The Carnian/Norian Swiss pterosaur Caviramus schesaplanensis, one of the earliest species to take pterosaur anatomy to strange new places. Anyone else want to make puns about 'Cave-iramus' with this picture? No? Anyone...?

What happens when you take the innate weirdness of the Triassic Period - the evolutionary equivalent of the late 1960s in terms of experimentation, weirdness and tragic ends to interesting lineages - and multiply it by a pterosaur? One answer is the marvellously strange Late Triassic flying reptile Caviramus schesaplanensis. This animal is a relative newcomer to the pterosaur roster, first being described in 2006 based on an incomplete lower jaw from Switzerland (Fröbisch and Fröbisch 2006), before better material in the form of an incomplete skeleton turned up a few years later* (Stecher 2008). Several cranial and dental features indicate Caviramus had kinship with other European pterosaurs such as Eudimorphodon and Campylognathoides, but that it was a rather distinctive animal compared to even close relatives. This 1.35 m wingspan animal had a chunky skull, large crests on both upper and lower jaws, densely packed and gnarly teeth, long, slender wings and a robust, lengthy set of hindlimbs (Stecher 2008). Several of these features are 'extreme' variants of pterosaur anatomy common to other Triassic animals, and others represent the most pronounced development of anatomical traits of any pterosaur. They mean that, even a decade after the first remains of this animal were published, Caviramus still gives us a lot to think about as goes its life appearance, lifestyle and functional anatomy.

*This skeleton was described as the holotype of a new genus and species, Raeticodactylus filisurensis, but a number of recent workers have shown it to be very likely congeneric, if not entirely synonymous, with C. schesaplanensis. I'm treating the two as the same taxon here.

The undignified end to the life of a large (6m wingspan) azhdarchid: being squabbled over by Saurornitholestes and other local ruffians. We know a scene like this must have occurred at least once thanks to an azhdarchid fossil discussed below, and a growing number of specimens are providing similar insights into the place of azhdarchids in Mesozoic food webs.

Discussions of the lifestyles of fossil animals primarily centre around their functional morphology - the use of comparative anatomy and biomechanical calculations to assess their anatomical suitability to certain habits and behaviours. We use these approaches to deduce their likely diets, locomotory strategies, likely interactions with ancient environments and other organisms, and so on. But despite the widespread and proven utility of these techniques, it's widely regarded that these approaches can only provide probabilities and hypotheses about fossil habits. They allow us to predict, but not necessarily know how ancient animals functioned in their respective ecosystems. For the latter, we rely on fossils to provide us with direct records of animal habits - gut content, evidence of animals attacking and ingesting each other, trace evidence of foraging strategies and so on. For vertebrates, these fossils are very rare - hence our general reliance on functional anatomy - and single examples of palaeoecologically-significant fossils can provide crucial insights into ancient lifestyles and ecosystems.

As you might expect, such fossils are particularly rare for pterosaurs. Flying reptiles were not prone to fossilisation at the best of times and this - through simple probability - dramatically lowers their chance of forming fossils with palaeoecological significance. As recently as the 1990s some authors lamented the lack of these fossils and tried to ascribe some significance to their rarity. But renewed interest in pterosaur science, an increased rate of discovery of flying reptile remains and greater alertness for details on fossil specimens has seen our sample size of palaeoecologically-significant pterosaur specimens grow considerably in the last few years. These records have been augmented more in some taxa than others so that our record of pterosaur palaeoecology is looking increasingly patchy: some groups now now have a half-dozen or more of these fossils to their names, others have none at all. There's probably no real significance to this other than the habits and anatomy of some pterosaurs being more suited to recording these fossils than others.

I thought it might be fun to take a look at two pterosaur taxa with increasingly good palaeoecological records. In an upcoming post, we'll look at the really quite excellent palaeoecological data for the Jurassic pterosaur Rhamphorhynchus muensteri, but today I want to discuss the palaeoecology of azhdarchids. That's right: the lifestyles of these sometimes giant, sometimes long necked, always edentulous, and increasingly famous flying reptiles are not only predicted by functional morphology, but can be deduced somewhat from fossils too. Thanks to a number of specimens discovered in recent decades we have an idea what happened to azhdarchids when they died, what sort of animals they must have encountered in day to day life, and maybe even how they foraged.

Meeting the (teeth of the) neighbours

The majority of the azhdarchid palaeoecological record pertains to specimens showing which animals ate them, their teeth and puncture marks being left on azhdarchid bones, or else azhdarchid remnants being found in the torsos of other animals as gut content. One of the most famous of these fossils is an incomplete azhdarchid skeleton from the upper Cretaceous Dinosaur Park Formation of Canada. This fossil is noteworthy for not only being one of the most substantial pterosaur fossils from Canada, but also for the tooth gouges and embedded dinosaur tooth found at the distal end of the bone (Currie and Jacobsen 1995). The tooth belongs to the 2 m long dromaeosaur Saurornitholestes langstoni, and the size and provenance of the gouges indicate they were probably made by the same species, perhaps the same individual. The size discrepancy between the pterosaur and dinosaur here is pretty dramatic. Check out the size of the tibiotarsus of the (c. 6 m wingspan) pterosaur compared to the embedded tooth:

Immature azhdarchid humerus from the Dinosaur Park Formation of Alberta, Canada, with an embedded dromaeosaur tooth (arrowed). Note the size of the pterosaur remains compared to those of the dinosaur. Image by Liz Martin-Silverstone, borrowed from her Twitter account.

This is not the only known occasion of a dromaeosaur interacting with an azhdarchid. Recently Dave Hone and colleagues (2012) described an articulated Velociraptor mongoliensis specimen from Tugrikin Shireh (Gobi Desert, Mongolia) with fragmentary remains of an azhdarchid pterosaur in its gut (below). That this reflects true gut content, and not just chance association of pterosaur bones with those of a dinosaur, is indicated by the articulation of the specimen and location of the pterosaur remains within an envelope of dorsal ribs. It's presumed that the dinosaur was eating bits of pterosaur bone with meat attached, not just swallowing chunks of bone.

A Velociraptor mongoliensis chest cavity with pterosaur remains, probably belonging to an azhdarchid, as gut content. Black arrows show pterosaur bone, white arrow indicates a pathological rib. Borrowed from Dave Hone's Archosaur Musings.

Crocodyliforms are also thought to have consumed azhdarchids. Possible puncture wounds from these reptiles are found on the holotype specimen of the Eurazhdarcho langendorfensis, from the upper Cretaceous Sebeş Formation of Transylvania (Vremir et al. 2013). Round bite marks and crushing are found on the cervical vertebrae (below) and distal metacarpal IV of this specimen. In this instance the azhdarchid was unlikely to have been receiving selective treatment by the local reptile fauna, as crocodyliform biting traces are common to many bones from this formation (Vremir et al. 2013).

Holotype cervical vertebrae III and IV of Eurazhdarcho langendorfensis, with possible crocodyliform tooth marks outlined and arrowed. From Vremir et al. (2013).

Azhdarchid bones as an insect hotel?

A further possible record of azhdarchid consumption pertains to strange oval punctures at the back of a Quetzalcoatlus sp. skull (Kellner and Langston 1996). These may record tooth marks, although there is no obvious indication as to what animal might have made them. A rather different take on them was suggested by Kellner et al. (2010), who noted that insect borings had been found the same Quetzalcoatlus material. Kellner et al. suggest that these borings were described by Kellner and Langston (1996) but, to my knowledge, this suggestion is an error as I can find no mention of insect borings in the 1996 paper. I assume this comment provides a different interpretation of the skull punctures, but it might not. I'd really like to know more about this, as there are as yet no confirmed cases of pterosaur bones being utilised by insects. I wonder if this is a simple mistake, or might pertain to details of as-yet undescribed portions of Quetzalcoatlus anatomy?

An azhdarchid foraging trace?

Azhdarchid terrestrial stalking, the infographic. From Witton and Naish 2015.

References

Protoceratops, the Late Cretaceous horned dinosaur widely suggested as being the inspiration for the griffin myth. This image shows the lesser seen P. hellenikorhinus, a larger, more ornamented species of Protoceratops than the familiar P. andrewsi.

One thing that everyone 'knows' about the mid-sized, Late Cretaceous Asian horned dinosaur Protoceratops is that it's thought to be a fossil with historical mythical significance. Specifically, it's said to be the origin for the griffin, the lion-bodied, bird-headed chimera that has appeared in art and folklore for thousands of years. You could be forgiven for thinking that this idea is quite old and established because it's mentioned frequently in books, TV shows, and online articles, but it's actually a relatively modern invention. What I'll be calling the 'Protoceratops-griffin hypothesis' was first proposed by Adrienne Mayor and Michael Heaney in the 1993 Folklore paper "Griffins and Arimaspeans" and then developed by Mayor across two editions of the book The First Fossil Hunters: Paleontology in Greek and Roman Times (2001, 2011). These authors were not the first to suggest that the griffin had a basis in ancient interpretations of fossil animals (Mayor and Heaney 1993), but they presented the first argument linking griffins to horned dinosaurs as well as a suite of historic evidence supporting their interpretation. The idea has been praised by several palaeontologists and is celebrated as one of the superior accounts of fossils influencing ancient mythology.

Bird-griffin statue, 7th century BCE. Was Protoceratops the inspiration for this creation? From Mayor and Heaney (1993).

The basic premise of the Protoceratops-griffin hypothesis is straightforward. Tales of Ancient Greek explorers of the 7th century BCE (but first written about in the fifth century BCE) include discussion of vicious, beaked, gold-guarding quadrupedal animals living in deserts to the northeast of Greece. These stories are said to have originated with the Scythians, nomadic peoples who mined gold from central Asia from localities close to the bonebeds of Protoceratops in Mongolia and China. It is reasoned that Scythian nomads saw the weathering skeletons of Protoceratops as they prospected for gold and told others of their existence. The Greeks interpreted these as real-life versions of the griffins they knew of from history and the mythology as we know it was born. The hypothesis argues that specific aspects of griffin anatomy were based directly on these accounts of Protoceratops: the beaked jaws and quadrupedality are obvious, but griffin wings are argued to be Protoceratops neck frills or shoulder blades, taloned hands are thought to reflect Protoceratops claws and so on. As the Greeks continued to hear about these animals, eventually from direct trade with the Scythians in the 7th century BCE, their interest in griffins grew so that they became familiar components of Greek culture. For hundreds of years Greek scholars and artists would continue adding to griffin lore, always referencing the same touchstones of desert settings, of powerful, beaked quadrupedal animals, and gold guarding. Their depictions and stories would be passed through to medieval times and, ultimately, the modern day.

I recently became genuinely interested in this interpretation as part of research into the earliest accounts of palaeoart - if griffin art is indeed of horned dinosaur origin, it might qualify as some of the oldest on record. But reading about the Protoceratops-griffin hypothesis (in Mayor and Heaney 1993; Mayer 2011) did not deliver the proverbial 'nugget of truth' behind the griffin myth I expected based on its fame. My impression was that evidence cited for this hypothesis was generalised to account for as much griffin lore as possible, that several major, obvious questions remained unanswered, and that there was not any attempt to refute other, non-fossiliferous takes on griffin origins. Digging into the primary literature on griffin iconography seemed to confirm my concerns, suggesting that the Protoceratops-griffin hypothesis is unfavourable among archaeologists (e.g. Frankfort 1937; Goldman 1960; Wyatt 2009; Tartaron 2014). Moreover, there are far more parsimonious and well substantiated takes on these creatures which do not rely on fossil data. In the interests of providing a counter-argument to all the 'pro'-Protoceratops-griffin hypothesis media out there, I'm sharing the products of my research here.

The griffin timeline

Perhaps the largest issue with the Protoceratops-griffin hypothesis is the fact it largely ignores griffin lore before the 7th century BCE. Griffin iconography extends deep into human history with one of their best early appearances dating to 4th millennium BCE Susa - an ancient city in what is now Iran (below, Frankfort 1937). Similarly aged or older artefacts from Egypt also show griffin-like forms (Wyatt 2009), and by the 3rd millennium BCE griffins were a regular component of art in many Near Eastern countries. The role of griffins in these communities remains a matter of controversy because we have little or no written explanation of their significance. Nevertheless, they are abundant enough to suggest some importance in these cultures, and modern scholars have attempted to interpret griffin imagery based on religious and cultural practises of these times (e.g. Wyatt 2009).

Line drawing of perhaps the oldest known image of a griffin, from Susa, 4th millennium BCE. From Frankfort (1937).

As noted above, the Protoceratops-griffin hypothesis relies on Greek and central Asian evidence no older than the first century BCE, picking up the griffin story at least 2000 years after it begins in the Near East. How does it account for this older period of griffin history? It's actually quite dismissive. Mayor and Heaney (1993) simply write "...we have no way of knowing what kind of folklore, if any, was attached to these creatures" (p. 41), and a similarly brief discussion is presented by Mayor (2011). What is clearly needed is a link between Protoceratops and the oldest Near Eastern griffin art, especially if these fossils were meant to have directly inspired griffin appearance. To my knowledge, no such link has been presented, and this is a problem: whether we understand them fully or not, these early griffins still provide basic information on where and when griffins entered ancient cultures. Therefore, they must be addressed fully by any attempt to explain griffin origins. As it is, the fact that Near Eastern griffins substantially pre-date any from central Asia is a clear argument against the Protoceratops-griffin hypothesis, and one that really needs an explanation if we're to think this myth has a basis in fossil data.

Taking this point further, overlooking the early history of griffin art also means that the Protoceratops-griffin hypothesis does not engage with current, mainstream interpretations of the spread of griffin culture to Ancient Greece. Griffins are thought to have become popular in Greece during the 'Orientalizing Period', a cultural event occurring around the 7th century BCE when Greek art, technology and literature became heavily influenced by Near Eastern civilizations (Tartaron 2014). Put simply, the uptake of griffins into Greek culture coincides exactly with their sudden interest in the guys who'd been drawing and sculpting griffins for thousands of years. It's easy to understand why this is the preferred explanation for the rise of Grecian interest in griffin imagery. It involves the civilisations known to have depicted these animals before anyone else, fits the dates attributed to Greek and Near Eastern griffin art perfectly, and is easily explained as part of a well-established period of cultural exchange between these peoples. A compelling explanation is needed here to explain why this interpretation is inferior to the far more complex one involving distant peoples, a disjointed chronology and fossil animals found 6000 miles away to the East.

Griffin appearance, variation and the 'need' for exotic fossil anatomy

The Protoceratops-griffin hypothesis also presents a simplified interpretation of griffin iconography. Numerous variants on griffins are found in the ancient world, reflecting differences in anatomy, pose and behaviour. The 'bird-griffin' - the winged lion with an avian head (see images, above and below)- is the type Protoceratops is thought to have inspired, but is just one of many griffin chimeras identified by researchers. Reflecting taxonomy on real animals, the identification of distinctive griffin 'species' varies between researchers, but they are generally thought to include wingless sphinxes (human head on a recumbent lion), bipedally standing winged lions with human heads, winged humans with avian heads, winged lions, long necked 'lion-griffins' (sometimes called 'lion-dragons'), and lions with avian heads, wings and forelimbs (Frankfort 1937; Goldman 1960; Wyatt 2009; Gane 2012). Within these forms are more variation: they may or may not include wings, tails, ears, 'crests' or horns on the snout, manes of hair or feathers, and teeth, as well as differences in neck length, mouth gape and claw size. The animal species used in these chimeras differ too. For instance, there are bird-griffins with eagle, peacock and falcon heads, a variety of big cat species are thought to be used for the body and limbs. Tails may be of either avian or felid identity.

A selection of griffins forms from Goldman (1960). Note variation in tails, faces, neck length and ears.

Both Mayor and Heaney (1993) and Mayor (2011) use different griffin types from a variety of cultures in their argument for the Protoceratops-griffin hypothesis, including wingless forms, lion-griffins/dragons, 'classic' bird griffins, as well as toothed and long necked variants. It's argued that these can be distilled to common elements reminiscent of Protoceratops in size and form despite their (sometimes major) anatomical differences, and that this implies a common origin. Variable interpretation of broken fossils are said to explain some features which differ from genuine Protoceratops anatomy. For instance, the horns and ears of some griffins might reflect misinterpreted broken skulls and neck frills, and wings may also be broken frills or misidentified shoulder blades. Embellishment of stories passed on from distant lands might explain other variations.

However, this homogeneous treatment of griffin imagery is troublesome, for two reasons. Firstly, the disregarding of griffin form shows a somewhat selective approach to evidence gathering, highlighting elements that suit the Protoceratops origin while ignoring those which are problematic. The fact is most griffin artworks do not look like Protoceratops beyond the superficial similarity of being being beaked quadrupeds (see below). Furthermore, griffin art remains differentiated even after Greek and Scythian cultures were known to have been communicative and, in theory, tales of Protoceratops could influence griffin depictions. This homogenising of griffin forms also contradicts modern interpretations of griffin art. Many researchers stress the unique histories, origins and cultural significance of different griffin forms, some authors even directly cautioning about treating these chimeras as interchangeable for fear of obscuring their true meaning and history (e.g. Goldman 1960; Wyatt 2009; Gane 2012). Most scholars simply see griffins as chimeras - creatures invented from components of animals and human individuals for symbolic or literary intent (Wyatt 2009; Gane 2012). As with other chimeras, the difference between griffin types likely reflects efforts to convey information about these creatures or the scenarios they're depicted in. For example, the addition of wings may indicate swiftness or divinity; large, erect ears suggest alertness; claws suggest ferocity and so on. These features were not added randomly to griffin art, and the development of distinctive griffin types can be traced over time (e.g. Goldman 1960). The message from mainstream archaeology seems to be that griffin iconography had complex origins and development within the framework of chimera creation common to ancient cultures, and that generalising their form is probably not the best way to understand them.

Superficial musculature of a lion, illustrated in Goldfinger 2004. The torsos and limbs of detailed griffin art shows the same characteristic muscle groups, specific anatomies and proportions as these cats, suggesting there are not generic quadrupeds but true chimeras of large felids and birds. This can easily be seen in some of the imagery posted below and above.

But is mainstream science correct to interpret the griffin as a traditional chimera of familiar, extant animals, or do we need the exotic, extinct form of a Protoceratops to explain their anatomy? I'm not going to compare this dinosaur with all variants on griffin composition here, but will suggest that the 'classic' bird-griffin clearly does not need Protoceratops. It's obviously composed of an avian head, a lion torso, limbs and tail, with a set of bird wings mounted on the shoulders. There are no especially weird or exotic anatomies that cannot be explained without reference to modern species, and even the oldest renditions of griffins show closely observed details of lion and bird anatomy that make their identification obvious. This is particularly true for the lion elements, where the forefeet often have lion-like thumbs, and large, padded, clawed digits. When griffin tails are not just clumps of feathers, they are long, slender and curve upwards in a very lion-like fashion, and their necks are often adorned with manes. I'm struck at how lion-like the proportions and musculature of the torso and limbs are in most griffin depictions: they are not just generic quadrupeds, but really obviously and specifically referencing big cats (above).

Sketch of a juvenile Protoceratops andrewsi skull, right lateral view.

It should be stressed that much of this contrasts with the anatomy of Protoceratops. I need to be careful that I don't set up a straw man here - after all, it's likely we know far more about Protoceratops than anyone who lived thousands of years ago, and the hypothetical passing of tales about Protoceratops from central Asia to eastern Europe is an incredibly long game of Chinese whispers. However, if the Protoceratops-griffin hypothesis is to be accepted it needs to pass some basic anatomical tests, even if they are very simple. Let's start with the head. Immediately obvious is that there is nothing projecting rearwards from the posterior head region of most griffins, whereas all Protoceratops (even very small juveniles) have some sort of frill extending posterodorsally from the back of the skull (above). The ears and crests of griffins, explained as being the broken frills of Protoceratops fossils, are structures which project upwards from the head, not backwards. If we must give these structures a basis in reality, we can look to the ornamental head feathers of birds for the crests (remember that the heads of some elaborate birds, like peacocks, are used in some griffin art) and any number of common mammal species for the ears. These are surely simpler alternatives than the broken skull bones of dinosaur fossils occurring thousands of miles away. It is often suggested that griffin wings might be mistaken interpretations of the Protoceratops frill, but the wings are clearly set on the shoulders in most reconstructions and behind lion-like neck manes in some imagery. Moreover, as noted above, not all griffins have wings. Protoceratops is also not toothless, its densely packed cheek teeth being obvious in even weathered skulls. The majority of griffin images show a fully toothless beak far more like that of a bird than a ceratopsian dinosaur.

Scott Hartmans's skeletal reconstruction of Protoceratops andrewsi. Borrowed from the excellent Scott Hartman's Skeletal Drawing.com.

Protoceratops also does not have lion-like hands or feet, nor any raptorial claws (above). Ceratopsians had relatively stout, blunt claws, and the hands of early taxa like Protoceratops are not especially big. I'm not sure anyone - even folks living thousands of years ago - has ever looked at Protoceratops and been amazed by its powerful limbs or ferocious talons, whereas these are striking characteristics of big cats. Finally, the tail of Protoceratops is proportionally deep, seemingly incapable of significant dorsal curvature, and not at all like that of a lion. So beyond being beaked animals with four legs, there's no striking similarity between Protoceratops and bird-griffins. Once we start considering the variance in griffin art - the long necks, manes, feathers and so forth - even more differences become apparent. In light of this, and the fact that living animal anatomies can easily account for all elements of ancient griffin depictions, there seems no need to invoke Protoceratops as a part of griffin anatomy. The mainstream view of griffins being simple chimeras of living animals has to be considered a far simpler and better supported interpretation of their form.

Written accounts of griffin behaviour, and the development of griffin lore

Even if Protoceratops did not inform the raw appearance of griffins, could it be referenced in written accounts of griffin appearance and behaviour, such as their desert-living, parental care and gold-guarding habits? It's perhaps these accounts which provide the best evidence for the Protoceratops-griffin hypothesis, as it's these which indicate the deserts of central Asia as the griffin's home and their association with gold. It's worth summarising some details of the first griffin accounts here as their nature and propagation is important. Please check out Phillips (1955), Bowra (1956), Mayor and Heaney (1993) and Mayor (2011) for more details.

Much of Greek griffin lore is derived from stories of the Greek poet Aristeas, who travelled through Asia in c. 675 BCE. His adventures and travels are first recorded in texts from 460-450 BCE (Mayor and Heaney 1993) and were so influential that they continued to be referenced well into the Common Era. However, it's worth stressing that these stories are semi-mythical tales of a semi-mythical man: Aristeas was a real chap, but he is described as seeing and doing things which are combinations of real and fantastic phenomena. Scholars still discuss the realities behind the locations, events, creatures, and peoples Aristeas encountered, and even ancient Greek authors, such as Herodotus, did not believe everything Aristeas was said to have seen and done (Phillips 1955, Bowra 1956). Among the earliest accounts of Aristeas' travels is the tragedy Prometheus Bound, a tale involving gods, titans, gorgons and other monsters. Here, griffins and other creatures were suggested to live to the far north-east of Greece in a desolate desert setting where nomadic barbarians (the Scythians) also hunted for gold. Other documents from the fifth century BCE, also influenced by tales of Aristeas, tell of griffins guarding the gold sought by men and other beasts. Griffin burrows were mentioned by Pliny the Elder's Naturalis Historia, written in 77 CE, as well as by Pausanias in 170 CE. These authors, again citing Aristeas, described how griffins were engaged in a constant war with a race of one-eyed men, the Arimaspi (Bowra 1956). Later accounts, penned in 200 CE, provide specifics of griffin anatomy and behaviour. They include the familiar accounts of their far eastern habitation of mountains and deserts, as well as new information: their membranous wings (considered useless for flight), the extent of their feathering, the colouration of different body parts, the fiery look in their eyes, the fact that men cannot best adult individuals but can capture their offspring, their nesting behaviour and parental nature, and how miners prospect for gold at night to avoid upsetting them.

