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Tuesday, 30 November 2021

The long, winding road to the first sauropod palaeoartworks

It's a well-verified fact that the best dinosaurs to draw are the sauropods, exemplified here by the mighty Giraffatitan brancai. But the route to this modern realisation was a difficult one. When sauropods were first discovered no one wanted to restore them at all: their fossils were always in the hands of the wrong people, at the wrong time, and our first attempt at restoring their life appearance was many decades after their discovery. A strange story awaits.
Is there any shape more emblematic of prehistoric life than the silhouette of a sauropod? The combination of long neck, long tail, round body and four robust limbs is universal visual shorthand for anything to do with dinosaurs and, more broadly, extinct life, such that sauropods are bone fide superstars of palaeontological pop-culture. The world-renowned Sinclair logo, Gertie, the leads of The Land Before Time and The Good Dinosaur, the scene welcoming us to Jurassic Park… all sauropods.

Much of the most famous sauropod iconography is, as with so much palaeontological media, related to fully-fleshed sauropod reconstructions rather than their fossil bones, so we can consider much of their popular appeal lying within paleoart. Given the undeniable spectacle and wonder associated with sauropod fossils, where even single bones can be jaw-dropping museum centrepieces, we might imagine that early scientists and palaeoartists jumped at the chance to put flesh on the skeletons of these long-necked reptiles as soon fossil material revealed their basic shape. And yet, this was not the case. The story of how sauropods entered the palaeoart canon and became ambassadors for all things dinosaurian and extinct is a peculiar one, where a full half-century passed between their discovery and their palaeoart canonisation. This is a story of how combative attitudes and egos, missed opportunities and perceived failures in early palaeoartworks stymied life reconstructions of sauropods for much of the 19th century.

(The following post owes much to the history of sauropod research outlined by Mike Taylor (2010) and Mark Hallett and Matt Wedel (2016). Be sure to check these out if you want a more detailed perspective on 19th century sauropod science.)

Fragmentary beginnings

Our tale begins, of course, with the discovery and description of the first sauropods Cetiosaurus and "Cardiodon" by Richard Owen in 1841. As with all the first dinosaur discoveries, our first sauropod fossils were isolated bones from southern Britain. Little could be said about the life appearance of the animals they represented other than that they were enormous reptiles. On account of their size, it was assumed sauropods must have been aquatic and – like all giant sea creatures – carnivorous. Perhaps, it was wondered, they were the arch predators of Mesozoic oceans: the devourers of plesiosaurs and ichthyosaurs. Owen speculated that such a creature must have borne a well-developed caudal fin perhaps similar to that of an ichthyosaur, but this awesome vision of sauropods did not lead to any life reconstructions despite the cavalier reputation of early 19th century Europeans for restoring extinct animals (if you’ve been reading my blog since its origins, you may remember an article on this very topic).

We might wonder why this was the case. After all, animals like Megalosaurus were initially represented by little more material than Cetiosaurus, but they were still restored within just a few years of their discovery. The absence of early 19th century sauropod reconstructions shows, to my mind, some level of nuance about early Victorian palaeoartists. Though often characterised as wild and speculative, the early Victorian palaeoart canon was surprisingly conservative, mainly showing similar scenes populated by the same species in the same anatomical guises. Many of their depictions were also of animals with decent fossil representation like marine reptiles, pterosaurs and fossil mammals, such that the restoration of poorly-represented species, like dinosaurs, can be viewed as exceptional. Moreover, and in further defence of the first palaeoartists, dinosaur anatomy wasn’t a total unknown in the early 19th century. Several species had been attributed characteristic anatomical features such as nose horns, body armour, or distinctive teeth, so there was something to hang restorations around. But sauropods lacked even a basic defining feature, and thus had no way of being distinguished or characterised from other restored giant reptiles. Should vindictive time-travellers ever force early Victorians to draw fleshed-out sauropods, the result would probably be nothing more than generic, giant carnivorous reptiles, perhaps little different to some of John Martin’s whale-sized, lizard-like dinosaurs.

John Martin's frontispiece to G. F. Richardson's 1842 book Geology for Beginners, entitled Age of Reptiles. A lot of early 19th century dinosaur palaeoart was not especially attentive to details of anatomy and form, such that sauropods, if they had been illustrated, probably would have looked much like the (?)Megalosaurus in this piece.


The whale lizard flounders in the palaeoart doldrums

A major step towards understanding sauropod life appearance was made in the late 1860s when a large haul of Cetiosaurus bones were found in Oxfordshire, UK. Described by geologist John Phillips in the 1871 book Geology of Oxford and the Valley of the Thames, this partial skeleton included limb bones, ribs, limb girdles and many vertebrae, and thus provided our first decent insight into the sauropod body plan. In what seems like a cruel twist of fate, no neck or skull bones were recovered, denying knowledge of the most defining characteristic of the group for another few years. Nevertheless, Phillips had enough anatomy to start making the first relatively informed insights into sauropod appearance and behaviour, and he devoted several pages of his book to discussing the size, habits and even skin of Cetiosaurus. Much of what we now think about sauropods was prophesied here, with Phillips describing very large, scaly reptiles that lived on land and ate plants. He made a number of favourable comparisons to Iguanodon in his discussion of Cetiosaurus habits such that he may have imagined it as an especially gigantic large-bodied, quadrupedal herbivore in the vein of Waterhouse Hawkins’ Crystal Palace Iguanodon and Hylaeosaurus. It is curious, therefore, in light of this evident interest, that Phillips did not attempt some sort of reconstruction. He had enough bones to at least construct a decent skeletal diagram. But, OK - maybe reconstructions weren’t Phillip’s thing. With all this anatomical information, surely someone else picked up the baton?

John Phillips' quarry map of a partial Cetiosaurus skeleton found in 1869-70. A lot of the vertebrae and smaller bones are amalgamated into packages in this drawing, but the glut of material is obvious. This was the first significant insight into sauropod life appearance... but not much came of it among Victorian palaeoart. From Phillips (1871).

And it’s at this point that our story becomes rather strange. Cetiosaurus, which was by now as well represented as other animals routinely featured in palaeoart, continued to be snubbed by artists. We have to take a step back from sauropod palaeoart history and expand our scope to the discipline as a whole to understand why. Along with Cetiosaurus, a number of genuinely important, game-changing dinosaur discoveries had been made across Europe in the mid-1800s that included Scelidosaurus (the first complete dinosaur skeleton), Compsognathus, Hypsilophodon, and Archaeopteryx. All were represented by excellent fossils that dramatically enhanced our understanding of dinosaurs and had major implications for reconstructing their life appearance, and yet none were canonised into palaeoart of the day. If you look hard enough you may find some simple line drawings of Archaeopteryx here and there, but there were no lavish paintings, no sculptures or elaborate lithographs celebrating these new animals.

Evidently, Cetiosaurus itself wasn't being snubbed. These superior sauropod remains had arrived while European palaeoart was in a funk that would last several decades, an era when most new palaeoartworks featured restorations recycled from the early 1800s instead of novel reconstructions of newly-discovered species. A contributing factor to suppressed creativity in late 19th century European palaeoart was, ironically, the Crystal Palace Dinosaurs (Secord 2004; Nieuwland 2019). Although popular with the public, most academic response to the 1854 unveiling of these models was negative. Criticisms were many, focusing on their speculated elements, the juxtaposition of modern landscapes with extinct animals, and accusations that they were simply scaled up, monsterised living species. Several Crystal Palace reconstructions were also rapid embarrassed by new fossil data, such that these flagships of Victorian palaeoart were now misleading or confusing the public more than educating them. The Crystal Palace Dinosaurs had given scholars of the 1870s good reason to be sceptical of palaeoart, and the creation of new life reconstructions fell out of fashion for a generation.

American palaeoart to the rescue… sort of

The awakening of American palaeoartistry is one of the few major events that occurred in palaeoart history in the early-late 19th century. While American palaeoartists slowly found their feet, the discovery of excellent sauropod material in western states in the 1870s finally revealed the full spectacle of these amazing, unique animals. Among the first relatively well-known American sauropods was Camarasaurus, found in 1877 and described by Edward Drinker Cope in the same year. These specimens, at last, revealed something of the iconic sauropod neck. Scientists were finally impressed enough to reconstruct a sauropod skeleton, and the result was John A. Ryder’s composite mounted skeleton of a ribless, sail-tailed Camarasaurus, complete with a speculated skull. This mount was around 50 ft long and exhibited at a meeting of The American Philosophical Society in Philadelphia in December 1877, but no images of it were not published until 1914. Nor, for that matter, was it accompanied or followed by a life reconstruction. In fact, I don’t know that anyone has attempted to restore Ryder’s Camarasaurus, so I set aside an hour or so in preparation of this article to finally correct this important injustice. I'd love to see more from different artists - #justiceforRydersaurus!

