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, “Plesiosaurus” macrocephalus, 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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References

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• Benton, M. J., & Gower, D. J. (1997). Richard Owen's giant Triassic frogs: archosaurs from the Middle Triassic of England. Journal of Vertebrate Paleontology, 17(1), 74-88.
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• Damiani, R. J. (2001). A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli). Zoological Journal of the Linnean Society, 133(4), 379-482.
• Doyle, P., & Robinson, E. (1993). The Victorian ‘Geological Illustrations’ of Crystal Palace Park. Proceedings of the Geologists' Association, 104(3), 181-194.
• Frey, E., Mulder, E. W., Stinnesbeck, W., Rivera-Sylva, H. E., Padilla-Gutiérrez, J. M., & González-González, A. H. (2017). A new polycotylid plesiosaur with extensive soft tissue preservation from the early Late Cretaceous of northeast Mexico. Boletín de la Sociedad Geológica Mexicana, 69(1), 87-134.
• Hawkins, B. W. (1854). On Visual Education as Applied to Geology: Illustrated by Diagrams and Models of the Geological Restorations at the Crystal Palace. W. Trounce
• Kammerer, C. F., Angielczyk, K. D., & Fröbisch, J. (2011). A comprehensive taxonomic revision of Dicynodon (Therapsida, Anomodontia) and its implications for dicynodont phylogeny, biogeography, and biostratigraphy. Journal of Vertebrate Paleontology, 31(sup1), 1-158.
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How to spot palaeontological crankery

Pterosaurs, such as the newly described Jurassic species Klobiodon rochei, are magnets for palaeontological cranks: those individuals who harbour and promote idiosyncratic and problematic ideas about palaeobiological topics. Some cranks are a genuine nuisance for educators, but they are easy enough to spot and avoid if you know their characteristics. Say, that sounds like a good idea for a blog post.

Like many popular sciences, palaeontology attracts individuals harbouring what can kindly be called ‘alternative’ or ‘fringe’ ideas: interpretations of evolutionary relationships, animal biomechanics or other facets of palaeobiology that contrast with ‘mainstream’ science. Such individuals are generally referred to as "cranks" - a term defined at Wikipedia as "a person who holds an unshakable belief that most of his or her contemporaries consider to be false". While most crank palaeontology is confined to obscure literature or forgotten corners of the internet, and is therefore pretty harmless, some cranks are major sources of misinformation thanks to their prominent, professional-looking websites, deals with mainstream book publishers, or careers in public outreach exercises.

Cranks are thus a real issue for palaeontological educators and science communicators. Students, teachers and naive members of the public are all potential victims of crankery, and many of us have witnessed crank media being embraced or shared by well-meaning individuals. Among those of us interested in science and outreach, cranks are a semi-regular topic of conversation: how do we combat their miseducation? Ignore them? Engage them on social media? Take them on in public debates? I don't know that there's a right answer, but one approach we can use is helping less experienced individuals recognise crankery when they find it. As with most peddlers of alternative ideas and pseudoscience, palaeontological cranks have characteristic behaviours and interests that stand out quickly once you learn what they are, and this can only help us avoid being hoodwinked by their unique brand of miseducation.

This, then, is my attempt to prime readers for recognising palaeontological crankery. In the interests of making this article as accessible as possible I've attempted to use easily understood, plain-English throughout. I'm dividing the post in two: first, we'll outline the commonest subjects of palaeontological crankery, so as to let readers know when to be extra alert for crank output; and in the second section, we'll look at some crank red flags which should set our sceptical systems to maximum alert. It's worth noting before we dive in that I'm only concerned with 'true' palaeontological cranks here, and will not be tackling young earth creationism, evolution deniers or palaeo-themed cryptozoology. Those are all worthy topics but are well beyond our scope today. I'm also going to generally avoid naming and linking to specific cranks or sources in this article, on grounds that any publicity is good publicity.

The favoured subjects of palaeontological cranks

Claims of remarkable fossil discoveries
Probably the commonest form of palaeontological crankery is the claim of having a significant fossil discovery, yet to be recognised by science. This might be an amazing new fossil, such as a complete pterosaur head in amber, or it could be the identification of overlooked extra bones, soft-tissues or other features on an existing specimen. Cranks making these claims vary as to whether or not they've actually seen the specimens they're discussing, and sometimes they work only from images found in papers, books or on websites. These 'discoveries' are often the crux of all subsequent output from that individual, whether they are simply showing off their specimens on a website or using them to inform ideas about evolution and biomechanics.

Most fossils don't escape some damage en route to discovery by humans: cracks, breaks, distortion of other kinds are common, as shown here on the broken holotype skull of the pterosaur Lacusovagus magnificens. But some individuals will not see these as artefacts of preservation and instead assume that they represent overlooked structures such as teeth, bone divisions or vestigial elements. Given that this work is often based on photos alone, this implies that the experts who spent hours or days studying the actual specimens have missed obvious structures, but that the crank is able to see them without difficulty in a photograph.

A phrase tossed about lots when talking about these claims is 'pareidolia' - the phenomenon of seeing significant patterns or forms in what is actually random visual data. Like perceiving a face on Mars or Jesus on a slice of toast, these individuals 'find' significance in rock structures, cracks on fossils, detritus in amber, or even artefacts of image reproduction. Overwhelmingly, the response from people who've experienced the fossils in question is that these claims represent major over-interpretation of specimens.

Rearranging evolutionary trees
Most would agree that determining the relationships of species with one another is a challenging endeavour, but that generations of anatomical and genetic-based investigations have created a reasonable insight into the broad outline of life's evolution. Not so, according to many cranks, several of whom argue that major branches of evolution (mostly certain charismatic tetrapods) are misplaced in 'mainstream' takes on life's evolutionary tree. Oddly, few cranks agree on exactly which relationships are incorrect. Are birds pterosaurs? Are mammals archosauromorphs? Are pangolins late-surviving stegosaurs? There are lots of alternatives out there, leaving only a smattering of die-hard BAND ("Birds Are Not Dinosaurs") supporters agreeing over where we've got our interpretation wrong.

These contrary opinions are mostly informed by nothing but intuition or cherry-picked data. On rare occasions, actual phylogenetic software is used to predict non-standard evolutionary trees, but it's well documented that these analyses are so broken and misinformed by problematic anatomical data that their results are meaningless. Darren Naish's article on the claims made at the infamous website ReptileEvolution.com offers a great insight into a particularly egregious example of this, and is recommended reading for anyone researching paleontological subjects online.

