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Sunday, 30 June 2019

Monsterising prehistory! The "how", "why" and "so what" of monstrous palaeoart


Just a quick heads up and some steering links in this post, normal service will be resumed next month.

I recently wrote an article about the palaeoartistic monsterisation of prehistoric animals for the Popularizing Palaeontology blog, a web offshoot of the workshop series of the same name organised by Chris Manias of Kings College London. The PopPalaeo workshops are a series of discussions and presentations by scientists, historians, artists and curators about the public face of palaeontology, and they're always fascinating and fun events.

The most recent UK workshop - held in December 2018 - focused on how palaeontology connects with wider scientific discussions about evolution, biological progress and perception of nature. Chris invited me to speak at this event and I chose to cover how many palaeoartworks deliberately 'monsterise' their subjects, using enhanced or distorted anatomy and compositional techniques to exaggerate the ferocity of their depicted species (opening slide from my talk, above). I think we're all familiar with examples of this: if not, just check out virtually any predatory dinosaur from cinema, or the dinosaur book covers at your local book shop. Monsterised palaeoart is a topic many of us have strong feelings about as it ties into nostalgia for childhood dinosaur media, our commitments to certain franchises, and our aesthetic preferences. But it's probably neither a wholly good nor wholly bad convention: there's lots to discuss about how and why we monsterise the past, as well as it's better points ("it's a PR win!") and drawbacks ("it distorts the truth about ancient life!").

Rather than reposting my essay here, you should steer your internet browsing machine to the PopPalaeo blog to read it there. While you're there, be sure to check out the rest of the PopPalaeo website, including recorded talks from each workshop (the latest set, including my monsterising talk, is here) - lots of goodness lies therein.

Coming soon: wrapping up our series on the Crystal Palace palaeoart sculptures with an in-depth look at the oft-neglected mammal island.

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Thursday, 30 May 2019

The science of the Crystal Palace Dinosaurs, part 3: Megalosaurus, Hylaeosaurus and Iguanodon

The Crystal Palace Iguanodon and Hylaeosaurus as illustrated in Matthew Digby Wyatt's 1854 Views of the Crystal Palace and Park, Sydenham. These Iguanodon are surely some of the most famous Victorian palaeoart in the world, and probably some of my favourite palaeoartworks of all.
Welcome to part three of our discussion of the science behind the Crystal Palace prehistoric animal sculptures. As you'll know if you've read the previous entries in this series (part 1, part 2), these articles are the result of my working with the Friends of Crystal Palace Dinosaurs charity to produce artwork and palaeoart notes for their new 'about the statues' web pages. Please check out part 1 for additional context about the work of the FOCPD and the need for continued care and maintenance of the Crystal Palace sculptures. Restoration work on the models continues, and you can help by donating money or volunteering your time to keep the site maintained.

Having now covered the bulk of the Palaeozoic and Mesozoic animals (Dicynodon, "Labyrinthodon", the marine reptiles, Teleosaurus, pterosaurs, and Mosasaurus), it's time to focus on what are, for many, the main attraction: the dinosaurs. The four dinosaur statues of the Secondary Island are the largest models of the entire display and their elevation above the surrounding landscape makes them imposing, conspicuous figures even from afar. They are undeniably the most famous and spectacular components of the Crystal Palace menagerie, but also routinely mocked and ridiculed for being so scientifically dated. Such derision is entirely unfair as it ignores how much of dinosaur anatomy they accurately recorded, how cutting edge they were in the 1850s, and how progressive Benjamin Waterhouse Hawkins was in his approach to their reconstruction. Though far removed from how we imagine dinosaurs today, Hawkins captured the foundation of what makes dinosaurs unique and charismatic in his takes on the Jurassic theropod Megalosaurus and two Cretaceous, Wealden species: Iguanodon and Hylaeosaurus.

As important milestones in early depictions of prehistoric animals, much has been said about the history and science informing the Crystal Palace dinosaurs. It must be said that a lot of the most familiar and popular tales about the sculptures are oversimplified or simply untrue. An example is the framing of the dinosaur sculptures within the context of the Richard Owen vs. Gideon Mantell rivalry, whereby Owen uses the statues to score some final points against Mantell by imposing his vision of Dinosauria on the Victorian public (e.g. Dean 1999; Torrens 2012). In actuality, Mantell was asked to be the consultant for the Crystal Palace prehistoric models before Owen, but he declined the offer on grounds of the models not being educational enough and, probably, his declining health (he died in 1852, before construction of the models was finished). Owen would attempt to re-write these affairs to position himself as first choice as technical advisor to the project, as well as the man who suggested to hire Hawkins (Dawson 2016).

Hylaeosaurus better side, as seen in 2018. Its face is all but invisible from public paths around the Geological Court and it's only by visiting the Secondary Island itself that you can get a good look at the whole animal. Note the presence of a nasal boss and enlarged, thickened scales over the neurocranium, recalling certain iguana species.
Owen’s well-documented disinterest in the Crystal Palace models (Secord 2004; Dawon 2016) is also inconsistent with him bending the models to his unique vision of Dinosauria. Hawkins did not always follow Owen's latest ideas in his Crystal Palace work: in some places the dinosaur models reflect older Owenian theory, and in others they are very Mantellian in form. Owen was unaware of important decisions being made about the appearance of the dinosaurs (Secord 2004) and he recorded several dissenting opinions about their anatomy in his 1854 Crystal Palace guidebook, including objections to the Iguanodon nose horn and a comment about the Hylaeosaurus armour being conjecturally restored. History suggests that Owen was not invested enough in the models to be using them in academic politics against Mantell's legacy.

The Crystal Palace dinosaurs were far from the first efforts to restore dinosaur form, and they represented significant advances over earlier efforts. John Martin's 1837 The country of the Iguanodon is more typical of early dinosaur art, depicting Iguanodon and Megalosaurus as whale-sized lizards. The Crystal Palace dinosaurs were more realistically sized and included more characteristic anatomy, including strong, upright limbs, and taxon-specific features, such as beaks and osteoderms. Hawkins' reconstructions were definitely 'dinosaurs v. 2.0', not just life-sized versions of art that came before. Image in public domain, borrowed from Wikimedia.
Although a substantial haul of dinosaur bones had been amassed from southern Britain by the 1850s, no dinosaur taxa were well-known at this time (despite Owen’s PR-friendly 1854 statement that all the sculptures were based on species for which “the entire, or nearly entire, skeleton had been exhumed in a fossil state”). Accordingly, the dinosaurs were constructed using Owen's basic dinosaur body plan (i.e. quadrupedal reptiles with mammal-like features, including proportionally large and erect limbs, strong, weight-bearing hips and terrestrial habits) and augmented with features either suggested by fossil material or else consistent with their predicted anatomy and lifestyles (Owen 1854). The results are far from the mark as goes modern interpretations of Iguanodon, Megalosaurus or Hylaeosaurus, but they are reasonable imaginings of dinosaurs given the material known to Hawkins at that time.

Although often mocked for their depiction of now archaic ideas, the models were actually a significant advance over earlier depictions of dinosaurs as whale-sized lizards. It could be argued that the models did not present the most progressive view of dinosaurs available in the early 1850s as they ignored Mantell’s insightful considerations of Iguanodon proportions and pose (Mantell 1848, 1851, see below) but, even so, each model references ideas about dinosaur anatomy that were, at the time, very modern and cutting-edge. Hawkins’ dinosaur sculptures are an excellent record of that short period in history when the unique and defining aspects of dinosaurs had been recognised, but our fossil data were still too incomplete to reveal their overall forms. They capture, on grandiose scale, an important intellectual milestone in the realisation of what dinosaurs were, and are a monument to the ingenuity of early palaeontologists.

Megalosaurus

Megalosaurus as seen in 2013 - more or less as it looks today, but the surrounding vegetation is lower so you can see the full extent of the powerfully muscled hindlimbs. Not visible in this photo is a long crack which runs down the length of the model on the right side of the neck and torso: these sculptures weigh several tonnes apiece, and putting all that weight on four limbs takes its toll.
Hawkins’ Megalosaurus is specifically meant to represent M. bucklandi, a species known to him from a jaw bone and teeth, a few vertebrae, pelvic bones and some hindlimb material. It is a fairly faithful representation of Owen’s vision of Megalosaurus, which we also have documented in his 1854 guidebook (below). This famous illustration, which blends life restoration with skeletal reconstruction, is the only instance of Owen providing us with his vision of a dinosaur to compare with Hawkins. Owen’s drawing - which is also one of the oldest known skeletal diagrams of a dinosaur (see Scott Hartman’s excellent History of Skeletal Drawings) - does not sugarcoat the volume of material known for Megalosaurus in the early 1850s and instead (perhaps inadvertently) showing us the huge gulfs of dinosaur anatomy that Hawkins had to restore from just a handful of remains.