Line drawing of a bird-griffin with offspring from Mayor (2011). The original hammered bronze relief dates to 7th Century BCE, Greece. Note the extremely lion-like torso, including strands of hair dangling from the mane. The original has texturing around the neck to further demonstrate the presence of long, shaggy hair.

These stories are the start of griffin lore as we know it today, as medieval scholars continued these basic elements in their griffin legends and we've maintained them until modern times. But do these stories strengthen the idea that Protoceratops is the 'real' griffin? Again, there are problems. For starters, the major early account of griffins are - at best - semi-mythical stories containing numerous imagined beasts and supernatural phenomena. Why we should consider griffins to have any more basis in reality than the gods, monsters or strange human races also mentioned in these stories? If griffins are based on actual phenomena, do we need to seek rationales for these other creatures, too? Secondly, these texts echo griffin art in providing no anatomical details specifically reminiscent of Protoceratops. Indeed, many of their embellishments (feathers, colours, wing membranes etc.) are clearly not based on anything to do with horned dinosaur fossils. These accounts also blatantly refer to living animals, not fossil (or even simply dead) ones, and their descriptions of griffin wars with one eyed men, the vulnerability of their offspring to human capture and so on fit better with fantastical yarns than accounts of fossil creatures. Mayor (2011) suggests that the some griffin behaviour identified in these texts supports Protoceratops as the griffin source, such as their parenting skills (see image, above). These might marry up nicely with the well-known occurrence of nests and juvenile Protoceratops alongside older individuals, but parental care is easily observable for many animals, including the mammals and birds that comprise the griffin chimera. There is no need to invoke a 'third party' fossil species to explain this behaviour in griffins when thousands of modern species could have provided the same inspiration. This trait is just not specific enough to implicate Protoceratops as being referenced in griffin lore.

Protoceratops localities (red) superimposed onto the map of ancient central Asian trade routes and alluvial gold sites presented in Mayor and Haeney (1993). Note the scale bar, bottom right, which represents 200 miles, and the distance between Protoceratops sites and gold deposits (black stars). Protoceratops locality information from Fastovsky et al. (1997) and Lambert et al. (2001).

What of the gold guarding, behaviour, though? This is a specific trait that cannot be casually dismissed for being common among living animals. Mayor and Heaney (1993) and Mayor (2011) identify a wealth of alluvial gold deposits that may well be the real inspirations of the gold described in griffin tales and found that some ancient trade routes do bisect central Asian Cretaceous dinosaur beds (see map, above). An argument for Scythian people at least seeing Protoceratops is starting to look compelling, but, again, closer scrutiny reveals complications. Mayor and Heaney (1993) and Mayor (2011) show maps with Cretaceous fossil sites right the way across central Asia, giving the impression that Scythian miners and traders would've been falling over fossils wherever they went. But we're not just after any old Cretaceous fossils: we're specifically after Protoceratops. Both species of this dinosaur only occur in a few select localities in the southernmost region of Mongolia and adjacent to the China/Mongolia border (Fastovsky et al. 1997; Lambert et al. 2001). Those ancient trade routes and mining sites need to approach these specific sites if we're to bring Protoceratops into this story. Comparing modern Protoceratops localities with the maps in Mayor and Heaney (1993) and Mayor (2011) shows that these dinosaurs occur several hundred kilometres east from the nearest alluvial gold deposits, and even further away from the most productive regions (above). The identified ancient gold sites are mostly west or southwest of the Altai Mountains, suggesting ancient folks would only encounter Protoceratops fossils if they travelled hundreds of kilometres away from these productive areas, and seemingly towards increasingly unproductive terrain.

This also present a further complication to the Protoceratops-griffin hypothesis: are Protoceratops localities likely to contain gold when they're so far away from the alluvial gold sites? Both Mayor and Heaney (1993) and Mayor (2011) argue that desert storms may have transported nuggets of gold to Protoceratops localities, and that seeing these transported nuggets alongside Protoceratops fossils may account for the gold-guarding element of the griffin mythos. This is something we can test because the geology of Protoceratops sites is well documented and understood. Assuming the same basic meteorological processes occur today as thousands of years ago, we should see evidence of windswept gold in the Protoceratops bonebeds. But as far as I'm aware, no gold has been reported from these sites, either as surface debris or as buried elements. Moreover, although the possibility of wind transportation is not excluded entirely, no gold is mentioned by the palaeontologists with Mongolian field experience interviewed by Mayor and Heaney (1993) or Mayor (2011). All this considered, the evidence for it seems the link between Protoceratops and gold deposits is not as strong as it first seems.

Finally, it's worth noting that the Greek accounts of griffins may no longer be the only texts on these creatures from the first century BCE. Gane (2012) discusses Babylonian and Neo-Assyrian literature which is tentatively thought to describe another take on griffin lore. They provide a very different interpretation of griffins, where they are divine guardians against evil spirits and possibly associated with funerary rites. This sounds little like the idea that they were desert-dwelling, gold-hoarding wild animals, and of course suggests no obvious link to fossil animals of China and Mongolia. The implication here is that the Greek stories are only one set of lore about griffins. They are more familiar to us because of their transition to the post-classical period, but they might not be the only, or even the original interpretation of these creatures. Thus, even if Protoceratops is something to do with the griffin - which is far from clear - it is likely only involved in one component of griffin folklore. This seems to echo points made above about the griffin is a very old and complex concept, and how interpretations of its origins are blurred by multiculturalism.

So... is Protoceratops the basis of the griffin myth?

Before we answer that, here's a quick summary of the main issues outlined here:

• Near Eastern griffin culture seems to occur thousands of years before we have evidence for it in central Asia, suggesting Protoceratops anatomy could not be referenced in any way by the original griffin artists.
• Griffin anatomies, in all their variants, are best and entirely explained as chimeras of extant animals. There is no need to invoke any exotic fossil anatomies in their design.
• Griffin iconography, and perhaps written legends, are sufficiently varied to suggest a complex set of origins and legends for these creatures.
• Ancient Greek writings seem to lack compelling references to Protoceratops, and aspects of appearance and behaviour they discuss clearly indicate they were not informed by fossilised animals. Several details of these accounts suggest they must be talking about imaginary creatures.
• Protoceratops fossils are found hundreds of kilometres from ancient Scythian gold mines, undermining the suggestion they might be the source of griffin gold guarding lore. There is no indication that these dinosaur fossils are associated with gold.

References

• Bowra, C. M. (1956). A Fragment of the Arimaspea. The Classical Quarterly, 6(1/2), 1-10.
• Fastovsky, D. E., Badamgarav, D., Ishimoto, H., Watabe, M., & Weishampel, D. B. (1997). The paleoenvironments of Tugrikin-Shireh (Gobi Desert, Mongolia) and aspects of the taphonomy and paleoecology of Protoceratops (Dinosauria: Ornithishichia). Palaios, 59-70.
• Frankfort, H. (1937). Notes on the Cretan griffin. The Annual of the British School at Athens, 37, 106-122.
• Gane, C. E. (2012). Composite Beings in Neo-Babylonian Art (Doctoral dissertation, University of California, Berkeley).
• Goldfinger, E. (2004). Animal Anatomy for Artists: The Elements of Form: The Elements of Form. Oxford University Press, USA.
• Goldman, B. (1960). The development of the lion-griffin. American Journal of Archaeology, 64(4), 319-328.
• Lambert, O., Godefroit, P., Li, H., Shang, C. Y., & Dong, Z. M. (2001). A new species of Protoceratops (Dinosauria, Neoceratopsia) from the Late Cretaceous of Inner Mongolia (PR China). Bulletin-Institut royal des sciences naturelles de Belgique. Sciences de la Terre, 71, 5-28.
• Mayor, A. (2001). The first fossil hunters: paleontology in Greek and Roman times. Princeton University Press. (First edition)
• Mayor, A. (2011). The first fossil hunters: paleontology in Greek and Roman times. Princeton University Press. (Second edition)
• Mayor, A., & Heaney, M. (1993). Griffins and Arimaspeans. Folklore, 104(1-2), 40-66.
• Phillips, E. D. (1955). The legend of Aristeas: fact and fancy in early Greek notions of East Russia, Siberia, and Inner Asia. Artibus Asiae, 18(2), 161-177.
• Tartaron, T. F. (2014). Cross-Cultural Interaction in the Greek World: Culture Contact Issues and Theories. In Encyclopedia of Global Archaeology (pp. 1804-1821). Springer New York.
• Wyatt, N. (2009). Grasping the Griffin: Identifying and Characterizing the Griffin in Egyptian and West Semitic Tradition. Journal of Ancient Egyptian Interconnections, 1(1), 29-39.

Juvenile, subadult and a big, old adult Rhamphorhynchus muensteri forage in a Jurassic lagoon. We know more about the position of this pterosaur in Mesozoic food webs than any other thanks to its excellent fossil record. The floating posture here is based on data from Hone and Henderson (2014).

The Late Jurassic, Solnhofen Formation pterosaur Rhamphorhynchus muensteri is an exceptional flying reptile. We tend to overlook it a bit now - it's been known for almost two centuries, which is long enough to temper enthusiasm for any fossil species - but it's a remarkable animal for a number of reasons. Far from a typical example of the rhamphorhynchid lineage, it's the rhamphorhynchiest of all pterosaurs with a jaw full of large, conical teeth, elongate extensions to its jaw tips, exceptionally long and slender wings, delicate hindlimbs and walking digits, and a long, stiff tail famously adorned with a diamond or triangular shaped vane*. It also arguably has the best fossil record of any pterosaur. It's known from over 100 specimens, many of them being complete, articulated skeletons with at least some three-dimensionality, as well as providing excellent soft-tissues remains. Excepting embryos, we have complete growth series from tiny juveniles to chunky adults with 1.8 m wingspans, and its preservation is such that fine details of bones can be gleaned through careful mechanical or acid preparation. Its osteology is subsequently better known that any other pterosaur. The Cretaceous pterodactyloid Pteranodon might be known from more fossils (>1400), but these flattened, disarticulated remains are nowhere close to the fossil quality of Rhamphorhynchus.

*We see these restored for numerous long tailed pterosaurs, but only Rhamphorhynchus is known, for fact, to have this 'classic' tail vane morphology.
On top of all this, Rhamphorhynchus also provides greater direct insight into its daily behaviour than any other pterosaur. Multiple examples of gut content, coprolites, predator-prey associations and its inclusion in a ball of vomited spittle provide us with insight into what this pterosaur ate, where it was feeding, and what was eating it. In this, a second and concluding foray into the pterosaur palaeoecological record (click here for the first), let's take a look into how this animal slotted into Jurassic ecosystems.

Snap my fish up

What did Rhamphorhynchus eat? At least three specimens suggest that it foraged for fish of various sizes. The most famous example of such a fossil is sometimes referred to as the 'greedy guts Rhamphorhynchus', an animal which swallowed a fish almost as long as its own torso. This specimen represents a smallish individual, first described by Wellnhofer (1975), with a partly articulated, partly digested fish fossil preserved inside the posterior 60% of the rib cage (below). The orientation of the fish tail fin suggests the fish was swallowed head first, and we have to assume that some major distension of the throat occurred when doing so. That pterosaurs were capable of doing this isn't that surprising considering that extant pterosaur relatives - crocodylians and birds - have mobile throats which aid swallowing of big food items. The relative proportions of these gut contents suggests this animal must've bolted its food like these modern archosaurs, a behaviour rare among mammals but known to occur in at least one large, yellow, bipedal primate. This specimen also presents several elongate elements which defy easy explanation: they're suggested as other food items or even bits of preserved gut tissue by various authors (dark grey in the line drawing below).

The fossil, interpretive drawing, and restored reality of Jurassic table manners. Disgraceful. Line drawing after Wellnhofer (1975).

Fish dietary remains have been reported from two other Rhamphorhynchus specimens. A complete, relatively small fish has been found in the throat region of one specimen, also swallowed head-first, and various scales and bones occur within the rib cage of another (Frey and Tischlinger 2012; Hone et al. 2013). These three specimens do not represent the limit of Rhamphorhynchus gut content, but they are the limit of identifiable examples: some specimens are known with indeterminate bones or massive, disorganised crystal growths in their stomach regions which represent poorly preserved gut matter, but they aren't of much use to us here.

The one, the only, pterosaur coprolite

Of the many questions that keep pterosaur experts up at night - what are they related to? how did they work as functional organisms? how are they related to each other? - none has been greater than what their poop was like. Expelled waste is a common form of fossils in some localities, but remained entirely elusive for flying reptiles until last year when Dave Hone and colleagues (2015) identified the first pterosaur coprolite dropping out of a complete Rhamphorhynchus specimen. Finally, pterosaur workers can sleep easy.

Rhamphorhynchus muensteri specimen with coprolite (cp). From Hone et al. (2015).

The compact shape of these remains and their proximity to the pelvic region suggest that they were expelled from the pterosaur shortly after it settled on the seabed of the Solnhofen lagoon. Some of the coprolite content is pretty indistinct, but one portion preserves thousands of tiny spines, likely indigestible bits of a recent meal. Exactly what they are is difficult to say - you can get a good look here if you'd like to figure them out - but a number of alternatives were considered by Hone et al. (2015). The tentative, albeit still problematic, suggestion is that they represent cephalopod hooklets. This situation is somewhat frustrating, as this coprolite shows that Rhamphorhynchus was not just a fish eater, but doesn't really tell us much else. Still, now that we know what we're looking for, perhaps more pterosaur coprolites might start coming to light.

Fossilised food chains

Several Rhamphorhynchus specimens reveal it was prey to other Jurassic animals. Among the least commonly discussed is a small pellet produced by something like a fish or crocodylomorph which contains several Rhamphorhynchus wing bones (Schweigert et al. 2001). This is a rare example of Rhamphorhynchus from the Nusplingen Limestone, a unit lithologically similar to Solnhofen but slightly older. As is so often the case with such fossils, the identity of the pellet maker remains elusive. My own suspicions are of a piscine origin, as modern crocodylians don't tend to spit out bones (they digest them, only regurgitating hair, feathers and other keratinous tissues that are difficult to break down). That may not have been true for fossil crocs, of course.

Rhamphorhynchus vs. Aspidorhynchus. I guess we should call this one a draw? From Frey and Tischlinger (2012).

Among the most remarkable Rhamphorhynchus fossils are five instances where it is preserved alongside the predatory fish Aspidorhynchus acutirostris, a long-bodied species that is often much larger than its Rhamphorhynhus prey (Frey and Tischlinger 2012; Weber 2013). These fossils are palaeoecologically notable for three reasons. Firstly, large Solnhofen vertebrates are hardly ever associated, and yet we have five instances of this same pterosaur and fish species being found in touching, or near touching, proximity. Secondly, all five are exquisitely preserved - one example includes a 'mummified' pterosaur with wing membranes, and all are completely articulated. Thirdly, the Rhamphorhynchus are invariably positioned around the skull of the fish, as if a specific, repeated behaviour saw these animals preserved together. These particulars make chance association of these animals unlikely and imply Aspidorhynchus sought out Rhamphorhynchus as food, probably hunting live specimens rather than scavenging floating corpses (as indicated by the excellent preservation of the individual pterosaurs). Frey and Tischlinger (2012) provide a plausible scenario for the deaths of these animals: they reason the Aspidorhynchus tackled prey that became entangled in their jaws before accidentally entering the toxic bottom waters of the Solnhofen waterways. In these anoxic depths the tangled pair would die pretty quickly (if the pterosaur wasn't already dead, of course), leaving us with perfectly preserved bungled predatory acts. The icing on the cake of these specimens is that one of these Rhamphorhynchus specimens has already been mentioned here - that individual with a fish in its throat (Frey and Tischlinger 2012). In this specimen at least, we can assume the pterosaur ate a fish shortly before being attacked itself: a rare instance of a fossil food chain.

The bigger picture of Rhamphorhynchus palaeoecology

Collectively, we have 10 specimens of Rhamphorhynchus telling us something about its position in Mesozoic food webs. That's not bad going for a pterosaur, a famously rare type of fossil, and is actually a pretty good palaeoecological record for any fossil vertebrate. 10 specimens is not enough to tell us everything about the lifestyle of a fossil animal, but does allow us to paint a general picture. They show us that Rhamphorhynchus was adapted to foraging on pelagic prey - often small, probably live fish - and that it must have spent a good amount of time in or around water, as it was clearly an attractant to aquatic predators. These specimens gel neatly with general models of Rhamphorhynchus lifestyle interpreted from their functional anatomy. It's generally thought that Rhamphorhynchus was adapted for life along shorelines - basically a Mesozoic gull. It's not uncommon to be suspicious of such claims nowadays, it being realised that the 'Mesozoic seabird equivalent' almost became a trope, or at least a tremendous over-generalisation, of pre-21st century pterosaur science. But in this case, a gull-like lifestyle is a cogent hypothesis based on studies of wing shape, flight style, tooth and jaw apparatus, and limb function (e.g. Wellnhofer 1975; Hazlehurst and Rayner 1992; Witton 2008, 2015; Ösi 2011). Perhaps research on Rhamphorhynchus was involved in creating the stereotype of pterosaurs as Mesozoic seabirds, but we should not regard it as a victims of this stereotyping itself.

But we should ask ourselves why Rhamphorhynchus palaeoecology is comparably well-represented in the fossil record. It might be something as simple as preservational conditions, but there are plenty of pterosaur Lagerstätten, some of them containing close relatives of Rhamphorhynchus in reasonable abundance, which provide no information about dietary preferences or interactions with predatory species. Is there something intrinsic to Rhamphorhynchus which makes it special? I find several reasons to wonder if Rhamphorhynchus was an atypically aquatic species, not only flying and feeding above water but actually routinely entering it. Firstly, Rhamphorhynchus has a hatchet-shaped deltopectoral crest (the process on the humerus which anchors the flight muscles), a small (or at least narrow) torso and short legs: these are features which Habib and Cunningham (2010) link to routine and efficient aquatic takeoff. Secondly, tests of pterosaur swimming suggest that Rhamphorhynchus had a pretty stable floating posture - not something that can be said for all pterosaurs (Hone and Henderson 2014). Thirdly, it also has comparably large but delicately constructed feet, which might suit paddling, as well as a slender set of forelimb bones (Witton 2015) which recall the streamlined arm bones of swimming and diving birds (Habib and Ruff 2008). Prolonged bouts of swimming might also account for its general abundance, excellent preservation and all-round good fossil record: being immersed in water puts it a step closer to being preserved than other, less aquatic species. Who knows: perhaps it even dived into Solnhofen's toxic bottom waters on occasion, explaining why so many specimens are excellently preserved? Hmmm.... perhaps this warrants further investigation.

Coming soon: could dinosaurs - gasp - lie down on their sides? My take on the greatest of palaeoart debates.

Rhamphorhynchus is supported by fish; this blog is supported by Patreon

The paintings and words featured here are sponsored by the finest human beings on the planet, those folks who support me at Patreon. Backing my blog for as little as $1 a month helps me churn out researched and detailed articles and paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress views and high-resolution artwork, and even free prints. Accompanying this post, we're going to look at the bigger picture of pterosaur palaeoecology: azhdarchids and Rhamphorhynchus are just two lineages with palaeoecological records - what about the rest of Pterosauria? Sign up to Patreon to join that discussion!

References

• Frey, E., & Tischlinger, H. (2012). The Late Jurassic pterosaur Rhamphorhynchus, a frequent victim of the ganoid fish Aspidorhynchus?. PloS one, 7(3), e31945.
• Habib, M. & Cunningham, J. 2010. Capacity for Water Launch in Anhanguera and Quetzalcoatlus. Acta Geoscientica Sinica. 31, 24-25
• Habib, M. B., & Ruff, C. B. (2008). The effects of locomotion on the structural characteristics of avian limb bones. Zoological Journal of the Linnean Society, 153(3), 601-624.
• Hazlehurst, G. A., & Rayner, J. M. (1992). Flight characteristics of Triassic and Jurassic Pterosauria: an appraisal based on wing shape. Paleobiology, 18(04), 447-463.
• Hone, D. W., Habib, M. B., & Lamanna, M. C. (2013). An annotated and illustrated catalogue of Solnhofen (Upper Jurassic, Germany) pterosaur specimens at Carnegie Museum of Natural History. Annals of Carnegie Museum, 82(2), 165-191.
• 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., Henderson, D. M., Therrien, F., & Habib, M. B. (2015). A specimen of Rhamphorhynchus with soft tissue preservation, stomach contents and a putative coprolite. PeerJ, 3, e1191.
• Ősi, A. (2011). Feeding‐related characters in basal pterosaurs: implications for jaw mechanism, dental function and diet. Lethaia, 44(2), 136-152.
• Schweigert, G., Dietl, G. & Wild, R. (2001). Miscellanea aus dem Nusplinger Plattenkalk (Ober-Kimmeridgium, Schwäbische Alb) 3. Ein Speiballen mit Flugsaurierresten. Jahresberichte und Mitteilungen des Oberrheinischen Geologischen Vereines, 83, 357-364
• Weber, F. (2013). Paléoécologie des ptérosaures 3. Les reptiles volants de Solnhofen, Allemagne. Fossiles. 14. 50-59.
• Wellnhofer, P. 1975. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Palaeontoographica A, 149, 1-30.
• Witton, M. P. (2008). A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana, 28, 143-159. 
• Witton, M. P. (2015). Were early pterosaurs inept terrestrial locomotors? PeerJ, 3, e1018.

Background: Javelina Formation forest. Mid-ground: the 4.6 m wingspan, super-famous azhdarchid pterosaur Quetzalcoatlus sp. Foreground: lunch.

As a consultant, the pterosaur I get asked about more than any other is the azhdarchidQuetzalcoatlus. In recent weeks I've been speaking to two completely independent media producers about this animal, and I think just about all my prior TV and film work has involved it somehow, even if not prominently. I suppose Quetzalcoatlus is so popular because it's not just the most famous azhdarchid pterosaur - which are now more popular than ever - but the first animal most people think of as the biggest ever flying creature.