Amazingly, there are still people out there who doubt the bird-dinosaur link, despite the literal thousands of fossils and hundreds of studies that evidence the origin of birds among theropod dinosaurs. Even relatively non-birdy theropods, like Gorgosaurus libratus, shown here, have skeletons littered with features that are otherwise only seen in bird-line tetrapods.

The lifestyles of fossil reptiles

The great size and peculiar anatomy of many fossil animals - but especially certain Mesozoic reptiles - draws crank attention when they don't buy into accepted modern interpretations of their lifestyles. How could large dinosaurs support their great weight on land? How did plane-sized pterosaurs fly? How could an animal the size and shape of a giant theropod be hidden from prey? Rather than deriving answers from disciplines that have a genuine bearing on these issues, such as biomechanics, fossil trackways, palaeoenvironmental interpretations, or the ecology of living predators, cranks instead propose radical solutions. Perhaps all dinosaurs were aquatic? Maybe Earth's atmosphere was thicker, or gravity was radically different from how we know it today?

Each of these 'solutions' is actually a rabbit hole of problems, errors and logical fallacies that we could disappear into for some time. It's common for cranks to cite something from their background that makes them uniquely able to see biomechanical problems where others can't. My favourite example is a high-school physics teacher who argues that they understand giant dinosaurs and pterosaurs better than anyone because of a particularly formidable understanding of square-cube law. What we're really seeing in these cases is Dunning-Kruger effect: a cognitive bias where individuals rank their cognition of a topic much higher than anyone else, even if they have only a slight or even problematic understanding of the subject in question. I can give no better example of this than the recent and public debate over Too Big to Walk, a book by microbiologist Brian Ford (published in 2018) which proposes that dinosaurs were incapable of supporting themselves on land and must have been confined to aquatic habits. Ford's thesis is outlined here and in other articles online, with responses by palaeontologist and dinosaur specialist Darren Naish here, here and here. All palaeontological crankery is reliant on Dunning-Kruger to a certain extent, but crank arguments about the lifestyles or biomechanics of prehistoric reptiles are particularly good examples.

10 Red flags and pointers for spotting crank palaeontology

If these are the current hot topics in palaeontolgical crankery, how do we distinguish genuine scientific discussions of these matters from crank nonsense? Given that most cranks seem to regard themselves as somehow 'special' - being of unique abilities and insight, or at least due respect for authoring some critical scientific breakthrough - it must pain them to learn that they are actually extremely similar and predictable in how they present their work, talk about themselves and interact with others. This is to our benefit, as it gives us excellent means to guauge the general reliability of whatever it is we're reading or listening to. Some of these checks and tells are listed below. This list is not exhaustive, but if an article, presentation or book hits a number of these marks you probably want to treat their content with extra scepticism.

1. The creation of a problem to solve
Our first red flag is the prediction of cranks to manufacture problems that need solving. They confidently make grand claims like "scientists have never explained this" or "subject X has never been satisfactorily investigated". Such statements are an essential foundation of crank thinking because if these 'problems' didn't exist, the crank would have nothing to 'solve'. While many palaeontologically savvy readers will smell these rats immediately, such claims stand a chance of duping naive readers. Be cautious when reading any sweeping, unreferenced suggestion that we're entirely wrong or misinformed about a particular facet of palaeontology. It's actually very difficult to think of a major palaeontological area where all previous work is totally useless, and such claims are more likely to be someone sidestepping science in order to create space for a pseudoscientific approach.

2. Avoidance of conflicting data or fields of study
A sure-fire crank giveaway is the dismissal of data contradicting with their ideas, even if that means rejecting an entire scientific discipline. Science works by testing ideas using different methods, not through cherry picking the results and methods that best support our preferred ideas. If someone states that DNA-based methods for reconstructing evolutionary trees are bogus, or that fossil footprints have no bearing on the habitat preferences of giant extinct animals, there's a good chance that they're attempting to deflect data that conflicts with their ideas.

3. Over-confidence
One of the most defining features of cranks is their confidence. Genuine palaeontologists, like all scientists, learn early in their careers to be careful about overstating certainty. Outside of describing raw data (e.g. reporting measurements or the outcomes of analyses) they use cautious phraseology like "this infers", "our findings indicate", and "we were unable to replicate Author X's findings". This accepts that interpreting fossil life is always a work in progress and that our work is rarely the last word on a given topic. Cranks, on the other hand, tend to write boldly and without reserve: "this is", "I have shown" and "Author X is blinkered and wrong". This level of confidence is not only misplaced (cranks revise their ideas as often as legitimate scientists, often without documenting why) but characterises a dangerous level of self-belief for someone purporting to conduct legitimate science.

Cranks are drawn to large dinosaurs like Dreadnoughtus schrani when they cannot, or will not, accept that they were capable of walking on land, which leads to ideas of dinosaurs living largely in water, in denser atmospheres, or under reduced gravity. Huge swathes of data from anatomy, geology and dinosaur trackways show that none of these concepts are correct. It also seems lost on cranks that plenty of non-dinosaurian Mesozoic organisms would struggle to live in denser atmospheres, low gravity or waterlogged habitats. It's almost like these ideas are not well thought through.

4. An embarrassment of scientific riches
It's rare for cranks to make one bold claim. Instead, they frequently have a slew of amazing, game-changing discoveries. They don't have one amazing fossil, they have many. Palaeontologists have not got the anatomy of one species wrong, they've overlooked major anatomical characteristics across huge groups. And it's common for cranks to suggest that their work has a significant bearing on all manner of palaeontological mysteries: that their idea on dinosaur locomotion also explains giant pterosaur flight, that their anatomical criteria for understanding the evolution of reptiles can be applied, without modification, to mammals or birds. It's a hallmark of crankery to have all the answers - or at least more answers than 'mainstream' scientists.

Claims for so many ground-breaking discoveries should immediately trigger our scepticism. Yes, there are skilled and prolific scientists who make numerous significant contributions to our collective knowledge, but they do not make them every week. Good science takes time: time to collect and analyse data, time to document and report the findings, time for peers to check the work, and time to publish it in a suitable venue. While the crank may view their churning out of game-changing revelations as the inevitable consequence of a self-led scientific revolution, they're actually exposing their lack of rigour, willingness or ability to have their work vetted by relevant experts.

5. An abundance of self-citation
Does the article you're reading extensively cite the work of the author, and almost always in an affirming light? It would be wrong to say that genuine scientists do not self-cite, or even that some do not over cite their own work (scientists have egos too, many have rather big ones), but if you're reading a work that is extensively citing and complementing the author's own work, be wary: this is often a sign of crankery. This red flag flies especially high if the author is demeaning the work of others while holding their own work in high regard (see below).