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Owen's skeletal restoration of Megalosaurus bucklandi from his 1854 Crystal Palace guidebook, a significant illustration in the development of skeletal diagrams of fossil animals and the only hint in his guidebook as to what was truly known of the species restored by Hawkins. The Crystal Palace sculpture is pretty faithful to this, but note the lack of the shoulder hump and smaller head.
Curiously, Owen did not include the full 1854 inventory of Megalosaurus fossils in his drawing or text, omitting some potentially significant vertebrae from the Wealden that had been referred to this taxon (see below). This suggests that Hawkins’ Megalosaurus was based entirely on Jurassic material that we still regard as M. bucklandi, and that it narrowly escaped being a chimaera of several theropod taxa. Even in the 1850s Megalosaurus was becoming a wastebasket of carnivorous dinosaur material that would eventually contain dozens of species. Today M. bucklandi is regarded as the only species of Megalosaurus (Benson 2010), and while its exact proportions remain unknown, it is imagined as a large-headed creature with a robust, three-fingered hand, and most likely similar to Torvosaurus in general form. It was probably 6-7 m long - mid-sized for a theropod dinosaur, but large for one from the Middle Jurassic.

Although working from little material, Hawkins did not simply take Owen's dinosaur concept and bolt some sharp teeth into the jaws. Rather, his Megalosaurus has several hallmarks of predatory species that reflect close observation of living animals. The limbs, for instance, are not pillar-like as in the Iguanodon but have flexed joints and bulging musculature. This pose recalls the limbs of rhinos - relatively fast, sprightly large animals - more than the columnar-limbs of slower paced giants, like elephants. The body is trim and streamlined, tapering from the muscular shoulders towards the hips, and also lacks an expansive gut. Hawkins would have known that carnivorous animals have smaller, shorter guts than herbivores, and he probably modelled his Megalosaurus with this in mind. The massive head (some five feet in length, probably based an older Owen estimate (1842, 1854), and not reflecting the revised 2' 6" length published by Owen in 1856) is held in place with deep neck muscles anchoring to an enlarged shoulder skeleton. Hawkins was clearly referening large-headed mammalian herbivores such as bovids and rhinos here, and his transference of their head-supporting apparatus to a predatory reptile shows his resourceful approach to reconstructing these poorly known animals. The result is a creature that looks undeniably powerful and predatory, a mix of bear, buffalo and crocodile. It’s difficult not to imagine the model as eying the adjacent Iguanodon as a potential meal.

Megalosaurus bucklandi as we understand it today: a large-ish theropod that roamed Jurassic Britain, posing in ways that loosely homage Charles Knight's work.
Hawkins' Megalosaurus is restored with mouth slightly ajar, and it’s clear from both the model and associated Hawkins’ artwork that the teeth are modelled on those of crocodylians - in other words, they would be visible even when the mouth was closed. Today, the subject of dental exposure in dinosaurs and other fossil forms is a hot topic among palaeoartists, but we can view Hawkins’ take as being in line with general ideas of dinosaur palaeobiology c. 1850. The situation of dinosaur teeth in sockets was identified early on as being more crocodylian- than lizard-like, and it was not unreasonable for Hawkins to extrapolate this to a full crocodylian-grade jaw. Curiously, his other dinosaur models have lips: perhaps he felt that their more lizard-like teeth warranted more lizard-like facial anatomy?

Having mentioned the shoulder hump, it would be remiss not to outline the interesting history of this structure. Darren Naish (2010) proposed that the shoulder hump of Megalosaurus was based on Altispinax dunkeri, three Wealden theropod vertebrae with tall neural spines known to Owen in the 1850s. Owen (1855, 1856) regarded these as the shoulder vertebrae of M. bucklandi and remarked that their tall spines must have anchored powerful, head-supporting muscles used to aid Megalosaurus in pulling apart carcasses. Circumstance suggests that Owen must have given Hawkins advance notice of this but... surprisingly no - other data suggests otherwise. Secord (2004) reports that Owen actually had no idea about the Megalosaurus shoulder hump until the models were completed and installed, and the absence of either Wealden bones or an obvious shoulder hump in Owen's 1854 illustration confirms that he was not envisaging Megalosaurus in such a guise in the early 1850s. Secord also reports an ambivalent 1855 newspaper quote from Owen regarding the accuracy of the shoulder hump. When asked if the hump was a genuine feature of Megalosaurus, Owen replied that "no one could say that the bump was not there”, and he once again did not mention Altispinax despite the kudos they would have brought to the model and his skills as a consultant. Post-1854 boasting from Hawkins confirms the fact that Altispinax was not referenced in the Crystal Palace Megalosaurus, as he used the discovery of these 'shoulder hump' bones as evidence of his sharp skills for anatomical prediction (Secord 2004). It's perhaps significant that Owen presented older Megalosaurus size predictions in his 1854 guidebook, possibly indicating that his Crystal Palace consultancy pre-dated the analysis he presented in his 1855 Megalosaurus monograph, or that he was keeping his later work under wraps.

The Witton-Macleans and Hawkins' Megalosaurs, in 2018. Though small compared to estimates of dinosaur size from the early 1800s, the Crystal Palace dinosaurs are still big, imposing artworks. It occurs to me that this might be the first picture of me and the Disacknowledgement on this blog, which I've been writing since 2012. Well, we don't want to rush things, right?
The skin texture of Hawkins’ Megalosaurus is also interesting. Rather than obviously scaly, as per his other dinosaurs, the skin has deep fissures and wrinkles that recall elephant skin. The decision to not depict individual scales was actually quite precedent, as the eventual discovery of dinosaur scales would reveal their surprisingly small nature (typically less than a centimetre across). Alas, the thought process behind Hawkins’ decision to use this skin texture is not clear, there being no mention of wrinkled Megalosaurus skin in Owen’s guidebook or in other literature of the time. A generous interpretation could be of Hawkins having an intuitive sense that dinosaurs might be ‘more than just reptiles’, a fact later vindicated by their skeletal proportions and the discovery of diverse skin types and feathering. More cynically, perhaps he wanted a skin type to distinguish the Megalosaurus from the other dinosaurs? Or maybe he just ran out of time to complete the model with the detailed scaly finish used on Iguanodon and Hylaeosaurus?

Hylaeosaurus

The most overlooked dinosaur of the Crystal Palace trio is Hylaeosaurus armatus: the first ankylosaur known to science. It’s easy to ignore this species even when visiting the Geological Court in person as, although prominently placed between the Megalosaurus and Iguanodon, the sculpture’s face is not visible from the public paths around the Secondary Island. Instead, we can only see the hindquarters and left side. This is great for showing off the armoured back, but undeniably leaves a lesser impression on visitors - especially as it competes for attention with very imposing and charismatic statues either side.

Hawkins' take on Hylaeosaurus armatus in 2018, seen as standing on the Secondary Island and not from the path on the Crystal Palace 'mainland'. Note the armoured back (not just the spines, but also the prominent tubercles) and iguana-like face. The head of this model is a fibreglass replica, the original having fallen off and put on display elsewhere in the park.
I recall an explanation for the peculiar orientation of Hylaeosaurus being that cranial material was unknown to science at this time, so the model was positioned facing away from the public to obscure its face. I can’t remember where I learned this, but it’s incorrect in any case. Today, Hylaeosaurus is chiefly represented by a slab containing a portion of skull, several neck and shoulder vertebrae, elements of the pectoral girdle and the large spike-like scutes that covered its skin (Barrett and Maidment 2011). But in the early 1800s Hylaeosaurus inventories were much broader, also containing referred jaws, teeth, limb bones, and hip and tail elements (Owen 1842). This rendered Hylaeosaurus c. 1854 comparable to Megalosaurus in representation, so lack of anatomical reference does not account for Hawkins hiding its face. Modern takes on Owen’s additional Hylaeosaurus specimens sees his referred jaw belonging to a stegosaur (the only one known from the British Wealden) and the teeth pertaining to a sauropod (Barrett and Maidment 2011). The other elements probably represent indeterminate ankylosaur bones. Accordingly, Hawkins’ Hylaeosaurus is the most chimeric of all the Crystal Palace dinosaurs, mixing elements from not just several related species, but several major dinosaur groups.

Hawkins’ restoration of the Hylaeosaurus armour was very reasonable given the material he was working with. Two types of osteoderm were recognised for Hylaeosaurus in the 1830s and 40s: large spikes, and low elliptical structures that sometimes bore tubercles at their summit. Both feature prominently on the dorsal surface of Hawkins' sculpture, covering the braincase, shoulders, back, haunches and tail. The spines are arranged in a single row along the midline and are flanked either side by extensive sheets of smaller, elliptical scutes. Whether Hylaeosaurus had one or more rows of spiny osteoderms was the subject of discussion among early palaeontologists, and ultimately Hawkins decided to side with Mantell, not Owen, in depicting a single row. Mantell (1833) interpreted the Hylaeosaurus spikes as being from a spiny midline fringe, akin to those of iguanine lizards, while Owen initially had reservations about them being osteoderms at all. Writing in 1841, Owen stated that he did not disagree with Mantell's idea of them being armour, but he also thought that the 'spines' could be displaced abdominal ribs. By 1854 Owen conceded that Mantell’s identification of the structures as dermal spines was accurate, but he also remarked that Hawkins’ arrangement of the spines was conjectural. A few years later Owen returned to the issue of the spines again, and provided insightful reasoning for the spines being arranged in two parallel rows (Owen 1858). The evolution of Owen’s ideas saw him creeping closer to the reality of ankylosaur life appearance and, today, we know that he was close to the truth: ankylosaurs were indeed covered with multiple rows of scutes, spines and spikes. Alas, this realisation came too late to be incorporated into Hawkins’ models.