OK, yes, John A. Ryder's 1877 Camarasaurus skeletal is a little bizarre, but the essence of sauropod form is there. It's a stone-cold crime that no one reconstructed the life appearance of this skeleton, so I've had a go here. Some attempt has been made to give the restoration a classical 19th century, Hawkinsian palaeoart flavour.

The absence of an 1877 Camarasaurus life restoration is all the more curious because of Cope’s association with this specimen. Cope is most famous for his feud with Othniel Marsh and the ‘Bone Wars’ period of American vertebrate palaeontology, but he was also one of the main instigators of American palaeoartistry. During the 1860s Cope produced iconic artworks of dinosaurs known from New Jersey which can be considered among the first flesh reconstructions of recognisable, basically anatomically accurate dinosaurs, as well as well-known depictions of taxa from the Western Interior Seaway. He was an advisor in the 1868 reconstruction of Hadrosaurus by Joseph Leidy and Benjamin Waterhouse Hawkins, and thus had connections to the first grandmaster of palaeoart himself, who was often based in the US for palaeoartistic purposes in the 1860s and 1870s. And yet, around all this, Cope never produced a published sauropod life reconstruction, and nor did his relationship with Hawkins yield any (published) sauropod illustrations. We may ascribe the latter to Hawkins’ dislike of Cope, whom he regarded as an overbearing, fussy collaborator. On at least one occasion he threatened to abandon a project entirely if Cope was involved (Bramwell and Peck 2008). Who knows how the early history of American palaeoart would have played out had these two giants of their disciplines been on better terms.

Othniel Marsh's 1883 restoration of Brontosaurus - a significant advance over the Ryder sauropod skeletal of just a few years prior.

Cope was, of course, not the only major player in the discovery of American sauropods. Indeed, Cope’s rival, Marsh, probably has a greater legacy with these animals, not only naming more species but also coining the name ‘Sauropoda’. Marsh named and described many now-iconic sauropods including Brontosaurus, Apatosaurus and Diplodocus, and in 1883 he published a Brontosaurus skeletal reconstruction that was, anatomically speaking, vastly superior to Ryder's Camarasaurus. Marsh was thus another person well-placed to facilitate the first artistic resurrection of sauropod life appearance… if only it weren't for his career-long disdain for palaeoart. Here's what he said on this topic in 1875:

I do not believe it possible at present to make restorations of any of the more important extinct animals of this country that will be of real value to science, or the public. In the few cases where materials exist for a restoration of the skeleton alone, these materials have not yet been worked out with sufficient care to make such a restoration perfectly satisfactory, and to go beyond this would in my judgment almost certainly end in serious mistakes. Where the skeleton, etc., is only partly known, the danger of error is of course much greater, and I would think it is very unwise to attempt restoration, as error in a case of this kind is very difficult to eradicate from the public mind… A few years hence we shall certainly have the material for some good restorations of our wonderful extinct animals, but the time is not yet.

(Marsh 1875, quoted in Dodson 1996, p.74)

Marsh’s criticism of palaeoart has a lot of implications for the development of the discipline in general, and almost certainly contributed to the delayed canonisation of sauropods. He held many of the best cards when it came to understanding sauropod life appearance but was the last person who would include a life restoration in a publication. Moreover, his reputation, influence, and longstanding criticism of palaeoart may have further dampened drives to restore newly discovered taxa in Europe, where some of his fiercest denouncement of palaeoartworks were expressed. Marsh’s views were surely a major contributor to the strange fact that the Bone Wars era - one of the most intense periods of discovery and analysis in early dinosaur history – was entirely bereft of associated palaeoart. And while Cope could, in theory, have picked up these palaeoartistic pieces, the ferocity of his feud with Marsh surely meant that he avoided reconstructing Marsh taxa, no matter how spectacular they were. There’s some irony in Marsh and Cope being so instrumental to our early conceptualisation of sauropods but that their various hang-ups - with each other, with other people, and with palaeoart - only kicked the can further down the road.

Finally, a life reconstruction! ...that everyone ignored

By this time - the late 1870s or early 1880s - sauropods had been known to science for about 40 years, with decent, restorable remains on record for at least half that time. Their gigantic size and spectacular anatomy were well appreciated and, thanks to Marsh, their skeletal anatomy had been committed to scientific literature. In these circumstances, surely someone was going to crack and attempt a flesh restoration? Yes, finally, someone did - but not in either of the historic homes of sauropods, Britain and the US. Rather, it was the French author Nicolas Camille Flammarion who provided the first (to my knowledge) sauropod life restoration in his 1886 book Le Monde Avant la Création de l’Homme, courtesy artist J. Blanedet. Behold:

Finally, a sauropod life restoration! J. Blanedet's 1886 Atlantosaurus poses with an elephant for scale. From Flammarion (1886).

Flammarion’s book is a landmark work for depictions of prehistoric life, containing a mix of old and new restorations that went some way to relieving the drought of new reconstructions in the late 19th century. Perhaps reflecting Flammarion’s outsider position from sauropod research, his choice of sauropod was not something well-known like Cetiosaurus, Camarasaurus or Brontosaurus, but the obscure “Atlantosaurus”. This was one of the first discovered Morisson Formation sauropods but, on account of its scrappy remains, it was on its way to becoming a historic footnote in 1886. Today, Atlantosaurus is generally considered a nomen dubium. Obscure taxon choice aside, here, finally, was a sauropod in the flesh. And, all things considered, the reconstruction was pretty good. Marsh’s 1883 Brontosaurus reconstruction was featured in the same book and its shared DNA with the Atlantosaurus illustration is obvious. In the accompanying text, Flammarion describes several sauropods in essentially accurate ways: as gigantic, long-necked animals with small heads, of herbivorous character, and as denizens of terra firma, not lakes and swamps. This was a pretty progressive take on sauropods that built on ideas expressed by Phillips, and they stand in contrast with sauropods’ fast approaching 20th-century relegation to semi-aquatic life.

In a different universe, Flammarion’s Atlantosaurus and other novel reconstructions were the start of a new wave of palaeoartworks based on updated science and newly discovered species. Alas, in our universe, the new artworks in Flammarion’s book made little impression on palaeoart development, and didn’t shake older takes on extinct animals from their foothold in 19th century palaeoart. Even as the 20th century loomed, Hawkinsian, Kuwassegian and Copeian dinosaurs were still populating artworks of Deep Time. From a historic perspective, Flammarion’s Atlantosaurus is more of an Easter egg than the moment sauropod palaeoart truly arrived.

The 1890s: the dam bursts

Joseph Smit's 1892 Brontosaurus, from Henry Hutchinson's Extinct Monsters: A Popular Account of Some of the Larger Forms of Ancient Animal Life. Although not as influential or well known today as the sauropod artworks of Charles Knight, the success of Hutchinson's book would have made this the first life restoration seen by many people, certainly in the English speaking world.

It was only as the sandgrains in the 19th century hourglass ran dry that a collective epiphany about sauropods struck the minds of museum developers, artists and book authors around the world. Finally, after more than a half-century of avoiding sauropod palaeoart, flesh restorations of long-necked dinosaurs entered the mainstream during the 1890s. But, again, it was not America, with its embarrassment of sauropod fossils, that instigated this. Rather, it was a revived British interest in palaeoart that championed sauropods, with one book, in particular, cresting a new wave of new palaeoartistic reconstructions: Henry Neville Hutchinson’s 1892 ;Extinct Monsters: A Popular Account of Some of the Larger Forms of Ancient Animal Life. This featured illustrations by the Danish artist Joseph Smit based on Marsh's skeletal diagrams and the results were so successful that Extinct Monsters was reprinted several times over the next two decades. It was also eventually repackaged with another Hutchinson book, Creatures of Other Days. Smit illustrated both Diplodocus and Brontosaurus in these works, based on Marsh's groundwork, establishing their canonical presence in palaeoart from then onwards.

One of the most iconic palaeoart images of the late 19th century: Charles Knight's 1897 swamp-bound Brontosaurus and grazing Diplodocus. Knight's affiliation with the American Museum of Natural History and the publicity-hungry Henry Osborn brought palaeoart into a new era where dinosaurs would become increasingly dominant art subjects, and sauropods would become superstars.