All the pictures, museum exhibitions, sculptures and animations of Quetzalcoatlus suggest it must be a well-understood animal, but it's actually very difficult to provide consultancy on, for several related issues. The first is that the science on the animal itself is unfinished, largely unpublished, and the existing body of work is decades old. The second is that our general understanding of azhdarchid pterosaurs has moved on considerably in the last two decades, and largely without a good grounding of what Quetzalcoatlus actually is. The third, and final, issue is that most parties think Quetzalcoatlus is better understood than it really is, to the point where whole media projects are locked in around it, and consultants are asked to make calls that have little scientific backing. That third point is an important one: 'Quetzalcoatlus the media concept' is a very different beast to 'Quetzalcoatlus the scientific entity'. This can create difficulties when creating programmes, games or artwork of this animal, as the expectations for what can be achieved with Quetzalcoatlus are often beyond what scientists can provide.

In the interests of helping out those who want to use Quetzalcoatlus in their projects, I thought it might be useful to show how 'common knowledge' about Quetzalcoatlus differs from its actual, objective status within 21st century pterosaur science. An important caveat before we go further is that scientific work on Quetzalcoatus is ongoing. A full description and functional assessment is rumoured to be in the works (as, er, it has been for 40 years...) and this will change the way we view this animal tremendously. It can't not do this: the data available on this animal are minimal, so publication of any new details will augment the current situation. In all likelihood this post will be moot, at least in part, when this document is finally published. This piece is being written in May 2016, so please bear in mind that things might have changed if you're reading this at a later date.

The concept.Quetzalcoatlus is a giant azhdarchid pterosaur from Texas, known from substantial remains.

The science.The popular view of Quetzalcoatlus is really a conflation of two taxonomic entities, Quetzalcoatlus northropi and Quetzalcoatlus sp. Both occur in the Late Cretaceous (Maastrichtian) Javelina Formation of southern Texas*. Q. northropi is currently the only 'officially' named species of Quetzalcoatlus, and is the reason we think this animal was so huge. It's also only known from bits and pieces of a gigantic left wing and cannot be regarded as a well known animal. Do not, if you're a TV producer or whatever, expect to film a room full of real fossils for this thing - any skeleton you see of a giant Quetzalcoatlus is almost entirely reconstruction - still impressive, but nearly all calculation and extrapolation.

*It's worth mentioning that Quetzalcoatlus has been identified outside of Texas, scraps of azhdarchid bones from both North America and Europe being allied to this genus. I suspect that most of these should not be referred to Quetzalcoatlus proper, as they're fairly 'generic' azhdarchid bones and, moreover, we have no criteria for what constitutes Quetzalcoatlus within Azhdarchidae itself (see below). I don't want to discuss these now, however, and only mention them for the sake of completeness. 

Q. sp., by contrast, is much better represented. Several incomplete skeletons are known (an example can be seen below) that collectively give a near complete picture of Q. sp. osteology. Its this material that gives us our familiar image of Quetzalcoatlus:the long neck, the oversize pointy face, the long limbs and so on. Almost all discussions about the detailed anatomy of Quetzalcoatlus pertain to this material, not the giant wing. The Q. sp. fossils are also a key source of the proportional data used in calculating the 10 m wingspan for the giant Q. northropi animal, even though Q. sp. is much smaller - the complete wing metrics of one specimen give a wingspan of 4.6 m (Unwin et al. 2000).

Q. sp. partial skeleton figured by Kellner and Langston (1996).

How the two Quetzalcoatlus species are related to each other, and other azhdarchids, remains critically unexplored and uncertain. It is no exaggeration to say that taxonomic considerations of this important, well-known genus comprise no more than a few sentences in the entirety of technical pterosaur literature. The name Q. northropi was not even erected in a descriptive paper, but as an aside in a brief comment on the likely wingspan of the giant wing specimen (Lawson 1975a). This gave us the northropi name and designated a type specimen (the big wing), and suggested that the smaller specimens were just diminutive, presumably immature versions of the giant species. However, other elements key to species creation - diagnoses, specimen inventories, supporting description or illustrations were not provided, the best alternative being a very short 1975 science paper (Lawson 1975b). Nessov (1991) provided an attempt to diagnose the genus (along with other azhdarchids) but his characters are not useful. Later, Kellner and Langston (1996) suggested that the smaller Quetzalcoatlus skeletons were not juveniles of the giant species, but a distinct species that would be named at a later date. It was this paper that created the 'Q. sp.' moniker, a place-holder for a name we'll perhaps see published in time. Alas, Q. sp. was also created using drive-by taxonomy without justification for separating sp. from northropi, or providing characters to unite these species in a distinct genus among other azhdarchids.

This might all sound like tedious detail irrelevant to reconstructions, media portrayals etc., but the upshot is that the pterosaur community is still largely in the dark about Quetzalcoatlus. We can't really comment on what makes it unique, whether all these bones from Texas should be considered one or two species, how accurate it is to scale up the smaller Quetzalcoatlus to the size of the big wing and so on: that information has been made public yet. Some specific folks might be able to provide those details, but they are not peer-reviewed 'common knowledge'. Therefore, most researchers (including myself) can only talk about Quetzalcoatlus in terms of the few details that have been published, and fill the rest in with 'generic' details of azhdarchid pterosaur palaeobiology.

The concept. Quetzalcoatlus was like all azhdarchids: a long-necked, long-skulled creature with long limbs.

Quetzalcoatlus sp. skeletal, using data from Kellner and Langston (1996); Witton and Naish (2008), several other sources of azhdarchid neck data, and Unwin et al. (2000). Yes, it was that long-necked and long-legged.

A question I have much more trouble answering is what Q. northropi looked like. When we see a giant long-necked Quetzalcoatlus in TV shows or comics, we're seeing a hybrid of the two Quetzalcoatlus animals - the anatomy of sp. crossed with the size of northropi. This approach is not without merit: it's consistent with the existing taxonomy of this animal (such that it is), and other pterosaur fossils confirm that some giant azhdarchids were long-necked, perhaps Q. sp-like creatures.

On the other hand, we only have an incomplete northropi wing skeleton to work from. It's widely recognised that pterosaur wings are among the more conservative aspects of their anatomies - great for identifying pterosaurs to specific groups (we have characterised azhdarchid wings, for instance) but above a basic level of taxonomy they don't tell us much about life appearance. It wasn't always this way. When Quetzalcoatlus was found in the 1970s the smaller Q. sp. skeletons provided our only comprehensive insight into azhdarchid anatomy, and thereafter we assumed that Q. sp. typifies the group. However, azhdarchid pterosaur science has progressed considerably in the last two decades and the group can no longer be considered anatomically uniform. Their skulls can be short and broad, long and narrow, and have deep or slender lateral profiles (Witton 2013). They can have cranial crests (Kellner and Langston 1996), but they might not (Cai and Wei 1994). Their necks can be extremely long, or of more typical pterodactyloid lengths (Vremir et al. 2015). Some had stilt-like limb bones, but others had short forelimb anatomy (McGowan et al. 2001). Such variation seems present in the giants as much as their smaller cousins. I don't think we know what an 'average' azhdarchid looked like yet, but Q. sp. should be viewed as representing only one, relatively exaggerated take on azhdarchid anatomy. It historically seemed safe to make Q. sp. a giant version of this form, but that cannot be regarded as the only option today. For all we know, Q. northropi could be a short-armed, short-necked species with a truncated, deep jaw - quite the opposite of Q. sp..

A selection of azhdarchid skull and mandibles. A and B, posterior skull bits of Hatzegopteryx; C-D, Q. sp., E. Zhejiangopterus; F-G, Bakonydraco; H, TMM 42489-2, the Javelina Formation azhdarchid which isn't Quetzalcoatlus. Q. sp. must be regarded as a long-snouted, gracile form: does this also apply to Q. northropi? Image from Witton 2013.

I would be more comfortable with reconstructions of Q. northropi as a giant, scaled-up Q. sp. if we had good reason to believe the two were closely related**. As mentioned above however, necessary work on this has yet to be presented and, as evidence-led scientists, it is not unreasonable to call the situation ambiguous until more data is forthcoming. I suppose one reason we might think northropi and sp. are congeneric is because they're from the same formation. However, the remains of northropi and sp. were not associated, being found 10s of kilometres apart (Lawson 1975b), and we have increasing evidence of multiple azhdarchid taxa occurring in the same geological units (e.g. McGowen et al. 2000; Godfrey and Curry 2005; Vremir et al. 2013). Where azhdarchids do coexist, they differ markedly in anatomy and overall form (Vremir et al. 2013). An additional complication is TMM 42498-2, a large, deep-jawed Javelina Formation azhdarchid which is clearly not Q. sp. (bottom panel in the image above). If this represents cranial remains of Q. northropi and not an additional Javelina species (we currently have no way of telling), northropi would look would look very different to our usual depictions.

**I'm expecting people to wonder if Quetzalcoatlus taxonomy has been looked at in detail via cladistic methods. The most complete published assessments I'm aware of are those by Brian Andres (e.g. Andres and Myers 2013) which use seven azhdarchid OTUs, including the two Quetzalcoatlus taxa. The results of such studies remain ambiguous about the affinities of Quetzalcoatlus (Q. sp. and northropi form a polytomy with Arambourgiania). I'd like to see an analysis with more azhdarchid taxa, including some of the more unusual types such as Hatzegopteryx and Montanazhdarcho.

I don't have any real answers or insight on these points. Rather, I'm getting at the fact that our 21st century understanding of azhdarchids and other flying reptiles is becoming complicated, and with our current, superficial insights into what Quetzalcoatlus is and how it's related to other azhdarchids, there may not be one 'right' way to restore northropi. We might be correct to represent it as a giant Q. sp., as per tradition, but we might not.

The concept. Quetzalcoatlus was the biggest animal to have ever flown, even larger than other giant azhdarchids

The science.As with modelling the size of most giant extinct animals, it's difficult to say what giant azhdarchid was the biggest. Q. northropi was certainly up there, recent estimates of its wingspan being in the region of 10 m and predicted body masses of 200-260 kg. But other giant pterosaurs are predicted to be about the same size (see Witton and Habib 2010 for a recent discussion)... and that's about all we can really say. Every giant azhdarchid is represented by scrappy material, so the error bars on any size estimate are large and the calculations themselves are highly sensitive. We would be foolish to use them as anything other than ballpark figures. We can say that Q. northropi was one of the biggest flying animals of all time and, along with other giant azhdarchids, it dwarfed other flying species including most pterosaurs, and all birds and bats. I appreciate some folks will find this lack of clarity frustrating, but that's just how it is: we can't say any more until we understand all the giants - not only Quetzalcoatlus - in more detail. 

The concept. The outstanding flight capabilities of giant azhdarchids allowed Quetzalcoatlus to be a continent-hopping animal that occurred in Europe as well as the USA, although the European bones were given a different name: Hatzegopteryx. Some chap called 'Witton' suggested this.

The science.Thanks, I think, to Wikipedia, I've been confronted several times about suggesting the Romanian giant azhdarchid Hatzegopteryx thambema should be synonymised with Quetzalcoatlus. I feel a bit misquoted on this. Yes, I (and colleagues) mentioned this as a qualified possibility in a 2010 abstract and conference talk (Witton et al. 2010), but as part of a broader, detailed discussion about the need to tighten up giant azhdarchid taxonomy. Specifically, we discussed the three named giant azhdarchids - Arambourgianiaphiladelphae, Quetzalcoatlus northropi, and Hatzegopteryxthambema - and stressed issues with their current taxonomy. These issues - hitting some points already tackled here - included the lack of a description and diagnosis for Quetzalcoatlus; the uncertainty over the relationships between Q. northropi and Q. sp.; the scrappy nature and general incomparability of giant azhdarchid fossil remains; their representation by anatomies generally considered unnameable by pterosaur workers, and the identification of several alleged autapomorphies of giant species in other azhdarchid remains.

Holotypes of giant azhdarchids. A, Arambourgiania philadelphiae, B, Q. northropi (humerus only, the other holotype wing elements have never been published) C, the damaged proximal humerus of Hatzegopteryx thambema (humeral head and cranial remains not figured here). From Witton (2013).

Concerning Quetzalcoatlus and Hatzegopteryx, we pointed out that overlapping bits of Q. northropi and Hatzegopteryx (proximal humeri) are similar enough that they could be considered synonymous, but this says more about the use of wing bones for the Q. northropi type material than anything else. As mentioned above, wing bones aren't always that useful in detailed taxonomy. The overlapping bits of Hatzegopteryx and Q. sp. (jaw joints), however, are different enough to demonstrate they are separate taxa. We went on to say that the significance of all this isn't clear because the relationships between Q. sp and Q. northropi are not evaluable at this stage. Our take-home message, then, wasn't that Hatzegopteryx and Quetzalcoatlus are the same thing, but that the diagnoses, validity and relationships of named giant azhdarchids warrant detailed assessment in future. Since writing this abstract six years ago, ongoing work on Hatzegopteryx seems to be supporting its separation from other azhdarchids - more on that in time.

So... how can Quetzalcoatlus be used in art, film, games etc.?

Three Sinornithoides youngi, one standing, one sitting, one sunbathing. But would these animals really have adopted resting poses like those of modern birds, as shown here, or would they have relaxed in completely different postures?

A recurrent topic of conversation among palaeoartists concerns how non-avialan dinosaurs rested. Specifically, were they constrained to crouching down and lying on their bellies like modern birds (above), or could they lounge on their sides, rest with limbs beneath their bodies, and generally adopt more varied resting poses? I've always thought that there's no reason to confine depictions of reposed dinosaurs to avian-like squatting poses and, based mostly on personal experiences of modern animals, it has never seemed outlandish to depict a theropod resting on its side, or a horned dinosaur sitting on its legs or whatever. This is evidenced by some of the art I've posted here in the last few years, some of which is reproduced below. But reasonably frequent mention of this topic on social media suggests that not everyone has this attitude, so I thought it might be of interest to discuss this in more depth. What do Mesozoic dinosaur skeletons, trace fossils, and modern animals tell us about Mesozoic dinosaur resting poses, and how might we approach this topic as artists?

A necessary caveat

Asking general questions about how extinct dinosaurs did anything is increasingly difficult to answer in a succinct, concise manner. Dinosauria is an enormous group of animals with huge diversity in body size, gait, proportions, soft-tissue anatomies and so on. These are all things which impact the way an animal might sit or lie down, and in all likelihood there is no one answer to this inquiry. What works for a troodontid may not work for an ankylosaurid, and what works for these may not apply to a sauropod. While there's some merit to taking a general approach to this discussion (and that's what we'll be doing here), this point is something to bear in mind as we go through. The actual answer to this question will be multifaceted, and found through dedicated study of specific dinosaur groups.

What the fossil record tells us

Crouching dinosaur traces attributed to bipedal theropods and ornithopods are known from the track record (e.g. Lockley et al. 2003; Milner et al. 2009 and references therein), and these are often used as evidence for dinosaurs generally adopting bird-like, crouched resting postures. Such impressions cannot be regarded as common, but are easily identified by the elongate footprint impressions where the long metatarsal bones and ankle are impressed into the ground behind the toe prints. That at least some of these crouching traces show stationary behaviours, and not crawling or stooping, is evidenced by the symmetrical position of the footprints and impressions of an ischial callosity (the soft-tissue covering the posterior prong of the dinosaur pelvis). These pelvic traces show that the body was in contact with the ground when these traces were made, and that it was not being dragged forwards. Clearly, these animals were, at least partly, letting the ground take some of their weight.

We don't just have to look to trace fossils for evidence of crouching behaviour. On rare occasions, remains of dinosaurs are found that were more-or-less entombed alive in ash or sediment, revealing details of their postures at time of death. Famous examples of such occurrences include several troodontids (Russell and Dong 1993; Xu and Norell 2004; Gao et al. 2012) and protoceratopsids (Fastovsky et al. 1997). These also consistently show dinosaurs resting on their bellies in crouched postures, legs folded up either side of their bodies in a very avian manner.

Protoceratops (P. hellenikorhinus shown here) is among the dinosaurs known from skeletons that are thought to reflect near-life position at death. The pose depicted in this painting, with the animal leaning on its left leg, is at odds with the poses of such skeletons.

This is starting to seem like we've already solved the debate, but we might want to think about what these data are actually telling us. Our footprint data, and much of our crouching-death-pose skeletons, pertains to smaller bipedal dinosaurs, and we don't have any comparable data for the other bauplans. I don't know about you, but my chief interest in this discussion isn't really the small bipeds: it's the stegosaurs, the sauropods, the ceratopsids etc: those big animals that are different enough from modern species that their day-to-day behaviours are not obvious. And there's certainly enough strange stuff going on in their anatomy to caution against simply applying what we see in small bipedal dinosaurs across the entire group.

Secondly, it's interesting that we only sometimes see hand prints associated with crouching traces (Milner et al. 2009). When we do, we tend to see evidence of the palms and digits, not of whole forearms, as we might expect from a fully resting, lying animal. So are these animals actually lying down, or just sitting? Have they crouched down to truly rest, or are they performing some other behaviour (e.g. foraging, preening etc.)? I find it interesting that crouching traces can occur multiple times within trackways (Lockley et al. 2003), and that others show evidence of animals shifting weight and changing direction. Such instances seem to record sitting, but still 'active' individuals. Studies of modern animal behaviour are relevant here. When researching bird sleeping postures, I found Almaner and Ball (1983) had similar misgivings about the idea of immobile birds being 'inactive' or merely 'resting'. Based on their observations, they divided avian 'loafing' behaviour (that is, behaviour adopted when the bird is generally immobile) into multiple types of activity, of which only one is resting. Looking through their categories of loafing behaviour (below), none seem outlandish when applied to dinosaurs and I wonder what those prints made by stationary, crouched dinosaurs really represent: resting is really only one option. It may be that further examination of 'resting' traces can turn up more information. That said, I'm aware of slightly frustrating experiments with modern emus where even optimal substrates for track formation do not record additional trace evidence of activities like feeding from crouched positions (Milàn 2006). But, hey, we can still be optimistic that more data and insights will come in time.

What it means to be a stationary bird. Clearly, being crouched and immobile does not always mean 'resting'. From Almaner and Ball (1983).

Those skeletons preserved in life position are also worthy of further comment. Generally speaking, these represent animals caught in catastrophic events - volcanic eruptions, sandstorms and so forth - and we probably should not assume that these animals were just 'resting' when they were entombed in sediment. Indeed, the orientation of Protoceratops skeletons in Mongolian bone beds is non-random, and sedimentological data indicates they were facing into strong sandstorms when they died (Fastovsky et al. 1997). They were certainly crouched, but in all likelihood they were not relaxed and taking it easy: quite contrarily, it seems reasonable to assume they died during attempts to weather a storm, doing their best to hunker down against flying sand, collapsing dunes and all manner of other terrible events. An apt analogy here might be reading the Pompeii ash mummies as representing stereotypical human resting postures: some were found lying down, but that doesn't mean they were relaxing when they died.

On a related note, I also wonder how we would identify a dinosaur that died deliberately resting on its side rather than being moved into that pose by taphonomic processes. Most animals require effort to remain vertical, be it crouched or otherwise, and it's obvious when we find crouching dinosaurs that their pose reflects something of their final behaviours. But how do we distinguish a dinosaur preserved having a nap on its side from one that simply died and fell over, or was washed up on a riverbank or whatever?

All this considered, my point here is not that these data are meaningless when it comes to discussions of dinosaur resting postures. They clearly show that many Mesozoic dinosaurs did naturally crouch in an avian-like manner, and there's no problem with assuming this has some bearing on resting poses. But I do not think this data is without complications, nor that it is complete enough to tell us the whole story here. We probably need to look elsewhere for additional information.

The search for modern analogues

Torvosaurus tanneri in controversial 'reclining on a recline' pose.

Another approach we can take to this problem is to look at how modern animals sit and rest. Birds are often hailed as the best insight here, and for obvious reasons. But are birds good models for Mesozoic dinosaurs? Modern birds represent an extremely derived group of dinosaurs, and their anatomy has been heavily influenced by the development of flight adaptations. That means that many anatomical aspects we should consider here - body shape, flexibility of vertebrae and limb joints, muscle mass and so on - are quite far removed from their Mesozoic cousins. Their torsos, for instance, are proportionally short and broad, and rendered inflexible by osteological fusions and large flight muscle masses. Their hips are similarly broad, thanks to reconfiguration of their internal organs and their hindlimb musculature is immense - a consequence of their launch strategy as well as reconfiguration of the leg to primarily flex at the knee, rather than the hip, during terrestrial locomotion. Their necks and heads are also extremely lightweight, and capable of being withdrawn over the body to rest on the chest. All these things considered, it's not surprising that birds almost always (see below) rest in crouching postures. Some parts of their anatomy are well suited to it, and others almost dictate it. Despite these derivations, some dinosaurs - theropods and small bipedal ornithischians - are certainly closer to this morphology than any other living groups, and birds probably are their best analogue for resting behaviours.

But what about other species? We might look to other reptiles for further insight here. Lizards, turtles and crocodylians are like birds in that they rest on their bellies, although they tend to be less fussy about the placement of their limbs (I often find my own pet reptiles looking like they just flopped down mid-step, legs and arms at all sorts of angles. It doesn't look comfortable, but I guess it must be). But do these animals really have an alternative? Their bodies are very broad but shallow, and their limbs project laterally from the torso. It's hard to imagine them achieving a stable resting posture by doing anything other than lying on their bellies.

The body shapes of living reptiles are pretty distinct from those of sauropods or many ornithischians, and I don't think these animals provide much assistance with our inquiry. For these groups, a case can be made for their basic form being more akin to those of modern mammals than any living reptile. Like mammals, they tend to have deep, narrow chests, (see illustrations in Paul 2010 and Goldfinger 2005), and many lack the rigid structural bracing and expansive chest muscles that we see in birds. For some dinosaur groups, the limbs of large land mammals are better models than the light, flexible limbs of birds, and the fact many mammals are quadrupedal is also of utility here. The relative weight of mammalian heads, and flexibility of their necks, may be more comparable to some dinosaurian bauplans than avian ones too, and mammals are also our best (and only) modern analogue of larger Mesozoic dinosaur body masses. The latter is important to this discussion as shifting weight around between standing and reclining, as well as considering weight bearing during the rest phase, are factors here.

All these points considered, maybe the body shapes and masses of mammals offer some of the most useful analogues for non-bipedal dinosaur resting poses and related mechanics? Mammals are, of course, far more flexible in their approach to resting than reptiles. Even large mammals like elephants, hippos, rhinos and large bovids are capable of crouching and lounging on their sides, and even modest-sized species will sometimes rest on their backs. I imagine this is because deep-chested large animals are top-heavy when crouched, so flopping over to one side is likely to be far more relaxing and stable. The fact that our largest land animals can spend hours on their sides without dying of asphyxiation is a good indication that this may not have been a concern for large dinosaurs, either. A big elephant is going to weigh as much as many big dinosaurs and, while the biggest hadrosaurs and sauropods were likely heavier, it's useful to have confirmation that 5-6 tonne creatures can lie down for extended periods without problem. I often wonder if the idea of animals crushing their lungs and other organs when lying down is a bit of a myth, or at least overstated. Even large stranded whales, weighing many times more than our largest elephants, can survive for days on land before dying. The fact is most beached whales die of complications related to the injuries and diseases that led to their stranding in the first place, and this generally happens long before their lungs or other organs are crushed.