The Crystal Palace Hylaeosaurus is probably the most lizard-like of the three featured dinosaur species with its low, crouched pose, large feet and entirely scaly, lipped face. Aspects of the skin recall heavyset, tough-skinned iguanines such as the Galapogos genera Amblyrhynchus or Conolophus (viz. low tubercles and hornlets around the back of the head, a scaly nasal prominence, polygonal scales on the body and limbs), which accords with Mantell’s (1833) referencing of iguanas as a model for the Hylaeosaurus spiny fringe. Though sporting some very fine facial features (though lacking the beak of true ankylosaurs), Hylaeosaurus is Hawkins’ only dinosaur sculpture without visible teeth*. Given that Owen (1842, 1854) had referred teeth to this species, and that virtually all the other non-mammal statues have exposed dentition, this omission is peculiar. Perhaps, if the sculpture was always planned to face away from visitors, Hawkins decided that sculpting an open mouth with individually placed teeth was unnecessary.

*As an aside, it's worth specifying that the Crystal Palace dinosaur models have metal teeth inserted into their mouths, while the other models have teeth molded from concrete. The dinosaur's metal teeth were stolen as souvenirs by Victorian visitors (Secord 2004)!

Hylaeosaurus remains a poorly known animal even today, but it probably looked a little like the more familiar Polacanthus, another Wealden species shown in this 2015 illustration. In some repsects the Crystal Palace version is not a million miles off this.
Hawkins’ Hylaeosaurus is his most authentic dinosaur with respect to our modern understanding, accurately capturing an ankylosaur as a low-slung quadruped with a short neck, long tail and an armoured back. Unlike the Crystal Palace Megalosaurus and Iguanodon, which were soon embarrassed by the discovery of remains indicating entirely different body forms, the depiction of Hylaeosaurus as a heavyset quadruped was vindicated in 1858 with the discovery of Scelidosaurus harrisonii in Jurassic deposits of the southern UK. This specimen - the first near complete dinosaur skeleton ever found - matched many aspects of the Crystal Palace Hylaeosaurus as well as Owen’s general ideas about dinosaur form. However, despite describing Scelidosaurus in detail, Owen (1863) did not capitalise on this opportunity for personal vindication. David Norman (2000) ascribes this to Owen being ever busier from the late 1850s onwards, taking on prominent roles in establishing the British Museum of Natural History (today known as London's Natural History Museum), taking part in numerous debates about evolution and natural selection, as well as maintaining an enviable output of papers, books and monographs. I wonder if Owen’s general disinterest in the Crystal Palace animals has relevance here as well, as might the failure of the wider Crystal Palace Park project. Within just a few years of opening the Crystal Palace Company was struggling to recoup the great expense of their ambitious development and the primary business of Crystal Palace Park had shifted from education and enlightenment to festival, sport and spectacle (Secord 2004). While being involved with Crystal Palace evidently did not harm Owen’s career, perhaps he could not, or dare not, wear his association to the failing project with pride. Hawkins, whom we may also have expected to use Scelidosaurus to promote his anatomical insights, was by this point busy working on other dinosaur material in the United States. Both men seemed to have moved on surprisingly quickly from what would be, among the public at least, some of their best known and longest-standing work.

Iguanodon

Hawkins' Iguanodon: exemplar palaeoart from the Victorian age, seen in 2018. This photo is taken from immediately next to the Hylaeosaurus, allowing us to see the reposed model in anterior aspect: look those excellently modelled shoulders and neck. Remember that these things were constructed using materials typically employed for building houses, not fine sculptures: the detailing is superb.
Probably the most completely known dinosaur for Hawkins was Iguanodon, which might explain why this dinosaur was captured in two models rather than just one. The Crystal Palace Iguanodon are likely the most famous Victorian dinosaur restorations in the world but, today, it’s hard to say exactly what animals they represent. Until relatively recently Iguanodon was a wastebasket for iguanodont material from the southern UK, a long-standing problem deeply rooted in Iguanodon taxonomic history. Several distinct taxa have now been identified among the British "Iguanodon" material, and much needed taxonomic revisions anchored the name Iguanodon to I. bernissartensis, the famous species chiefly known from Belgian skeletons (see Norman 2013 for a review). I. bernissartensis is known from the UK, but it's relatively rare and geologically younger than most of the "Iguanodon" material used by Mantell, Owen and Hawkins to conceptualise Iguanodon in the early 1800s. An upshot of this is that the Crystal Palace Iguanodon were informed by fossils that we no longer recognise as Iguanodon today.

We do not have a definitive list of specimens examined for the Iguanodon models, but Owen (1854) and Hawkins (1854) allude to three important reference specimens. Firstly, Owen (1854) specifically identifies the models as being "I. mantelli", one of two names applied to the original set of Iguanodon teeth described by Mantell in the 1820s. These teeth are no longer considered diagnostic for any species, but are a close match for those from the Valanginian iguanodont Barilium dawsoni (Norman 2011). Many anatomical and proportional details were taken from a second specimen, the famous “Mantel-piece”, which is today regarded as Mantellisaurus atherfieldensis (though not incontrovertibly - see Norman 2013). Thirdly, Hawkins (1854) notes that a large iguanodont specimen (below) from Horsham was used to establish the size of the models. This specimen has been all but forgotten in modern literature despite earning the local nickname of the “Great Horsham Iguanodon” and being referenced as an exceptionally large specimen by Owen (1855). Details of the Horsham specimen suggest it is almost certainly another specimen of Barilium, being sourced from the Hastings Beds (deposits yet to yield true Iguanodon fossils, but definitely containing Barilium) and having a scapula bearing characteristic features of this taxon (Norman 2011). Note that none of these specimens contain a thumb spike - the source of the famous nose horn - so this must have stemmed from yet more reference material. Hawkins might have based the nose horns on the large thumb spikes published by Mantell in 1827 and, if so, they represent another iguanodont species for our list, Hypselospinus fittoni (Norman 2015). That gives us at least two, and possibly three, iguanodont species represented in the Crystal Palace "Iguanodon" sculptures, not one of which is actually Iguanodon as we define it today. We cannot rule out Hawkins examining some true Iguanodon material in his research for the models, but if he did, they were not significant enough to warrant mention in any known literature.

Rib (left) and portion of dorsal scapula (right) of the "Great Horsham Iguanodon", as seen on display in Horsham Museum and Art Gallery in 2019. There's more material to this specimen, including a toe bone, not on show here. This largely forgotten specimen which was pivotal in establishing a realistic size estimate for Iguanodon (Owen 1855). Notice how flared the scapular termination is: this is characteristic of material referred to Barilium dawsoni, and quite different from the scapula of Iguanodon (Norman 2011).
Hawkins’ Iguanodon are basically Owenian in form, but he conflicted with Owen by giving his restorations a Mantellian nose horn. Owen (1854, 1855) was strongly opposed to Iguanodon having such a structure, devoting several monograph pages to dismantling this identification and correctly identifying it as a spike-like claw in 1855. Owen’s observations on the ‘nose horn’ were entirely sound, but Hawkins, presumably like Mantell, was probably inspired by the presence of nose horns in many iguana species. Iguanas may have informed the models in other regards as well, including the large tympanic membranes (their conspicuous ‘ears’), dewlaps, midline body and tail spines, and details of their scalation. The edentulous beak and blunt claws are deviations from iguanas and were correctly restored for Iguanodon, these presumably being based on lower jaws and digit bones recovered during the early 1800s. Here, Hawkins was more accurate than Mantell, who’s final conceptualisation of Iguanodon included prehensile lips and a protruding tongue (Mantell 1851). The grasping hand of the reposed Iguanodon could be a Mantellian nod however, reflecting his proposal that Iguanodon used its forelimbs to grasp vegetation (Mantell 1849, 1851; Dawson 2016). If so, it's noteworthy that Hawkins did not follow Mantell's observation that the forelimbs were relatively slender, instead sticking to the convention of Iguanodon being a columar-limbed quadruped. Hawkins’ construction of Iguanodon at just over 10 m long was very ‘modern’ for the time, contrasting to earlier calculations of its length where scant bones were interpreted as belonging to creatures many tens of metres long (Mantell 1851; Owen 1854, 1855).

It should be observed how lifelike and detailed Hawkins Iguanodon are. More than any other reptile sculpture in the Geological Court, Hawkins Iguanodon give the impression of capturing real animals. Most of the other reptiles are posed fairly functionally: they lie or stand in ways that allow us to see their form clearly. But Hawkins’ Iguanodon have a touch more dynamism. The reposed individual looks relaxed with its subtly spreading belly and cycad-pawing hand, while the animal above and behind it looks vigiliant and alert. Their composition implies real behaviours and personalities in these anatomically fictional, but entirely believable restorations. Coupled with their enormous size, these aspects make them (for me, at any rate) the most spectacular models of the entire display.

