Two of them are even for decent, well-meaning causes. The other is my livelihood, which I also consider a good cause, but I'm aware I have a biased opinion on that.

1. Lots of new art at my print store, and a 20% discount for savvy types

In addition to updating this blog and Twitter, I also regularly add new artwork to my online print store. Much as I try to give each piece full airing and discussion here, I struggle to do this for all my work in a timely fashion, and they end up on sale before an accompanying article can be produced. Recent additions include:

• A Kayenta Formation scene, featuring the (possibly) semi-aquatic cynodont Kayentatherium, the stem-turtle Kayentachelys, and the Lower Jurassic's most famous predator, Dilophosaurus*
• A slipping Deinonychus, restored from track sites in Utah*
• A revamped painting of Leptocleidus superstes, a freshwater Wealden plesiosaur (original post)
• Conversing sauropods Mamenchisaurus youngi (the painting decorating the top of this post)

*Thanks to co-conspirators Robert Gay and ReBecca Hunt-Foster for concepts and assistance with these pieces!

If you'd like to own a high quality Giclée print of one of these, or any of the other 29 paintings in there, now is a good time to purchase one. Until the end of April you can obtain a 20% discount on the print costs by entering the promotional code 'APRIL2015' at the store checkout. The code doesn't apply to shipping costs, but knocks a hefty chunk off the prints themselves. Armed with this code, prices range from £16-40 instead of their £20-50. All purchases support the production of more art and articles, so every purchase is sincerely appreciated.

It's not official until there's a shareable image for social media.

2. It's fund-raising auction time at the Portsmouth's Natural History Museum!

My local natural history museum, Cumberland House, is attempting to raise money for a new bee hive exhibition via an eclectic auction next week. The auction takes place on April 15th and offers a huge range of stuff: furniture, artwork, days out, full-blown holidays, money off cruise fares and a whole lot more. There's lots of stuff here which will be of interest to those outside of the local area and bids can be made remotely - you don't have to attend the auction personally to obtain some of that cool stuff. There's even some palaeoart for sale - a framed print of my 'Tyrannosaurus vs. bees' painting. Details of this, and a full low-down on the lots, are available in the auction catalogue (here) and at the Friends of Cumberland House Facebook page. 

3. Mammoth is Mopey (again)

Yeah, I know I've mentioned this before, but it's such a good project that I want to make sure it's known as widely as possible. Mammoth is Mopey is a book for younger readers showing a different prehistoric animal for each letter of the alphabet, with each species accompanied by a fun, quirky illustration. In keeping with the sauropod themed opener of this post, here's the Mammoth is Mopey 'Boastful Brontomerus'.

From Mammoth is Mopey, which you can support here. Illustration by David Orr.

As you might tell by the inclusion of this relatively obscure species, Mammoth is Mopey is going to introduce children and their parents to a new suite of prehistoric animals in a very fun, memorable way. It's rare to see projects aimed at very young children trying to break new ground like this, and that alone seems good reason to support it. The book, by David and Jennie Orr (David being well known for founding Love in the Time of Chasmosaurs), is currently halfway through an Indiegogo campaign and received just over 50% funding. With outreach exercises also riding on the successful funding of this project, it would be great to see it meet the $10,000 target in the next 20 days.

Right, that's my attempt to fleece readers of their money done for now. Less commercially-minded posts will follow soon.

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.