To cheer everyone up after all that talk of dead whales, here's a male Asian elephant napping. D'aw. Photo by Wikimedia user Fruggo.

So maybe our best models are birds for bipeds, and mammals for everything else? Perhaps, but for all this talk of typical resting postures and so on, we should mention that some animals lie down in ways that would not be expected from their anatomy or taxonomic associations. This includes modern dinosaurs. For example, resting ratites (particularly young individuals) will sometimes sit with their legs completely stretched out behind them (Amlaner and Ball 1983). Sleeping ratites, and some other birds, do not tuck their beaks under their wings, or rest them on their chests, but rest their entire neck on the ground (Amlaner and Ball 1983). Sunbathing gamebirds (including poultry) are known to roll on their sides and back, both feet clearly visible on one side of the body, and will fall asleep in that posture if undisturbed (example). As is usual in biology, there are enough complications in our nice, neat rules to make us question whether we can ever predict anything with more than shaky confidence.

Resting postures of the Greater Rhea, depicted by Amlaner and Ball 1983. I recall seeing a rhea using the upper posture at Edinburgh zoo. It's... weird seeing a bird sitting like this in real life.

Functional studies of dinosaur anatomy

We've looked at direct evidence of reposed dinosaurs and their modern analogues, which leaves functional considerations of dinosaur skeletons as our last main area of consideration for this topic: is there anything about their anatomy to suggest resting on their sides or using other postures might be prohibited? The fusion of some dinosaur vertebrae is often mentioned as a problem here, particularly the ossified tendons common to many ornithischian dinosaur groups. These are suggested to have limited the motion of the vertebral column and limited dinosaurian abilities to shift their mass/wiggle out of lounging postures. Such suggestions are probably overstating the stiffening effect of ossified tendons. As a general point, it should be mentioned that ossified tendons are common across animals of all kinds, and occur in many places in their bodies. For example, they occur in the bodies of fish, in bird and human legs, along bird backs, in sauropod necks and in pterosaur forearms (e.g. Bennett 2003; Organ 2006; Organ and Adams 2010; Klein et al. 2012). Moreover, they are not necessarily anything to do with restricting skeletal motion. Sometimes the opposite seems true: they may be something to do with storing and releasing energy to increase arthrological efficiency, or simply reduce strain on musculature. Their functional roles are still being worked out, but it seems well grounded that their role varies with their position in the skeleton and their associated musculature. We also know that their histological composition varies, and this likely affects their mechanical properties too (Organ and Adams 2010).

In dinosaurs, ossified tendon distribution along the vertebral column is quite varied. As a general rule, ossified tendons occur around the hip and tail base, but they can cover many of the torso vertebrae in things like hadrosaurs. Studies suggest that their effect is to reduce vertebral motion in some planes, but they do not eliminate movement altogether (Organ 2006). The vertebrae can still move in all directions, and even relatively freely in some axes of motion, and that's likely all that was needed to enable animals to lift themselves from a non-crouching resting posture. We only need a few degrees of motion here and there to liberate a limb, or to gain better purchase on the ground, before the limb skeleton can take over in levering the body into a standing pose. For the sake of completeness, it's worth mentioning that the trunks of other dinosaurs - those without ossified tendons - were probably mobile enough for this job, too (e.g. Mallison 2010a, 2010b).

Finally, a practical consideration

From the new ITV show "Abelisaurs do the Darnedest Things".

One final point to make on this issue is a relatively pragmatic one. The idea that dinosaurs only adopted crouched resting poses implies a certain rigidity to their form, and one that would compromise their ability get into, or out of, anything other than deliberately chosen, specific poses. Against this I cite the general clumsiness of animals everywhere. Much as we like to glamourise and romanticise nature - beautiful in its savagery, red in tooth and claw, survival of the fittest and all that - the truth is that animals are as clumsy as we are. You don't have to be a dedicated wildlife observer to see animals slip, trip or fall. These things happen routinely, and they almost certainly did in the Mesozoic, too. Fighting and jostling animals would also almost certainly find themselves forced in compromised, awkward positions from time to time, too. We can be confident that Mesozoic dinosaurs fell on their sides, rolled onto their backs and got into other mischief by accident even if not by intent, and it seems unrealistic to assume they would not have recovered from these accidents as effectively as modern animals. If we assume they could escape such poses in emergencies, why should they not be able to rise from them at other times as well?

So, in summary...

Putting all these lines of evidence together - the limited direct fossil data, our ability to interpret that fossil data, the anatomy and behaviour of modern animals, and what we know of dinosaur anatomy - I still don't see any reason to think Mesozoic dinosaurs were constrained to crouched resting poses. I stress my use of the word 'constrained' there: as mentioned above, there is good reason to think crouching was utilised by dinosaurs for a variety of reasons, and I'm sure many of them rested in this way. Moreover, we can probably assume that most dinosaurs entering or rising from repose would have assumed a crouched position during that process. This seems fairly true of modern animals, after all. But there seems no reason to think they were incapable of other resting in other attitudes as well, such as reclining in classically 'mammalian' poses, using some of those strange ratite or galliform postures mentioned above, or doing something else entirely. It seems almost certain that different dinosaurs were suited to different poses, and different ranges of poses, when resting: maybe this is something to explore in future art.

Coming next: this:

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References

• Amlaner, C. J., & Ball, N. J. (1983). A synthesis of sleep in wild birds. Behaviour, 87(1), 85-119. 
• Bennett, S. C. (2003). New crested specimens of the Late Cretaceous pterosaur Nyctosaurus. Paläontologische Zeitschrift, 77(1), 61-75. 
• Fastovsky, D. E., Badamgarav, D., Ishimoto, H., Watabe, M., & Weishampel, D. B. (1997). The paleoenvironments of Tugrikin-Shireh (Gobi Desert, Mongolia) and aspects of the taphonomy and paleoecology of Protoceratops (Dinosauria: Ornithishichia). Palaios, 59-70. 
• Gao, C., Morschhauser, E. M., Varricchio, D. J., Liu, J., & Zhao, B. (2012). A second soundly sleeping dragon: new anatomical details of the Chinese troodontid Mei long with implications for phylogeny and taphonomy. PloS one, 7(9), e45203. 
• Goldfinger, E. (2004). Animal Anatomy for Artists: The Elements of Form: The Elements of Form. Oxford University Press.
• Klein, N., Christian, A., & Sander, P. M. (2012). Histology shows that elongated neck ribs in sauropod dinosaurs are ossified tendons. Biology letters, rsbl20120778. 
• Lockley, M., Matsukawa, M., & Jianjun, L. (2003). Crouching theropods in taxonomic jungles: ichnological and ichnotaxonomic investigations of footprints with metatarsal and ischial impressions. Ichnos, 10(2-4), 169-177. 
• Mallison, H. (2010a). The digital Plateosaurus II: an assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount. Acta Palaeontologica Polonica, 55(3), 433-458. 
• Mallison, H. (2010). CAD assessment of the posture and range of motion of Kentrosaurus aethiopicus Hennig 1915. Swiss Journal of Geosciences, 103(2), 211-233. 
• Milàn, J. (2006). Variations in the morphology of emu (Dromaius novaehollandiae) tracks reflecting differences in walking pattern and substrate consistency: ichnotaxonomic implications. Palaeontology, 49(2), 405-420.
• Organ, C. L. (2006). Biomechanics of ossified tendons in ornithopod dinosaurs. Paleobiology, 32(04), 652-665. 
• Organ, C. L., & Adams, J. (2005). The histology of ossified tendon in dinosaurs. Journal of Vertebrate Paleontology, 25(3), 602-613.
• Paul, G. S. (2010). The Princeton field guide to dinosaurs. Princeton University Press. 
• Russell, D. A., & Dong, Z. M. (1993). A nearly complete skeleton of a new troodontid dinosaur from the Early Cretaceous of the Ordos Basin, Inner Mongolia, People's Republic of China. Canadian Journal of Earth Sciences, 30(10), 2163-2173. 
• Xu, X., & Norell, M. A. (2004). A new troodontid dinosaur from China with avian-like sleeping posture. Nature, 431(7010), 838-841.

Two giant azhdarchids, Arambourgiania philadelphiae, attempt to portion a troodontid. The troodontid objects.

When people talk about giant azhdarchid pterosaurs (odds are most readers of this blog don't need an introduction to azhdarchids, but if you do, click here) they typically mention two taxa. The first is Quetzalcoatlus northropi, a giant Texan pterosaur discovered in the 1970s and now one of the most famous pterosaurs of all (Lawson 1975, Langston 1981). The second is Hatzegopteryx thambema, a relatively robust giant discovered in the 1990s and initially - because of its size and reinforced bone construction - thought to be a giant predatory dinosaur (see Buffetaut et al. 2003). From internet forums to TV show producers, if you want to chat about giant pterosaurs, these species are your most likely subjects.

Many readers will be aware that these aren't the only giant azhdarchids, however. The record of these animals cannot be described as extensive, but it is sufficient to indicate that they were present across most of the world and probably not particularly rare in Late Cretaceous ecosystems. But most fossils of giant azhdarchids are unnameable on account of being too fragmentary, being represented by parts of undiagnostic anatomy, or being too poorly preserved. This makes it all the more surprising that the third named giant azhdarchid doesn't get much attention: the Maastrichtian species Arambourgiania philadelphiae, known from several bones from phosphate mines in Jordan.

I'm not sure why we generally overlook this giant. Perhaps it's because Arambourgiania - 'Arambourg's giant' - is one of those old-fashioned names which works better in translation than the original Greek. It certainly doesn't sound as evocative or exotic as Quetzalcoatlus or Hatzegopteryx. Moreover, it's the least known of the three named giants, being primarily represented by a long - 620 mm - cylindrical neck vertebra, and not much else. The other named giants are not well represented either, but we have more than a handful of bones for them, and they're represented by intuitively intriguing anatomies: giant wing skeletons, bits of skull and jaw and so on. But whatever the cause, there are reasons to consider our relative neglect of Arambourgiania as unwarranted. It may not be as well-known as Quetzalcoatlus, or as immediately intriguing as Hatzegopteryx, but if you're interested in giant azhdarchids (and, hey, who isn't?) you this animal deserves your attention just as much as the other species. Here are just three reasons why.

History has been unkind to Arambourgiania

Arambourgiania is more than just a neck bone

It's rarely mentioned that Arambourgiania is known from material other than just a gigantic neck bone: a smattering of other bones from the same Phosphate mines might - probably- pertain to the same species. These were re-discovered and outlined by Frey and Martill (1996), and comprise the proximal and distal end of first wing phalanx (below), and a heavily eroded bone interpreted as a second cervical vertebra. Given the uncertainty about their association with the holotype - remember that the circumstance of its collection are lost to history - Frey and Martill classified these as cf. Arambourgiania.

Line drawing and reconstruction of the lesser seen cf. Arambourgiania first wing phalanx fragment (a, c-d). That's the wing phalanx of Quetzalcoatlus sp. in panel b. Scale bars equal 20 mm, which shows the cf. Arambourgiania bone as pretty darned big. From Frey and Martill (1996).

There isn't that much which can be said about the additional cervical - it has some identifiable features, but it's a few flecks of broken bone and bumps of internal mould away from being a featureless tube. It's a little smaller in diameter than the big holotype vertebra, and much shorter. I'm not sure it should be considered as belonging to an animal of the same size as the holotype individual.

The wing phalanx elements however, are more interesting. For one, they're enormous, and look proportionate to the holotype vertebra when juxtaposed in a skeletal reconstruction (below). If they're not from the same individual, they must be from a very similarly sized one. Frustratingly, the wing phalanx ends are broken in a way that hints at the bone shaft bone surviving to the modern day as well, but being lost in recent times.

Arambourgiania (known elements in white, restored, hypothetical neck length of 2.6 m indicated by grey vertebrae) compared to Quetzalcoatlus sp. Note the chunky wing finger bones.

It might be difficult to understand why these scraps of a wing bone are exciting, but they inform us of some fundamental aspects of giant azhdarchid anatomy and wing structure. There aren't many giant pterosaurs where we have recognisable wing and neck material from the same species so, however scrappy it might be, this is already useful material for building a picture of their proportions and appearance. From a functional perspective, they are interesting in showing that wing finger of Arambourgiania articulated with the metacarpal in exactly the same way as it did in smaller pterosaurs. This is good to know, as it confirms the notion that understanding the smaller azhdarchid species is our best route to fathoming the bigger ones. And of further mechanical note is that these elements show the wing finger as proportionally robust, with a big articular surface for the metacarpal/phalanx joint and a wide space for insertion of ligaments pulling the wing open in flight. Increased robustness is a sign of greater resistance to stresses and strains, and a good indication that Arambourgiania had scaled its wing bones to be flightworthy. This is an important counterpoint to proposals from some researchers that the extreme size of giant azhdarchids rendered them flightless. Of course, these scraps of wing bone don't tell us much about flight performance or style, but they are a good indication that flight of some kind was happening in these forms.

The neck of Arambourgiania was a high point of tetrapod evolution, and we need to learn more about it

References

Finally, my long promised palaeoart book Recreating an Age of Reptiles is available from online retailers! Conceived as a short, 'how long can it take to publish a print-on-demand book where I have full control?' sort of project, today marks the end of the year of design, illustration and writing work it actually took to take this broad, palaeoart-led look at various parts of the Mesozoic. The result is a Letter page-sized (that's 21.59 x 27.94 cm) full-colour paperback with 108 pages of text and imagery, and over 90 bits of artwork. About 20% of the artwork has not been published anywhere before, at least not in entirety, and virtually none of the pictures have been featured in other publications. So if you're after some new entries on your palaeoart bookshelf, or hard copies of images of mine that you've seen around the internet, this might be the book for you. You can access a preview of the book interior via its page at Lulu.com.

The opening spread of the azhdarchid pterosaur section. This is one of three sections featuring flying reptiles.

The book is divided into a number of thematic sections based around animal clades, specifics of behaviour, or types of habitat. In selecting the art and generating new pieces for this project I tried to keep things varied and interesting. This is not a book dominated by any one particular type of animal, nor a tome where every picture shows prehistoric animals ripping each other's throats out (if, indeed, that can be said to feature at all). Dinosaur groups account for 50% of the book's content, with the rest taken up by mammal-like creatures, Crocodyliformes, Triassic archosauromorphs, pterosaurs and others. Many of the pictures show atypical behaviours such as burrowing, swimming, sleeping, falling over, shyness and nocturnality, and weather - rather than just variably coloured skies - plays an active role in a good number of illustrations. I'm not going to boast that "you've never seen the likes of this before!" but, presented as a collective, I hope it presents a nuanced take on Mesozoic palaeoartworks.

Brontosmash! needs a double page spread.

Although primarily an art book, I've tried to make this something worth reading too. Each picture is accompanied with details about the research, artistic decisions and researcher collaborations that informed their production. The book is bracketed by essays musing on aspects of the palaeoartistic process: how many ways we can reconstruct extinct animals without leaving the realm of scientific credibility; the role of artistic personality and biases in palaeoart; whether we constrain our art by adhering too tightly to familiar parts of science, and whether we should view the inevitable outdating of our work as positive or negative. While (hopefully) avoiding naval gazing, I've tried to outline some of my own inspirations and philosophy concerning palaeoart production throughout this text. We don't really discuss our individuality as palaeoartists very much - why we prefer certain colours or animal behaviour, why we choose certain compositions - but it's something I'm curious to hear more about from the palaeoart community, so I've shared some of my views in this book. It seems that discussing palaeoart as 'art' rather than a strictly illustrative or scientific endeavour seems like an important step to improving its standing and perceived value among its patrons.

So, where can you buy it from, and how much is it?

The cover price for Recreating an Age of Reptiles is £26, and it's available now, direct from Lulu.com (below). You can also buy it at all major online book stores (e.g. Amazon, Barnes and Noble etc.). But before you click the Amazon link, note that Lulu.com is, and will always be, the cheapest place to buy Recreating an Age of Reptiles. I've set a 5% discount at their store which means it's retailing for £24.70, not £26. I'll be honest about why I've set this incentive: major retailers take 50% of sale profits before the rest can be divided up among printers, publishers and authors, which means book authors are not left with much from their sales. Lulu offers the same shop service as anywhere else online (and you can pay with Paypal, too) and their service, in my experience, is swift and efficient - you should have the book within a week from ordering.

Minor update (06/07/16): Thanks to Andrea Cau, a few additional citations and points of discussion have been made below - the thrust and arguments of the post are the same, but the context is improved. Thanks Andrea!

Hypuronector limnaios restored as a glider. Have palaeontologists been smoking something of variable legality, or is there some basis to this?

Assuming you've reached level 5 of palaeontological geekdom you can't fail to know of the exceptionally weird Triassic clade Drepanosauromorpha. These generally small, long-bodied reptiles are largely, but not incontrovertibly, thought to nest at the base of Archosauromorpha (so between lizards and crocs in the landscape of modern animals) and are famous for their highly aberrant anatomy. Gracile, bird-like heads and necks sit atop long, robust and tubular bodies with deepened tails and stout limbs. The hands and feet are highly modified in each species, some bearing powerful claws, others having chameleon-like opposable digits. The end of their tails are modified into either grasping, prehensile organs or sharp hooks, these being interpreted as adaptions for anchoring the tail to vegetation or substrata. Exactly what drepanosaurs did for a living has long been a subject of discussion among academics, and they are nowadays generally considered arboreal or fossorial - or a blend of both. They're pretty awesome animals.

Because the Triassic was evolution's drug-fuelled, rebellious college days, it can't be considered shocking to learn that there's a drepanosaur species which is to drepanosaurs what they are to everything else. This distinctive, strange, and controversial species is Hypuronector limnaios (above). Reasonably good fossils of this small (c. 12 cm long) animal have been known for decades from upper Triassic deposits of New Jersey, but it received its name only relatively recently (Colbert and Olsen 2001). Hypuronector is often regarded as a swimming creature because of its dorsoventrally expanded, 'leaf-shaped' tail which lacks a hooked or prehensile termination (Colbert and Olsen 2001). Its tail is remarkable for the enormous chevrons (prongs of bone projecting downwards from the underside of tail vertebrae) which extend far below and behind their vertebra of origin to create the majority of the tail depth and its 'leaf-like' profile. Some authors have likened the outline of the tail skeleton to the body shapes of gymntoid or gymnarchid fish and suggested that it propelled Hypuronector through the deep, freshwater lakes its fossils were buried in, perhaps in a newt- or crocodile-like fashion (Colbert and Olsen 2001). Although possessing unusually long legs relative to other drepanosaurs and swimming animals, it's been argued that these were also related to an aquatic lifestyle. Specifically, it's suggested that they held the long, deep tail off the ground during terrestrial bouts, the tail apparently being incapable of elevation at its base (Colbert and Olsen 2001). This aquatic Hypuronector hypothesis has been around for some time. The animal was informally known as the 'deep tailed swimmer' in the 1980s (Fraser and Renesto 2005) and this moniker was transferred more or less entirely to its scientific name in 2001: loosely translated, Hypuronector means 'deep-tailed lake swimmer'.

Hypuronector limnaios skeletal reconstruction, from Renesto et al. 2010. Scale represents 10 mm.

At first glance at least, none of this sounds too outlandish: the tail of Hypuronector certainly has an oar-like shape, and we all know that lateral undulation of a tail is the commonest means of water propulsion for vertebrates. But there are other interpretations of Hypuronector which suggest it may not have been a swimmer at all. These alternative views suggest it was more like other drepanosaurs in being suited to climbing but, more remarkably, possibly a glider (Renesto et al. 2010). Sharing early versions of my gliding drepanosaur art (above) suggests that the latter hypothesis is not well known, even among experts. However, I want to stress from the outset that this is not All Yesterdays-style artistic speculation or the bizarre opinion of a 'fringe' worker. Challenges to the aquatic Hypuronector concept and suggestions that Hypurnoector was a more 'typical' arboreal form have been made by several authors (e.g. Senter 2004; Spielmann et al. 2006; Renesto et al. 2010; Castielloa et al. 2015), and the notion that it may have been a glider has been raised on reasonable (if perhaps not yet conclusive) evidence (Renesto et al. 2010). It follows older suggestions that some drepanosaurids - Megalancosaurus specifically - were gliders (see below; Ruben 1998; Renesto 2000) and, though this all might seem bizarre, there is some genuine scientific basis to it.

The aquatic Hypuronector hypothesis under scrutiny

References

Pteranodon longiceps, Pteranodon sp. or something else entirely? In recent years one of our most famous and abundant pterosaurs has been carved up into multiple species, but is this overzealous taxonomic splitting, or is there more to it than that?

Writing about pterosaurs can be difficult because so much of their classification is disputed. The number of pterosaur species, their assignment to different groups, appropriate clade nomenclature and the arrangement of branches in the pterosaur tree are all contested, sometimes to polarising extents.

How understanding hundreds of Pteranodon specimens hinges on a handful of important ones

Line drawings of important Pteranodon/pteranodontid skulls from Witton (2013). A, skull still referred to P. longiceps; B, isolated crest and part of the braincase region referred to either longiceps (Bennett 1994) or Pteranodon sp. (Kellner 2010); C, holotype of longiceps; D, holotype of Pteranodon (or Geosternbergia) sternbergi. Note the twisted posterior skull face in B and how little of the skull remains in D.

Kellner (2010) argues that Bennett's interpretation accommodates too much morphological variation however, picking out several skull characters as sufficiently distinctive to warrant erecting new genera and species. The diagnoses for these new taxa are much more specific than those offered by Bennett, pertaining not only to crest shape and angle, but also size and shapes of skull bones, skull openings and rostrum morphology. Partly because these criteria are quite specific, these novel pteranodontids are currently represented by single specimens. And it's here that I think we hit a bump with the 'Pteranodon complex' hypothesis. The diagnoses are quite specific, and we have good reason to think a lot of the variation apparent in Pteranodon fossils is not taxonomic in origin. For instance, taphonomic damage and the significant crushing that affects all Pteranodon bones (most Pteranodon bones are reduced to thicknesses of mere millimetres) means no two Pteranodon skulls are identical, and many diagnostic characters suggested by Kellner (2010) - specifically those pertaining to bone lengths, fenestra sizes and so on - have yet to be demonstrated through illustrative or quantified means. We've yet to see the measurements, data tables or an illustrated series of Pteranodon skulls which show these features are atypical against a range of specimens, and thus suitable to base new taxa on.

It's not just taphonomic and diagenetic effects which are of concern: there are palaeobiological trends to consider, too. For example, Kellner (2010) uses the breadth of the crest base as a diagnostic feature for both Dawndraco and G. maiseyi, noting that the former has a crest base located largely behind the eye socket, while the latter is expanded to erupt well in front of the orbital region. But Bennett (1994) gives reason to think that crest base size is linked to growth and size, not taxonomy. As can be seen above, there's a steady correlation between crest base size and skull size: larger skulls have much thicker crest bases extending far in front of the orbit than smaller skulls (Bennett 1994, 2001a). Although Kellner (2010) mentions that Dawndraco is a relatively mature specimen, and thus maybe unlikely to change its crest size, there's no discussion of the fact that the Dawndraco skull is quite a bit smaller than some other 'large'Pteranodon skulls (below). The fact this small skull has a smaller crest is, of course, consistent with Bennett's crest scaling hypothesis. Similarly, the wide-crested maiseyi skull meets Bennett's predictions that it should - as a big individual - also have a relatively large crest base.