What does the inside of a Crystal Palace dinosaur look like, you ask? The standing models have holes in the bottom (presumably for drainage and maintenance access) which allow you to see inside, and they look like this. Here, we're seeing the interior view of the standing Iguanodon sculpture, with light shining through the open mouth. I'm not sure how much of this is original and how much represents conservation work, but it's evident that the bulk of the models are Victorian bricks, motar, concrete, and supporting metal struts. These old-school materials are one reason that the models are so fragile, why they need dedicated upkeep, and why we shouldn't be climbing and sitting on them (for shame, people in that photo!).
Just over a decade after the Crystal Palace dinosaurs were installed, discoveries of another ornithopod, Hadrosaurus, in New Jersey, USA began to erode the credibility of not only Hawkins’ Iguanodon but the entire Crystal Palace prehistoric project. Hadrosaurus showed dinosaur anatomy as very different to what was being imagined in Victorian Britain. Suddenly, the Crystal Palace dinosaurs looked, at best, like naive and over-eager attempts to interpret fossil bones or, at worst, like products of arrogant Victorians assuming they could command the anatomy of long dead species from nothing like complete skeletal material. Perhaps the truth is somewhere between. Later, fossil discoveries in Belgium in 1878 would essentially give us our modern take on Iguanodon anatomy and, in doing so, took away any lingering scientific credibility from Hawkins’ portrayals. A suite of Iguanodon skeletons recovered from a Bernissart coal mine revealed an animal with powerful hindlimbs; relatively slender, shorter forelimbs equipped with large thumb spikes; a beaked, horse-like head; and a long, deep tail. Initially restored as a kangaroo-like biped, Iguanodon would eventually be realised as we know it today: a horizontally-backed animal that could alternate between bipedal and quadrupedal gaits. Iguanodon is the only Crystal Palace dinosaur species now known from complete skeletons, making it a most poignant indicator of how far palaeontological science has moved from the era of Hawkins and Owen.

Iguanodon bernissartensis as we picture it today, some still standing, some still lying down.


We've got one more stop on our tour of the Crystal Palace sculptures: the mammals. These often overlooked parts of the Geological Court contain some of the most interesting and, to some extent, tragic portions of the Crystal Palace palaeoart project. Come back soon for the conclusion to our look at these Victorian palaeoartworks, and don't forget to check out the Friends of Crystal Palace Dinosaurs, who're actively striving to get these fine artworks the recognition and conservation they deserve.

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References

  • Barrett, P. M. & Maidment, S. C. R. (2011). Armoured dinosaurs. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 391-406.
  • Benson, R. B. (2010). A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society, 158(4), 882-935.
  • Dawson, G. (2016). Show me the bone: Reconstructing prehistoric monsters in nineteenth-century Britain and America. University of Chicago Press.
  • Dean, D. R. (1999). Gideon Mantell and the discovery of dinosaurs. Cambridge University Press.
  • Hawkins, B. W. (1854). On Visual Education As Applied to Geology, Illustrated By Diagrams and Models of the Geological Restorations at the Crystal Palace. Journal of the Society of Arts2 (78): 443-449.
  • Mantell, G. (1833). Memoir on the Hylaeosaurus, a newly discovered fossil reptile from the strata of Tilgate Forest. Geology of the South East of England.
  • Mantell, G. A. (1848). XIII. On the structure of the jaws and teeth of the Iguanodon. Philosophical Transactions of the Royal Society of London, (138), 183-202.
  • Mantell, G. A. (1851). Petrifactions and Their Teachings: Or, A Hand-book to the Gallery of Organic Remains of the British Museum (Vol. 6). HG Bohn.
  • Naish, D. (2010). Pneumaticity, the early years: Wealden Supergroup dinosaurs and the hypothesis of saurischian pneumaticity. Geological Society, London, Special Publications, 343(1), 229-236.
  • Norman, D. B. (2000). Professor Richard Owen and the important but neglected dinosaur Scelidosaurus harrisonii. Historical Biology, 14(4), 235-253.
  • Norman, D. B. (2011). Ornithopod dinosaurs. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 407-475.
  • Norman, D. B. (2013). On the taxonomy and diversity of Wealden iguanodontian dinosaurs (Ornithischia: Ornithopoda). Revue de Paléobiologie, 32(2), 385-404.
  • Norman, D. B. (2015). On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna). Zoological Journal of the Linnean Society, 173(1), 92-189.
  • Owen, R. (1842). Report on British fossil reptiles, part II. Report for the British Association for the Advancement of Science, Plymouth, 1841, 60-204.
  • Owen, R. (1854). Geology and inhabitants of the ancient world (Vol. 8). Crystal Palace library.
  • Owen, R. (1855). The fossil Reptilia of the Wealden and Purbeck Formations. Part II: Dinosauria (Iguanodon). Palaeontographical Society of London, Monograph 1854:1–54.
  • Owen, R. (1856). The fossil Reptilia of the Wealden Formations. Part III, Megalosaurus bucklandi. Palaeontographical Society. Monographs, 9, 1-26.
  • Owen, R. (1858). Monograph on the fossil Reptilia of the Wealden and Purbeck formations. Part IV. Dinosauria (Hylaeosaurus). Paleontographical Society Monograph, 10, 1-26.
  • Owen, R. (1863). Monographs on the British Fossil Reptilia from the Oolitic Formations. Part Second, Containing Scelidosaurus harrisonii and Pliosaurus grandis. Monographs of the Palaeontographical Society, 14(60), 1-26.
  • Secord, J. A. (2004). Monsters at the crystal palace. In: de Chadarevian, S, & Hopwood, N. (eds). Models: the third dimension of science, Stanford University Press. 138-69.
  • Torrens, H. S. (2012). Politics and Paleontology: Richard Owen and the Invention of Dinosaurs. In: Brett-Surman, M.K. Holtz, Jr. T. R., & Farlow, J.O. (eds). The Complete Dinosaur, second edition. Indiana University Press, Bloomington, 24-43 pp.
  • Wyatt, M. D. (1854). Views of the Crystal Palace and Park, Sydenham. Day and Son.

Friday, 17 May 2019

The science of the Crystal Palace Dinosaurs, part 2: Teleosaurus, pterosaurs and Mosasaurus

It's time to continue our palaeoartistic discussion of the famous 1850s Crystal Palace prehistoric animal sculptures. As you'll know if you've read part 1 of this series, I've been supplying artwork and palaeoart notes to the Friends of Crystal Palace Dinosaurs charity for their new 'about the statues' web pages. What started as a small project has ballooned into several weeks of illustration, research and writing based around these charming and fascinating early palaeoartworks, culminating in this series of blog posts. As before, we'll be reviewing the models in roughly sequential order. Previously, we looked at the Dicynodon, "Labyrinthodon" and marine reptiles, and today we'll be covering the Jurassic Teleosaurus, the Jurassic and Cretaceous pterosaurs, and the Late Cretaceous Mosasaurus. Those familiar with the Crystal Palace prehistoric menagerie will recognise a dinosaur-shaped hole in that line-up but, have no fear: we'll be covering them next time, and then the mammals after that.

As before, I want to point out that the following notes are expanded and referenced versions of content I've provided for the Friends of Crystal Palace Dinosaurs website, and readers are encouraged to check out those pages to supplement the dedicated palaeoartistic assessment provided here. Also, while I don't want to labour the need for increased interest and investment into the Crystal Palace sculptures - there's lots of that in the introduction to part 1 - I want to remind readers that these models, now approaching 170 years old, need a lot of care and maintenance. Efforts to restore the models are underway, and you can help by donating money or volunteering your time to keep the site maintained.

Teleosaurus

The Crystal Palace Teleosaurus sculptures as seen from the Secondary Island. Both Teleosaurus have been restored recently and look very handsome, the aim is to get all the models looking this good in the next few years. Note that these models are meant to be surrounded by water, but last year the entire site was covered in lush vegetation. Photo from 2018.
Two Teleosaurus bask on the banks of the Secondary Island as part of the Jurassic Oolite scene that also includes Megalosaurus and (before they went missing) small pterosaurs. As superficially crocodylian-like animals, Teleosaurus was perhaps the most straightforward fossil reptile for Hawkins to restore. The two Teleosaurus models are, in terms of detailing, some of the finest reptile restorations in the Crystal Palace arrangement. The general proportions of Teleosaurus are captured correctly with its short limbs, long body and narrow, gracile jaws, and their depiction as basking on a shoreline is consistent with predictions of teleosaurid habits. Teleosaurids were part of a marine radiation of crocodylian-line reptiles but they still bore limbs instead of flippers, and they lacked well-developed tail fins. In not being as specialised for an open water existence as subsequent marine crocodylomorphs, it’s entirely possible, maybe even likely, that teleosaurids returned to shore for rest and procreation.

There are several anatomical peculiarities about Hawkins’ teleosaurids that not only conflict with modern understandings of these animals, but also those of Victorian Era palaeontologists. Owen (1854) stressed the great similarity between teleosaurs and modern crocodylians - specifically the gharial - and it appears that modern crocodylians ultimately informed Hawkins’ take on these marine crocodylomorphs more than their actual fossils. Teleosaurid scalation was quite different from all modern crocodylians in that their dorsa bore two medial rows of large scutes from their necks to their tails, and their bellies were covered with a shield of interlocking scutes. This was well known to Victorian anatomists (e.g. Owen 1842), but Hawkins seems to have used Crocodylus scute arrangements instead, depicting several rows of smaller dorsal scutes and omitting any trace of belly armour. Over at Tetrapod Zoology, Darren Naish has suggested that saltwater crocodiles may have been specifically referenced for this arrangement. Gharial cranial proportions seem to have been used to model the posterior head, this region being short and narrow (like a gharial) instead of long and expanding outwards towards the back of the skull (as in teleosaurs).