Shortly after, American palaeoart finally woke up to the splendour of sauropods. The American Museum of Natural History, under the supervision of Henry Osborn, had identified the power of palaeoart as an educational, promotional and commercial tool and realised the role dinosaurs could play in this campaign. The result were sauropod illustrations by Charles Knight, which surely rank as the most famous of all early sauropod artworks. Knight’s iconic 1897 Brontosaurus and Diplodocus in a swamp, produced with direction from Osborn, was among the first of these works, but a lesser-known sketch of a snorkelling Amphicoelias was produced around the same time. The latter is notable for being produced under guidance from Cope, who sketched a rough version for Knight to replicate. Cope’s choice to depict the fragmentarily known Amphicoelias, which he named in 1878, over a better-known Marsh species is surely an instance of their old rivalry dying hard. Many Knight images of sauropods would follow in the next few decades.

In the last year of his life, Edward Drinker Cope tutored Charles Knight in the anatomy of extinct animals so as to help Knight better understand his palaeoart subjects. Among the images they worked on together was this 1897 scene of Amphicoelias, which Cope sketched out for Knight to replicate. Note the interesting stripes and spotting used here. Although now standard in palaeoartworks, such intricate patterning was rare in 19th century palaeoart.

And it’s here, at the turn of the 20th century, that our story picks up with more familiar beats. After their slow adoption into palaeoart and popularised palaeontology, sauropods quickly appeared everywhere dinosaurs were mentioned. American museums put sauropods front and centre of their galleries and, courtesy of Andrew Carnegie, many museums around the world soon sported Diplodocus in their dinosaur halls. Gertie the Dinosaur and the 1925 adaption of The Lost World, where Brontosaurus pioneered cinematic monsters smashing cities for our amusement, made sauropods the focus of early dinosaur films. Life-sized models of sauropods appeared in Europe by 1910 and then in the United States and Russia in the 1930s. Around all this, artists like Knight, Smit, Heinrich Harder and Alice Woodward cemented sauropods into the mainstream palaeoart canon. Surely helped by their palaeoartistic popularity, sauropods had become cultural icons almost overnight.

The story of sauropods entering palaeoart canon is more than a tale of 19th century attitudes to reconstructing extinct animals: it’s also a case study in the vagaries of science communication and gatekeeping. We often discuss why certain facets of science, like dinosaurs, are so popular, while others are not. How much of this reflects the inexplicable, innate interestingness of a topic, and how much of it is manufactured? Many of us would agree that sauropods are some of the most fascinating and spectacular animals to have ever lived but, even when their anatomy was well-realised, this was not enough for mainstream culture to adopt them passively. Even artists and scientists who knew about them were not falling over themselves to restore and promote them, and it really wasn’t until individuals at the turn of the 20th century wanted, or needed, to promote sauropods that they began their journey towards being palaeontological icons. I’ve argued in the past that dinosaurs have a certain fundamental appeal that draws us to them, and that might be true, but stories like this show that our awareness and access to spectacular, easy-sell science, such as that of the biggest dinosaurs to have ever existed, is managed by a privileged few.

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References

  • Bramwell, V., & Peck, R. M. (2008). All in the bones: a biography of Benjamin Waterhouse Hawkins. Academy of Natural Sciences.
  • Dodson, P. (1998). The horned dinosaurs: a natural history. Princeton University Press.
  • Flammarion, C. (1886). Le monde avant la création de l'homme: origines de la terre, origines de la vie, origines de l'humanité. C. Marpon et E. Flammarion.
  • Hallett, M., & Wedel, M. J. (2016). The sauropod dinosaurs: life in the age of giants. JHU Press.
  • Nieuwland, I. (2019). American Dinosaur Abroad: A Cultural History of Carnegie's Plaster Diplodocus. University of Pittsburgh Press.
  • Phillips, J. (1871). Geology of Oxford and the Valley of the Thames. Clarendon 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.
  • Taylor, M. P. (2010). Sauropod dinosaur research: a historical review. Geological Society, London, Special Publications, 343(1), 361-386.


Thursday, 28 October 2021

Theropod dinosaurs were a bunch of buttheads: the evidence for and development of ideas around theropod cranial combat

When it comes to imagining aggressive behaviour between large Mesozoic theropod dinosaurs, the main game in town is head-biting: individuals grappling with one another by locking jaws around each other’s faces (Tanke and Currie 1998; Peterson et al. 2009). Such actions are well-evidenced by the sometimes significant trauma found on theropod skull fossils, including tooth marks, gouges, and even teeth embedded in facial bones. Clearly, head-biting was a dangerous, bloody activity that could lead to significant injury, and we have to wonder if theropods might have had means of physically settling their differences without tearing each other’s faces apart. After all, while some modern animals don’t have much behavioural grey space between ‘idle’ and ‘psycho’, many species employ means of fighting that prevent, or at least diminish, the need for more violent encounters.

One non-lethal means of theropod interaction explored in dinosaur literature is head-butting, where the various crests, horns and bosses adorning their skulls are transformed into bludgeons, clubs and shoving aids. We don’t see or read much about theropods employing these behaviours in dinosaur popular culture despite its obvious appeal - if you don't find the idea of heckin' big predatory dinosaurs shoving each other around with their heads at least a little bit awesome, you might want to see a doctor. But, actually, theropod head-butting has a reasonable foothold in dinosaur technical literature, with some studies even dedicated to determining its feasibility.

Among the earliest proponents of theropod head-butting were Robert Bakker and Gregory S. Paul, who've been illustrating this behaviour and the anatomy related to it for decades. From left to right: Bakker's (1986) diagram of theropod head ornaments related to head-butting; Paul's (1987, but published in 1988) fantastic flank-butting Ceratosaurus; and a more recent Bakker work showing head-butting Tyrannosaurus from the Beyond Bones blog.
So far as I’m aware, the concept of theropod head-butting was a product of the Dinosaur Renaissance, perhaps an unsurprising occurrence given that it involves regarding theropods as relatively sophisticated, behaviourally-complex animals rather than the pea-brained dullards of pre-Renaissance times. Two of the most influential figures of that revolution - Bob Bakker and Gregory S. Paul - were strong advocates for theropod head-butting. Their famous books The Dinosaur Heresies (Bakker 1986) and Predatory Dinosaurs of the World (Paul 1988) both proposed that theropods engaged in these behaviours (above). Bakker’s take interpreted the stout ridges and crests of theropods such as Allosaurus and Tyrannosaurus as weapons for butting bouts and stressed their significance as nonlethal fighting devices. Paul considered head-butting likely for most theropods with robust cranial ornaments, from the elaborately horned Ceratosaurus and Carnotaurus to the massively-skulled tyrannosaurs. Paul favourably compared the various horns and bosses of such animals to those of giraffes (which, of course, are renowned head clubbers) and has maintained such views in more recent works (e.g. Paul 2016). I’m curious as to whether Bakker and Paul's affinity for drawing theropods played into the formation of these ideas, as they both were among the strongest critics of pre-Renaissance artists for not capturing the diverse morphologies and ornaments of theropod skulls and produced many artworks showing more accurate theropod depictions. Might their more precise renderings of theropod skulls have made them ponder the function of the bosses, ridges and crests they were illustrating?

In subsequent decades theropod head-butting has been mentioned semi-often by theropod workers. A minority of workers have been negative and dismissive of the idea (e.g. Rowe 1989; Molnar and Farlow 1990), but it’s mostly brought up in a confirmatory sense. Most discussions have centred around a few clades - tyrannosaurids (e.g. Bakker 1986, Paul 1988, 2016), carcharodontosaurids (e.g. Sereno and Brusatte 2008; Cau et al. 2013) and especially abelisaurids (e.g. Novas 1989; Mazzetta et al. 1998, 2009; Hieronymus 2009; Snively et al. 2011; Delcourt 2018; Cerroni et al. 2021) - and we now have a suite of typical anatomical features identified as potential head-butting structures, as well as dedicated biomechanical investigations into the plausibility of theropod skull combat (Mazzetta et al. 1998, 2009; Snively et al. 2011; Xing et al. 2015). Evidently, the concept of theropod head-butting is not - as is sometimes the case - an over-eccentric hangover from a particularly adventurous period of dinosaur research, but a legitimate and current behavioural hypothesis supported by a growing amount of data.

The postorbital bone of the carcharodontosaurid Eocarcharia dinops and its prominent orbital boss: a structure made for lateral head-butting? From Sereno and Brusatte (2008).
Let's get into this a little more: what, exactly, are the structures theropod workers are linking to head-butting? As will be well-known to anyone reading this blog, theropods were prone to augmenting their skulls with ridges, bosses, crests and horns, most commonly along the top of the snout and above their eyes. It’s among these that we find potential head-butting structures, but it's not thought that any and all ornaments were suitable for head-butting. Some theropod crests were surely too delicate for physical aggression, probably even allowing for the strengthening properties of their overlying skin tissues (see below). It’s hard to believe that the thin, tall crests of Dilophosaurus were being smacked into other animals, for example, and they instead surely served a purely signalling role (Bakker 1986; Rowe 1989). Indeed, studies of the Dilophosaurus-like crests of Sinosaurus found that they were prone to structural failure under mechanical loading (Xing et al. 2015), and likely ill-suited to weaponisation.