6. Knowing your authors
In science, what is said matters more than who says it, but when a questionable claim is made the integrity of the author can be a useful indicator of credibility. Whether we like it or not, reputation matters. We should be extra sceptical with proposals made by those with a history of quackery or no background in the field they're claiming expertise in. This is not to say that amateur or non-professional individuals can't or won't have insights on palaeontolgical matters overlooked by experienced researchers, but folks without experience or training in a relevant field are more prone to making mistakes and overlooking data. It’s quite easy to research scientists and educators nowadays by simply Googling their names, or by asking around in the right internet venues. Sometimes this very quickly reveals whether you should be taking that individual seriously, or if you need to take a more cautious approach to their ideas.

7. Misleading credentials and other trickery
While some cranks decry academic titles, others flaunt their credentials to add support to their claims. But simply having a high-level qualification does not make someone an expert in all subjects. If someone is making questionable claims, check out what their qualifications are actually in: having a postgraduate qualification in microbiology or graphic design does not automatically equate to an equivalent understanding of dinosaurian biomechanics. Similarly, be wary of cranks making up official-sounding institutions as their place of research. There's no restriction on naming your own institution or society so cranks can create 'scientific' or 'educational' bodies as easily as I can call my garden shed the "Mark Witton Institute of Natural History". A quick round of Googling will quickly expose these institutions and credentials for what they really are. Needless to say, if someone is distorting their credentials in order to seem more authoritative, you've got an excellent reason to question pretty much everything they say.

That most cranks have only a superficial knowledge of palaeontology is demonstrated by their focus on well-known and charismatic species such as big dinosaurs and pterosaurs. It's rare to see cranks applying their ideas to more routine, less exciting species like extinct fish, invertebrates or even crocodyliforms like Hulkeopholis willetti. My hunch is that most cranks learn about palaeontology largely through popular media and if so, this explains why their ideas are so easily dismissed. Even basic training in palaeontology is enough to expose major holes in their ideas.

8. A predilection for criticism and personal attacks of scientists
Because cranks believe they have a superior scientific insight they are often extremely critical of other researchers. This seems to get worse as the crank gets older and has faced long-term rejection from the scientific community, and it can manifest itself in particularly nasty and underhand ways: obsessive and ultra-detailed 'criticisms' of published works; personal attacks and harassment of scientists; accusations of institutions being dogmatic, blinkered or even fundamentalist in their adherence to 'mainstream' views; and even attempts to dissuade prospective PhD students from legitimate postgraduate programmes. You don't see comments like this in legitimate research because genuine science is concerned with hypotheses and ideas, not venting frustrations at individuals or institutions. Crank hostility can be especially obvious if they have a comment field on their websites: when challenged, they are often quick to vent their frustrations.

9. The Galileo Gambit
Another major red flag common to all cranks is their frequent comparison between themselves and scientists who received establishment pushback against their ideas - Wegner, Galileo, Darwin and so on. The folly of the Galileo Gambit is well established and we needn't outline it in detail here, it will suffice to point out that invoking these big names is clear evidence of self-belief in their own abilities against overwhelming evidence to the contrary. Note that scientists making genuine research contributions never use this defence when proposing ideas they know will cause upset or controversy. If you see someone comparing themselves in this way to a historically persecuted scientific figure, there's a very good chance they're a dyed-in-the-wool crank.

10. Beware of Big Palaeo!
Saving the best until last: yes, unbelievable as it is, there are individuals who suggest mainstream scientists are somehow organising against them to suppress their work. While maybe not imagining something as sinister as the Big Pharma conspiracy, some cranks infer that palaeontology is governed by individuals who dictate what is and what isn't acceptable science, and who forbid the publication of work that challenges the status quo. The plot thickens with universities not simply training scientists, but actually indoctrinating them into this way of thinking. This casts PhDs not as experts in their subject, but as brainwashed members of the Big Palaeo cult. In controlling the ebb and flow of palaeontological science these individuals are able to maintain lofty academic positions and secure grant money. In my experience, this claim tends to follow the crank's papers being rejected from academic journals or finding that no palaeontologists will agree with their interpretation of an (allegedly) amazing fossil.

As someone with academic experience myself, I find this mindset genuinely fascinating. It gives a real insight into how some cranks see the world: so convinced are they of their own findings and significance that their rejection from academia can only reflect a global, organised conspiracy. In reality, their lack of academic recognition reflects the fact that any average scientist can spot fatal errors in their proposals. Moreover, the idea that palaeontologists, or any scientists, suppress controversial new ideas is ludicrous. Within the well-publicised realm of dinosaur science, just some recently published contentious ideas include the recovery of soft, unlithified proteinaceous tissues in 80 million year old fossil bones (Schweitzer et al. 2005), that Spinosaurus was a weirdly proportioned, archaeocete-like quadruped (Ibrahim et al. 2014), and that major branches of the dinosaur evolutionary tree have been incorrectly arranged for a century (Baron et al. 2017). These are bold claims that remain debated, but they were published nonetheless. The difference between these papers and crank ideas is simply the evidence and methodologies used to justify their conclusions - that's all there is to it. We could write a whole essay on how flawed the idea of a Big Palaeo conspiracy is but, in short, if you encounter anybody claiming their work is being silenced by a conspiracy of palaeontologists they are, without doubt, an embittered crank of the highest order.

These are just a few giveaways that you're dealing with a palaeontological crank, hopefully they're of use to folks less familiar with the more questionable parts of palaeontological outreach. Some readers may have identified some parts of the above list as common hallmarks of more general crankery, and that's no coincidence: as mentioned above, although crank subjects change, their behaviour and public presentation is remarkably consistent. There are longer, more detailed discussions of crank detection available online, but what we've outlined here should be enough to equip most readers with an early warning system for crankery. We've not, of course, answered the question about what to do with cranks when we identify them. Should we ignore them? Alert others about them? Contact them about their bad science? That's another long discussion (and a much murkier one) however, so that'll have to wait for another time.

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References

• Baron, M. G., Norman, D. B., & Barrett, P. M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543(7646), 501.
• Ford, B. J. (2018). Too Big to Walk: The New Science of Dinosaurs. HarperCollins UK.
• Ibrahim, N., Sereno, P. C., Dal Sasso, C., Maganuco, S., Fabbri, M., Martill, D. M., ... & Iurino, D. A. (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science, 345(6204), 1613-1616.
• Schweitzer, M. H., Wittmeyer, J. L., Horner, J. R., & Toporski, J. K. (2005). Soft-tissue vessels and cellular preservation in Tyrannosaurus rex. Science, 307(5717), 1952-1955.