Lemmysuchus obtusidens, a teleosaurid of similar size as the Crystal Palace Teleosaurus, but the skull and dentition are more robust. Note the osteoderm arrangment along the back and proportions of the skull - teleosaurids had a much longer and broader temporal region than Hawkins captured, perhaps because of his referencing living crocodylians. As an aside, note that this artwork has a pretty obvious homage to another classic piece of Victorian palaeoart, John Martin's 1840 The sea dragons as they lived.
The result is a blend of crocodylian and teleosaurid anatomy, and it is not obvious why Hawkins did not reflect the anatomy of teleosaurids more faithfully when this effort was made for other models. Subsequent artworks by Hawkins (e.g. his 1862 posters produced for the Department of Science and Art - see Rudwick 1992) show the same erroneous interpretations, so he may have simply been misinformed or unaware of what teleosaurids really looked like. To be fair to Hawkins, he is far from the only palaeoartist to apply scalation patterns from modern crocodylians to their ancient, distant relatives. Perhaps he just assumed - as many still do today - that all crocodylian-like animals are and were pretty much alike. It’s more interesting that Owen knew the precise nature of teleosaurid scale arrangement - even down to the differences between species - and yet Hawkins’ models turned out as they did. Did Owen not tell him? Did Hawkins ignore him? Was there a practical reason for why the design couldn't be altered? Even more intriguingly, despite Owen being unafraid of pointing out aspects of the models that he disagrees in his 1854 sculpture guide, he made no mention of this error. Is this evidence of Owen not having much regard for these models, or maybe not wanting to draw attention to a mistake he could have fixed? I'm not sure we know what happened there, but this obvious difference between Hawkins' models and Owen's knowledge certainly fits wider evidence that Owen gave very little input to the Crystal Palace project (Secord 2004; Dawson 2016).

Pterosaurs

Two sets of pterosaurs were created for the Crystal Palace display: two larger individuals representing pterodactyloids from British Cretaceous Chalk deposits, and two smaller animals from the Jurassic Great Oolite Group. As originally positioned, these models flanked the dinosaur sculptures in the centre of the Geological Court. Alas, the original models of the smaller pterosaurs went missing in the 1930s (McCarthy and Gilbert 1994) and fibreglass replacements installed in 2002 were stolen and destroyed by vandals in 2005. The larger models are still standing but are in disrepair, owing to both their relative delicacy and continued vandalism.

The large Chalk Pterodactylus models of Crystal Palace, as photographed in 2018. The models are replete with fine anatomy that cannot be appreciated from afar, such as variable scale sizes and individually crafted digits. Close inspection reveals many obviously avian-inspired features, and I suspect they were not closely based on the excellent pterosaur fossils known to early 19th century palaeontologists.
Images of the pterosaur models in their prime show that all four shared a similar bauplan: long necks terminating in smallish, toothed heads; scaly skin; large torsos; crouching hindlimbs and - of course - enormous, membranous wings supported by long forelimb bones and hypertrophied wing fingers. In this respect Hawkins’ pterosaurs were fairly typical of pterosaur restorations from the 1800s, and they are somewhat different to how we imagine them today. Contrary to Owen’s confident and entirely unfounded guidebook assertion that pterosaurs were scaly (Owen 1854), the German zoologist Georg August Goldfuss had recorded solid evidence of pterosaurs having a fuzzy, hair-like covering as early as 1831. The absence of fibrous integuments on Hawkins’ pterosaurs is not an example of Owenian arrogance, however. Just about everyone ignored Goldfuss’s claims about pterosaur skin and it was not until the 1970s that pterosaur fuzz would be an accepted fact of their palaeobiology. Goldfuss has recently been vindicated by modern fossil imaging techniques proving beyond all doubt that his soft-tissue interpretations were accurate (Jäger et al. 2018). This is one of two places were Goldfuss’ research could have enhanced the portrayal of prehistory at Crystal Palace had some of his papers not been so widely ignored by other researchers (see discussion of Mosasaurus, below).

The rarely seen posterior end of the remaining complete Chalk Pterodactylus. Note the deep chest and pelvic region, bird-like limb posture and blunt, deep tail. This is the body of a bird, not a pterosaur. The triangular structure on the left of the image is the wing of the neighbouring pterosaur. Photo from 2018.
Less explicable mistakes in the pterosaurs are their overall proportions. The very first pterosaur fossils known to scientists were complete skeletons showing that their heads were longer than their bodies, and yet Hawkins - like virtually all artists of the 1800s - restored them with small heads and massive torsos. My assumption is that this reflects Hawkins modelling his pterosaurs with an avian physique rather than with exacting attention to fossil material. Close inspection of his models reveals many bird-like details that are inconsistent with pterosaur remains, such as an emphasis on ventral flight muscles, deep bellies, horizontally-held thighs, an extensive pelvic region with a short, poorly defined tail, and a proportionally small head. It is also noteworthy that Hawkins anchored the wing membranes to the body alone, leaving the hindlimbs free. This creates the impression of a bird-like wing arrangement, even though most of his peers were illustrating more accurate bat-like membranes that stretched all the way to the hindlimb (e.g. see illustrations by Soemmerring (1817); Newman (1946) and even Owen (1859)). Though Hawkins observed some aspects of pterosaur form correctly - such as posing one animal quadrupedally, and placing the full length of the foot on the ground - the overall impression is of a goose or swan-like creature with pterosaur features, not a precise reflection of the fossils he had available to him. Hawkins was not alone in making such mistakes, and very few pterosaur restorations from the early decades of palaeontology have accurate body proportions. Indeed, it took a full century before pterosaurs were restored in ways that reflected their anatomy more precisely (Seeley 1901).

A modern take on Cimoliopterus cuvieri, the large toothed Chalk pterosaurs imagined by Hawkins for Crystal Palace. It took us years to get there (and some of us are still in transit), but the message that pterosaurs have enormous skulls and tiny bodies is finally being reflected in art.
The exact identification of the Chalk pterosaurs is left somewhat vague by Owen (1854), but he indicates that large bones (indicating 5-6 m wingspan individuals) of animals such as “Pterodactyluscuvieri were influential on the models. The Oolitic species, in contrast, are precisely identified as “Pterodactylus bucklandi”. None of these taxa were well known in the 1800s (and, indeed, they remain poorly known today) so it’s likely that Hawkins based all four models on complete Pterodactylus antiquus skeletons known from Germany. Aspects such as the long necks and low, homodont teeth are consistent with this hypothesis. Today, we recognise that the species informing the Crystal Palace models are distantly related to Pterodactylus and had very different proportions. The large Chalk species were long-winged soaring specialists with sophisticated dentition adapted for snagging fish, as in Cimoliopterus cuvieri, above. “P. bucklandi” was probably a long-tailed, short-necked animal with procumbent teeth, although the fossils bearing this name are too poor to consider it a valid species (O'Sullivan and Martill 2018). Whatever “P. bucklandi” was, it may have looked somewhat like the contemporary Oolite species Klobiodon rochei, below.

Hawkins' Oolite pterosaurs were based on scrappy material once referred to "Pterodactylus bucklandi", which later became subsumed into the genus "Rhamphocephalus". We now know that "Rhamphocephalus" has little taxonomic utility, being based on teleosaurid fossils and containing no valid pterosaur species. The Oolite species Klobiodon rochei is a rhamphorhynchid, the sort of animal that the "Pterodactylus bucklandi" material likely represents.

Mosasaurus hoffmanni

Lurking behind the dinosaurs and pterosaurs, sometimes almost out of sight, is a partial restoration of the giant mosasaur Mosasaurus hoffmanni. The choice to depict a mosasaur at Crystal Palace was unusual and very progressive. Although their skulls have been known since the 1700s mosasaurids were rarely depicted in palaeoart in the early 19th century, probably owing to being overshadowed by the better-known ichthyosaurs and plesiosaurs. Mosasaurs would become more routinely featured in artwork after palaeontologists excavated their skeletons from the American midwest in the 1860-70s, but it’s rare to see a restoration of a mosasaur of 1850s vintage. Indeed, I’m fairly certain that the Crystal Palace Mosasaurus is among the first attempts at restoring the life appearance of one of these animals. Hawkins’ take was influential enough that other artists heavily referenced his sculpture (e.g. see 1860s work by Louis Figuier), but the discovery of superior mosasaur fossils just two decades after Crystal Palace Park opened dated the model relatively quickly.