The 'Trix' specimen of Tyrannosaurus, on display in Glasgow 2019, showing the massive postorbital bosses which dominate the posterior skull region of this species. Researchers have associated these with head-butting behaviour, which seems reasonable given their structure, location, and the general grumpy attitude evidenced for Tyrannosaurus.
Head-butting structures are better inferred from the sizeable, prominent and robust components adorning certain theropod skulls. In carcharodontosaurids, ornament indicative of head-butting consists of swollen, laterally-prominent bosses above their eyes (Sereno and Brusatte 2008) or, more unusually, dorsally-prominent domes in the same region (Cau et al. 2017). Unfortunately, taxa with these features - Eocharchia and Sauroniops - are not especially well-known so we can’t see if these features were somehow echoed across the rest of the skull: might they have sported other enhanced bosses and ridges as well? This is not a problem for tyrannosaurids, of course, which have skulls of extreme familiarity to theropod researchers. Both Bakker (1986) and Paul (1988, 2016) have linked the robust nasal bones (forming the top of the snout), lacrimal cornual processes (horns in front of the eye) and postorbital bosses (swollen, rounded structures behind the eye) of tyrannosaurs with head-butting behaviour. Predictions of armoured skin around their eyes and snout (Carr et al. 2017) are consistent with this idea, too. Tyrannosaurus needs special mention here for its uniqueness among theropods - even other tyrannosaurs - in having flattened its lacrimal cornual processes into swollen, highly-textured expansions of the skull roof and inflated its postorbital bosses to a great extent, sometimes even capping the latter with osteoderms (Carr et al. 2017). The enlarged postorbital bosses are among the tallest parts of the skull and also project outward from the eye socket by a considerable margin. Significant rugosities and other properties of these lacrimal and postorbital features indicate a covering of especially thick, toughened skin, but no true horns (despite what you see in lots of artwork and films, there’s nothing pointed or horn-shaped about the ornament of big T. rex specimens). If Bakker and Paul are correct in Tyrannosaurus having a head adapted for head-butting, it’s difficult not to see this reconfiguration as the skull of a theropodan bulldozer: a flattened, shovel-shaped cranium to heave and bash other animals around with.

Tyrannosaurus is unusual among tyrannosaurids for lacking a hornlet in front of the eye, but it compensated for this with armoured cranial skin and two prominent postorbital bosses. Bolted to something like six or more tonnes of angry tyrannosaur, this must have made for one heck of a battering ram. So let's see... if there's BRONTOSMASH!ArSUMOitherium, then this must be... TYRANNOBUTT? Yes, make it so.
Neither tyrannosaurs nor carcharodontosaurid head-butting has received much in the way of dedicated research attention, however, leaving our best insights into this behaviour coming from abelisaurs, especially Carnotaurus. The head-butting potential of these short- and gnarly-faced, sometimes horned theropods has been remarked on for decades (e.g. Paul 1988; Novas 1989; Mazzetta et al. 1998) and, via Carnotaurus, encouraged several rounds of dedicated biomechanical investigation (Mazzetta et al. 1998, 2009; Snively et al. 2011; Méndez 2012). These initially regarded Carnotaurus cranial combat as a brutal affair, with spinal dampening allowing combatants to impact their heads at rhinoceros-grade speeds of 20 kph (Mazetta et al. 1998). But subsequent investigations have curbed these ideas somewhat, finding that Carnotaurus skulls were incapable of sustaining strong forces during simulated head-butting (Mazetta et al. 2009). Instead, their skulls were better suited to low-velocity impacts, blows that targeted softer parts of animal bodies (e.g. flank butting), or maybe even quasi-static bouts of head-shoving (Mazzetta et al. 2009). This isn’t too surprising: Carnotaurus is a relatively robustly-skulled theropod, but its cranium is still a relatively vacuous, air-filled structure adaptively balancing maximised strength and minimised weight. Compared to the massive and thickened skulls of more dedicated headbutters, theropod skulls look relatively delicate. Abelisaur necks are no longer considered shock absorbers for running impacts either, but their recognition as strong, powerful elements means they still have a role in head-butting hypotheses (Méndez 2012): the utility of a powerful neck in energetic, sustained use of a weaponised head is obvious (Delcourt 2018).

Epidermal correlates covering the heads of abelisaur species, from Delcourt (2018). Carnotaurus stands out with its indications of especially reinforced, cornified snout and horn tissues - a 'carnivorous bull' indeed.
Further information on abelisaur head-butting stems from their facial skin. The rugose surface textures of abelisaur skulls are indicative of particular skin types, such as cornified sheaths (think bird beaks and cow horns), cornified pads (muskox heads) or thickened, armoured dermis (rhino and hippo skin) (Sampson and Witmer 2007; Hieronymus 2009; Delcourt 2018; Cerroni et al. 2021; Hendrickx and Bell 2021). These are exactly the tough, reinforced skin types we’d expect to see in animals that used their heads as clubs or shoving implements, and it’s been noted that these dermal types, in extant animals, correlate with intraspecific fighting (Hieronymus 2009). We’ve touched on these data before, discussing that abelisaur faces may have looked quite different to their skulls thanks to thick skin. This is especially so for Carnotaurus, which had a snout covered by an extensive cornified pad. Because the evidence for thick, armoured skin on abelisaur faces is especially prominent compared to other theropods, it seems reasonable to infer a behavioural emphasis on head-butting within the group.

Carnotaurus sastrei, a species that - among theropods at least - is probably the most head-butting adapted of all. Exactly how its head, equipped with a cornified pad and sheathed horns, was used in aggressive behaviours has been interpreted differently over the years and boils down to assumptions of shock-absorption capability: was it a high-impact or low-impact headbutter, a shover, or a flank-butter? Whichever it was, it certainly looked awesome.
But these neat dermal insights bring complications along with insight, adding important caveats to the biomechanical studies outlined above. We know from living animals that head-butting capability is best modelled by factoring both bony and soft-tissue data (e.g. Drake et al. 2016), and that such simulations can turn bone-only models of skull strength on their heads. So far as I know, no studies of abelisaur cranial strength in head-butting simulations have modelled their armoured and cornified skin tissues yet, and so we await such analyses before real confidence can be drawn about abelisaur head-butting capability. The same is true, of course, of any other theropod we’d want to investigate head-butting behaviour for. I'm sure I'm not the only one thinking such studies, and other insights into this relatively unexplored but fascinating facet of theropod palaeobiology, would be very welcome additions to dinosaur research.