Plesiosaurs on the rocks: the terrestrial capabilities of four-flippered marine reptiles

Maurice Wilson's charming c. 1958 painting of plesiosaurs coming ashore, from the Daily Mail Boys Annual (note "boys": girls aren't allowed to be interested in prehistory. Get out of our tree house!). Such depictions were commonplace until a few decades ago, but are all but extinct now. So what's happened to the idea that plesiosaurs could venture onto land?

Until comparatively recently it was not uncommon to see depictions of plesiosaurians* on rocks and beaches as if they had hauled themselves from the sea like breeding sea turtles or basking pinnipeds. Such restorations have a long history. Some of the earliest marine reptile palaeoart shows plesiosaurians on beaches or very shallow water, and we've even seen land-based plesiosaurians in feature films and documentaries, including notable sequences in When Dinosaurs Roamed the Earth (1969) and Walking with Dinosaurs (1999, below).

*Why 'plesiosaurians' rather than 'plesiosaurs'? Though a common vernacular, the term 'plesiosaurs' is potentially confusing as it could either refer to a number of marine reptile clades (e.g. plesiosauroids, plesiosaurids) or body plans (plesiosauromorphs). 'Plesiosauria' has a less ambiguous meaning as it specifically refers to the clade encompassing rhomaleosaurids, pliosauroids and plesiosauroids, so it might be a preferable catch-all term this marine reptile clade.

Today, it's much rarer to see plesiosaurians depicted outside of the aquatic realm. For... reasons, I'm restoring a number of marine reptiles at the moment, so I've been wondering if it would be acceptable to revive artwork of these creatures on rocky shores, beaches and other coastlines, if only to bring some variation to my marine scenes. As usual, this inquiry began with a literature crawl. Because 19th century palaeoart suggests palaeontologists once imagined these animals as routinely emerging from the waves, I expected marine reptile papers to be full of discussion about the terrestrial prospects of plesiosaurians, perhaps with an in-depth analysis of the concept bringing an end to the artistic tradition of depicting them on land. The transition from imagining plesiosaurians as semi-aquatic to fully aquatic seems to have happened organically, however: if there's a watershed paper or significant debate behind this, I've missed it. Richard Ellis' 2003 book Sea Dragons - perhaps the closest thing we have to an all-encompassing introductory review of marine reptiles - seems to confirm my independent findings, portraying plesiosaur terrestrial abilities as highly doubtful, but also a question without a firm answer in scientific literature.

Jurassic plesiosaur Cryptocleidus sits around the coasts of the Oxford Clay Sea in 1999's Walking with Dinosaurs. Uploaded to Youtube by user MARTINEZZZ365.

The idea of plesiosaurians leaving water has been strongly tied to historic uncertainty about their reproductive habits. It stands to reason that, if plesiosaurians laid eggs, they must have somehow dragged their way out of the sea to construct their nests (Taylor 1981, 1986). The notion that plesiosaurians could have given birth to live young is pretty old (e.g. Seeley 1896) but scant evidence of their reproductive strategies prevented dismissal of land-based nesting habits until relatively recently. We now have evidence of live birth in plesiosaurian relatives (nothosauroids, Sander 1988; Renesto et al. 2003; Cheng et al. 2004) as well as a true plesiosaurian (a polycotylid, O'Keefe and Chiappe 2011), and so we needn't imagine plesiosaurians hauling out onto beaches to lay eggs, turtle-style.

But I'm going to keep pulling at this thread. While their capacity to give birth to live offspring eliminates the behavioural necessity for leaving water, it does not, in itself, demonstrate that plesiosaurian anatomy was functionally incapable of land-based locomotion, or that they did not leave the sea to find refuge or seize prey - orca style - from shorelines. After all, viviparity does not mean that seals, sea otters or even manatees have committed to a fully aquatic life (a voluntarily beached manatee deserves a citation - see Motani et al. 2015). Is there a cogent functional argument for why plesiosaurians might struggle out of water that will let me (and others) escape painting nothing but blue and green pictures?

How plesiosaurians might have moved on land

Our discussion will be aided by first outlining what we might realistically expect of a walking or crawling plesiosaurian. No one, for instance, predicts that plesiosaurians could stride around like sea lions or the plesiosaur in When Dinosaurs Roamed the Earth. Their flipper skeletons were essentially inflexible so they were incapable of being articulated into a walking limb. This precludes walking on their hands and feet in the way that eared seals can. They were also likely incapable of bouncing along in the manner of true seals, where the flexibility of the spine is used to 'hump' their way forward while powerful, gripping claws pull and steer them around. Plesiosaurian bodies were pretty rigid - their robust gastralia and ribs are sometimes superficially compared to turtle shells - and likely incapable of the twisting and bending necessary to bounce their way over shorelines. And in lacking claws, the only contribution their flippers could make to crawling would be crude pushing and lifting actions.

True seals, such as the grey seal (Halichoerus grypus), are far less terrestrially proficient than the eared seals (sea lions, fur seals etc.) and have to bounce or drag themselves around when ashore. Large claws on their flippers help in this activity (and are also useful for scratching). Grey seal cow photo by Georgia Witton-Maclean.

If plesiosaurians could leave the water at all, we have to imagine something more akin to turtle locomotion: using their flippers to push and pull themselves along while lying on their bellies. Their weight and a likely inability to clear their bodies entirely from the ground predicts that much of their energy would go into overcoming drag incurred by their wide bodies and tails. Terrestrial plesiosaurians would need to make full use of their powerful flipper downstroke muscles (soundly evidenced by the enormous muscles of their chest and the underside of their hips; see Carpenter et al. 2010; Araújo and Correia 2015) to lift their bodies and propel themselves forward. The exact motion of their flippers remains controversial, but is likely to have been a wingbeat-like action (Taylor 1986; Carpenter et al. 2010; Liu et al. 2015; Muscutt et al. 2017) that may have been enough to shove plesiosaurians over shorelines. The picture we're building here is of a slow and laborious means of locomotion. If plesiosaurians did intentionally leave water, they almost certainly visited locations inaccessible to terrestrial predators.

Polycotylid Dolichorhynchops bonneri demonstrating a fairly typical plesiosaurian torso and flipper construction. At face value, the retention of four limbs and stout limb girdles looks like terrestrial locomotion shouldn't be too hard for these guys - they certainly look more terrestrially capable than many other marine tetrapods. From Carpenter et al. (2010). Scale bar is 1 m.