A view of the Crystal Palace Mosasaurus that Luis Rey would approve of. Note the pterygoidal teeth, left forelimb and extensive body - there is a lot more to this model than just a head, as is sometimes reported. The low water level exposes the uniquely incomplete nature of the restoration. This could reflect a lack of complete mosasaur skeletons in the 1850s, but Hawkins also made complete Dicynodon despite just having skulls, so a lack of material may not have phased him. Photo from 2018.
The holotype of Mosasuarus hoffmanni is an enormous, disarticulated skull, and it was this material that largely informed the Crystal Palace reconstruction. The Mosasaurus is the only deliberately incomplete restoration in the entire Geological Court, comprising just a head and neck, a nondescript back, and a single flipper. This is sometimes attributed to Hawkins not having sufficient material to complete his restoration, and yet his Dicynodon, which were also only known from skulls at the time, were given entirely speculative limbs, bodies and tails. An absence of fossil material was no deterrent to Hawkins' vision, and the fact that he made one forelimb suggests he had ideas about what the front end of the animal should have looked like at least. The idea that Hawkins was attempting to hide unknown anatomy underwater is inconsistent with his otherwise bold reconstruction approach, so might other factors - perhaps time and money - have influenced the execution of this model? We know that the models were not ready for the opening of Crystal Palace Park in 1854 (McCarthy and Gilbert 1994), so it’s not inconceivable that Hawkins might have been looking to cut corners somewhere.

The head of Hawkins' Mosasaurus is wide and boxy, consistent with Owen’s (1854) interpretation of the holotype skull dimensions being 2.5 x 5 feet. As with “Labyrinthodon”, Hawkins accurately captured the palatal teeth of Mosasaurus. He seems to have modelled the soft-tissues on monitor lizards, these being realised as close relatives of mosasaurs as early as 1800. Extensive lips, voluminous tissues around the eye socket, and laterally-facing, posteriorly-positioned nostrils are obvious monitor features, and the skin texture of the body shows large ossicles surrounded by smaller basement scales. This recalls the osteoderm-studded skin of certain large and robust monitor species, including komodo dragons and white throats.

Mosasaurus hoffmanni, as restored in 2019. Our understanding of mosasaur life appearance has changed in recent years: rather than crocodile-like swimming lizards, they were highly convergent with whales, sharks and other strongly pelagic fish. The dorsal fins in this restoration are conjectural, but based on their presence in numerous large marine vertebrates.
Hawkins’ take on M.hoffmanni is pretty insightful given the material he and Owen had to work with. Though wide of the mark with many anatomical details, he was on the right track by essentially interpreting them as giant, waterborne monitor lizards. Today we understand mosasaurs as being fully committed to a marine existence - the lizard equivalent of toothed whales. Among their many marine adaptations were shark-like caudal fins, streamlined paddles and smooth skin formed of tiny scales (e.g. Lindgren 2013). But hindsight shows there were some aspects of Hawkins’ sculpture that could have been more precise. In 1845 Georg August Goldfuss described a near complete and undistorted skull of “Mosasaurus maximiliani” (now classified as M. missouriensis) from the midwestern United States. This skull demonstrated a narrower cranial profile than assumed by Hawkins and Owen, and also that the nasal openings were on the dorsal surface of the snout. Williston (1914) reports that scholars generally ignored Goldfus’s Mosasaurus work for decades, with his observations effectively being repeated by Leidy, Cope and Marsh as they uncovered American fossil vertebrates in the 1860s and 1870s. This might absolve Owen and Hawkins for overlooking this important find, though it was nevertheless a second occasion where Goldfuss' work could have futureproofed some of the Crystal Palace models.

That rounds up this entry in the series, but come back soon for part 3: a post dedicated to the least famous and popular Crystal Palace models, the dinosaurs. 

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References

  • Dawson, G. (2016). Show me the bone: Reconstructing prehistoric monsters in nineteenth-century Britain and America. University of Chicago Press.
  • Goldfuss, A. (1831). Beiträge zur Kenntnis verschiedener Reptilien der Vorwelt. Nova Acta Physico-Medica Academiae Caesareae Leopoldino-Carolinae Naturae Curiosorum, 15:61-128.
  • Goldfuss, A. (1845). Der Schädelbau des Mosasaurus, durch Beschreibung einer neuen Art dieser Gattung erläutert. Nova Acta Academa Ceasar Leopoldino-Carolinae Germanicae Natura Curiosorum 21:1-28, pl. VI-IX.
  • Jäger, K. R., Tischlinger, H., Oleschinski, G., & Sander, P. M. (2018). Goldfuß was right: Soft part preservation in the Late Jurassic pterosaur Scaphognathus crassirostris revealed by reflectance transformation imaging (RTI) and UV light and the auspicious beginnings of paleo-art. Palaeontologia Electronica, 21(3), 1-20.
  • Lindgren, J., Kaddumi, H. F., & Polcyn, M. J. (2013). Soft tissue preservation in a fossil marine lizard with a bilobed tail fin. Nature Communications, 4, 2423.
  • McCarthy, S., & Gilbert, M. (1994). The Crystal Palace dinosaurs: The story of the world's first prehistoric sculptures. Crystal Palace Foundation.
  • O'Sullivan, M., & Martill, D. (2018). Pterosauria of the Great Oolite Group (Middle Jurassic, Bathonian) of Oxfordshire and Gloucestershire, England. Acta Palaeontologica Polonica, 63(4), 617-644.
  • Owen, R. (1842). Report on British fossil reptiles, part II. Report for the British Association for the Advancement of Science, Plymouth, 1841, 60-204.
  • Owen, R. (1854). Geology and inhabitants of the ancient world (Vol. 8). Crystal Palace library.
  • Owen, R. (1859). On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles. Report for the British Association for the Advancement of Science, 28, 97-103.
  • Rudwick, M. J. (1992). Scenes from deep time: early pictorial representations of the prehistoric world. University of Chicago Press.
  • Secord, J. A. (2004). Monsters at the crystal palace. In: de Chadarevian, S, & Hopwood, N. (eds). Models: the third dimension of science, Stanford University Press. 138-69.
  • Seeley, H. G. (1901). Dragons of the air: an account of extinct flying reptiles. Methuen & Company.
  • Williston, S. W. (1914). Water reptiles of the past and present. University of Chicago Press.

Tuesday, 30 April 2019

The science of the Crystal Palace Dinosaurs, part 1: marine reptiles, Dicynondon and "labyrinthodons"

The southerly approach to one of the most spectacular collections of historic palaeoartworks on the planet: the Crystal Palace prehistoric animals. Over 30 sculptures depict Victorian takes on prehistoric faunas in a remarkable and unique feat of engineering, artistry and scientific outreach. Much about how the models were assembled and the specific science informing their anatomy is lost to history, leaving us to piece it together from written accounts, surviving draft artwork, and the models themselves. This photo is from 2013, some of the models have been restored since then.
The Crystal Palace Prehistoric Park is one of the most spectacular and historically significant pieces of palaeoart in the world. Unveiled in 1854, it features more than 30 models of over 20 extinct species captured in concrete, brick and steel. Each model was crafted by a team of sculptors lead by the zoological artist Benjamin Waterhouse Hawkins under the guidance of Britain's preeminent Victorian naturalist, Sir Richard Owen. The Crystal Palace depictions are often overlooked or dismissed in coverage of early palaeontological history, which is entirely unfair. The scale, ambition and success of the project made it a milestone in not only palaeontological outreach but scientific communication in general, and they had a clear impact on future depictions of fossil animals, both scientifically and educationally (Rudwick 1992; McCarthy and Gilbert 1994; Secord 2004). Most of the models still survive today thanks to ongoing work by conservators and the Friends of Crystal Palace Dinosaurs charity, and a trip to Crystal Palace Park is thoroughly recommended if you're a fan of palaeoart or the history of science. The models are National Heritage Grade 1 Listed Monuments but, on account of their age, exposure to weather and vandalism, they are in continuous need of repair. Phases of renovation have been carried out since at least the 1950s (McCarthy and Gilbert 1994) and are ongoing today. Such work is expensive (conservation began in 2015 is expected to cost £1.2 million when completed) so please consider supporting the Friends of Crystal Palace Dinosaurs if you can. The FOCPD also appreciate volunteers to maintain the landscape around the models, which is a great way to visit them up close - keep an eye on their website for opportunities.

Part of the enduring appeal of the Crystal Palace sculptures is the mysteries of their construction. While the generalities of the project are well documented (e.g. Rudwick 1992; Doyle and Robinson 1993; McCarthy and Gilbert 1994; Secord 2004, also see this FOCPD summary), few documents are known specifying how the sculptures were built, and the scientific rationale behind them. Some details of their construction can be deduced by examination of the models themselves, and both Hawkins and Owen put their general scientific approach on record (Owen (1854) in particular reads like a modern summary of palaeoart practises), but it remains difficult to ascertain exactly how Hawkins decided on the form of each species. Adding depth to the mystery are suggestions that Owen's contributions may have not have been as substantial as generally assumed, and that his expertise was only sought as the designs approached their final phase and full-size construction was set to begin - too late, perhaps, for major revisions to Hawkins' drafts (Secord 2004). Moreover, while Hawkins' attention to Owen's work is clear, he also evidently relied on other sources of information and his own intuition on many occassions. This may explain why Owen sometimes distanced himself from aspects of the models in a 1854 guidebook to the models, as well as in newspaper interviews (Secord 2004). Nevertheless, documents authored by both Owen and Hawkins suggest mutual respect and admiration for one another (Owen 1854; Hawkins 1854), although it's interesting that each eventually claimed to be the greater intellectual influence on the project (Secord 2004).