Dawndraco (red) is a bit of a wimp compared to the largest Pteranodon skulls. Black is the sternbergi holotype, blue is the maiseyi holotype. Note how the crest bases of the black and blue skulls are much broader than that of Dawndraco. Illustrations adapted from Bennett (1994).

Pteranodon stratigraphy and the significance (or not) of geological boundaries

Both Bennett's and Kellner's taxonomies consider Pteranodon distribution through the Niobrara Formation and neighbouring rock units, but there are fundamental differences in how they treat this data. Bennett's (1994) approach sees morphology trump stratigraphy in that the ranges of his species are dictated wholly by specimen anatomy. This is essentially the approach typically taken by biostratigraphers, where it is considered (and relied upon) that species distribution is not linked to our designation of rock units. In this scheme, it doesn't matter where the specimen occurs, but what it looks like that matters. The fact that all the 'sternbergi morphs' occur at the base of the Smoky Hill Chalk Member, and all the 'longiceps morphs' occur at the top (and somewhat beyond - see below) is the basis for Bennett's (1994) idea that our Pteranodon sample is a single, evolving population which entered the fossil record as sternbergi, and left as longiceps. The fact that these species do not overlap can be viewed as helping the verify the Pteranodon chronospecies hypothesis.

specimens, black lines show those associated with skull illustrations. Skull diagrams from Bennett (1994), data from Bennett (1994); Hargrave (2007) and Kellner (2010). These discussions touch on almost philosophical elements of palaeontological science, and I expect readers will differ as to which approach they think is most useful. Personally, I don't agree with the use of stratigraphy in taxonomic considerations. It's generally accepted that paleontology uses a morphology-based species concept (morphospecies) and, if that's the case, we have to stick by it. This means letting morphology dictate the ranges of fossil species and not deciding a priori that a span of time/extent of rock exceeds an acceptable 'species range'. For abundant, well-documented groups we may be able to bolster such concepts with a sense of their speciation frequency but, with rare fossils like pterosaurs, we know next to nothing about their evolutionary rates. And as unusual as it may seem for a pterosaur to span several formations, there are taxa that seem to do this (Anhanguera, Istiodactylus, Quetzalcoatlus, Rhamphorhynchus are well known examples). Moreover, plenty of other groups pay little attention to the stratigraphic boundaries that we set. Indeed, the whole science of biostratigraphy is is more or less founded on this fact: we can date the rock record using fossils because so many species do transcend stratigraphic boundaries. Stating that a fossil cannot be conspecific with another just because it occurs in younger or older rocks seems presumptuous and at odds with trying to understand evolutionary history.

Giant, Oligocene rhinocerotoids Paraceratherium transouralicum engage in some early morning flirting. Because, in rhino speak, playing hard to get involves shoulder barges and head-butts.

Depictions of the giant indricotherines, relatives of modern rhinoceros that lived across mid- and eastern Asia during the Oligocene, have varied over time. We've known about these animals - which are part of a longer-lived (Eocene-Miocene) indricotherine lineage that includes a number of smaller, almost okapi-or horse-like species - for over 100 years and they have become regular fixtures in museums, books and those rare documentaries which offer glimpses into ancient life outside of the Mesozoic. Any yet, when we think of our favourite indricothere paintings - including those by our most celebrated mammalian palaeoartists such as Knight, Burian, Anton, and Buell - they often differ markedly in their depiction of these 15-20 tonne animals. Most notably, their neck proportions, overall robustness, the development of a proboscis or trunk, and - most recently - the size of the ears are all inconsistent. Why are these animals so differently depicted, and should we rule out some of the anatomies we've seen in palaeoart in the last century? Having faced these questions recently when asked to restore this animal myself (above), I thought I'd share some of what I learned in my research here.

The obligatory note on nomenclature

It almost seems tradition that any article or paper on indricotherines requires an aside on their confused taxonomy. As has been the case for decades now, the taxonomy and systematic nomenclature of these giant rhinocerotoids are a matter of ongoing discussion. It is widely appreciated that several giant indricotherine species from roughly contemporaneous Oligocene Asian sediments can be identified, but how many species they represent, and how they are related to each other, is not clear. At least seven generic titles and many more species names have been given to the largest of these animals over the years (Indricotherium and Baluchitherium are perhaps the most famous generic labels), but some authors (e.g. Lucas and Sobus 1989, Prothero 2013) tidy all or most of these taxa into three species of the oldest established genus, Paraceratherium. Arguments persist, however, that at least one other, perhaps slightly smaller genus existed, Dzungariotherium (Qiu and Wang 2007). Geologically older indricotherine genera such as the Eocene Urtinotherium are also wrapped into these discussions as remains attributed to the Oligocene genera are sometimes argued as having greater affinity to these older taxa (Prothero 2013).

This confusion is sometimes framed as a 'lumper/splitter' philosophical distinction, but it does not help that the fossil record of these giant rhinocerotoids is far from exemplar: giant indricotherine specimens can be fragmentary, of starkly contrasting size with one another, and many suffer from distortion. The fact that 20th century indricotherine science developed with Asian and American teams working largely in isolation, with limited access to certain specimens and literature, has also contributed to the confused history of this group. Those interested in the history of indricothere taxonomy should check out Prothero (2013) for an overview. For now, it will serve us to simply state that the best known, biggest and most famous of these animals currently resides as the taxonomic address of Paraceratherium transouralicum. This is the species most of us think of as 'the' giant indriotherine as well as the taxon that has carried both the Indricotherium and Baluchitherium label at one time or another. It's also the focus of most artwork of giant rhinoceratoids, and thus forms our primary interest here.

Giant rhino, bulky giraffe or giant workhorse?

One reason we see such variation in indricotherine appearance is that researchers have produced vastly different interpretations of its anatomy in the last 100 years. But unlike, say, dinosaurs, where older reconstructions have been (for the most part) abandoned in favour of newer, more accurate interpretations, educators and researchers continue to publish skeletal reconstructions published in the 20s and 30s despite our improved knowledge of indricotherine anatomy, documented criticisms of these older works, and the availability of more modern, theoretically better-informed reconstructions.

Many readers may be aware that the first reconstruction of Paraceratherium, published by Osborn (1923a),showed a form not too far off a giant rhinoceros - a heavyset, short-necked animal with a deep torso and short legs. Osborn published a revised version almost immediately after his first effort, which had a much longer neck and longer legs thanks to data provided by additional fossil material (Osborn 1923b). A shorter-necked version was then produced by Granger and Gregory (1935, 1936), who scaled the remains of numerous, differently-sized individuals from a range of collections to create their robust, gigantic take on indricotherine anatomy. Although this reconstruction has been quite influential, Fortelius and Kappelman (1993) have been critical of the scaling methods used by Granger and Gregory, calling their interpretation 'a highly speculative creation indeed'.

Paraceratherium has been variably reconstructed over the years, with particular disagreement over how long the neck was compared to the body. So far as I can tell, a consensus on the life appearance of these animals has yet to be reached.

A third contrasting reconstruction was published a few decades later by Gromova (1959), based on a composite mounted skeleton in the Paleontological Institute, Russian Academy of Sciences. This reconstruction, executed by N. Yanshinova, was accompanied by several wonderful muscle and skin reconstructions which palaeoart fans will not want to miss. Both the mount and reconstruction show a gracile, giraffe-like form with a remarkably long neck and, in being based on a relatively complete set of giant indricotherine remains, some have argued it is a superior take on indricotherine anatomy than those produced by Osborn, or Granger and Gregory (Fortelius and Kappelman 1993). The most striking aspect of this reconstruction is its very long neck. We have to stress that this is extrapolated from a few incomplete cervicals associated with postcranial material, and its exact length remains uncertain - a complete set of neck bones remains elusive for Paraceratherium. This is another reconstruction which has been quite influential (helped, no doubt, by its apparent basis for the BBC's Walking with Beasts 'Indricotherium') but, again, it has not escaped criticism. Paul (1997) suggested that multiple aspects of this mount and reconstruction were erroneous, including the length of the neck, the size of the pelvis and depth of the ribcage, the length of the feet, and the ratio of the humerus and femur, as well as the fully erect posture of the limbs.

And so we turn to another indricotherine skeletal reconstruction, produced by Paul (1997). This restoration incorporated data from the same specimens used in the efforts above and came out somewhat 'averaged' between the more heavyset restorations of the early 20th century and the gracile interpretation of the 1950s. It looks, in overall form, more like a giant workhorse than it does a giant rhino or bulky giraffe. Paul (1997) provides some discussion of the reconstruction process - this is worth a read if you're interested in the life appearance of Paraceratherium and its relatives. Paul's interpretation has, to my knowledge, escaped criticism to date and, to the contrary, Larramendi (2016) described this reconstruction as 'accurate', although did not elaborate on why it should be considered superior to older efforts.

The million dollar question here is obvious: which one of these different takes on Paraceratherium is 'right'? To be honest, I'm not sure. The situation is compounded by the fact that a lot of indricotherine literature is obscure, that the specimens fragmentary and that many of them await description. I was hoping that Donald Prothero's recent (2013) book Rhinoceros Giants, which is solely dedicated to Paraceratherium, would provide some insight on this matter, but it's not a great help here - it provides no real evaluation on the different reconstructions and does not even mention Paul's 1997 effort. My work above is primarily based on Paul's (1997) skeletal but this is largely because of principle rather than real insight. Paul's work is the most modern and, of course, he's made a career out of reliably reconstructing extinct animals. The brief endorsement from Larramendi (2016) helps here too, of course, but a longer discussion of the relative merits and detriments of each interpretation would be useful. Opinions from others with more insight into this matter are welcome in the comments below.

A tapir-like proboscis... on a rhino?

Turning our attention to the face, did Paraceratherium and its relatives have relatively short-lipped faces like those of rhinos, or long, mobile proboscides like their more distant relatives, the tapirs? Despite mammal lips and nasal tissues being highly fleshly and thus only rarely entering the fossil record, this is a surprisingly easy question to answer. Whether rhino, tapir or anything else, a suite of osteological characters seem to correlate well with the presence of proboscides. Briefly summarised, these are: narrow snouts; retraction of the nasal openings towards the orbits; the presence of large muscle scars, bony knobs and other muscle attachment markers around the nasal opening (particularly in the dorsal region); retraction of the nasal bone (the 'roof' of of the nasal opening); deepening of the premaxillary bone (the bone making the jaw tip); anterior migration of the orbit; a large intraorbital canal (a foramen situated in the cheek region, just in front of the eye - it houses the nerves and blood vessels for our anterior face muscles); and strengthening of the posterior skull regions related to supporting the weight of the head on the neck (Wall 1980). Note that the criteria for elephant-like trunks are similar, but slightly different.

Paraceratherium transouralicum (formerly Baluchitherium grangeri) skull in dorsal, lateral and ventral views. Note features around the skull anterior linked to proboscis development (see text). From Osborn (1923b).

Paraceratherium skulls (above) meet these criteria well and, all else being equal, we have to say that yes, it looks likely that these giant rhinoceratoids had short proboscides in life, presumably to assist browsing from trees and bushes (Prothero 2013). The view that they had more typically rhinoceros-like faces is hard to defend in light of these cranial features: mammal skulls just don't have those retracted nasal openings, associated deep muscle scarring etc. unless they were doing something unusual and sophisticated with their upper lip and nasal tissues. The reality of giant indricotherines with dangly noses may seem hard to swallow for those of us used to shorter lipped versions, but given the relationships between rhinos and tapirs, the fact that some other fossil rhinocerotoids probably had proboscides as well (e.g. Wall 1980), and the independent development of long, flexible noses in numerous mammal lineages, we can't really see this as unusual. Moreover, we need to remember that modern rhinos are derived animals in their own right and separated from the indricotherine lineage by tens of millions of years. They aren't necessarily always going to be the best models for the life appearance of their fossil ancestors.

And big, elephant-like ears, right?

Finally, let's tackle the component that everyone now mentions about indricotheres since seeing the Carl Buell's cover art for Donald Prothero's Rhinoceros Giants:

Indiana University Press.

Yikes, elephant ears? For those of us familiar with the history of indricotheres in art, where their ears are restored as typically rhinoceros-like, this is a shocking, double-take image. Within the book, Prothero justifies the restoration:

"...indricotheres were larger in body mass than any living elephant and almost certainly had problems regulating their body heat at such large size. Elephants must do all they can to increase the surface area of their bodies to release as much excess heat as possible, which is why they have huge fan-like ears full of blood vessels that are essentially giant radiators. Given the huge size of indricotheres, it seems likely that they too should have had elephant-like ears, or at least very large ears of some shape, much larger than they are usually drawn."

The text continues to suggest that this appearance is not without anatomical support, the prominence of the mastoid and paroccipital processes (projections of bone situated behind the ear opening, adjacent to the posterior surface of the skull) being similar to the condition in certain elephants and mastodonts, and therefore indicative of large, flappy ears (Prothero 2013).

I have mixed feelings about this reconstruction. I like it for two reasons. The first is that it's nice to see indricotheres being distanced from their depiction as giant, long-necked rhinoceroses - again, it's not unreasonable to think they may have looked quite different in to modern rhinocerotids in many aspects. I also like these ears for being an All Yesterdays-style speculation on soft-tissue adaptations in extinct species. If we can use this as an excuse to give fat stores to desert sauropods or fuzzy hides to Arctic ceratopsids, then we can give large ears to giant rhinoceratoids.

On the other hand, I'm not convinced that they're as likely as Rhinoceros Giants suggests. It's clear from our modern fauna that ear size does not correlate with body mass in terrestrial mammals. By this logic many rhinos and giraffes should have proportionally large ears too, which they evidently do not. We also have to consider that even larger animals than indricotheres, dinosaurs, almost certainly got by without giant ears to help lose heat. And yes, while dinosaurs may have used different metabolic strategies to mammals, one inescapable consequence of giant size is a constant high body temperature. At least some investigations into the proportions of large dinosaurs suggest that development of their features - such as sauropod necks - were not driven by thermoregulatory pressures (Henderson 2013).

We should also consider the unusual nature of elephant thermoregulation: they are not typical mammals when it comes to controlling body heat. For one, they're atypically compact compared to other large mammals because they have extremely short necks, giant, round heads, and big, rotund torsos. This is a suboptimal bauplan for thermoregulation because it minimises surface area with respect to volume, and thus reduces the available area for elephants to dump excess heat. Moreover, unlike most mammals, they lack sweat glands (Wright and Luck 1984), do not pant, and they live in climates which are so warm that for much of the day they cannot shed heat through simple convection, big ears or not (Weissenböck et al. 2012). Elephants can, of course, regulate their temperature, but they need to employ different strategies to the rest of us mammals. These include maintaining moist skin with mud bathing and trunk spraying (Wright and Luck 1984), maintaining a sparse set of body hair to aid thermal escape (Myhrvold et al. 2012), using heterothermy (Weissenböck et al. 2012), the development of 'thermal windows' in their skin (Weissenböck et al. 2010), having loose and highly wrinkled skin to boost surface area and - of course - fanning their blood-vessel rich ears to help lose heat, when ambient temperatures are low enough for this to make a difference.

Silhouettes of the largest land mammals of all time, Paraceratherium transouralicum and Palaeoloxodon namadicus. Note the relatively gracile build of Paraceratherium - all the better for improving surface area:volume ratio, and thus superior for radiating heat. The numbers at the base of the image refer to estimated shoulder heights and tonnage. From Larramendi (2016).

These facts suggest elephants should not be used as direct thermoregulatory models for a giant rhinoceratoid. Modern rhinos other perissodactyls are much more typical in their thermoregulatory approaches: they have sweat glands and use panting behaviours (Hiley 1977) as well as some special tactics, such as enhanced vascularisation in the skin folds of certain rhino species (Endo et al. 2009). We have to assume that indricotherines at least had these entry level perissodactyl adaptations and, if so, they would have an advantage over elephants in hot climates. Indricotherines also benefit from being more complicated in form than elephants. They have longer limbs and necks, as well as a proportionally smaller head, and this enhances their surface area:volume ratio. Again, makes them better adapted to cope with heat as they have a shape better suited to radiating excess body heat. And of course, there's no reason to assume this could not have been augmented with wrinkled or folded skin or sparse hair. The picture emerging from these points is that big ears are only one strategy that big animals may use to keep cool, and maybe one that will only arise in specific circumstances. The idea that indricotherines would have big ears just because of their size is far from certain.

Basic muscle layout and trajectories (arrowed lines) of a modern horse. Note their superficial attachment and position high on the head - the ear canal itself is about halfway down the back of the skull. The 's' is the scutiform cartilage, which hangs out in front of the ear over the jaw muscles. From Goldfinger (2004).

But isn't all this moot because of Prothero's (2013) observations about the mastoid and paroccipital processeses being expanded, and thus giving big ears something to hang off? I'm suspicious about the significance of this observation. So far as I can determine, neither the mastoid or paroccipital have anything to do with anchoring ear tissues in modern perissodactyls (or perhaps any mammal). This might be because in most mammals - primates being one obvious exception - the ear pinnae are vertically displaced from the ear canal and attach to the head via a series of muscles and cartilages at the top of the skull (above). Only select few of the ear muscles reach the skull directly and these anchor, with very small attachments, to the skull midline, dorsoposterior margin and zygomatic arch. The rest have no osteological connection at all, anchoring instead to cartilage, membranes overlying facial musculature, or even the side of saliva glands. The paraoccipital and mastoid processes do have important roles in the muscular system but these are to do with neck, jaw and tongue muscles, not ears. Thus, unless indrictotheres were doing something different to modern mammals, those particularly big processes behind their ear openings were probably more to do with supporting and moving the head than they were holding big ears, and may have little significance to the big-eared indricotherine hypothesis.

So...

Putting all this together, it seems that there might be less need for uncertainty about indricothere appearance than our various artworks suggest. We should be saying 'yes' to some sort of proboscis, and 'probably not' to big ears (or, at least, 'there's no reason for them'). The elephant (or, giant rhino, if you prefer) in the room is the proportion issue, and it would be good to see folks who really know rhinocerotoid anatomy pore over those various reconstructions to ascertain which (if any) are the best representation of indricotherine form.

Next time: either the Next Big (but also kinda small) Thing in pterosaur research, or another trip to the Triassic.

Big rhinos need big support - thank goodness for Patreon

The paintings and words featured here are sponsored by another group of (metaphorically) giant mammals, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be taking a further look at the anatomy of the Paracertherium in my painting, above. Why do they have little manes and stripy faces? Are those child rhinos at the back a bit fuzzy? And why do the main animals look like they're fighting? Head over, and sign up to Patreon to get access to this and the rest of my exclusive content!

References

• Endo, H., Kobayashi, H., Koyabu, D., Hayashida, A., Jogahara, T., Taru, H., Oishi, M., Itou, T., Koie, H. & Sakai, T. (2009). The morphological basis of the armor-like folded skin of the greater Indian rhinoceros as a thermoregulator. Mammal Study, 34(4), 195-200.
• Fortelius, M., Kappelman, J., 1993. The largest land mammal ever imagined. Zoological Journal of the Linnean Society, 108, 85-101.
• Goldfinger, E. (2004). Animal Anatomy for Artists: The Elements of Form. Oxford University Press.
• Granger, W., & Gregory, W. K. (1935). A revised restoration of the skeleton of Baluchitherium, gigantic fossil rhinoceros of Central Asia. American Museum of Natural History, 787, 1-3.
• Granger, W., & Gregory, W. K. (1936). Further notes on the gigantic extinct rhinoceros, Baluchitherium, from the Oligocene of Mongolia. American Museum of Natural History, 72, 1-73.
• Gromova, V. (1959). Giant rhinoceroses. Trudy Paleontologiskei Institut Akademie Nauk, 71, 1-164.
• Henderson, D. M. (2013). Sauropod necks: are they really for heat loss?. PloS one, 8(10), e77108.
• Hiley, P. G. (1977). The thermoregulatory response of the rhinoceros (Diceros bicornis and Ceratotherium simum) and the zebra (Equus burchelli) to diurnal temperature change. African Journal of Ecology, 15, 337-337.
• Larramendi, A. (2016). Shoulder height, body mass and shape of proboscideans. Acta Palaeontologica Polonica, 61, 537-574
• Lucas, S. G., & Sobus, J. C. (1989). The systematics of indricotheres. In: Prothero, D. R., and R. M. Schoch (eds.) The Evolution of Perissodactyls. Oxford University Press, New York, 358-378.
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As the Cretaceous fossil record enters its final two stages - the Campanian and Maastrichtian - several unusual things seem to happen in the world of flying reptiles. Firstly, we see the end result of a steady drop off in pterosaur diversity leaving only azhdarchids - those often long-necked, long faced animals that we cover here with some regularity - with a strong, widespread fossil record. It's known that nyctosaurids and (thanks to recent discoveries) perhaps pteranodontids survived until the very end of the Mesozoic in at least two locations, but azhdarchids are globally distributed and dominate the pterosaur fossil record at this time. The overwhelming precedence of azhdarchids in the Late Cretaceous is an anomaly: at no other point in the pterosaur fossil record does one clade feature so prominently.

Secondly, Campanian and Maastrichtian pterosaurs are, without exception, pretty big animals. Many species from this time are renowned for their gigantic size: it's these stages which give us the famous 10 m wingspan, 250 kg colossi like Quetzalcoatlus,Arambourgianiaand Hatzegopteryx, as well as a number of other giant azhdarchids which are too poorly known for generic titles. Coinciding with the evolution of the giants is a loss of small pterosaur taxa - those animals less than 2.5 m across the wings which are present, more-or-less, throughout the rest of pterosaur history. This shift in body size is sometimes interpreted as pterosaurs demonstrating 'Cope's Rule', the somewhat controversial proposal that species evolve towards large body size over time (Hone and Benton 2007; Benson et al. 2014). It's argued by some that competition from birds may be the driver behind this trend, as early avians fought small flying reptiles for ecological space and ultimately forced pterosaurs into larger sizes (e.g. Benson et al. 2014). Note that this concept is not without its detractors, including myself - I won't go into my reasons now but I plan to outline them here eventually.

Whether you agree with the bird-pterosaur competitive displacement hypothesis or not, we can't disagree that the end of the Cretaceous is almost entirely devoid of small pterosaur remains. Only a handful of specimens record small pterosaurs in the Campanian and Maastrichtian, and they're all tricky to work with. Aside from being highly fragmentary, some are controversially identified (such as Piksi barbarulna, an alleged small pterosaur from the Two Medicine Formation - see Agnolin and Varricho 2012 for the pro-pterosaur case) and others represent probable juvenile individuals (Godfrey and Currie 2005). Whatever it signifies, the lack of diminutive pterosaur specimens from the close of the Mesozoic is a real phenomenon of our fossil record, and any new specimen of a small, latest Cretaceous flying reptile has to be something to get excited about.