I also think we should rule out raw body size as a compelling reason to doubt land-based locomotion in plesiosaurians. There's no reason to regard plesiosaurians as atypically heavy compared to other marine animals (Everhart 2000, Henderson 2006) and, indeed, their general lack of pachyostosic skeletons might make them lightweight compared to some other aquatic tetrapods (e.g. Street and O'Keefe 2010). Many species were probably within the mass ranges of living species known to transition between land and sea. The known maximum limit for this lifestyle is set by bull elephant seals which, according to Wikipedia, reach 3,000 - 4,000 kg. We don't have many plesiosaurian mass estimates to compare this figure to, but a few noteworthy values are Everhart's (2000) predicted mass of 2.8 tonnes for a 9 m long plesiosauroid, and Henderson's (2006) 217 kg 3 m Cryptocleidus. Truly giant plesiosaurians - 10 and 11 m long individuals - are beyond the masses of big elephant seals (Henderson 2006), but this still leaves plenty of small and mid-sized species at or below the mass threshold of marine species that we know can venture onto land, assuming they have the right adaptations. For me, our question is most appropriately addressed through assessment of anatomy and functional morphology, not a priori judgements about size.

Scrutinising the model

The bar we've set for plesiosaurian terrestrial locomotion is thus pretty low: even if they can only shamble up a beach we could consider our conditions met. But how feasible is even this laborious means of getting around on land? To cut to the chase: not very. There are multiple aspects of plesiosaurian anatomy that probably precluded even very basic terrestrial capabilities.

Plesiosaurian flippers, for instance, seem poorly suited for use on coastal substrates. Semi-aquatic species such as turtles, seals and terrestrially-roaming fish have a degree of jointing or articulation in their forelimbs which transforms them from flippers or paddles into walking limbs (Mazouchova et al. 2013, also see this post on the potentially amphibious ichthyosaur Cartorhynchus). A jointed limb performs considerably better on loose substrates (such as those common on beaches, mudflats and other shoreline locations) because it enables greater control of force distribution as animals move. Immobile flippers tend to skim over or dig into sand or mud, while jointed limbs can respond to yielding substrates to maximise lift and propulsive forces. Where substrates have already been disturbed, fixed-shape flippers can struggle to get any purchase at all (Mazouchova et al. 2013).

The evolution of the plesiosaurian flipper - represented here with early sauropterygians (A - B) and true plesiosaurians (C - D) involves the development of tightly fitting bones and removal of joint mobility. This makes for a superior flipper for an underwater flier, but compromises their terrestrial capacity. Image and caption from Storrs (1993).

Assuming these findings apply to plesiosaurians - and there's no reason they shouldn't - their effectively immobile flippers present a major barrier to terrestrial activity. Plesiosaurian flippers lack both obvious bony joints or significant cartilaginous regions that would allow them to flex, so they best fit those modelled flippers which skid around or dig into the substrates they're meant to traverse. We must consider that their flippers are married to animals that are already encumbered by large size and weight, as well as the additional difficulty of drag forces operating on their bodies as they moved forward. It is not hard not to imagine a beached plesiosaurian like a heavy vehicle stuck in sand, spinning its wheels as it tries to move forward.

The issues with plesiosaurian limbs do not stop there, as their limb girdles are also ill-equipped for supporting their weight on land. While augmented ventrally to accommodate big downstroke muscles, the upper regions of plesiosaurian shoulder and pelvic girdles are only weakly developed. This isn't unusual for aquatic species as a major role of expanded upper limb girdles - specifically the scapulae of the shoulder, and ilium in the hips - is stabilisation of the limb girdles during terrestrial locomotion (some readers may recall us discussing this recently in context of another marine reptile, Helveticosaurus). But while adequate for life at sea, on land these small girdle elements provide only weak girdle support and thus impede locomotion, and this was probably true for plesiosaurians. Though retaining a connection between the ilia and sacral vertebrae, the articulation is weak and ligamentous, and thus unsuited to weight-bearing (O'Keefe and Chiappe 2011). Similarly, their small scapulae leave little space for muscles associated with stabilising the shoulder against the body, and the shoulder is poorly braced for terrestrial locomotion (see Rieppel 1989 for discussion, also Araújo and Correia 2015). We thus have flippers ill-suited to land-based locomotion attached to limb girdles which are maladapted to weight-bearing. These are not the features of animals that were regularly hauling themselves onto shorelines.

Pelvis of Brancasaurus brancai in lateral (A) and medial (B) view, from Carpenter et al. (2010). Note the extremely narrow ilium: this structure articulates with the vertebrae overlying the hip to act as an important brace for the pelvic girdle during terrestrial locomotion, so its small size does not bode well for the prospects of plesiosaurs leaving water.

And there are further impacts from the reduction of the scapula to be explored. The muscles that elevate our heads and necks are anchored to our scapulae as well as our vertebrae, so the size of bones making up our shoulders dictates how large muscles important to neck elevation and control (e.g. the trapezius, levator scapulae) can be. Plesiosaurians famously have large necks and/or heads, but lack the weight-saving adaptations seen in similarly-proportioned land animals, such as pneumatic tissues and reduction or displacement of neck musculature towards the body (e.g. Taylor and Wedel 2013, also see this discussion of the lifestyle of Tanystropheus). Their necks and heads must have thus been heavy compared to those of large necked or big-headed terrestrial reptiles**, so we might expect substantial shoulder bones to anchor massive neck elevators if they were routinely leaving water. This casts their tiny scapulae as the exact opposite of what we might expect if these animals were routinely crawling around on land.

**To put some numbers on this, Henderson (2006), modelled plesiosaurian heads and necks with tissue densities of 1.05 g/l, about 1.5 times heavier than a value we assume for a bird or bird-like dinosaur.

The pectoral region and musculature of Rhomaleosaurus, modified from Araújo and Correia (2015). While the humerus is well muscled, the scapula is proportionally tiny compared to the chest, which has implications for shoulder stability and carriage of the head and neck.

Plesiosaurians could have developed an alternative approach to supporting the weight of their heads and necks out of water, such as bulking up the muscles surrounding their neck vertebrae. If so, we could predict structures equivalent to withers (elevated vertebral spines over the shoulders related to expanded neck musculature) in species with particularly large heads and necks. Such structures are not to be found plesiosaurians however, so I don't think this idea is compelling. This being so, it looks like neither the shoulders or anterior trunk vertebrae provide sufficient space for the powerful neck muscles needed to elevate their necks and heads on land for sustained periods. The impact of struggling to lift their heads for long intervals could include further impedance to their locomotion (additional drag, difficulty overcoming obstacles) as well as exposing their facial tissues to abrasion and other damage.