Scene from Benjamen Waterhouse Hawkins' temporary workshop: a large wooden structure in the grounds of Crystal Palace Park. Images like this - which feature (clockwise from top left) Palaeotherium, Iguanodon, Hylaeosaurus, Dicynodon and "Labyrinthodon" - give valuable insights into the creation of the Crystal Palace Prehistoric Park, but shed little light on the science influencing their restoration from fossil bones. Note the corvid and rodents in the foreground: written accounts suggest Hawkins' workshop was not always a luxurious place to be. Illustration by Philip Henry Delamotte, 1853, image in public domain.
Recently, I've been working with the Friends of Crystal Palace Dinosaurs to restore the Crystal Palace extinct animals as we know them today for their website. As part of that process, I've been providing notes on how accurate the models are to current science as well as against fossil data available to Hawkins in the early 1850s. This has proven fascinating, confirming Hawkins' talents and insight while also raising several questions about his process and palaeoart philosophy. We may never know Hawkins' thought process in detail, but we might be able to 'reverse engineer' his models back to specimens known pre-1854 and, through clues worked into his models, establish what science, artworks and extant species influenced his designs. Over the next three posts, I thought it would be of interest to share some of these thoughts, as well as my modern takes on the Crystal Palace species. Edited versions of these notes also appear at the Friends of Crystal Palace Website, and more will follow in the near future as we wrap up this project up. I'm going to tackle the sculptures more or less as they appear in the park as you walk from the geologically oldest models (the Dicynodon) to the youngest (Megaloceros).

Dicynodon

The Crystal Palace Dicynodon, as seen in 2013. The larger model in the top photo, and the focus of the lower photo, is D. lacerticeps, the smaller sculpture is D. strigiceps. Note the turtle-like bodies and long tails, but also the presence of obvious clawed feet instead of flippers.
There are two Dicynodon sculptures in Crystal Palace, one large, one small. Particulars of their bodies and size indicate that they are meant to be different taxa. Owen (1854) indicates that the larger statue - "with the bulk of a walrus" - is D. lacerticeps, but he did not specify the identity of the smaller animal. He provides a clue, however, in stating it is a species with somewhat owl-like facial features. This must indicate that the smaller model is D. strigiceps, a species Owen named in 1845 that literally translates to 'owl-faced Dicynodon'. D. lacerticeps is the type species of Dicynodon and remains valid today, but strigiceps was regarded as a nomen dubium by Kammerer et al. (2011). The identification of D. lacerticeps as the large animal is peculiar, as it is not a large species - its skull was just over 15 cm long. We know that Hawkins attempted to capture the size of his animals accurately (Hawkins 1854), so perhaps other Dicynodon material factored into this decision.

The Crystal Palace Dicynodon are famously turtle-like in form, a circumstance reflecting Dicynodon being almost entirely represented by cranial material in the 1850s. These skulls demonstrated the basic shape of the skull and their strange turtle-meets-walrus nature but, as noted by Owen (1854), the rest of the sculptures are purely conjectural. Owen regarded dicynodonts as amphibious (Owen 1845, 1854) and Hawkins seems to have ran with this concept, presumably also inspired by the turtle-like features of the skull. Details of the sculptures' feet show that Hawkins was probably modelling these creatures on more terrestrially-adept turtles, and I wonder if the three ridged, sculpted keels, developed claws and long, scute-lined tails specifically indicate influence from snapping turtles. As we'll see, Hawkins often took inspiration, and entire anatomies, from living species in his work.

Today, we imagine dicynodonts very differently to our Victorian colleagues. This image shows Aulacephalodon bainii (the larger species, an animal known to Owen, and possibly referenced in the size of the D. lacerticeps sculpture) and the smaller dicynodont is Cistecephalus microrhinus (a species only distantly related to D. lacerticeps and A. bainii). This image will be featured in an upcoming book, also themed around historic palaeoart.
Dicynodont anatomy is now very well known and contrasts markedly with Hawkins’ sculptures. While their heads are reasonable proxies for dicynodont crania and consistent with contemporary reconstructions (e.g. Owen 1845), they seem a little ‘snouty’ compared to the short, shear-faced muzzles we now known from well-preserved dicynodont skulls. More obvious differnces are that dicynodonts have robust limbs adapted for terrestrial life, and many species were burrowers: they accordingly had rotund, longish torsos, not wide, flat ones. Though no dicynodonts had shells or armour, we are still uncertain what sort of skin they had. Given their relationship to mammals some artists restore dicynodonts with fur, but we have yet to find any evidence of this integument type so deep within our evolutionary history. The recovery of hair from a Permian coprolite (Bajdek et al. 2016) suggests some synapsids from this time may have been furry, but the most parsimonious candidates are our closest Permian ancestors, the cynodonts, not the more distantly related dicynodonts. We still think, as demonstrated in Hawkins’ model, that dicynodont snouts were largely covered with a cornified beak sheath however, with the tusks projecting either side (Kammerer et al. 2011).

“Labyrinthodon”

A trio of "Labyrinthodon", photographed in 2013. There are two species here, the larger being "L. salamandroides", the smaller "L. pachygnathus". Note the palatal teeth in the right animal and the similarity between L. salamandroides and an Owen sketch of Labyrinthodon as the Chirotherium trackmaker.
The three Crystal Palace “Labyrinthodon” reconstructions are attempts to rationalise several pieces of unrelated fossil data, so it is unsurprising that the results are far from the reality of the species they are meant to represent. But while some of the most dated models scientifically, they raise some interesting questions about how Hawkins approached his reconstructions.

Depicted as giant frog-like creatures, Hawkins’ sculptures show close attention to illustrations of “Labyrinthodon” as interpreted by Owen (e.g. Owen 1841a, 1842; also see Benton and Gower 1997) and capture some details of the skull and tooth material then referred to this genus. Particularly notable are the palatal teeth - this excellent attention to anatomical detail, especially given that visitors have to be right next to the sculptures (or looking with binoculars) to see them. Their mix of smooth and warty skin is surely based on living amphibians, and serves to distinguish the models of “L. pachygnathus” (smaller, warty-skinned) from “L. salamandroides” (the larger, smooth-skinned model) (McCarthy and Gilbert 1994). Owen famously linked "Labyrinthodon" with trackways now referred to pseudosuchians, but in doing so rationalised and illustrated the trackmaker as making prints with opposite limb sets, so the left prints were made with the right feet, and vice versa. This detail is absent from Hawkins’ models, despite his general attention to Owenian ideas. Perhaps even he struggled to make this bizarre hypothesis a reality.

Modern takes on “Labyrinthodon” are very different to the creatures displayed at Crystal Palace. What Owen and Hawkins considered “Labyrinthodon” is now rightfully called Mastodonsaurus, the former name being Owen’s attempt to replace Mastodonsaurus with a title he thought better suited the animal (Owen 1841a). Of the depicted species, “L. salamandroides” has been subsumed into M. jageri, and the fossils referred to “L. pachygnathus” are a mix of mastodonsauroids and archosaurian remains (Benton and Gower 1997; Damiani 2001). The latter point vindicates Hawkins' now archaic-looking approach to restoring Mastodonsaurus. The idea of a sheep-sized prehistoric frog seems outlandish in the 21st century, it was an entirely sensible interpretation of Owen's take on the available fossil material, from the proportions of the body to the upright limbs. I find the capturing of the "L. pachygnathus" jawline and dentition especially commendable.

Mastodonsaurus jageri, the 'real' "Labyrinthodon", striking at the rhynchosaur Fodonyx spenceri. Far from being an oversize frog, M. jageri occupies anatomical space somewhere between a salamander and alligator.
We now know that Mastodonsaurus resembled a giant salamander more than a frog, though in truth no living amphibian is a close analogue for this often giant Triassic form. A large, flattish head dominates a long, slender body with reduced limbs. The skull is covered with sculpted and textured bones somewhat reminiscent of crocodylian skull surfaces, and detailed investigation suggests this records a tight, tough facial skin (Witzmann 2009). Also like crocodylians, Mastodonsaurus eye sockets are situated on the top of the skull, not the sides as depicted at Crystal Palace. This was a peculiar decision from Hawkins, given that good Mastodonsaurus skulls were known in the early 1800s (e.g. Plieninger 1844), and that Owen knew about them (1854). Hawkins older illustrations and draft Labyrinthodon model (which was presumably shown to Owen) also show flatter heads. Do the fleshy-faced, side-eyed Crystal Palace amphibians reflect Hawkins paying more attention to frogs than Mastodonsaurus fossils? It may, as there are several other examples of Hawkins' models overriding fossil data with extant animal form, as we'll see throughout this review. Alternatively, were they errors? A misguided revision suggested by Owen or someone else? Was Hawkins simply following the illustrations of others, such as that presented in Owen's (1854) guide? Whatever the cause, this is a clear example of Hawkins not using fossil data where he could have done, in contrast to his sometimes exacting reproductions of anatomy in other areas.