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References

  • Bakker, R. T. (1986). The dinosaur heresies: new theories unlocking the mystery of the dinosaurs and their extinction. William Morrow.
  • Cau, A., Dalla Vecchia, F. M., & Fabbri, M. (2013). A thick-skulled theropod (Dinosauria, Saurischia) from the Upper Cretaceous of Morocco with implications for carcharodontosaurid cranial evolution. Cretaceous Research, 40, 251-260.
  • Carr, T. D., Varricchio, D. J., Sedlmayr, J. C., Roberts, E. M., & Moore, J. R. (2017). A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports, 7(1), 1-11.
  • Cerroni, M. A., Canale, J. I., & Novas, F. E. (2021). The skull of Carnotaurus sastrei Bonaparte 1985 revisited: insights from craniofacial bones, palate and lower jaw. Historical Biology, 33(10), 2444-2485.
  • Delcourt, R. (2018). Ceratosaur palaeobiology: new insights on evolution and ecology of the southern rulers. Scientific reports, 8(1), 1-12.
  • Drake, A., Donahue, T. L. H., Stansloski, M., Fox, K., Wheatley, B. B., & Donahue, S. W. (2016). Horn and horn core trabecular bone of bighorn sheep rams absorbs impact energy and reduces brain cavity accelerations during high impact ramming of the skull. Acta biomaterialia, 44, 41-50.
  • Hieronymus, T. L. (2009). Osteological Correlates of Cephalic Skin Structures in Amniota: Documenting the Evolution of Display and Feeding Structures with Fossil Data (Doctoral dissertation, Ohio University).
  • Mazzetta, G. V., Fariña, R. A., & Vizcaíno, S. F. (1998). On the palaeobiology of the South American horned theropod Carnotaurus sastrei Bonaparte. Gaia, 15(185), 192.
  • Mazzetta, G. V., Cisilino, A. P., Blanco, R. E., & Calvo, N. (2009). Cranial mechanics and functional interpretation of the horned carnivorous dinosaur Carnotaurus sastrei. Journal of Vertebrate Paleontology, 29(3), 822-830.
  • Méndez, A. H. (2012). The cervical vertebrae of the Late Cretaceous abelisaurid dinosaur Carnotaurus sastrei. Acta Palaeontologica Polonica, 59(3), 569-579.
  • Molnar, R. E., & Farlow, J. O. (1990). Carnosaur paleobiology. In: Weishampel, D. B., Dodson, P., & Osmólska, H. (eds.). The Dinosauria. University of California Press. 210-224 pp.
  • Novas, F. E. (1989). Los dinosaurios carnívoros de la Argentina. PhD thesis, La Plata: Universidad Nacional de La Plata.
  • Paul, G. S. (1988). Predatory dinosaurs of the world: a complete illustrated guide. Simon & Schuster.
  • Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs. Princeton University Press.
  • Peterson, J. E., Henderson, M. D., Scherer, R. P., & Vittore, C. P. (2009). Face biting on a juvenile tyrannosaurid and behavioral implications. Palaios, 24(11), 780-784.
  • Rowe, T. (1989). The early history of theropods. Short Courses in Paleontology, 2, 100-112.
  • Sampson, S. D., & Witmer, L. M. (2007). Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology, 27(S2), 32-104.
  • Sereno, P. C., & Brusatte, S. L. (2008). Basal abelisaurid and carcharodontosaurid theropods from the Lower Cretaceous Elrhaz Formation of Niger. Acta Palaeontologica Polonica, 53(1), 15-46.
  • Snively, E., Cotton, J. R., Witmer, L., Ridgely, R., & Theodor, J. (2011). Finite Element Comparison of Cranial Sinus Function in the Dinosaur Majungasaurus and Head-Clubbing Giraffes. In Summer Bioengineering Conference (Vol. 54587, pp. 1075-1076). American Society of Mechanical Engineers.
  • Tanke, D. H., & Currie, P. J. (1998). Head-biting behavior in theropod dinosaurs: paleopathological evidence. GAIA: revista de geociências, (15), 167.
  • Xing, L., Wang, Y., Snively, E., Zhang, J., Dong, Z., Burns, M. E., & Currie, P. J. (2015). Model-based identification of mechanical characteristics of Sinosaurus (Theropoda) crests. Acta Geologica Sinica, 89(1), 1-11.


Monday, 27 September 2021

A tale of plesiosaur tails: vertical fins or horizontal flukes?

The giant elasmosaurid Albertonectes vanderveldei forages for invertebrates and small prey deep underwater. From this posterolateral view, the vertical tail fin is unmissable - but should I have drawn it as a horizontal fluke instead? Welcome to yet another challenge for restoring the life appearance of plesiosaurs!
It’s fair to assume that, when painting or sculpting plesiosaurs, most palaeoartists favour attention to their heads, necks and flippers, these being the most characteristic parts of their anatomy and the components most of our audience will focus on. Plesiosaurs are, of course, famously tricky animals to restore with any degree of certainty, their body plans being entirely unlike anything alive today, their mechanism of swimming - underwater flight with two sets of flippers - being the source of much debate and controversy, and their fossil record giving us few direct insights into their soft-tissue anatomy. So here’s more good news: in recent years another part of plesiosaur anatomy has joined their flippers and necks in artistic and scientific contention, their tails.

Plesiosaur tails have traditionally been little more than afterthoughts in palaeoartworks: cone-shaped structures tapering from the body without much in the way of interesting features. In the last decade or so, however, research interest in plesiosaur caudal anatomy and the resurrection of certain historic observations (e.g. Dames 1895; Smith 2007, 2013; Wilhem 2010; Sennikov 2015, 2019; Otero et al. 2018) has seen plesiosaurs with more interesting tails making regular palaeoartistic appearances. This artistic shift initially showed plesiosaur tails having fish- or ichthyosaur-like vertical fins but, more recently, newer research has made a case for another configuration, horizontal tail flukes (note the terminological distinctions), and such reconstructions are now also appearing with regularity. These fins and flukes, it must be stressed, are not mere whimsy or speculation but based on osteological correlates for some kind of extensive skin structure around the tail tip, and we should clarify that no-one thinks these represent a hitherto unappreciated propulsive organ - plesiosaurs do not suddenly have five ‘engines’ for swimming. Instead, these fins or flukes surely represent devices to act as some kind of rudder or stabilising aid, perhaps helping to offset the impact of swimming around with those giant necks and heads.

Recent skeletal reconstructions of plesiosaurs (or parts thereof) showing different interpretations of caudal rudder anatomy. It is increasingly common to see these features in plesiosaur skeletals and this compilation image could be much bigger, but I've restricted it to those from papers specifically making cases for fins or flukes.

One thing is clear: the evidence for tail rudders in plesiosaurs is pretty strong in several plesiosaur clades and any credible palaeoart of these animals should show them with some kind of fin, flipper or fluke at the tail tip. But, clearly, our current conflicting interpretations of plesiosaur tail anatomy can’t both be correct. I’ve gone back and forth on these ideas in my plesiosaur art over the last couple of years and decided that it was time I looked into this in more detail. What is the evidence for tail fins or flukes in plesiosaurs, and which is most compellingly argued for? Can we even make a call on this topic at the moment? Let's find out.

One of several plesiosaur artworks I've drawn recently showing a fluked tail, rather than (as was my previous preference) a fin. This is Plesiosaurus dolichodeirus scavenging a pterosaur carcass, because plesiosaurs are meant to eat pterosaurs in palaeoart, consarnit.

Something old is new... etc. etc.

First, let's briefly familiarise ourselves with the history of this controversy. It may seem that notions about plesiosaur caudal fins and flukes are part of the Brave New World of changing up old reconstructions of fossil reptiles for radical new ones, but that’s not the case here. Actually, osteological features and soft-tissue remains evidencing caudal rudders in plesiosaurs were identified in the 19th century, and even the dichotomy of interpretation between fins vs. flukes is over 100 years old. Our modern discussions of these concepts are a revival of relatively early investigations into plesiosaur functional morphology and life appearance.

The holotype of Seeleyosaurus guilelmiimperatoris, famous for having a soft-tissue outline around its tail. This specimen was the only plesiosaur fossil on record with direct bearing on the fin vs. flipper controversy, but the tail soft-tissues have been painted over and are no longer accessible for study. Yeah, frustrating, right? From Dames (1895).

The concept of plesiosaur caudal fins was first broached by Richard Owen, who proposed that lateral compression of the terminal tail vertebrae of Archaeonectrus rostratus indicated a caudal fin (Owen 1865). Owen’s observation had little impact on reconstructions of plesiosaurs at the time, but seeming confirmation of his prediction arrived a few decades later when, in 1895, a specimen of the Jurassic plesiosaur Seeleyosaurus guilelmiimperatoris was described with a soft-tissue outline around much of tail tip (Dames 1895). To date, this specimen remains the only fossil on record that provides direct confirmation of a caudal fin or fluke but, alas, it can no longer be investigated or even validated as the soft tissue component of the fossil has been painted over (BUT - see update at the end of the post). This presents a problem deeper than merely obscuring the body outline. Many marine reptile specimens were often ‘improved’ with forged soft-tissues and realigned bones by 19th century preparators such that anything especially amazing and interesting - like the only known plesiosaur tail fin outline, for instance - really needs verification from modern researchers to be accepted as genuine. I’m not aware of any plesiosaur experts who consider the Seeleysoaurus soft-tissues especially suspicious, but this inescapable caveat hangs around any discussion of this specimen: we can only put so much stock in any interpretation of it, modern or historic. This said, scholars of the late 1800s certainly regarded the body outline as genuine, leading to a few late 19th and 20th-century palaeoartworks in which Seeleyosaurus and other plesiosaurs sported tall, diamond-shaped tail fins. Among the most famous of these were the reconstructions published in Wilhelm Dames' 1895 Die plesiosaurier der süddeutschen Liasformation and the generic pliosaurid reconstruction published by Newman and Tarlo (1967).

Neither finned nor fluked plesiosaurs really caught on in historic palaeoart, but finned reconstructions almost did. Here's a rarely seen example: Woodward's (1896) reconstruction of "Plesiosaurusmacrocephalus, from A Guide to the fossil reptiles, amphibians, and fishes in the Department of Geology and Palaeontology of the British Museum (Natural History).