Ventral view of rhomaelosaurid Meyerasaurus victor, as figured by Smith and Vincent (2010). Note that the extensive bones of the chest, hips and gastric regions are entirely unfused: like many secondarily marine animals, plesiosaurian skeletons were likely far more cartilaginous than their terrestrial ancestors. Scale bar is 1 m.

A final, but no less significant, consideration for our inquiry is the high volume of cartilage associated with the plesiosaurian skeleton. A glut of unfused bones and loosely fitting contours between closely associated elements betrays a skeletal system held together primarily through extensive amounts of cartilage tissue. This includes areas of relevance to land-based locomotion, such as the shoulder and hip joints, the limb girdles and the region between the gastralia and ribs. In water, these softer connections wouldn't cause any issue, but on land the flexibility and softness of cartilage might weaken skeletal support and strength. The hypothesis outlined above posits that land-based plesiosaurians are essentially moving around with brute force, shoving their large masses around with motions of their flippers against large drag forces. Under this scenario, a relatively rigid and uncompromising skeletal frame would be ideal, whereas one with large volumes of cartilage would make movement less efficient.

What about small-bodied plesiosaurians?

Without any aspects of plesiosaurian anatomy looking incompatible with terrestrial activity, we might need to play a biomechanical get-out-of-jail-free card to prevent abandonment of this concept altogether: small body size. Inescapable rules of scaling mean that a given bauplan, expressed at smaller size, can perform biomechanical feats impossible for bigger individuals. Might small plesiosaurian species or juveniles exploit greater relative tissue strength ratios, lower body masses and improved muscle power:weight ratios to haul themselves onto land, leaving only larger plesiosaurians confined to water?

The pliosaurid Thalassiodracon hawkinsi is one of the smallest plesiosaurians known at c. 2 m long, and yet it bears all the same hallmarks of incompetent terrestrial abilities as its larger relatives. Are the virtues of small size enough to justify thinking animals of this size could leave the water? Photo from Wikipedia, by the paleobear, CC BY 2.0.

I must admit that I'm skeptical even here. Anatomically speaking, small plesiosaurians have the same terrestrially-inhibited anatomy as their larger relatives: inflexible flippers, high cartilage volumes, and low weight-bearing capabilities for the body, head and neck. Smaller size could make all the difference, but size alone is of ambiguous significance to predictions of extinct animal behaviour. It's clearly a factor in what fossil species could and couldn't do, but it should not overshadow better-established relationships between form and function when considering extinct animal lifestyles (see also: flight in giant pterosaurs). So while small size theoretically makes terrestrial locomotion more achievable for an aquatic animal, it's ultimately circumstantial evidence for this behaviour and not an especially compelling counterargument.

And as a final, closing thought on this, it's also worth considering that plesiosaurians were generally large-bodied creatures. Genuinely small species (such as the c. 2 m long Thalassiodracon hawkinsi) are rare and even their offspring were large (e.g. 1.5 m calf lengths in 4.7 m long mothers - O'Keefe and Chiappe 2011). Mesozoic shorelines were probably not swarming with small plesiosaurians even if they did have superior terrestrial capabilities, because by and large plesiosaurians weren't small creatures.

Bring on the blue paints

So, should palaeoartists get back to painting plesiosaurs out of water? Sadly, no. Any notion that plesiosaurians were capable of hauling themselves onto land is not only unnecessary in light of what we know of their reproductive biology, but also contradicts much of what we understand about the functional morphology of semi-aquatic animals. Their four-flipped construction looks a little more terrestrially-capable than the body of a whale or ichthyosaur, but I suspect an accidentally beached plesiosaurian would be in just as much trouble as these more classically-shaped marine forms. History shows that we can make beached plesiosaurians look half convincing in art, but it's a hollow victory: the science is not on our side.

I still find it odd that there isn't a more detailed discussion of plesiosaurian - or maybe broader sauropterygian - terrestrial capability in marine reptile literature. After all, many clades generally regarded as relatives or even ancestral to plesiosaurians are regarded as semi-aquatic (e.g. nothosaurs, Helveticosaurus) and there has to be an interesting story there regarding the progressive abandonment of land. Hopefully, studies along these lines will be performed before we're much older. But for the time being, I'll be restoring all my plesiosaurians in water, where they almost certainly belonged. I'll leave you with this painting of Pliosaurus kevani in their rightful habitat.

Pliosaurus kevani large and small, at home in the sea. Junior is particularly happy that it doesn't have to venture out onto land, probably because it's always freezing cold getting out of the water, and pliosaurids were surprisingly wimpy about that sort of thing. #palaeofact

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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

• Carpenter, K., Sanders, F., Reed, B., Reed, J., & Larson, P. (2010). Plesiosaur swimming as interpreted from skeletal analysis and experimental results. Transactions of the Kansas Academy of Science, 1-34.
• Cheng, Y. N., Wu, X. C., & Ji, Q. (2004). Triassic marine reptiles gave birth to live young. Nature, 432(7015), 383.
• Ellis, R. (2003). Sea dragons: predators of the prehistoric oceans. University Press of Kansas.
• Everhart, M. J. (2000). Gastroliths associated with plesiosaur remains in the Sharon Springs Member of the Pierre Shale (Late Cretaceous), western Kansas. Transactions of the Kansas Academy of Science (1903), 64-75.
• Henderson, D. M. (2006). Floating point: a computational study of buoyancy, equilibrium, and gastroliths in plesiosaurs. Lethaia, 39(3), 227-244.
• Liu, S., Smith, A. S., Gu, Y., Tan, J., Liu, C. K., & Turk, G. (2015). Computer simulations imply forelimb-dominated underwater flight in plesiosaurs. PLoS computational biology, 11(12), e1004605.
• Mazouchova, N., Umbanhowar, P. B., & Goldman, D. I. (2013). Flipper-driven terrestrial locomotion of a sea turtle-inspired robot. Bioinspiration & biomimetics, 8(2), 026007.
• Motani, R., Jiang, D. Y., Chen, G. B., Tintori, A., Rieppel, O., Ji, C., & Huang, J. D. (2015). A basal ichthyosauriform with a short snout from the Lower Triassic of China. Nature, 517(7535), 485.
• Muscutt, L. E., Dyke, G., Weymouth, G. D., Naish, D., Palmer, C., & Ganapathisubramani, B. (2017). The four-flipper swimming method of plesiosaurs enabled efficient and effective locomotion. Proc. R. Soc. B, 284(1861), 20170951.
• O’Keefe, F. R., & Chiappe, L. M. (2011). Viviparity and K-selected life history in a Mesozoic marine plesiosaur (Reptilia, Sauropterygia). Science, 333(6044), 870-873.
• Renesto, S., Lombardo, C., Tintori, A., & Danini, G. (2003). Nothosaurid embryos from the Middle Triassic of northern Italy: an insight into the viviparity of nothosaurs? Journal of Vertebrate Paleontology, 23(4), 957-960.
• Rieppel, O. (1989). Helveticosaurus zollingeri Peyer (Reptilia, Diapsida) skeletal paedomorphosis, functional anatomy and systematic affinities. Palaeontographica Abteilung A, 123-152.
• Sander, P. M. (1988). A fossil reptile embryo from the Middle Triassic of the Alps. Science, 239(4841), 780-783.
• Seeley, H.G. (1896) On a pyritous concretion from the Lias of Whitby. Annual Report of the Yorkshire Philosophical Society, 1895, 20–9.
• Storrs, G. W. (1993). Function and phylogeny in sauropterygian (Diapsida) evolution. American Journal of Science, 293(A), 63.
• Street, H. P., & O'Keefe, F. R. (2010). Evidence of pachyostosis in the cryptocleidoid plesiosaur Tatenectes laramiensis from the Sundance Formation of Wyoming. Journal of Vertebrate Paleontology, 30(4), 1279-1282.
• Taylor, M. A. (1981). Plesiosaurs-rigging and ballasting. Nature, 290, 628-629.
• Taylor, M. A. (1986). Marine reptiles: Lifestyle of plesiosaurs. Nature, 319(6050), 179-179.
• Taylor, M. P., & Wedel, M. J. (2013). Why sauropods had long necks; and why giraffes have short necks. PeerJ, 1, e36.