Ichthyosaurs

In terms of scientific credibility, Hawkins’ three ichthyosaur statues have probably held up best of all his non-mammalian sculptures. This undoubtedly pertains to ichthyosaur skeletons being entirely known from very early in palaeontological history, as well as their familiar whale- or fish-like form. I consider them a good measure of Hawkins’ skill as a palaeoartist because it puts him on a more equal footing with modern practitioners, and suggests that when he had comprehensive datasets and suitable modern analogues he was able to produce very reasonable interpretations of fossil forms. It was largely a lack of information, not poor knowledge of anatomy and zoology, that lead to the inexactitude of the Crystal Palace models. There are three species of ichthyosaur on display, each distinguished by size and proportions, and once all considered different taxa of Ichthyosaurus. In modern parlance, they are Ichthyosaurus communis (the mid-sized ichthyosaur model), Temnodontosaurus platydon (the largest) and Leptonectes tenuirostris (smallest).

The Crystal Palace icthyosaurians in various states of visibility and repair. Top, Leptonectes tenuirostris as photographed in 2018 (I don't have any good photos of this model on account of it being hard to access and, when I was able to see it properly, the site was overgrown with lush vegetation); middle, Ichthyosaurus communis in 2018; bottom, Temnodontosaurus platydon (another 2013 photo, but this reflects the current state of the model - notice the contrast with the restored sculptures).
Much about Owen’s views on ichthyosaurs, and much of how Hawkins rendered them, remains accurate today. Owen (1854) specifically mentions the presence of smooth, scale-less skin, predicts some sort of fin at the end of their tails (identified in by Owen in 1840(a), though he was uncertain of the shape) and large eyes in these animals. We still restore ichthyosaurs in this way, albeit with some additional guidance and confidence from fossilised ichthyosaur body outlines and soft-tissues (e.g. Lindgren et al. 2018). Major additions to post-Crystal Palace reconstructions include the presence of a dorsal fin, tall and crescent-shaped tail fins, and more generous allocations of soft-tissue across the body as befitting fully marine, whale-like creatures. The presence of large eyes was then, as now, deduced not from large eye sockets but from the enormous scleral bones found in fossil ichthyosaur skulls. Owen’s statement that the function of these bones was supporting and protecting the eye is also correct, although it’s unlikely that the sclerotic ring was conspicuous in life as Hawkins depicted it. Plenty of living animals have large sclerotic rings, but they are hidden beneath eyelids and other anatomy.

An unusual property of the Crystal Palace models is the skin on their flippers, which has a very obvious scaly appearance. This reflects the Owenian hypothesis that the bones of the flippers were somehow reflected in the overlying skin scales (Owen 1841b), which Hawkins faithfully reproduced on his models. This seems unlikely given what we now know of fossilised ichthyosaur skin and the relationships between bone texture and skin anatomy. Hawkins was not solely guided by fossils in his restorations however, with details of the ichthyosaur faces reflecting whales and dolphins. This is particularly evidenced by the dolphin-like grooves and lips along their jaws, and seems entirely reasonable given what we know of ichthyosaurian skulls and the relationship between jaw bone surfaces and facial features.

A modern restoration of Temnodontosaurus eurycephalus (the larger, strand-feeding species) and Ichthyosaurus breviceps (the prey animals). In many ways, not so different from Hawkins' take.
Two aspects of the models date them firmly to palaeontology's early years. The first is that they are meant to be crawling around in shallow water, not swimming along the water surface (Owen 1854). This reflects a now long-abandoned view these reptiles could come ashore to sleep or for reproductive purposes. Secondly, all three ichthyosaur models have a great degree of flexibility in their tails, which is no longer considered plausible. The three sculpted species likely had varied capacity for tail flexion in life, with two species (Temnodontosaurus and Leptonectes) probably having more flexible tails than the relatively thunniform ('tuna-like') Ichthyosaurus communis. None had an ability to attain the eel-like tail shape reflected in the Crystal Palace models, however. This was not a mistake unique to Hawkins, but a fairly typical way of restoring ichthyosaurs in th early 1800s.

Plesiosaurians

Complete plesiosaurian skeletons allowed Hawkins to reconstruct them in a generally credible light, though the results were not as precedent as his takes on ichthyosaurs. To be fair, plesiosaurians are not as intuitive to reconstruct as ichthyosaurs and many aspects of their anatomy and functionality are debated even today. Making three-dimensional plesiosaurian sculptures just decades after their fossils were found was no mean feat, and Hawkins' models no less credible than other mid-19th century takes on these animals. Three models were created and, though similar, they have varying proportions and sizes on account of representing three species. Today, we classify these as Plesiosaurus dolichodeirus, “Plesiosaurusmacrocephalus, and Thalassiodracon hawkinsi.

Plesiosaurians of Crystal Palace. These are all restored to their former glory now (as per the top image) but, as with the ichthyosaur images above, I'm forced to use older, shoddier photos for two models because of all that fantastic greenery. Top, “Plesiosaurus” macrocephalus in 2018; middle, Thalassiodracon hawkinsi (2013 - note missing flipper, now replaced); bottom, Plesiosaurus dolichodeirus (2013). I've taken these identifications from McCarthy and Gilbert (1994), but I'm not sure they're correct. Surely the middle is the short-necked macrocephalus? Owen's guide is not entirely clear on the matter, unfortunately.
The proportions of Hawkins plesiosaurs are not exact to fossil data, a fact especially obvious for "P." macrocephalus, which lacks its characteristically large skull. They capture the main characteristics of plesiosaurians however, with “P”. macrocephalus - undersized head aside - being especially pleasing with its robust, deep tail and powerful-looking shoulders (see this blog post for a run down on plesiosaurian life appearance). These attributes make it the most ‘modern looking’ of all three sculptures. Additional fine details include the eyes being angled upwards, and might the obvious teeth reflect a suggestion that they were permanently visible? I’m not sure where we are regarding ideas about plesiosaurian facial tissues, but it’s not unreasonable to assume liplessness, or at least lipless regions, for some or most plesiosaurians (and it seems near certain for some taxa, like pliosaurids). The presence of smooth skin does not entirely align with what we now know of plesiosaurian anatomy, but it’s not a bad inference given that their scales were actually tiny - just millimetres across (Frey et al. 2017). It’s difficult to imagine how the materials available to Hawkins and his team could have been crafted to show such fine detail even if such data was available to them.

There are several major differences between Hawkinsian plesiosaurians and our modern takes. The most obvious of these is their thin, highly flexed necks, which recall those of long-necked birds or snakes even down the obvious neck/skull junction. It is highly unlikely that plesiosaurians could bend their necks as depicted at Crystal Palace, nor do their neck vertebrae imply a light covering of musculature (Noè et al. 2017). Today, we assume plesiosaurians were capable of a reasonable degree of neck flexion, but perhaps only to the extent of forming broad arcs, not multiple tight curves. The Crystal Palace plesiosaurians also have slender, flexible bodies, more like those of lizards (to which they were often compared in early palaeontological literature) than their actual stiffened, barrel-shaped torsos. The P. dolichodeirus and Thalassiodracon hawkinsi models are particularly afflicted with this issue, and their long, flexible tails accentuate their lithe forms further. We can perhaps rationalise this by the holotypes of these plesiosaurs having relatively narrow torsos (a taphonomic influence is probable in both cases) as well as the prevalent early-19th century idea that plesiosaurians were more closely related to lizards than other marine reptiles ("Plesiosaurus", roughly translated, means "allied to lizards" - Owen 1854). Unbeknown to Hawkins and Owen, we would eventually find soft-tissue outlines of plesiosaurians showing substantial soft-tissue around their tails, perhaps reflecting hindlimb musculature (assuming they anchored some major leg muscles on their tails, as is the case for most reptiles) as well as body-contouring fatty tissues (Frey et al. 2017). Their flippers were also augmented with soft-tissue expansions, something Owen knew about for ichthyosaurs, but would not be apparent for plesiosaurians until the late 19th century.

George Scharf's illustration of "P. macrocepahlus", featured in Owen (1840b). The skull is obviously very large in this species, but Hawkins did not capture this in his model.
Further contrast with modern plesiosaur reconstrusions concerns the attitude and flexion of the statues' flippers. They are shown as having ample fore and aft motion as well as obvious elbow and knee joints. This was pretty typical of plesiosaurian art in the 19th century, and probably reflected Victorian assumptions of a turtle-like locomotory capacity in these reptiles. Today, we regard plesiosaur flippers as having more limited flexion. They had no joints along their length, and forward and backward motions were the most limiting axes of their shoulder and hip articulations (e.g. Carpenter et al. 2010; Liu et al. 2015). These properties have bearing on another difference: the portrayal of all three plesiosaurians as crawling in shallow water. It’s near certain that plesiosaurians would struggle to move around out of water (see this blog post for details), and evidence that they gave live birth negates the need for land-based behaviour (O'Keefe and Chiappe 2011). But for Hawkins, Owen and other 19th century scholars, who still regarded even ichthyosaurs as using land-based reproduction, plesiosaurians crawling around on land would have seemed reasonable.

Plesiosaurus dolichodeirus as we know it today: not a million miles off the Crystal Palace reconstruction, but significantly different in several aspects.

That's all for now, but we'll soon move on to teleosaurids, pterosaurs and - the star attractions: dinosaurs! Remember to check out the Friends of Crystal Palace Dinosaurs website if you haven't already, and please consider getting involved with supporting these fantastic, significant models if you can.

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