Enter: a new small, latest Cretaceous pterosaur specimen to get excited about

Title slide of my SVPCA 2016 talk, discussing the findings of Martin-Silverstone et al. 2016, out today. If you don't get the reference, you clearly get out too much, have too many friends and aren't watching enough crap TV.

It's this point where a new paper, published today by Liz Martin-Silverstone, myself, Victoria Arbour and Phil Currie comes in. Our new work, which you can check out without restriction at the open access journal Royal Society Open Science, presents a new small pterosaur fossil from the Campanian Northumberland Formation of British Columbia. The specimen number - RBCM.EH.2009.019.0001 - is pretty unwieldy, so I've been calling it the 'Hornby azhdarchoid' or the 'Hornby pterosaur' after it's discovery on Hornby Island, just off the coast of Vancouver. As you can see  below, the Hornby specimen is not pretty. Following our presentation of the fossil at SVPCA 2016, pterosaur guru David Unwin suggested we might have the ugliest pterosaur fossil on record (or at least tied the game). But while not well preserved, we do at least have several bones to play with: most of a humerus, three fused vertebrae (from the notarium, a set of fused shoulder vertebral elements), a few loose dorsal vertebrae and some other odds and ends that defy identification. This makes it the first set of associated bones of a small latest Cretaceous pterosaur, which is at least a step in the right direction for their paltry fossil record. For reasons discussed in the paper (concerning taphonomy, element size and likely identifications) we assume these remains represent one individual.

RBCM.EH.2009.019.0001, a fragmentary azhdarchoid pterosaur from the Campanian Northumberland Formation, British Columbia. It's, er, not the prettiest pterosaur specimen you'll ever see. Combination of figures from Martin-Silverstone et al. 2016.

I don't want to rehash the full gory details of our study here - please read the paper for the technical aspects - but instead want to outline our main points. The first thing to clear is that we've been careful to rule out an avian ID for the specimen. The Northumberland Formation contains several bird fossils and the quality of the specimen means that many obvious pterosaur features are missing. The Royal British Columbia Museum was kind enough to ship the specimen all the way from Vancouver, Canada to Southampton, UK just so Liz and I make a thorough assessment on this issue. Happily, we found the specimen to be very pterosaur like in every aspect (even as fragments, pterosaur bones are quite distinctive) as well as differing from Mesozoic birds in several ways. It particularly contrasts in having a notarium, which seem absent from Mesozoic birds (note that we compared the notarium element compared carefully with Mesozoic bird synsacra to be sure of our identification), as well as having a pterosaur-like, rather than avian, proximal humerus morphology. But we're not bird workers so, to be extra sure, we showed the material to fossil bird experts in Canada and the UK (including people who've identified and published on the Northumberland Formation avians). No-one we spoke to suggested an avian ID and, moreover, we are aware that other people with expertise in both birds and pterosaurs (including our paper editor) have seen the material and prefer a pterosaur ID. Based on our research and the testimonials of others, we're as confident as we can be that the Hornby fragments represent a pterosaur, not a bird.

We've identified the Hornby specimen as an azhdarchoid, and noted several features indicative of, but not conclusive to, an azhdarchid ID. We suspect the specimen is an azhdarchid because of its provenance and its basic anatomical characteristics, but the specimen does not contain the right bits to confirm an azhdarchid identity. Nonetheless, narrowing the specimen down to Azhdarchoidea allows us to estimate its body proportions and confirm that the specimen was indeed a small animal when it died. We estimated its wingspan using two methods factoring both the humerus and vertebrae, and each pointed to a wingspan between 1.4 and 1.6 m. That puts our pterosaur at a comparable size to a good sized-seagull and, while these are respectably-sized modern birds, this is small for a latest Cretaceous pterosaur. Rather than poking giraffes in the face, our little chap would only just be beyond predation risk from an average housecat (below). The only contemporary pterosaur competing with the Hornby azhdarchoid for size is Piksi, a poorly known possible pterosaur from the western US. Our new study lists a number of reasons why the pterosaurian characterisation of Piksi is problematic however: in short, its morphology is all wrong for a flying reptile and we suspect a non-pterosaurian ID is more likely. The Hornby specimen is thus a contender for the smallest latest Cretaceous pterosaur currently known.

A 1.5 m wingspan azhdarchoid next to one (SI) MrTiddlesmetre. From Martin-Silverstone et al. (2016).

This million dollar question, of course, is whether the specimen is a small juvenile or a small adult. The former would be neat, but the latter is potentially significant. The findings of recent, detailed histological examinations of pterosaur fossils are permitting increasingly good understanding of their growth regimes (e.g. de Ricqles et al. 2000; Prondvai et al. 2012), so we made a section of the humerus to understand how old the Hornby animal was when it died. Our section showed a mix of bone textures, some indicating that the specimen was still growing, but other features (secondary osteons, an endosteal lamella, lines of arrested growth and a large structure forming on the internal bone surface) are indicative of relative maturity (de Ricqles et al. 2000; Prondvai et al. 2012). We found the endosteal lamella (a band of bone deposited around the internal bone cavity) of particular interest, as this seems to signify the end of internal bone expansion in azhdarchoids, and is thus a hallmark of near-mature animals (note that this is not true for all pterosaurs - see Prondvai et al. 2012). The fused dorsal vertebrae are a further marker of maturity, as pterosaurs do not develop these features until they're at least subadults. The exact timing of notarium formation seems to differ from taxon to taxon (e.g. Bennett 1993; Kellner 2015), but their development does not seem to start until these animals were near to full size, if not at full size already. Putting these and a few other observations together suggests that the Hornby pterosaur was a latest-stage juvenile or subadult: in other words, it looks like a genuinely small pterosaur, not just a juvenile one. We don't know how much larger it might have got before it reached full size, but its ontogenetic characteristics and what we know of pterosaur growth regimes suggests it was close to maximum size at time of death. Given its estimated 1.5 m wingspan, it had a good chance of remaining smaller than the next smallest, 2.5 m wingspan pterosaur currently known the Campanian or Maastrichtian (McGowen et al. 2002).

What's inside the RBCM.EH.2009.019.0001 humerus? A mix of things, but among them are features indicative of late-stage juvenility/subadulthood. Please see the paper for details of this figure. From Martin-Silverstone et al. 2016.

A small pterosaur amongst the pigeons

Two Garjainia madiba decide who gets the table scraps. The reconstructions here are modified from the life reconstruction I provided for Gower et al. (2014).

I find erythrosuchids, large, big-headed Triassic archosauriforms, very charismatic fossil animals. If nothing else, it's hard not to admire their no-nonsense approach to carnivory. Take a fairly standard reptilian bauplan, weld an oversize theropod dinosaur face to the front, then point it at the things you want to die: simple. They're the Mesozoic equivalent of mounting a howitzer on a golf cart and calling it a tank. We might question the rudimentary nature of the design, but we can't argue with the results.

Alas, erythrosuchids don't get as much love from palaeoartists or outreach projects as they deserve. Their marriage of a proportionally huge, sharp-toothed skull with a crocodile- or lizard-like body is unlike anything around today and it's difficult not to wonder how they functioned as living animals. Closer inspection of their anatomy reveals more sophistication than we might assume from the few illustrations of these animals available online or in books, and it seems that their role in Mesozoic ecosystems and reptile evolution was an important one. These were a successful, abundant group of predators with an evolutionary run spanning the Early and Middle Triassic (12 million years in total) and a near cosmopolitan distribution. Moreover, they remain important species for understanding the early evolution of archosaur-line reptiles. They really do have a lot going for them, but they just haven't quite caught public imagination.

A few years ago I was commissioned to reconstruct the small(ish), early erythrosuchid Garjania madiba for David Gower and his colleagues for their 2014 descriptive paper (below). The brief was for a straight illustration of the animal rather than a restored scene, and I promised the team I would put this reconstruction in a landscape one day. Two years later, I've finally got around to it: the results are above. Posting this painting seems like as good an excuse as any to lavish some much needed attention on these most encephalised of reptiles, so let's get stuck in.

G. madiba reconstruction from Gower et al. (2014). Note prominent bosses on the face, a characteristic feature of this species.

What, exactly, is a erythrosuchid?

You can find erythrosuchids in Triassic rocks on every continent except North America and Antarctica and, although relatively complete specimens are not common, many species are represented by large inventories of bones. Despite this relative glut of material, the classification of erythrosuchids - from the fine anatomical characteristics of the group, to their position in the reptilian tree and the number of species contained in the clade - has been the subject of long-standing, ongoing discussions among palaeontologists. Older erythrosuchid literature is confused by a multitude of different classifications which entwine erythrosuchids with other large-headed, carnivorous archosauriforms such as raisuchians and proterosuchids. Researchers have long realised the problems with these schemes, but unpicking the relationships of these groups and other early archosaur-line reptiles has been tricky. With the arrival of extremely detailed and well sampled cladistic analyses of archosauromorphs (e.g. Nesbitt 2011; Ezcurra 2016) we might be moving towards greater consensus on the systematics of these animals, however. In modern schemes, erythrosuchids are recovered as non-archosaur archosauriforms close(ish) to the base of Archosauria. More specifically, they are the sister clade to the the Eucrocopoda, the large clade that contains the likes of Euparkeria and proterochampsids, as well as the true archosaurs(Ezcurra 2016).

Erythrosuchus africanus skull, restored by Gower (2003). Note the extremely robust construction of the bones and expanded areas for neck muscle attachment.

Several erythrosuchid species are well known: Erythrosuchus africanus from the Middle Triassic of South Africa, Garjainia prima from the Early Triassic of Russia, and Shansisuchus shansisuchus (that's not a typo) from the Middle Triassic of China. These species are represented by associated remains as well as large numbers of fragmentary referred specimens, and allow for a relatively complete insight into their overall form. The largest taxa, like Erythrosuchus, are big animals with head-tail lengths approaching 5 m - the length of a good-sized car - and even small taxa like Garjainia are over 2 m long. The most arresting aspect of eyrthrosuchid anatomy is, of course, their skulls (above). Superficially theropod-like, these long, deep and robust structures are sub-rectangular in lateral view, but taper markedly towards the snout in dorsal or ventral aspect. These animals are yet another reminder that restoring fossil animals needs more than a lateral view of a skeleton: those massive skulls are considerably narrower than we might expect. Their teeth are thecodont, large, serrated and recurved. A characteristic of the group is the complicated shape of the upper jaw, where the jaw tip is vertically displaced from a ventrally bowing maxillary region (Parrish 1992), creating something of a 'notch' towards the front of the jaw. Beneath this, the mandible has a slightly dorsoventrally expanded tip, as well as a swollen posterior region. At least the skull of Erythrosuchus is essentially akinetic, although minor movements of some bones may have been possible (Gower 2003). Although erythrosuchid skulls are fairly conservative in morphology, some species were not above frivolous accessorising: prominent bosses above and below the eye are known from Garjainiamadiba (Gower et al. 2014 - see reconstructions, above), and Pickford (1995) reports a long, low boss on the snout of an undescribed Karoo Basin specimen.

Although erythrosuchid skulls were almost certainly pneumatised in some areas, the largest opening in the skull is not, as we might expect in such large headed animals, anything to do with a pneumatic cavity. Rather, it's the lower temporal fenestra, an opening typically associated with allowing bulges of the jaw adductor muscles. This, as well as the presence of a small sagittal crest between the superior temporal openings (which overly the same muscle block) and the depth of the posterior mandible likely betrays the presence of massive adductor muscles in temporal region of the skull. Eryhtrosuchid skull bones certainly look sufficiently robust to withstand powerful biting, the bones forming the temporal fenestra, jaw and orbital margins being extremely massive and thick and tightly interlocking with complex sutures between each bone. Interestingly, Shansisuchus has the same partly invaded orbit shape that Henderson (2003) linked with reinforcement against heavy bite forces in theropod dinosaurs: perhaps similar buttressing was taking place in these Triassic reptiles

The dorsal extent of the occipital face in Eryhtrosuchus africanus, posterior view. The rounded flanges at the top poke above the rest of the skull, and perhaps indicate expanded neck muscles in this and other species. From Gower (2003).

The posterior surface of the skull is interesting. Rather than the relatively flat surface we see in most animals, the posterior erythrosuchid skull is recessed so that several aspects of the skull - the jaws and lateral extents of the occipital surface - extend further back than the vertebral/skull joint. The area which anchored the neck musculature extended across this recessed surface, even exceeding the dorsal margins somewhat by means of a pair of semiscircular flanges projecting above the rest of the skull (visible in at least Erythrosuchus and Garjainia - see above). Assuming a typically reptilian muscle plan, these indicate that muscles anchoring above the skull-neck articulation were larger than usual, as might be expected for animals with ginormous heads. Similar dorsal expansion of the occipital region is seen in tyrannosaurids, and is also thought to reflect large cervical musculature (Paul 1988). It thus seems the vertebrae and posterior skull of erythrosuchids were deeply buried in neck tissues, befitting animals with a giant head to support and utilise in predatory acts. But I wonder if all this support and strength compromised the mobility of the skull-neck joint somewhat. Moving the neck articulation forward to sit within the boundaries of the skull likely shortened the length of the skull flexor muscles, as well as buried the joint in masses of potentially restrictive muscle and bone. Motion of the head may have been limited at the front of the neck, then, but unfortunately for erythrosuchid prey, the size of the shoulder skeleton and stoutly built humeri suggest this was accounted for with powerful muscles at the base of the neck, as well as forelimbs able to shove the forequarters around at speed. Dashing left or right against a charging erythrosuchid was unlikely to save you from a nasty, gigantic and powerful bite.

Behind the skull we see a fairly typical Triassic archosauriform body (below). The neck is short, and especially so in some of the larger species, and the majority of the vertebrae are adorned with tall neural spines: these almost certainly provided anchorage for axial musculature related to supporting the head and back. The pectoral elements, which are also employed somewhat in neck musculature, are also robust. Their tails are moderately long, with deep chevrons in the anterior region likely related to hindlimb musculature. Behind these, the tail becomes rather slender. Gower (2001) proposed that Erythrosuchus vertebrae possessed pits and depressions possibly related to the development of post-cranial pneumaticity, the first found outside of pterosaurs and dinosaurs. This would be a significant find, telling us something of erythrosuchid lung structure as well as the early evolution of postcranial pneumaticity in archosaur-line reptiles. However, both O'Connor (2006) and Butler et al. (2012) argued against this interpretation, noting that the features in question were not associated with internal cavities, thus failing to meet criteria for structures of pneumatic origin. An important caveat to this, however, was raised by Butler et al. (2012): the phenomenon of pneumatic tissues invading vertebrae and other postcranial bones almost certainly did not evolve in one swoop. Its earliest stages may have simply been pneumatic tissues 'pushing' against external bone walls, forming pits and cavities, rather than invading them entirely. If so, the sort of thing Gower (2001) found in Erythrosuchus might be what we'd expect of early stage, postcranial pneumaticity. So while we have to concede that these structures do not meet our current definition of a postcranial pneumatic structure, perhaps we also need to learn more about the early evolution of postcranial pneumaticity before this hypothesis can be ruled out entirely.

Mounted Garjainia prima skeleton as mounted at the Paleontological Institute, Moscow. Certain aspects of this skeleton are reconstructed or sculpted, so take some details with a pinch of salt. From Ivakhnenko and Kurochkin (2008).

The limbs of erythrosuchids are not, to my knowledge, completely known from any species but their major limb bones are powerfully built and surprisingly lengthy: you could never call them 'long-limbed', but they are not the stumpy-legged animals we often see them reconstructed as. Their hands and feet are poorly known. Rare examples of erythrosuchid ankles are thought to indicate an mesotarsal condition (Gower 1996), and their pelves show signs of advanced features that we see developed further in true archosaurs. These features led to our G. madiba reconstruction having semi-erect hindlimbs, while the forelimbs remained sprawling. The typical pose of erythrosuchids remains to be determined from further study of their limb bones.

A point of contention among researchers is whether or not erythrosuchids had osteoderms. Two examples of such structures have been found in association with a specimen of Erythrosuchus, but they show no consistency in their morphology (Gower 2003). Moreover, the extensive inventory of Erythrosuchus and other erythrosuchids have yet to show additional evidence of dermal bones (Ezcurra et al. 2013). The safe bet, for the time being at least, is to assume these reptiles did not have osteoderms, and that those previously referred to the group were a fluke association from another animal.

The life and times of Triassic big-heads

We have much to learn about many aspects of erythrosuchid palaeobiology: details of their dietary preferences, locomotor mechanics and likely habitats remain only provisionally researched. Much of what we've learned about their lifestyles comes from 'bigger picture' assessments of Triassic diversity and faunal turnover, so we can only paint a broad-brush picture of their ecology at this time. That's not to say we have no specific palaeobiological insights into these animals, however. For instance, there is consistent histological evidence that erythrosuchids grew quickly, perhaps at rates comparable to pterosaurs and dinosaurs, until they reached reproductive maturity (de Ricqlès et al. 2008; Botha-Brink and Smith 2011; Ezcurra et al. 2013). Given that this trait is not limited to erythrosuchids among Early and Middle Triassic reptiles, this is one reason it's thought that archosaur-line reptiles may not be ancestrally ectothermic. Whatever the cause, rapid growth may have played some role in the success of erythrosuchids and other reptiles as ecosystems were rebuilt in the early Mesozoic (Sookias et al. 2012).

Erythrosuchid ecology remains only lightly investigated, but they have been considered arch terrestrial predators by some (Sennikov 1996 - see below). Interestingly, their size puts them among the largest terrestrial animals known from their respective faunas (Sookias et al. 2012). This is unusual: in post-Middle Triassic ecosystems we generally find herbivores are the largest animals in terrestrial ecosystems, so what's going on here? It's thought that physiological distinctions between large Early-Middle Triassic reptiles and the synapsid herbivores they coexisted with may explain the size difference (briefly summarised, archosauriform growth rates and respiratory anatomy may have permitted larger overall body size than therapsids - see Sookias et al. 2012), but how did this translate into ecological balance? Energy is lost as it is transferred between species in food webs, so how did populations of relatively 'giant' top-tier erythrosuchids sustain themselves on consistently smaller prey? Perhaps they were simply comparatively rare, or very energy-efficient, or maybe they supplemented their diet with non-terrestrial food items - did they also take food from aquatic realms, perhaps?

An Early Triassic terrestrial food web, reconstructed for the Yarenga Formation by Sennikov (1996). In this scheme, most things ended up in the bellies of erythrosuchids or rausuchians.

Speaking of aquatic habitats, the concept of erythrosuchids as strictly terrestrial predators is not the only interpretation of their habits. Indeed, for much of the 20th century erythrosuchid proportions were considered evidence of aquatic or semi-aquatic habits: their huge heads and robust limbs were thought to permit only cumbersome, laboured movement on land (see Ezcurra et al. 2013 for a brief review). The words offered by Reig (1970) paint an excellent summary of these older interpretations: "We doubt that bulky and clumsy animals like Erythrosuchus and Shansisuchus should be considered very active animals... It is more likely that they were inhabitants of swamp marshes, able to prey upon big, slow herbivorous vertebrates, inhabiting the same environments, which could be caught by a relatively slow and heavily built predator" (p. 261). Potentially further evidence of semi-aquatic lifestyles are the relatively thick limb bone walls common to all erythrosuchids, these being comparable in thickness to those of modern alligators (Botha-Brink and Smith 2011; Gower et al. 2014).

In recent years, however, erythrosuchids seem to have been perceived as more terrestrial animals (Sennikov 1996; Botha-Brink and Smith 2011; Ezcurra et al. 2013). Their thick bone walls are explained as being a consequence of their large size rather than aquatic habits (Botha-Brink and Smith 2011) and the deficit of obvious aquatic adaptations in their skeletons has been noted by several authors (Botha-Brink and Smith 2011; Ezcurra et al. 2013; Gower et al. 2014).

Aquatic, semi-aquatic or fully terrestrial? This guy's meant to have taken a dip in the water, but was it intentional or accident? We may not have the data to say exactly what erythrosuchids did for a living yet.

All this said, I must admit to desiring more work in this area. The habits of strange Triassic animals are difficult to fathom in many instances, and we're yet to see particularly comprehensive assessments of the most basic elements of erythrosuchid functional anatomy, let alone application of modern techniques like isotope analysis, stress modelling of jaws and so on to this problem. My gut feeling - and thus in no means a basis for a hypothesis - is open to both interpretations of erythrosuchid habits, and I wouldn't be surprised if terrestrial and aquatic prey were on their radars. I'm suspicious about the weight of the head being a problem for terrestrial locomotion. A decade of looking at terrestrially-competent, large-headed pterodactyloid pterosaurs and recent monkeying about with mass fractions of giant-necked Tanystropheussuggest our intuitive grasp of front-heaviness might be poorly calibrated. Animal heads and necks are often much lighter than we think in contrast to torso and limb masses, and we should remind ourselves that erythrosuchid skulls are actually quite narrow, presumably well-pneumatised structures. This is the sort of thing that can be relatively easily investigated using digital models, and we might hope this approach is applied to erythrosuchids in future. But if that supports a terrestrial habit, the notched upper jaw and swollen mandibular tip of erythrosuchids argues contrarily: similar jaw tips are seen in fish-eating animals like modern crocodylians and pike conger eels, as well extinct presumed fishers such as spinosaurids and some pterosaurs. Might this not imply that small swimming animals were sometimes eaten by erythrosuchids, too? Lest we forget, animals do not necessarily need to be dedicated swimmers to be able to eat aquatic prey. There's a lot of scope for further work and investigation here, and it would be great to see some dedicated functional assessments and ecological investigations of erythrosuchids in future.

I love it when a bauplan comes together

Perhaps one of the most interesting things mentioned recently about erythrosuchids is how little their postcrania differs from those of other archosauriforms, despite their substantial cranial modifications (Ezcurra 2016). This is something we see again and again in Triassic reptiles: relatively conservative bodies with highly localised outlandish anatomy, and is true even for the weirdest Triassic creatures. For example, Tanystropheus isn't that strange aside from its incredible neck, and (what we know of) the body of Sharovipteryxis not that atypical in spite of its leg-wings. I wonder if Triassic animals get the short shrift in popular circles because they're viewed as boring 'also rans' taxa which evolved strange, untenable anatomies but without moving too far from a typically 'reptilian' visage.

But perhaps what we're seeing with these animals is far more interesting than it first appears: a display of the intrinsic adaptability of the archosauromorph bauplan, and how applicable it was to many lifestyles with only localised modification. We can be particularly impressed with erythrosuchids because of their rapid evolution so early in the Triassic: they very quickly and successfully jumped into the niche of large, hypercarnivorous apex-predator after the end-Permian extinction event, and then held that niche worldwide for 12 million years. The fact they did so without much additional modification to the postcrania is evidence that their success was not a fluke, and that the basal archosaur-line body plan was a strong one. Perhaps instead of looking at erythrosuchids and other Triassic archosauromorphs as those strange, but ultimately dull animals that struck it lucky before the more successful ones took over, we might view them as some of the earliest evidence that the archosaur-line bauplan had real potential, and a sign of what was to come.