No, Cretaceous sharks did not leap from water to eat flying pterosaurs

How the heavy hitters covered Hone et al. 2018: a short, open-access and easy-to-read paper about a shark tooth preserved with Pteranodon. The Sun gets bonus stupid points for making their own graphic. 

Sigh.

Major news outlets have been reporting this week that a new study evidences prehistoric sharks predating pterosaurs by leaping from the water to snatch them in mid-air. It would be an awesome discovery, if it were true. In reality, these headlines are nothing but a construct by journalists based on a misread palaeoart image, ignorance of some basic facts of animal biology, and lazy science reporting. I'm particularly angry because the study being misreported, and the art being misread, stems from a paper that I recently published with with my friends and colleagues Dave Hone and Mike Habib (Hone et al. 2018). The paper is in PeerJ, and is thus open-access. Anyone - including our dear media - can fact check what we have to say without hitting a paywall.

The nature of modern news is that stories can spread like wildfire, and it's effectively impossible to correct major gaffes once a story gains momentum. With that in mind, the best I can do is outline here what our new paper actually says, what our artwork actually shows, and hope that readers link to this post wherever they see this ridiculous press story being shared. It must be said that a number our outlets are reporting the story more accurately, but enough have mangled our findings that I feel I need to do something. I genuinely care about the accurate conveyance of science, and I've found this distortion of our work and my painting very distressing.

What our paper actually says

OK, first up: a summary of our paper. Mike, Dave and I have documented a series of neck vertebrae from the famous Late Cretaceous pterosaur Pteranodon associated with the tooth of a lamniform shark, Cretoxyrhina mantelli. The vertebrae and their teeth were found in 1965 but our records about their discovery are confused and we don't know whether they were part of a larger discovery of bones, or just a few isolated remains. There are hints that they may have been part of a more impressive skeleton, but it's pretty hard to tell. In any case, today this string of vertebrae is on display at the Los Angeles County Museum as part of a composite skeleton.

Vertebrae are not diagnostic for different Pteranodon species so we refrain from identifying the pterosaur beyond Pteranodon sp. The specimen was found in Niobrara Formation rocks that traditionally yield P. longiceps however, and this is probably the likely species identity- we just can't verify it*. The identification of the shark is better constrained as the tooth is a perfect match for C. mantelli. Indeed, we can even tell which part of the mouth it came from thanks to Cretoxyrhina mantelli being exceptionally well known: even complete skulls and skeletons have been found. This allows us to roughly gauge the size of the Cretoxyrhina as c. 2.5 m long, which makes it a small individual compared to the 6-7 m specimens known from other remains. Our Pteranodon was on the small size as well at c. 5 m across the wings. This is within the upper size range of Pteranodon fossils, but still 1-2 m off the full wingspread of this species.

*If anyone's wondering, yes, we follow the traditional Bennettian concept of Pteranodon taxonomy. It was actually writing the manuscript for this paper that prompted my blog post on Pteranodon taxonomy.

Pteranodon sp. specimen LACM 50926 as mounted as part of a composite skeleton in the Los Angeles County Museum, and in more detail with their hitchhiking Cretoxyrhina mantelli tooth (arrowed). Scale bar is 50 mm. From Hone et al. 2018.

The Cretoxyrhina tooth does not actually penetrate the pterosaur bone, but is wedged beneath a vertebral process in a complex, intimate manner. We assume this evidences the shark biting into the pterosaur neck and shedding a tooth into its soft-tissues. An alternative - that the specimens became associated through actions of currents or storms - is less plausible given the strange position of the tooth, its tightness to the specimen, as well as the gentle, low-energy marine conditions of the Niobrara Formation.

But what sort of circumstances brought these animals together? It's here that our questions go beyond what the fossils can tell us. There's only so much a single tooth and string of vertebrae can objectively reveal about an ancient animal interaction, and we conclude that either a predatory and scavenging act could have produced the association - there's just no way to tell. While a scavenging story explains itself (short version: pterosaur dies over water; shark gets a meal), we explored how a predatory scenario may have played out given the known fish-eating habits of Pteranodon and hypotheses that this pterosaur regularly dived or swam to catch its prey (e.g. Bennett 2001; Hone and Henderson 2014; Witton 2013, 2018). Swimming pterosaurs are a new idea to many but substantiated by several lines of evidence, including swimming tracks, modelling of their aquatic launch strategy, and studies of their floating capability (Lockley et al. 2003; Habib and Cunningham 2010; Hone and Henderson 2014). We propose that if Pteranodon was a regular swimmer it would be vulnerable to sharks and other large predators, and its flight muscles would surely be a decent meal for many carnivores. Pterosaurs were probably pretty sinewy across their limbs, but there'd be some sizeable steaks to carve from their shoulders and chests. As big, powerful predators, it seems entirely plausible that even a half-size Cretoxyrhina would be capable of subduing a large Pteranodon, assuming they could catch one.