Not everyone accepted Seeleyosaurus as evidence of caudal fins in plesiosaurs, however. Both Fraas (1910) and Wegner (1914) felt that their caudal skeletons were indicative of a horizontal fluke, citing the absence of a tail bend, the dorsoventral flexibility of the vertebrae, and the size of the caudal ribs as evidence of this feature. I’m not aware of any historic reconstructions showing this configuration (this is not to say that none exist, of course) and assume that fluked plesiosaurs gained even less traction in technical literature and artwork than their finned counterparts. This left most academic and artistic consideration of plesiosaur caudal anatomy assuming featureless, tapering tails for the next century, despite the continued cataloguing of peculiar caudal anatomy in plesiosaurs - most notably, their fused terminal tail vertebrae, recalling the pygostyles of birds (see review by Smith 2013). Today, such structures are considered part of the evidence package for a caudal rudder, but this significance seems to have been mostly overlooked in older publications.

Evidence for fins, evidence for flukes

The story of plesiosaur caudal rudders is thus one of three parts: an initial set of pro-rudder proposals and observations; a period of relative disinterest in the idea; and our modern era of belated engagement with those original hypotheses. This latter stage began about 10-15 years ago when observations made by Owen and Dames were resurrected and augmented by modern plesiosaur experts to make a case for plesiosaur tail fins. Perhaps the most in-depth investigations supporting finned tails to date are those by Benjamin C. Wilhelm (2010) and Adam Stuart Smith (2007, 2013), both of whom looked at the tails of Jurassic plesiosaurs and identified features also seen in swimming animals with vertical caudal fins. Using the relatively completely known tails of the cryptoclidids Cryptoclidus and Muraenosaurus, Wilhelm (2010) catalogued a suite of anatomies correlating with vertical fin lobes, including a relatively large neural spine close to the tail tip (the 17th caudal vertebra in Cryptoclidus); several neural spines with expanded ends; a shift in the orientation of the neural spines at the tip of the tail (from posteriorly-directed to anteriorly-directed) and lateral compression of the terminal caudal vertebrae (see diagram, above). These features recall the finned tails of mosasaurs, Triassic ichthyosaurs and thalattosuchians (e.g. Lindgren et al. 2013; Renesto et al. 2020), where enlarged neural spines mark the start of a caudal fin and shifting neural spine orientations characterise the vertebrae embedded in the fin itself. As with tail-finned reptiles and fish, plesiosaur tails had increased flexion in two regions, both at the tail base and immediately anterior to the enlarged and reorientated neural spines. A slight vertical peduncle - a thinning of the tail structure to minimise its drag profile when being moved through water - was also identified anterior to the enlarged neural spine region. By analogy with the preserved soft-tissues of other marine reptiles, Wilhelm’s study allowed for a prediction of the possible fin outline for cryptoclidids: a small triangular lobe with a concave posterior margin on the upper side of the tail (above). This is quite different from the diamond-shape interpreted by Dames and others from the Seeleyosaurus fossil, but Wilhem’s thesis argues that a large ventral lobe is not suggested by that fossil and we can infer - if Wilhelm’s reconstruction is correct - that only a small amount of material is missing from the dorsal margin (see diagram, below).

Advocates for plesiosaur tail fins highlight similarities between their tail anatomy (see illustrations, above) and those of certain finned marine reptiles, such as early ichthyosaurs and mosasaurs. There are indeed obvious similarities, although the plesiosaur fin supports are clearly far less developed than the examples shown here - a reflection, almost certainly, of tails being adapted for locomotion vs. those adapted for ruddering. Images from Renesto et al. (2020) and Lindgren et al. (2013).

Although working with more fragmentary material, Smith (2007, 2013) found similar features to those reported in Benjamin Wilhelm’s thesis, as well as further evidence of finned tails. This included lateral compression at the tail tip of Rhomaeleosaurus, as well as peculiar ‘node’ vertebrae that might indicate a zone of flexion or even a slight downturn of the tail tip - another feature of finned tails. A wedge-shaped vertebra was noted in another rhomaleosaurid, Macroplata, which might indicate a slight tail downturn, although this taxon curiously lacks laterally compressed distal vertebrae. Agreeing with Benjamin Wilhelm’s thesis, as well as Wilhelm and O’Keefe’s (2010) examination of further caudal material, Adam's study concluded that the flexibility evidenced in the proximal tail region would allow the caudal fin of plesiosaurs to augment steering and stability.

A few years after these works reignited interest in plesiosaur caudal rudders, artistic and academic champions of fluked plesiosaurs also resurrected, retooled and expanded the initial observations and arguments made by Fraas and Wegner (e.g. Sennikov 2015, 2019; Otero et al. 2018). At the core of these proposals were ideas that plesiosaur tails were more convergent with those of whales and manatees than with swimming reptiles or fish, and thus suited to dorsoventral motion and sporting horizontally-aligned soft-tissues at their tips. Some researchers have endorsed this idea by including fluked reconstructions in their papers (e.g. Sachs et al. 2016). 

Were plesiosaur tails reptilian variants of sirenian-like caudal anatomy? Again, there are similarities, especially in the great width of the vertebrae. In lieu of decent sirenian skeletons online, I've borrowed these Florida manatee (Trichechus manatus) skeleton replica images from Bone Clones.

Some of the evidence for plesiosaur flukes is the same as that used for finned reconstructions, such as the two zones of flexion in the plesiosaur caudal skeleton, and the recognition of a distinctive, often stiffened vertebral region at the end of the tail (Sennikov 2015, 2019). This is representative of fluked and finned tails having functional similarity, each essentially being the same thing operating in different planes. Fluke-specific evidence includes the presence of long caudal ribs along much of the tail length which, in making some vertebrae wider than tall, are suggested to create a relatively wide, flat tail with restricted lateral movement (Sennikov 2015, 2019; Otero et al. 2018). Otero et al. (2018) noted that the tips of the caudal ribs of Aristonectes are fibrous for potential attachment of extensive soft-tissue, potentially implying a much wider tail than shown by osteology alone (something seemingly confirmed by soft-tissue data of Mauriciosaurus). The absence of convincing downturned tail tips has also been flagged up, even for taxa with ‘node’ vertebrae (Otero et al. 2018), and has been negatively compared against the finned condition of ichthyosaurs and marine crocodylomorphs (Sennikov 2019). The small size or absence of chevrons, and the low, variable orientation of caudal neural spines, are features thought to have allowed the fluke to move vertically and independently of the rest of the tail (Otero et al. 2018; Sennikov 2019). The plesiosaur torso - a pachyostotic, relatively inflexible trunk - has also been regarded as similar to that of sirenians and thus potentially indicative of a fluked tail (Sennikov 2019). For the fluke model to be correct, of course, the traditional interpretation of Seeleyosaurus having some kind of tail fin has to be wrong. Sennikov (2019) states that this is indeed the case, and provides an alternative view where the Seeleyosaurus soft-tissues represent a horizontally-aligned structure within which the vertebrae have fallen over. The asymmetry of the fluke as preserved is explained as a result of vertebral displacement, soft-tissue decay and incomplete fossilisation.

Problematic as it is, proposals of plesiosaur rudder shape have to contend with the now-lost Seeleyosaurus data to some extent. Some fin models posit that not much has happened to the caudal region of the Seeleyosaurus holotype, whereas the fluke model requires a little more modification. While the fin model seems simplest, the fluke version hardly seems implausible.

Fins vs. flukes, head to head (er... tail to tail?)

Having briefly reviewed this evidence, can we see which of these models seems strongest? I stress my word choice in that sentence: our understanding of plesiosaur soft-tissues is not yet sufficient to make claims of absolute certainty, so any conversation on them should be peppered with appropriate caveats and considerations. This is a case where it’s much easier to be a researching scientist, where “we don’t yet know” is a perfectly acceptable response, than a palaeoartist, where you have to come down on one side of a debate or another. So, with the proviso that I’m not sure we can really make a definitive call yet… and with some urging of readers to check the papers mentioned above for themselves to make up their own minds... and with appropriate caution… and having now run out of ways to stall writing this sentence... I find myself... more persuaded by arguments for a tail fin at present. The fin hypothesis seems to explain more of the peculiar anatomy of plesiosaur tail tips than its rival, and it presents an overall simpler, and thus more likely correct, interpretation of our available data. The highlighted similarities between plesiosaur tails and those of certain other fin-tailed swimming reptiles are prudent observations not yet accounted for in the fluke model and, when thinking about the evolution of such features, it seems a shorter developmental distance for a plesiosaur to evolve a fin than a fluke. I’m especially thinking of the switch from primarily lateral to vertical spinal flexion, the former being ancestral to reptiles and thus common to many in swimming reptile species. Significant vertical caudal flexion has developed among diapsids of course, in birds, and some swimming birds even use their tail fans in a rudder-like fashion (Felice and O’Connor 2014), so we shouldn’t rule out this capability for plesiosaurs entirely. Moreover, this is not to say that the observations from Team Fluke are redundant. Maybe the wide, potentially muscular tails of plesiosaurs were indeed capable of an unusual amount of vertical motion, even with a fin? If, indeed, plesiosaur tails operated as ruddering aids, some surely had a big job on their hands: there’s no way moving those giant necks and heads didn’t have a tremendous rotational impact when swimming and their tails may have had an important role in keeping their owners on course. A weedy tail with limited mobility in either plane might not have been up to that task. It would be neat to see simulations of this sort of thing.