Big blog posts about big headed reptiles need big support - thank goodness for Patreon

The paintings and words featured here are sponsored by a group of tetrapods with more modestly proportioned skulls, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be looking at the history of the painting up top, documenting its long 2-year journey from illustration to, er, a more detailed illustration. I'll also share the bizarre, sausage piglet monster version of Garjainia that you were never meant to see. Sign up to Patreon to get access to this and the rest of my exclusive content!

References

Bear-sized gorgonopsid Inostrancevia latifrons. Sabre-teeth? What sabre teeth?

It is something of a trope that prehistoric animals must bare their teeth in palaeoart, even when their mouths are closed. Historically, the majority of palaeoartists covered the teeth of their subjects with lips, cheeks or other types of tissues and only select species – sabre-toothed carnivorans or mammoths – were depicted with exposed tusks or sabre-canines. This changed when artists working in the 1980s and 1990s - Paul, Hallett, Stout - and a certain 1993 movie started showing predatory dinosaurs with toothy overbites and perpetually exposed teeth. This convention has since expanded to all kinds of prehistoric animals, and some galleries of Deep Time now have more toothy grins than a holiday photo album. Theropod dinosaurs in particular are almost always shown with alligator-like overbites that perpetually expose their upper teeth, the large canines of stem-mammals protrude over their lower jaws, and even herbivorous animals with relatively unimpressive dentition (like sauropods) are shown without lips or other forms of dental covering.

Many words – mostly published at blogs, online mailing lists and social media - have been typed to discuss the credibility of lipless palaeoart, but the subject has traditionally received only cursory attention from academics. Happily for artists, this is starting to change. A small set of literature exists which debates the presence of extra-oral tissues in dinosaurs (e.g. Ford 1997; Knoll 2008; Morhardt 2009; Keilor 2013; Reisz and Larson 2016), and most this agrees that some sort of soft-tissue - at least 'lips' - covered their teeth. However, a running theme of these works is that reliably inferring soft-tissues of the face is not a simple task, and we really need more data to be sure of anything. Work on more recent fossil mammals shows more reliable inferences (e.g. Wall 1980; Antón et al. 1998), obviously benefiting from soft-tissue data from a range of extant, close relatives. New insights on the evolution of mammal cranial nerves are helping to understand the development of sensitive lips and cheeks in stem-mammals (Benoit et al. 2016). It's still early days for understanding fossil facial tissues, but at least it feels like we're off the line.

Collectively, there seems to be recognition among the academics interested in this topic that understanding the tooth coverage of fossil animals lies largely in understanding living animals. Attempts to understand tooth exposure from skulls alone - through making inferences about tooth size, jaw closure and speculations on how extensive soft-tissues can be before they become untenable - do not consider all necessary data. For example, Prehistoric Times palaeoart adviser Tracy Ford (1997) looked solely at the skulls of predatory dinosaurs to infer the absence of lips, suggesting their teeth were so long that they would pierce lip sheathing once the jaws were closed. This study assumed that predatory dinosaurs closed their mouths to the extent that the teeth of the lower jaw contacted the roof of the mouth, and that the preserved tooth configuration was the condition in life. These points are common issues raised against lipped dinosaurs, but there are several major problems. Dissections and CT scans of reptile heads show that jaw muscles and other soft-tissues have a major influence on mouth closure, to the extent that reptile jaw skeletons are typically loosely closed under their skin, even when the mouth is fully sealed. Taphonomic studies show that teeth slip readily from their sockets after death and often fossilise in far more vampiric states than they were in life. And undermining this further is that no extant taxa with lipped jaws were used to calibrate a limit for oral soft-tissues. Arguments about tooth coverage based on simply looking at skulls, without detailed consideration of modern animals and their anatomy, border on being arguments from incredulity : "I don't believe the anatomy could do that."

Modern animals and their tooth coverage

For an upcoming project, I've been trying to crystallise my approach to restoring ancient animal facial tissues, and deciding whether to cover their teeth or not is an important part of that discussion. I've been deliberately broad in this assessment to attempt to try to sort the wood from the trees: discussions of oral tissues can sometimes get lost in the minutiae of tissue types, uncertain osteological correlates and so on - and many of these discussions result in the same answer: they can't be resolved with current data. That's not to say they aren't important discussions, but it's helpful to step back to see if we can answer the simpler questions as well: what gauge of teeth can be covered by oral tissues? When are teeth actually exposed? And what questions should we, as palaeoartists, be looking to answer when restoring facial tissues?

Reviewing literature and galleries of modern animals, we can see that overwhelming majority of living tetrapods have covered teeth, including all amphibians, most mammals and most reptiles (excluding birds, naturally. Hey, if they wanted to be involved they shouldn't have lost their teeth). Exposed teeth are actually really rare, and a character completely absent in many major clades. The soft-tissues involved in covering the teeth are variable, but 'lips'– either slightly fleshy margins of skin, or skin overlying true muscle - are so universal among tetrapods, as well as living relatives like lungfish, that we might assume lip tissues of some kind were ancestral to the group, and breaching these with large teeth is a derived condition evolved independently in a minority of lineages. Crocodylians are the only living tetrapods with fully exposed teeth, but it's increasingly obvious that they're also pretty specialised/derived/downright weird (Grigg and Kirshner 2015). Far from being 'living fossils' frozen in evolution, they have so many anatomical nuances and specialisations that their use as model organisms for other extinct taxa is increasingly questionable. This applies to aspects of their facial anatomy too - we’ll discuss this in more detail below.

Fossil big-tooths - species almost universally depicted with exposed teeth - versus modern animals with huge, but completely covered teeth teeth. A, Inostrancevia latifrons; B, Tyrannosaurus rex; C, Smilodon fatalis; D, crocodile monitor Varanus salvadorii; E, mandrill Mandrillus sphinx; E, hippopotamus Hippopotamus amphibius. With the exception of Smilodon, the fossil taxa are out-toothed by the extant animals, and yet we know their oral tissues can accommodate their teeth without problem. Blue lines approximate lip margins in living species. A, after Kemp (2005); E, after Goldfinger (2004).

Looking inside animal heads (above) shows that facial soft-tissues can cover very, very large teeth – perhaps much larger than we might intuitively expect. Examples from a range of tetrapods – including rhinoceroses, sloths, tapirs, mandrills, baboons, camels, tuataras, snakes, peccaries, bullfrogs, hippopotamuses, monitor lizards, clouded leopards, numerous rodents and others – show that large fangs, robust tusks and other forms of enormous dentition can be retained within lips or cheeks. These large teeth are truly ‘hidden’ without bulges, changes in lip direction or other features to betray their presence, and are thus undetectable unless their owners open their mouths (and sometimes not even then). Many people are shocked by the size of animal teeth when they see their skulls, and the savagery of mammalian herbivore dentition – horses and camel fangs, rhino tusks, baboon canines - are particularly startling.

We owe many of these surprises to animal lips, which are generally much more extensive than we casually assume. Large teeth can slide into soft-tissue sheaths located between gums and lips, and these are quite visible in the open mouths of some species. Amphibians, lizards and many mammals have upper and lower lips of similar size which meet over the teeth and sheaths can form on either jaw, but some mammals – including most carnivorous forms - have very large, fleshy upper lips over thinner, tightly-bound soft-tissues of the lower jaw (Antón et al. 1998). In these species, the canine teeth overbite the lower lip but the upper ‘over-lip’ is large enough to obscure the fact that the tooth is outside the lower mouth tissues. I am unaware of a reversed situation with the lower lip covering a thin upper lip: this may reflect the fact that overbiting dentition is much more common than underbiting. Regardless of the specific configuration, it is clear that we should not underestimate the capacity for facial tissues to obscure even very large, sharp and ferocious-looking teeth. The assumption that all conspicuous teeth of fossil animals were on display in life is thus problematic and does not agree with what we can observe in modern animals (below).

Applying palaeoart-esque considerations of oral tissue capacity to modern mammals suggest hippos are giant hogbeasts and mandrills evolved in Mordor. Restoring modern animals using palaeoart approaches is a completely original concept which in no way owes anything to some book called All Yesterdays (Conway et al. 2013).

When do teeth breach the confines of soft-tissue? Mostly, it seems teeth used to process food remain covered. Mammal tusks and the exposed canines of certain deer are not directly involved in food processing, although this is not to say they are non-functional overall (e.g. elephants use their tusks to break branches, dig, topple trees; deer fight with their large canines). It seems that teeth of extreme size relative to the rest of the dentition are most likely to escape covering with soft-tissue, and it helps – though is not mandatory – if they grow obliquely or directly away from the jawline (this accounts for the majority of living mammal tusks). Teeth can remain covered even when their tips extend to the dorsal or ventral limits of the jaw skeleton, so long as they are aligned more or less vertically within the jaw (e.g. the mandrill skull illustrated above).

What's up with crocodylians?

The elephants – or rather large semi-aquatic reptiles – in the room here are crocodylians: why do they have exposed teeth when all other tetrapods have largely covered mouths? Their teeth are not overly large, nor acutely angled. Some (Reisz and Larson 2016) have argued crocodylian dentition is only possible because of their semi-aquatic habits. The (unpublished, currently conference abstract only) Reisz and Larson hypothesis is that exposed teeth – specifically their enamel component – are at risk from desiccation and breakage without constant hydration from saliva or environmental water (Reisz et al. 2016). This is an interesting idea which potentially gives artists a useful, practical guide to restoring prehistoric animals: anything living outside water with enamel-covered teeth must have covered them with soft-tissue. Despite its unpublished status, this idea has already chimed with some quarters of the online palaeoart community who're restoring anything with enamel-covered teeth with full sheathing.

We need to talk about enamel and exposed teeth. The exposed canines of male wild boars, Sus, have enamel (white shading) coatings on 3/4 of their surface, despite being exposed (dentine is dark grey, cementum is light grey). What does this mean for the enamel desiccation hypothesis outlined below? Image from Hillson (2005).

However, this proposal may not be as simple to implement as it first appears. For one thing, there is a real lack of consistency in tusk composition in living animals (see Hilson 2005). It is true that, as noted by Reisz et al. (2016), the tusks of elephants have caps of enamel and cementum that wear off rapidly, leaving their tusks composed of dentine alone. This would seem to support the desiccation hypothesis, it implying that enamel is a liability outside of the jaw soft-tissues. However, living elephants may not be typical in lacking enamel on their tusks, there being fossil and living mammals which do have substantial enamel components on their exposed teeth. For example, the tusks of several gomphothere species have broad bands of enamel along their lateral surfaces, even as adults (Padro and Alberdi 2008), while the canines of male musk deer are enamel covered on the external surface. The tusks of male wild boars and warthogs only bear dentine on the posterior surface and wear facet, the rest of these large, exposed teeth being covered in enamel. In all these species these are not just small bits of enamel that get worn off, but sustained coatings that persist on the tooth indefinitely and influence tooth wear (Koenigswald 2011). To confuse things further, walruses have dentine tusks like elephants, despite their aquatic habits seemingly precluding desiccation as a risk for their teeth, and the spiralling tusks of another marine mammal, the narwharls, are covered in enamel. If there is a relationship between enamel and tooth exposure, it is clearly a complicated one: the presence of absence of enamel in itself seems to have little bearing on tooth exposure in at least modern mammals. (Readers interested in tooth composition should check out the second edition of Samuel Hillson's Teeth (2005), for its extensive documentation and illustration of mammalian dentition).

Musk deer, Moschus, canines in lateral and medial view. Note the (white) enamel layer on the lateral surface, but dentine (grey) on the medial. From Hillson (2005 - the scale bar is likely erroneous!).

Our second reason to be sceptical of the enamel desiccation hypothesis concerns crocodylian behaviour. It is not widely appreciated that several crocodylians species ‘hibernate’, or more accurately aestivate, for months at a time in dry underground burrows during the hottest summer months (Grigg and Kirshner 2015). During these intervals they do not access water at all. Other, South American species spend dry spells as fully terrestrial carnivores, abandoning aquatic habits and obtaining water largely from the prey they kill (Grigg and Kirshner 2015). These states have to be explained against the suggested need to frequently moisten crocodylian teeth, because they suggest dental desiccation is not as risky as we're all assuming it is. Alternatively, it suggests that the requirement for hydration is so relaxed – literally months can pass without getting the teeth wet – that it probably has little influence on tooth anatomy.

Furthermore, there are important caveats about crocodylian facial tissues that we have to factor into any discussion of their lipless configuration. Crocodylian faces are far more specialised and unusual than they first appear, and this may factor into their lipless mouths. Their highly keratinous facial skin undergoes a developmental pathway unlike that of any other amniote (their facial skin is essentially have one, highly 'cracked' scale) (Milinkovitch et al. 2013) and their heads are riddled with hyper-sensitive Integumentary Sense Organs (ISOs). ISOs are another unique crocodylian feature and are attuned, among other things, to sensing tiny vibrations in water (Soares 2002, see Grigg and Kirshner 2015 for a recent overview). In at least some parts of the crocodylian skull ISOs are situated over tiny foramina, presumably housing nervous tissues, and the overlying epidermis is thinned, with a reduced keratin component, to enhance their sensitivity (Soares 2002). We can thus see that ISOs do have a role to play in configuring crocodylian skin, and they present many questions that palaeoartists should be interested in. Are ISOs an important reason for crocodylian faces having such tight, contour hugging and lipless skin? Do the major functional and developmental distinctions of croc faces explain the lack of crocodylian lips? It might explain why virtually no other aquatic tetrapods have abandoned lips - aside from the the odd (and perhaps only) exception like the South Asian river dolphin*, there are no whales, snakes, seals or otters with crocodylian-like, fully exposed teeth. And given that no other lineages have osteological correlates for ISOs, should we put huge caveats around using crocodylians as models for facial tissues in anything other than their own ancestors? I don't know if anyone has answers to these questions yet, but they're food for thought when using crocodylians as ammunition for lipless reconstructions of fossil animals.

*Thanks to Ádám Lakatos for pointing out the toothiness of some river dolphins!

It's still very early days for the enamel/oral covering hypothesis, but modern animals suggest that interpretations of enamel precluding extraoral teeth are definitely more complicated than they first appear, and may even be flawed. If so, the simple presence of enamel on the teeth of fossil organisms may not be as useful to artists as some are currently suggesting. But this conclusion is preliminary, and we need to wait for this idea to mature before it's shot down entirely. We know, for instance, that there's more than one type of enamel among vertebrates. Reptilian enamel, for instance, is both thinner and of different microstructure to mammalian enamel, and these clades have rather different approaches to tooth longevity. This may mean something for enamel desiccation and long-term tooth exposure, and we may think differently on this matter once this research has been completed.

Predicting tooth exposure in fossil species

Fully 'lipped' gorgonopsids and theropods: maybe not be as exciting as their toothy variants, but are they more credible? Well... if modern animals are anything to go by, probably.

All this said, what can we say about the decisions to show prehistoric animals with exposed teeth? My reading of modern tetrapods is that covered teeth is their ‘default’ configuration, and we should apply the same logic to extinct animals. If so, maybe only the more extreme examples of fossil dentition should qualify for perpetual display. Perhaps instead of asking ‘does this animal have lips?’ we should ask why they should not have them. We have to concede that the dentitions of many fossil animals frequently shown with exposed teeth – particularly theropod dinosaurs, gorgonopsids and other carnivorous stem-mammals – are relatively no larger, and in some cases a great deal smaller, than those enclosed inside the oral tissues of living animals, especially once taphonomic tooth slippage is corrected (above). For these species, it is very difficult to justify why their teeth should not be covered.

If this is so, only especially long teeth which project a considerable distance from the margins of the skull and lower jaw should be considered strong candidates for permanent exposure. Select examples might include the canines of certain mammalian carnivores (e.g. Smilodon and other machairodont felids), the tusks of fossil elephants and their relatives, and the larger tusks of dicynodonts. We should also note those fossil reptiles – such as certain crocodyliformes, pterosaurs and marine reptiles – where entire toothrows are composed of dentition so long that their tips extend well beyond the margins of the jaw skeleton. Such extensive dental apparatus would seem to preclude the development of any sheathing tissues, at least akin to those exhibited by from modern animals, and these animals probably had fully exposed toothrows in life. Of course, this conflicts with the observation that food-processing teeth are almost always covered in the modern day. However, we can defend this approach by arguing that their morphology gives a strong reason for ignoring this guideline: it answers the "why we shouldn't give them lips?" question.

The large, procumbent dentition of plesiosaurs and certain pterosaurs argues against them being sheathed in life, although I do wonder if some plesiosaurs are in a 'grey area' here. Could animals like Leptocleidus (right) have covered its teeth with lip-like tissues? Hmm....

We might also set aside this guideline when extant relatives of modern forms provide us with means to predict unusual lip anatomy. For instance, the aforementioned ‘over-lip’ of modern mammalian carnivores is common enough across this group to assume it was present in their fossil relatives. Because we understand how the lips of these animals work, we can make more specific predictions concerning tooth exposure in species with particularly impressive teeth. Thus, we can look at classic reconstructions of machairodontid cats like Smilodon with perpetually bared fangs as reasonable because, unless their lips were arranged differently to virtually all their living relatives, that’s simply how their lip tissues would respond to a massive set of canines. And yes, I'm aware of Dunae Nash's recent discussions about sheathing Smilodon: given that this rests heavily on enamel being a no-no in exposed teeth, I'm unconvinced for the reasons explored above.

The concluding caveat

Of course, it must be reinforced that these are just guidelines - and guidelines based on my own qualitative studies, nonetheless, your mileage with them may vary - and there are exceptions to the suggestions made above. As is well known, for all the suggestion that restoring sabre-toothed cats with exposed teeth is reasonable, one living cat species – the clouded leopard – does cover a set of long upper canines in a lower lip sheath. We would not predict this based on other cat species and, if known only from fossils, clouded leopards would probably be restored with a slightly exposed canine. Likewise, the exposed tusks of some deer are not especially massive, and if we followed the suggestions above we'd probably cover them up in a reconstruction. But palaeoart is ultimately a game of prediction and probability, attempting to restore what is most likely to fill gaps in our data, and any game of odds will have some failures. That’s not to say we shouldn’t ignore these exceptional examples - they show that guidelines can't be trusted all the time - but it makes sense for us to know where the guidelines are in the first place. As with all aspects of palaeorestoration, all of us stand a chance to be proved wrong about our artistic decisions: if and when that happens, the best we can hope for is to have been wrong for the right reasons.

This blog post was covered by Patreon

The paintings and words featured here are sponsored by a group of animals which also have sheathed dentition, Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. Sign up to Patreon to get access to this and the rest of my exclusive content!

References

• Antón, M., Garcia‐Perea, R, & Turner, A. (1998). Reconstructed facial appearance of the sabretoothed felid Smilodon. Zoological Journal of the Linnean Society, 124(4), 369-386.
• Benoit, J., Manger, P. R., & Rubidge, B. S. (2016). Palaeoneurological clues to the evolution of defining mammalian soft tissue traits. Scientific reports, 6.
• Conway, J., Kosemen, C. M., Naish, D., & Hartman, S. (2013). All yesterdays: unique and speculative views of dinosaurs and other prehistoric animals. Irregular Books.
• Ford, T. L. (1997). How to Draw Dinosaurs. Give Theropods no Lip! Prehistoric Times, 25, 49-50.
• Hillson, S. (2005). Teeth, Cambridge Manuals in Archaeology Series. Cambridge University Press, Cambridge, 373.
• Goldfinger, E. (2004). Animal anatomy for artists: The elements of form. OUP USA.
• Grigg, G., & Kirshner, D. (2015). Biology and evolution of crocodylians. Csiro Publishing.
• Keillor, T. (2013). June, in the Flesh: The State of Life-Reconstruction in Paleoart. In: Parrish, J. M., Molnar, R. E., Currie, P. J., & Koppelhus, E. B. (eds). Tyrannosaurid Paleobiology, Indiana University Press. 157-176.
• Kemp, T. S. (2005). The origin and evolution of mammals. Oxford University Press.
• Koenigswald, W. V. (2011). Diversity of hypsodont teeth in mammalian dentitions—construction and classification. Palaeontogr. Abt. A, 294, 63-94.
• Knoll, F. (2008). Buccal soft anatomy in Lesothosaurus (Dinosauria: Ornithischia). Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen, 248(3), 355-364.
• Morhardt, A. C. (2009). Dinosaur smiles: Do the texture and morphology of the premaxilla, maxilla, and dentary bones of sauropsids provide osteological correlates for inferring extra-oral structures reliably in dinosaurs? (Doctoral dissertation, Western Illinois University).
• Prado, J. L., & Alberdi, M. T. (2008). A cladistic analysis among trilophodont gomphotheres (Mammalia, Proboscidea) with special attention to the South American genera. Palaeontology, 51(4), 903-915.
• Reisz, R. R. & Larson, D. (2016) Dental anatomy and skull length to tooth size rations support the hypothesis that theropod dinosaurs had lips. 2016 Canadian Society of Vertebrate Paleontology Conference Abstracts, 64-65.
• Soares, D. (2002). Neurology: an ancient sensory organ in crocodilians. Nature, 417(6886), 241-242.
• Wall, W. P. (1980). Cranial evidence for a proboscis in Cadurcodon and a review of snout structure in the family Amynodontidae (Perissodactyla, Rhinocerotoidea). Journal of Paleontology, 54, 968-977.

The best holiday of the year is just around the corner: Halloween! It's the season to celebrate the macabre, the weird, the dark and the terrifying. It's the best excuse to watch all your favourite horror movies. And it's the time to spend hours making costumes that you can't really see out of or eat or drink in, but that's OK because you're doing this for the art, not the practicality. Yes, it's Halloween: king of the holidays.

This year, an impending honeymoon and my attendance at Dinosaur Days 2016 (a palaeontology/palaeoart event being held at the WWT Wetland Centre, London, 28-29th October - it's going to be awesome, and you should come along) means I can't celebrate Halloween as normal. But dammit, I'm going to do something, even if that means just celebrating a little here by sharing some off-topic art.

Sometimes, very rarely, I take a break from painting and writing about palaeontology and turn my attention to vintage science fiction, producing paintings of some of my favourite stories, characters or monsters, and the creatures of H. P. Lovecraft are a frequent subject. With Halloween being just around the corner and Lovecraft's tales of sinister cults, strange creatures and other-worldly horrors being pretty note-perfect fodder for this time of year, I'm going to take the blog off-road with a short gallery of my Lovecraft paintings. Although we're going to be pretty palaeontology-lite for this post (folks here for coverage of extinct creatures may be pleased to know we'll be back to normal very soon) we're not abandoning the concepts of biology and evolution altogether. One of the things I find appealing about Lovecraft's work is the frequent nods to biology, geology and evolution, and creating biologically plausible(ish) versions of his creatures was a primary goal of the work shared here. We're not quite in the territory of full-on speculative evolution with this post, but I've tried to make my discussion at least a little informed. Right, enough preamble, let's get stuck in. (Oh, and a major SPOILER WARNING for those of you who haven't read Lovecraft's most famous stories and books.)