And that is as far as we go in our paper - it's pretty conservative stuff. You can read another summary of the paper at Dave Hone's Archosaur Musings.

The illustration

Rocket shark eats flying pterosaur? No. Artwork of a small Cretoxyrhina mantelli attacking a group of floating Pteranondon longiceps, erupting from the sea with one in its jaws. Note the other swimming pterosaurs in this picture - it's almost like pterosaurs weren't always flying, or something. From Hone et al. 2018.

Mike, Dave and I are palaeoart fans and we all - perhaps myself especially - enjoy well-illustrated papers, so we decided to include a reconstruction of Cretoxyrhina vs. Pteranodon in our paper (above). Having recently drawn an image of Pteranodon being hounded by another Cretaceous shark, Squalicorax, at the water surface, I wanted to do something different with this illustration and decided on a more exciting breaching scene: a shark leaping from the water with a Pteranodon in its mouth. Anyone who's watched even a few wildlife documentaries will know this behaviour is far from speculative: it's a widely-filmed, photographed and documented behaviour of South African white sharks (see Planet Earth excerpt from BBC Earth, below). These sharks strike floating prey with such speed that they leap entirely from the water. It's very dramatic, very awesome and seemed like great inspiration for a palaeoartwork. And sure, we have no idea that Cretoxyrhina did this, but a breaching attack is no more or less speculative than any other means of depicting a shark tooth lodging in a Pteranodon neck. I won't bore you with some additional practical factors that influenced the composition (in short, this image is being featured in an upcoming book where I have some firm ideas about visual narrative, and this strongly influenced choices of posture and colour).

In my mind, shark breaching is a widely known, instantly recognisable behaviour that shouldn't be foreign to folks writing science articles. It's routinely covered in major documentary programmes like Planet Earth, as shown here in this YouTube clip from BBC Earth. It's weird to me that folks are assuming my artwork has to be something more awesome than this, just because a pterosaur is involved.

A number of swimming and water-launching pterosaurs were added in the background of the image to make it clear that the Pteranodon was caught from a floating position. In my mind, the image shows a flock of pterosaurs busying themselves in the sea before Cretoxyrhina crashes their party - you can invent your own reasons for all the Pteranodon milling about. Maybe they're foraging, maybe they're congregating for another reason - it doesn't matter too much, what matters is that the sea has six or so Pteranodon either floating or launching from the water. Also note that water is shedding from the main pterosaur's wings, as if it's just left the water along with the shark. I carefully referenced how much water should be flying about using footage and photos of breaching sharks around the peak of their arcs: we often overdo water dynamics in palaeoart, and I was keen to make this image grounded in spite of its spectacular action.

So what's gone wrong?

What we've ended up with, then, is a pretty simple, conservative paper with an illustration that is pretty bleeding edge in terms of pterosaur science (flying reptiles as swimmers) and radical in terms of shark behaviour (breaching). But the two are entirely compatible with one another and the image is appropriately grounded in zoology and palaeontology. It looks extreme, but it's not ridiculous compared to what happens in modern natural history.

Unfortunately, this broader face of our project has been neglected in the media. Instead, our artwork - or rather a knee-jerk, lunkhead interpretation of it - has become the media story and we now have 'science-endorsed' headlines stating that sharks shot out of the water to grab pterosaurs (or even 'flying dinosaurs' in several articles) when they soared overhead. As I've outlined here, this is entirely false, and not representative of our ideas at all. Any hope that our paper could be used to broadly communicate some cool ideas about pterosaur ecology, the role of sharks as important predators throughout the Mesozoic, or even the simple fact that pterosaurs could likely swim has been lost behind ridiculous headlines based on erroneous readings of my picture.

So that's basically that - this is essentially a tale of how quickly false information can spread when it's attached to a pretty image, and why we shouldn't believe everything we read. Perhaps there's a lesson here in the power of imagery, and I am certainly now wondering if I erred in my reconstruction being too complex (to my defence, I did not contribute to the PR campaign for this and did not get the opportunity to sign off on an appropriate description for the picture). Perhaps we're looking at the reality of naive audiences assuming that anything to do with sharks or prehistoric creatures must automatically be the most awesome, badass thing. Maybe I erred in my assumption that people would be familiar with the basics of breaching shark behaviour.

But what this hits home hardest for me is the reality of science reporting in our digital, content-fuelled age. Anyone who led with the stupid shark vs. flying pterosaur headline went nowhere near our actual paper to check what we said, even though it was literally just a link click away. They simply parroted one another to make sure their outlets have the same stories as everyone else. Only a few thought to double check what our conclusions were, and I find that distressing. Remember folks, these are the same guys who're reporting news about far more important things than pterosaurs: vaccinations, climate change, health and environmental issues, and so on: these pterosaur-devouring rocket sharks are stark reminders of how they work. If you've seen accurately reported examples of this story (and they do exist) then add those news services to your bookmarks: they are rare examples of media outlets that aren't jumping our shark.

If understanding pterosaur ecology through fossil associations is of interest, be sure to check out this series of three blog posts: part 1, part 2, and part 3.

Enjoy monthly insights into palaeoart, fossil animal biology and occasional reviews of palaeo media? 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

• Bennett, S. C. (2001). The Osteology and Functional Morphology of the Late Cretaceous Pterosaur Pteranodon Part II. Size and Functional Morphology. Palaeontographica Abteilung A, 113-153.
• Habib, M. B., & Cunningham, J. (2010). Capacity for water launch in Anhanguera and Quetzalcoatlus. Acta Geoscientica Sinica, 31, 24-25.
• Hone, D. W., & Henderson, D. M. (2014). The posture of floating pterosaurs: ecological implications for inhabiting marine and freshwater habitats. Palaeogeography, Palaeoclimatology, Palaeoecology, 394, 89-98.
• Hone, D. W., Witton, M. P., & Habib, M. B. (2018). Evidence for the Cretaceous shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation. PeerJ, 6, e6031.
• Lockley, M. G., & Wright, J. L. (2003). Pterosaur swim tracks and other ichnological evidence of behaviour and ecology. Geological Society, London, Special Publications, 217(1), 297-313.
• Witton, M. P. (2013). Pterosaurs: natural history, evolution, anatomy. Princeton University Press.
• Witton, M. P. (2018). Pterosaurs in Mesozoic food webs: a review of fossil evidence. Geological Society, London, Special Publications, 455(1), 7-23.