I also agree with Wilhelm’s (2010) assessment of the Seeleyosaurus tail outline, which looks - so far as can be seen in Dames’ (1895) illustrations, more like a vertical structure than a horizontal one. I’m not sure how much stock we should place in interpretations of the drawings of this specimen given that the original soft tissues are now inaccessible, but, for what it’s worth, the relatively neat margins and asymmetry of the tissue outline, the general position of the vertebrae and location of possible ‘fin’ tissues above the tallest neural spines look consistent with a small dorsal lobe (sensu Wilhelm 2010), while a fluked interpretation relies on a fair amount of distortion from decay and disarticulation. But there is certainly plenty of ambiguity around that specimen and I could be convinced otherwise. Needless to say, more plesiosaur specimens with soft-tissues preserved around the tail tip would be incredibly useful in this discussion.

Plesiosauria was a diverse group with a huge array of body proportions, sizes and lifestyles. Did the gigantic pliosaur Kronosaurus queenslandicus share the same caudal rudder shape and size as Cryptoclidus? We need more research to say either way.

Of course, this tentative endorsement of vertical fins comes with many caveats. Despite the antiquity of proposals that plesiosaurs bore a soft-tissue rudder on their tails, these discussions are still in their infancy. Very few studies have directly addressed this topic and our analyses have, thus far, been largely limited to qualitative descriptions and comparisons with other vertebrates. Our taxon sampling is also relatively limited and has not yet incorporated the most extreme examples of plesiosaur size or body plans. I can’t be the only one wondering what the extremely long-necked elasmosaurids and giant pliosaurids were doing with their tails and, given the innumerable studies linking tail shape to ecology in swimming animals, it’s not crazy to assume plesiosaurs of different lifestyles might have had differently shaped rudders. We may even already be finding evidence of such variation, it being observed (for example) that elasmosaurids may not have had the mobile terminal tail region identified in some cryptoclidids (Otero et al. 2018). Moreover, might plesiosaurs have done something unusual with their tails, such that the fin vs. fluke dichotomy is an oversimplification of a more complex organ befitting their unique swimming style? Could other structures - keels or projecting stabilisers - have augmented a larger fin? It will be interesting to see what further research reveals and, in particular, what quantified comparisons between the caudals of plesiosaurs and those of fluked and flippered animals have to tell us. Many of the features discussed above are relatively subtle - a taller neural spine here, a slight wedging of the centrum there. Careful, quantified comparisons of a suite of features with modern and extinct analogues may help us distinguish whether fins or flukes are the better tail rudder model, or if such analogues are useful guides at all.

And that, with one foot off the fence on this matter, but still not feeling like a conclusion has really been reached, is where we'll leave off for now. Hopefully, more definitive evidence for plesiosaur tail morphology will appear soon but, until then, the best thing artists can do is not take the comments above as gospel: check out the papers discussed here (most are open access or otherwise available online) to make up your own mind which is the better-supported model. I suspect I'm still going to remain uncertain about my plesiosaur tails for some time, but there's comfort knowing that this isn't really something we can be especially confident about until more data is gathered.

UPDATE: 28/09/2021 (the day after posting). In what is clearly good news, it turns out that the paint covering the Seeleyosaurus holotype soft-tissues has been removed and that the specimen is, at time of writing, under study by plesiosaur expert Sven Sachs. You can see a photo of the restored specimen at Sven's website, here. The paint was actually removed some years ago but this has not, to my knowledge, been mentioned in more recent papers discussing this specimen, hence the error in reporting here. Thanks to Sven and others who have pointed this out.

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References

  • Dames, W. (1895). Die plesiosaurier der Süddeutschen Liasformation. Abhandlungen der
  • Königlich Preussischen Akademie der Wissenschaften zu Berlin 1895, 1–81.
  • Felice, R. N., & O’connor, P. M. (2014). Ecology and caudal skeletal morphology in birds: the convergent evolution of pygostyle shape in underwater foraging taxa. PLoS One, 9(2), e89737.
  • Fraas, E. (1910). Plesiosaurier aus dem oberen Lias von Holzmaden, Palaeontographica, 57, 3–4, 105–140.
  • 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(1), 1-8.
  • Newman, B. & Tarlo, B. (1967). A giant marine reptile from Bedfordshire. Animals, 10, 61-63
  • Otero, R. A., Soto-Acuña, S., & O'keefe, F. R. (2018). Osteology of Aristonectes quiriquinensis (Elasmosauridae, Aristonectinae) from the upper Maastrichtian of central Chile. Journal of Vertebrate Paleontology, 38(1), e1408638.
  • Owen, R. (1865). A monograph on the fossil Reptilia of the Liassic Formations. Part 3. Sauropterygia. Monograph of the Palaeontographical Society, 17, 1–40, pl. 1–16.
  • Renesto, S., Dal Sasso, C., Fogliazza, F., & Ragni, C. (2020). New findings reveal that the Middle Triassic ichthyosaur Mixosaurus cornalianus is the oldest amniote with a dorsal fin. Acta Palaeontologica Polonica, 65(3), 511-522.
  • Sachs, S., Hornung, J. J., & Kear, B. P. (2016). Reappraisal of Europe’s most complete Early Cretaceous plesiosaurian: Brancasaurus brancai Wegner, 1914 from the “Wealden facies” of Germany. PeerJ, 4, e2813.
  • Sennikov, A. G. (2015). New data on the herpetofauna of the Early Triassic Donskaya Luka locality, Volgograd Region. Paleontological Journal, 49(11), 1161-1173.
  • Sennikov, A. G. (2019). Peculiarities of the Structure and Locomotor Function of the Tail in Sauropterygia. Biology Bulletin, 46(7), 751-762.
  • Smith, A. S. 2007. Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). Unpublished PhD thesis, School of Biology and Environmental Science, National University of Ireland, University College Dublin.
  • Smith, A. S. (2013). Morphology of the caudal vertebrae in Rhomaleosaurus zetlandicus and a review of the evidence for a tail fin in Plesiosauria. Paludicola, 9(3), 144-158.
  • Wegner, T. (1914). Brancasaurus brancai Wegner, ein elasmosauride aus dem Wealden Westfalens. Borntraeger.
  • Wilhelm, B. C. (2010). Novel anatomy of cryptoclidid plesiosaurs with comments on axial locomotion (Doctoral dissertation, Marshall University Libraries).
  • Wilhelm, B. C., & O'keefe, F. R. (2010). A new partial skeleton of a cryptocleidoid plesiosaur from the Upper Jurassic Sundance Formation of Wyoming. Journal of Vertebrate Paleontology, 30(6), 1736-1742.

Tuesday, 27 April 2021

Film review: Ammonite (2021)

After a long wait and much online discussion, the Mary Anning-inspired historic drama Ammonite is finally on general release. As goes the popularisation of palaeontology, Ammonite is something of a big deal: it’s the first film treatment of the iconic 19th-century fossil collector Mary Anning, a rare major feature to focus on genuine 19th-century palaeontology, and - in what might be another first - is a palaeontology-inspired film aimed squarely at adults. It has also, however, been controversial since its announcement for not focusing on traditional aspects of the Mary Anning story, such as her significance to the discovery of Mesozoic marine reptiles, her relationship with palaeontologists of the early 1800s and her tragically short, poverty-stricken existence. Instead, the film invents a narrative about an imagined romance between Anning and another historic figure, the geologist Charlotte Murchison. The appropriateness of this angle and what it means for Anning’s legacy has been the subject of much social media discussion, although the actual release of the film on premium streaming services has not, to my knowledge, generated the same level of debate. Curious to see if all our hopes, fears and general anticipation were worth our time, I recently checked out Ammonite and have come away with a mixed reaction. Is it a good film? I thought so. Is it a good ‘Mary Anning film’? I thought not. Are these answers mutually exclusive? It depends what you want from your Anning cinematic experience.

Let’s talk about the positives first. There is a lot I liked about Ammonite. It’s well-acted, well-directed, and delivers an outwardly strong reflection on sexism and classism in a strongly patriarchal Victorian society. The film is not subtle in its messaging: the opening shots show a maid scrubbing a museum floor being rudely pushed aside by bustling, suited men rushing an Anning-discovered Temnodontosaurus to its cabinet. It does, however, do a commendable job of showing, without preaching about, the contrast between rich and poor and the gulf in privilege that existed, and still exists, between men and women. Anning’s simple clothes, her empty, tired home and shop, as well as the sometimes bleak Lyme Regis coastline contrast well against the wealth, comfort and extravagance of richer characters and establishments. It provides a warts-and-all look at life on the poverty line in the 1840s where Anning and her elderly, poorly mother eat thin vegetable stews, illuminate their home with solitary candles, and several shots show their rough, tattered hands resulting from a lifetime of hard graft. Actors are not prettied up to look miraculously glamorous despite their lifestyle: there's an honest rawness to their appearance and costumes.

The tone of Ammonite is reflected with a sparse musical score and suitably bleak, although not lifeless, colour palette. Anning’s house is the core location of the film, but grubby British mudstone cliffs are its second home. I admit to finding these fossiliferous landscapes a refreshing sight for the setting of a palaeontological drama instead of, as is so often the case in palaeo media, vast deserts or badlands. The ever-present roaring waves and changeable weather of the southern UK coastline are excellently captured, and the cinematography manages to balance the grey colours of the Dorset coast and Anning’s home with stronger hues, especially the blues of Anning’s clothing, and the sea and sky. The film has a washed-out, slightly tired look that doesn’t feel forced, and perfectly suits the rest of the subject matter.

The first act features what most will expect of a Mary Anning picture, showing her looking for fossils in poor weather and clambering up slippery cliffs to excavate nodules containing ammonites. We are not explicitly told when the film is set, but the film’s version of Anning, played by Kate Winslet, imagines her in her later years - so presumably in the early 1840s. Portrayed as an embittered, middle-aged and experienced fossil collector with little time or interest in social graces, she also has a physical presence and resourceful quality entirely atypical for a 19th century female character. It's hard not to see some of this as making Anning the match for any man you'd care to put in her position. She's a woman of few words, wears trousers under her dresses, pees wherever she likes in the field (and then wipes her hands on her clothes), smokes hand-rolled cigarettes and deploys several harsh swears. Although outwardly a cold, embittered character with little patience for others, she is not unlikeable, and Winslet’s portrayal is genuinely excellent, her face showing an unspoken history of sadness, loneliness and world-weariness that needn’t be explained through dialogue. Her performance and frame have a stiffness that is at once both imposing and awkward, and much of what Anning thinks and feels is conveyed through forced stillness and suppressed reaction. It's a terrific performance that has unsurprisingly drawn much praise from critics.

As you’re no doubt inferring, Ammonite is not a breezy, lighthearted film. Nor, in contrast to virtually all other palaeo-inspired motion pictures I can think of, is it a family film. Ammonite has a ‘15’ rating in the UK (equivalent to an ‘R’ in the US), and for good reason: there’s male and female nudity, graphic sex and several strong swears. This is not the film to show your kids the Mary Anning story: it’s a slow, character-driven drama aimed at mature audiences. Although seemingly ruling out large chunks of its potential audience, for science communicators, this is a Good Thing. The last century of palaeo-related cinema can be largely boiled down to people running from animated dinosaurs, and Ammonite is going to draw attention from audiences who have no interest in this sort of thing. There is no shortage of child-friendly Mary Anning media out there, so it's great to have something that will draw the attention of older audiences.

But it’s also on the science communication front that Ammonite is going to prove most divisive. My take on films, TV shows and so on is that we have to rate them based on what the creators set out to do, not what we wanted them to do, and in this sense Ammonite might be free of criticism over its loose take on history. But I think it’s fair to ask whether Ammonite really needed to hang its narrative around Mary Anning at all, such are the liberties it takes with the subject matter. I have two main thoughts on this.

First, for a story about one of the most famous fossil hunters in history, Ammonite is strangely empty of what we might call palaeontological character. I understand that Ammonite is not a Marvel film or Star Trek episode where fans are deliberately fed blink-and-you-miss-them references, callbacks and easter-eggs, but the early 1800s yielded so many iconic specimens, books and palaeoartworks that I was surprised the film was so stripped back of palaeo-based content. Anning’s shop and home are virtually empty of specimens, which runs contrary to just about every fossil collector home, shop and lab I've ever been to. Invariably, such locations are full of stuff related to extracting and understanding extinct life: field gear, books, fossils, notes, rocks, unprepared specimens and other curios. I think the emptiness of her home is meant to stress her poverty, but the effect was that she looked more like she was a hobbyist fossil collector rather than the grandmother of palaeontology.

This bareness has another effect: it denies the sense that Anning made any multiple significant discoveries. We see Anning collect and prepare an ichthyosaur skull at one point but, other than this, a bookending cameo by the famous Temnodontosaurus fossil Anning found with her brother (the first ichthyosaur studied by scientists) and a quick shot of Anning sketching the Plesiosaurus dolichodeirus holotype from memory, there’s really nothing to represent her remarkable contribution to marine reptile palaeontology. It’s these discoveries that Anning is primarily remembered for and their absence will be noticed by anyone familiar with her history. Indeed, I’m not sure anyone watching Ammonite without prior knowledge of Anning would really think she was anyone especially important. By the end of the first act, Ammonite is basically done with palaeontology, and the rest of the narrative could easily be about any other downtrodden 19th century female professional you care to name or invent.

Second, yes, it’s time to address that topic: the decision to make Anning a character in a fictionalised romance rather than tell a component of her real history. Ammonite is only a Mary Anning film in the loosest sense: it has the right character names, the right location and the basic Anning backstory, but that's about it. Along with speculating about Anning’s sexuality (we have no data at all on Anning’s romantic interests), her character is also changed. We don’t know much about Anning’s personality, but historic notes - such as those cited in Deborah Cadbury’s 2000 book The Dinosaur Hunters - imply a very different character to that invented for the film. Quotes about later-life Anning describe a patient, kindly woman grateful for shop patrons, for example, which is a world apart from the icy, blunt Anning of Ammonite. The biggest historic casualty of the film, however, is not Anning, but her love interest, Charlotte Murchison. In real life, Murchison was a well-travelled, experienced geologist of great professional inspiration and importance to her geologist husband - the eventual Director-General of the British Geological Survey, Roderick Murchison. She was also a trailblazer for women’s rights in science, protesting against Charles Lyell for the right for women to attend scientific lectures. Ammonite’s Charlotte Murchison, in contrast, is a character defined only by her relationships with other people: a lonely wife grieving over the loss of her child, left with Anning in the hope that she may take up geology as a hobby. It’s certainly true that Ammonite is about an intelligent, important woman being brushed under the carpet of society, but there’s a meta quality to this that wasn’t expected.

It’s in this area that I find myself most conflicted about Ammonite. On the one hand, Ammonite’s narrative and the real stories of Anning and Murchison draw similar conclusions about sexism and classism, so the deviations from history might not matter too much: the imagined and real history meet, more or less, to impart the same message. On the other, the real Anning story is not only unique (and thus more interesting than any imagined drama) but also much more powerful. Women like Anning and Murchison literally changed the course of history and their lives couldn’t be more relevant to modern concerns: feminism, societal inequality, the power of rich white men, and the issue of privilege are all inescapable truths of their biographies. Ammonite replaces some of these with an equally important cause - LGBTQ representation - but - to our knowledge - this was never Anning’s fight, and it’s strange that she’s now been pushed as a figurehead in this movement too. As Riley Black mused in her excellent piece on Ammonite last year, we are at risk of asking Anning to carry too much, and thus diluting her real importance and legacy. The irony of Ammonite, a film that seemingly celebrates Anning, sidelining her scientific and intellectual achievements so it can impress its own narrative and significance onto her life is not lost on me. It’s not quite the same as writing her out of history like so many Victorian gentlemen scientists, but it’s certainly another example of people using her reputation for their own ends.

And that’s where Ammonite leaves me: a commendable historic drama with some great attention to characterisation and some great performances, levelled against disappointingly little interest in the richness of its source material and a confused, perhaps even self-defeating relationship with its principal characters. For all this, I still think Ammonite is, on balance, a Good Thing. While not delivering the sweeping Anning biopic many palaeontologists and historians might want to see, it still promotes - however contrarily in light of historic facts - the importance of women in science, gives a general idea of who Mary Anning was, and may spark some important thoughts and conversations among more interested audience members. And, lest we forget, behind all the talk about representation and legacies is a good film that can be watched and enjoyed, and it's OK to switch our brains off from time to time. Ultimately, whether you should check out Ammonite will depend on what you want from this picture. If you can get past the fact that Ammonite is little more than watered-down palaeontological fanfiction (perhaps the most niche genre in cinema), you may enjoy it. If you're unable to leave your scientific and historical brain at the door, this might not be for you. Whichever of these opposing views you land on, I agree with you.

Enjoy these 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 like a trivial 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 upcoming books, papers, paintings and exhibitions. 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!