The Innsmouthians 

First up is a take on some of my favourite Lovecraftian creations, the residents of the decrepit fishing town Innsmouth, as described in The Shadow Over Innsmouth. They're among the few Lovecraftian creatures which stand a chance of being depicted well in art because they're real, physical beings rather than elemental or transmaterial whosermerjiggers that are meant to drive people mad simply by violating the laws of physics.

Deep Ones and their allies search Innsmouth for the narrator. The one in the middle seems to have forgotten what he was doing.

The Deep Ones, the hybrid humans and their devious human counterparts are terrific, enigmatic villains and they feature in one of the most exciting of Lovecraft's stories. The Shadow Over Innsmouth is one of his few tales with a sustained action sequence, and it was this that forms the focus of the painting above where men and inhuman, bactracian beings pursue the narrator. I approached illustrating the Deep Ones using both Lovecraft's brief descriptions as well as keeping some basics tenets of biology in mind. In the novella, these creatures are described as sharing ancestry with humanity and retaining a capability to breed with us too, the resultant hybrid phenotype passing through a human stage before attaining Deep One characteristics. It's hard not to see this as a nightmarish variant on peramorphosis, the evolutionary process where growth is accelerated or extended to produce exaggerated features (it's the opposite of paedomorphosis, a more familiar evolutionary phenomenon where growth slows or ceases so that juvenile features are retained to adulthood).

I wanted to keep my Deep Ones fairly 'grounded', looking like beings that up until their latest growth stages passed for strange looking people, as well as sharing some of the basic tetrapodiness that we might expect of clade we have recent ancestry with. Thus, they still have anthropoid proportions and faces, with the exception of a certain tall froginess about the head, and a further exception being elongate hindlimbs to permit more effective swimming and bounding, as described in the novella. Their feet are also large to aid their swimming potential. I took inspiration from early tetrapods and tetrapodomorphs in removing some of the distinction between the head and shoulders and widening the oral tissues to create an amphibian-like mouth instead of a cheeked human face. The gills were kept relatively subtle, as they appear to be in Carboniferous tetrapods, rather than wacky fin-like structures that recall the designs of Ray Harryhausen. My hope is that creating a set of more grounded creatures rather than slimy-finny-tentacle-beings makes them a little creepier, too. My own responses to horror imagery are that distortions of real life are much scarier than all-out fantasy entities.

It also seemed important to show some of the creatures wearing clothes, something we rarely see in artwork of these creatures but mentioned several times in the story. I think this helps show that they are meant to be intelligent creatures on par with humans in terms of civilisation and culture, even if one of them - the bounding individual on the right - only wears a dirty, ill-fitting human shirt as a remnant of its former life (note the shirt is now incapable of buttoning properly around its fattened, gilled neck). The figure on the left wears a tiara and robes, another nod to specific references in the story and suggesting some sophistication in this species. A few normal-looking people are in the scene too, nodding to the fact that the whole town is associated one way or another with Innsmouth's peculiar goings-on. I think this is why the Innsmouthians are great villains: even those who aren't tainted with 'the Innsmouth look' are in on the game, and those who have lost their humanity remain man-like abilities, intelligence and malevolence. At the heart of The Shadow over Innsmouth is a story about how corrupt and nasty real people can be when they have things to hide.

Dagon: benthic whale wrestler

Moving on, the next image shows another famous Lovecraft creature, one we've come to know as Dagon, from the story of the same name. How Dagon fits into the rest of the Lovecraft universe is a bit murky. Some do not count it as part of the Cthulhu Mythos (indeed, Call of Cthulhu can be seen as a elaborate, Mythos 'canon' retread of Dagon) and the creature in Dagon is never explicitly identified as 'Dagon' itself. We assume it is the titular beast because of its prominence and because several aspects of its nature correspond with the popular, if erroneous, fish-god interpretation of the near-eastern deity also known as Dagon, but confirmation of this is not provided in the story. But something known as Dagon is continually referred to throughout other Lovecraft stories however, and we might assume that - as with his other in-universe references - these are nods to the creatures and scenarios outlined in his earlier work. My work and discussion here assumes that all references to 'Dagon' in Lovecraft's work point to the same entity, including all references to beastly creatures in the Dagon tale itself.

Dagon, imagined as a giant, facultatively-bipedal, whale-murdering member of the benthos, here taking a trip over land to visit his favourite monolith.

Dagon doesn't really give many details about the appearance of the titular creature and there are lots of different takes on this being available online. The best description we get are the narrator's observations of glyphs on a monolith, and they describe a man-like figure large enough to wrestle with whales. I've tried to follow those basic guidelines here. My version also has deliberate nods to my designs of the Deep Ones, it being alluded to as both a relative of their kind as well something they recognised and worship. With the intention to create something biologically practical as well as weird and freaky, I again turned to the early days of tetrapod evolution for inspiration. The barbels around the mouth, posteriorly-placed jaw musculature, sprawling limbs, expanded appendages and long, axolotl-like gills are nods to various amphibians as well as some tetrapod-like fish, but I resisted the urge to add a long tail because of the need for a generally man-like bauplan. 

With a human-like bauplan not being terrific for swimming, I assumed Dagon is a member of benthic communities and gave it large, weight-dispersing feet and hands to facilitate walking on soft marine oozes at the bottom of the sea. It's meant to be a facultative biped, something which can locomote like a man if needed but probably spends more time moving like a gorilla. Its limb girdles and musculature are small and on account of it being a bulky creature mostly living in and supported by water, and we could see this being a sluggish being on land. I don't recall any references to Dagon being a particularly intelligent creature in Lovecraft lore, and think this design conveys a slightly more animalistic, rather than humanistic, creature than the Deep Ones illustrated above. I quite like the idea that this thing may be a figure of worship for the Deep Ones not because its wise or divine, but simply because it's a giant monster that they fear. Sort of the Lovecraft equivalent of King Kong, I suppose. Now that's a movie I'd pay to see.

Echinoid Men from Beyond the Moon!

Echinoid Men from Beyond the SpaceMoon. Is that the best caption I've ever written? Yes. Yes it is.

Lovecraft provides an extremely detailed overview of Elder Thing anatomy courtesy the reported dissection of the first thawed individual. Thus, they can be depicted in some detail and there's strong consistency among Lovecraftian artists of their general form. It's obvious that Lovecraft was highly influenced by various types of echinoderms in his description of this species, particular regular echinoids. Pentameral symmetry, their use of tentacle-like appendages to interact with the world and locomote, as well as pinnulate arms atop their frames are all echinoderm-like features. Furthermore, their barrel-shaped bodies are essentially just stretched versions of the globular tests seen in regular echinoids. But what makes the Elder Things particularly biologically interesting is that this bauplan is given to a species which is meant to be smart, emotional and even artistic. They're the answer to the question of 'what would a sentient, intelligent echinoderm look like?'. Granted, that's not a question most people would think to ask, but it chimes with discussions about 'dinosauroids' and other speculations about the rise of human-grade intelligence in other species. I don't think this was Lovecraft's intention, but we can still view this species as a particularly bizarre take on alternative evolution.

Painting the Elder Things was challenging because it is a little tricky to make them look, well, sensible and viable. I think this is partly because their appearance - based though it seems to be on living species - is pretty out there and grinds against creature designs that we're more familiar with. I mean, how many illustrations or movies show creatures that look the same from five different angles? I've done my best to honour Lovecraft's description here, the only omission from his overview being the absence of wings. However, these are mentioned as being retractable in the novel and thus consistent with all large flying animals to have ever evolved on Earth: wings, frankly, get in the way unless you're flying, so it makes sense for them to be stowed away until needed. Thus, although you can't see them in this illustration, the wings were considered and would be hidden between the bulges of the test (this also solves the problem of how to draw an animal with five wings). The bioluminescence is an exercise of artistic license as it is not mentioned in the novel, but I figure it adds both a sense of sophistication and eeriness to these figures. It's also in keeping with Lovecraft's echinoderm sources, several species of this clade having developed bioluminescent body parts. More by accident than design, the patterning created by the bioluminescent channels reminds me of body painting and masks of some human tribes, which seems appropriate for a race of super intelligent beings... even overgrown echinoids.

And finally...

OK, we're just about done scratching this Halloween itch scratched for this year - I hope you've enjoyed it, or at least tolerated my indulgence. If this sort of thing is appealing let me know in the comments below and I'll consider posting similar post in future. I'm also making these images available as prints at my website shop should you want some Eldritch horrors for your own home. But enough seasonal fun: back to dinosaurs next time!

Except for one more thing... how could we have a Lovecraft Halloween special without a picture of Cthulhu?

"In his house at R'lyeh, dead Cthulhu waits dreaming. And singing '100 bottles of beer on the wall'. He loves that song." Folks interested in the development of this picture, including a previous version, should check out this post at Matt Wedel's (yes, he of SV:POW! fame) blog Echo Station 5-7.

Happy Halloween everybody!

This blog (but not this post) is haunted by Patreon

The paintings and words that make up my blog posts are sponsored by a group of sentient, intelligent, non-echinoderm beings: my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. There's no bonus content or charge for this post because it's so far off my normal topics and not what people have signed up for, but, all the same, sign up to Patreon to get access to past and future exclusive content!

Plateosaurus engelhardti restored as a) speculatively filamented and b) speculatively smelly (note the cloud of insects buzzing around its head). Scientists have good reason to think that sauropodomorphs could not be routine shower users, but what about that fuzz? PS - Blogger has added some weird watermark on this picture that I can't figure out how to remove. If anyone knows, please let me know!

Palaeoartistry is not a science. Even a conservative reconstruction requires artists to stretch data and evidence further than would be allowed for any scientific study and the whole process relies more on inference and speculation than many of us would like to admit. Yes, palaeoart is data-led and evidence-based, but only in rare circumstances do we have enough data to bring us to a single, reliable interpretation of a fossil species. Most of us would agree that there are some aspects of reconstructions that we can and should be getting 'right' for many species - basic proportions and musculature being top of the list - but beyond these science can often only narrow our choices, not present definitive answers. In lieu of clear scientific guidance, what guides these decisions may be our personal preferences, logical thinking, the demands of a project, or the penchants of our consultants. This means that, odd as it may seem, vastly contrasting reconstructions can be construed equally credible. A weird, alternative take on a fossil species might be just as ‘accurate’ to our knowledge as another preferred or familiar one. When evidence is equivocal for two or more states, we have to concede that one interpretation can be just as 'correct' as another.

With this in mind, I thought it might be pertinent to talk about the above reworked reconstruction of Plateosaurus engelhardti with a filamentous coat, and why – at time of writing at least - it’s perhaps neither ‘right’ or ‘wrong’ to depict this animal in this way. I could have covered it with scales as an alternative and not necessarily been ‘correct’ or ‘incorrect’, either. The question of whether sauropodomorphs were wholly scaly has not escaped discussion in many quarters - it was even mentioned at this blog briefly back in 2013 - so, for a change, and perhaps to mirror the sometimes antagonistic way that similar matters are discussed on social media, I’m going to present my thoughts here as a conversational debate between… myself. The idea is that it will allow for fuller discussion of opposing points, but I suspect it really just reflects the amount of time I spend alone at home with no-one but some chickens and various squamates for company. Whatever, hopefully the 'conversation' below will be balanced: both ‘pro-filaments’ and ‘pro-scales’ have important points to make, and I’m not strongly advocating one or the other here: the point is that both sides have valid points to make, so warrant an equal platform. Over to, er… me, then.

Me¹, meet Me²

Me¹ (filaments, opening statement). Should we restore Plateosaurus and other sauropodomorphs with filaments? Maybe. The evolution of dinosaur integument is an increasingly complicated area of study, and the idea that scales alone were the most likely ancestral condition for the major dinosaur lineages is no longer certain. As is well known to many, in the last decade we’re discovered filaments occurring in not only theropods but also in disparate parts Ornithischia too, and detailed new studies are suggesting that filaments in the likes of Psittacosaurus are structurally similar to those of other ornithischians as well as extant and extinct theropods (Mayr et al. 2016). They may even be similar enough to suggest true homology (Mayr et al. 2016), which strongly implies dinosaur skin may have been at least partly fuzzy in its ancestral form. Indeed, with pterosaurs thrown into the mix as well, an ancestrally-filamentous Ornithodira remains not only a valid hypothesis, but one that has passed several important tests in recent years. This being so, a filamented Triassic sauropodomorph is a sensible extrapolation of modern data.

Me² (scales, opening statement). Should we restore Plateosaurus and other sauropodomorphs with filaments? Maybe not. Firstly, studies have shown that our reconstructions of the ancestral ornithodiran integument type remains highly sensitive to the condition of its basalmost species, and we lack fossil data on these forms (Barrett et al. 2015). The 'ancestrally filamentous hypothesis' is enjoying some invigoration from new discoveries and research, but the game is not over yet. Virtually all of our dinosaur skin samples stem from derived species that had plenty of time to modify their integument from the primitive condition, and we have to concede that - whatever we think about the ancestry of dinosaur skin - they were very plastic in integument types. Thus, an important test of this hypothesis will be the recovery of good fossil skin samples from Triassic dinosauromorphs and pterosaurs, and their close relatives. Until we find these, or a fuzzy sauropod fossil, the recovery of scales from all three major dinosaur clades means the argument for 'ancestrally scaled' remains valid.

What's the likelihood of sauropodomorphs having filamentous structures on their skin? Not much, according to Barrett et al. (2015), even in models where dinosaurs are given their best chance of being scaly. But does the absence of skin impressions from non-sauropod sauropodomorphs come into play here?

Secondly, accepting that the evolution of dinosaur integument is complicated, sauropodomorph skin impressions are exclusively scaled. With our current data we can’t say whether this is a derived, reversed condition from a filamentous ancestor or retention of a ‘primitive’ scaled skin type, but whatever: all evidence we have from the sauropodmorph branch of the dinosaur tree seems to show scales. Granted, these specimens all pertain to true sauropods, not their ancestors, but as the closest relatives of Plateosaurus we should probably be using these as guides for our reconstructions. This is supported by the probability study of Barrett et al. (2015), who calculated that sauropodomorphs only have a slim chance (<10%) of non-scaly skin, even when the likelihood of filaments in Ornithodira was maximised.

Me¹. Three points in response here. Firstly, admittedly playing Devil’s Advocate, a <10% chance of sauropodomorphs being filamented is still a chance, right? A filamentous Plateosaurus may not show what is most probable, but it still shows something that science shows is ‘possible’.

Secondly, and more constructively, the fact that skin impressions are not known outside of true sauropods means we may want to question what that the sauropodomorph stats of the Barrett et al. (2015) study really tell us. Does it reflect the condition for all sauropodomorphs, or just Sauropoda? The same probability assessments gives a 50% chance of filaments being ancestral to Saurischia, so the the first sauropodomorphs must have a somewhat higher chance of being filamentous, or at least being closely related to filamented species. Presumably, that 50% chance of filaments doesn’t just plummet the moment we steer evolution to the sauropod line: it’s a long evolutionary road from a basal saurischian to the sorts of sauropods we have with skin impressions, and we have no idea if or when filaments were abandoned on that road. We have a data vacuum of skin at the base of Saurischia: after sauropods, the next closest saurischian with skin impressions to Plateosaurus is the abelisaurid theropod Carnotaurus - hardly a close relative at all. Our absence of skin impressions around the phylogenetic neighbourhood of Plateosaurus, and our data about the likelihood of filaments in saurischians as a whole favours open-mindedness about the life appearance of these animals.

The third point is that if recent claims about dinosaur filament homology are correct, we have to assume that these structures were present in some form in the stock that gave rise to all major clades. Seeing as theropods retained filaments after the theropod/sauropodomorph split at the base of Saurischia, we should probably assume that sauropodomorphs lost their filaments after that divide. If so, a fuzzy Triassic sauropodomorph is not a far stretch.

Me². But - even assuming homology of filaments - if Carnotaurus is scaly, and so are sauropods, we can contrarily hypothesise that saurischians were secondarily-scaly ancestrally. This might even be the most objective reading of the data we have.

Me¹. Perhaps, but is the data supporting that interpretation really reliable? Carnotaurus is actually a weird outlier among theropods, it being the only theropod known with extensively scaly skin impressions. We have to wonder how significant this is against the wider backdrop of extensively filamented coelurosaurs sitting just a little higher up the theropod tree. As the rootward-bracket of the theropod integument bracket it's almost irritatingly important - it has a lot of sway in our reading of dinosaur integument evolution - but we still have to view it as a single outlier against the wider picture of theropod integument. As with any outlier, we have to be cautious about over-interpretation, or thinking one datum can give us the whole picture. As with so many palaeontological issues, we need more information.

The ornithodiran integument evolution 'choose your own brackets' game. When clades without skin samples are featured alongside those with them the amount of missing data becomes apparent, and trying to find obvious patterns becomes tricky. Osteroderms are considered evidence of scales because of their relationships with scaly coverings in modern animals. Compiled from various sources.

And if we need an example of how sensitive our dataset still is, we need only consider Psittacosaurus, Kulindadromeus. Both are deeply nested within Ornithischia but basal to clades dominated by scaly species, and yet both have filaments. No-one would have predicted their integument type from their relatives. Not only does this show that our data may not be reliable enough yet to make confident predictions about integument types, but it suggests skin types might have been quite a bit more varied among even closely related dinosaurs than we anticipated.
Me². The risk here is that we’re pandering to exceptions, unknown data and slim chances. Arguments about the unknown nature of sauropodomorph or early saurischian skin seem like threading loopholes more than effective rebuttals. They play on what we don’t know rather than what we do, and that’s not how science works. There’s lots to be said for keeping an open mind, but we shouldn’t ignore data. Sure, there’s room for doubt here and we may be proved wrong in the future, but palaeoart should probably err on the side of caution, using the best supported, highest probability models to inform reconstructions. ‘Being wrong for the right reasons’ is perhaps the motto we should take when faced with the data gulfs associated with restoring partly known animals.

Me¹. The flip side of this is that ornithodiran integument has been proved complicated and surprising often enough that assuming variation in the poorly known areas is justified. Who expected Kulindadromeus and Psittacosaurus, or Tianyulong? Who, for that matter, would have predicted the first fluffy pterosaur fossils among - at that point - entirely scaly relatives? The point about exploiting unknown data is an important one, but we have a strong precedent for filaments in poorly sampled areas of ornithodiran evolution now. This is less exploiting a loophole than admitting we don’t have a full picture yet, and simply portraying one of the two more likely options of integument form.

Furthermore, Kulindadromeus and Psittacosaurus are great examples of how dangerous our approach to integument reconstruction is when we only have scraps of soft-tissue. It’s only because of their extensive soft-tissue preservation that we know they mixed scales and filaments in different body regions. And it’s not just these dinosaurs that show us that. Pterosaurs have scaly feet to counter their fluffy bodies (Frey et al. 2003), and the extinct mammal Spinolestes is known to have had scales, bristles, and variably long and short fur (Martin et al. 2015). Andrea Cau has even cast doubt on our presumed reasonable knowledge of Carnotaurus skin, pointing out that its skin impressions all pertain to the underside of the animal and that the dorsal surface could be entirely different. We thus have to ask what we really know about sauropod skin: are the bits we have representative of whole animals, or the group as a whole? The most extensive set we have - those from a diplodocid that might be Kaatedocus, described by Czerkas (1992) - show a lot scaling on the body, which meets the predictions we’ve made from smaller pieces of skin found with other sauropods. But it might be naive to think this offers a significant insight into these species, or rules out the chance of localised filaments on some sauropodomorph species.

Me². But where do we draw the line here? There has to be a point where we can say ‘we haven't seen evidence of filaments yet, and we should factor this into our science’ without someone going ‘you don’t know the whole animal yet!’. Some artists take this to an extreme, restoring animals like Edmontosaurus with large filamented regions despite this species being known from several well-studied and extensively-scaled mummified individuals. These have no evidence of filaments whatsoever, despite preserving scales down to millimetre resolution, and yet some folks are still unconvinced, speculating that filaments were poking through gaps between scales and so on. Palaeoart like this Plateosaurus reconstruction almost holds palaeontology to a standard of knowledge that it’s unlikely to ever attain: no, we don’t have skin impressions from every species, we don’t have good skin impressions from many species at all and fossils are never perfect records of animal appearance. But we have to use what we have: science does not work on a philosophy of 'assume whatever until proven otherwise'.

Excellent fossils show that animals like the Cretaceous mammal Spinolestes xenarthrosus had regionalised integument variation, just like modern species. So how much skin do we need from a fossil animal before we can rule out major variation in integument types? Note that the tail fluff in this picture is speculative - the integument preservation of Spinolestes doesn't extend to the tail region.

Me¹. Of course, if we restore animals however we like in our artwork then we’re not doing real palaeoart, just palaeo-based artwork. Palaeoartists must constantly ask where the boundary between informed, sensible extrapolation of data ends and where unbridled speculation begins. So I suppose the question here is ‘does this reconstruction go too far?’ Is a filamented Plateosaurus just nutball craziness, or a reasonable idea based on what we currently know? The fact this discussion has got this far suggests that there must be some validity to this idea, even if some might think it's ultimately a flawed one. But 'flawed' is not the same as 'nonsense'. Depictions of filamentous or scaly sauropodomorphs simply reflect emphasis on different datasets. A scaly interpretation prioritises skin impressions from close relatives, but downplays emerging 'bigger picture' interpretations of ornithodiran integument, and a filamentous one does the opposite. From a 'big picture' perspective we're entering a time when reconstructing any dinosaur with filaments should not be considered ridiculous or outlandish, save for those with well sampled scaly skin tissues. It's not necessarily the best approach, but it's not an invalid one.

Me². It must be said that it would be easy to construct this conversation around a scaled version of this animal, and discuss why it doesn’t have filaments. Our base expectation for dinosaur integument and life appearance is in a state of flux, no matter what we personally prefer or assume.

Me¹. I think a point often lost on viewers of palaeoart is that these artworks are not, and cannot, be definitive, incontrovertible renditions of these animals. There are some animals so well represented in fossils that they lend themselves well to ultra-detailed reconstructions which are hard to quibble over to significant degrees - the awesome Bob Nicholls Psittacosaurus model being a great example (Vinther et al. 2016) - but for lesser known animals like Plateosaurus we are only painting hypotheses, not fact-based reality. This painting is one possible reconstruction of Plateosaurus as known in 2016, a time when interpretations of dinosaur skin evolution remain in flux. Time will tell if it's the product of over-interpretation of fossil data, or a lucky gambit later borne out with fossil evidence. I don’t mind getting stuff like this wrong: I’m more interested in painting and exploring credible possibilities of what we know now, not being ‘right’. We may never know what is ‘right’, so there’s not much point worrying about it. There are a couple of essays on this topic in my new book,Recreating an Age of Reptiles (Witton 2016).

Me². You’ve seen RecARep? I hear it’s awesome and that everyone should buy a copy.

Me¹. Wow, that’s desperate. Any actual final points?

Me². In a previous post on the role of pterosaurs in interpreting dinosaur filaments I concluded that: “Forcibly arguing for either scales or filaments at the base of Dinosauria seems premature at this stage, and, whatever our personal hunches are, it seems sensible to accept some ambiguity in this situation for now.” I think that’s true here too. There are certainly arguments to be had on both sides, some stronger than others, but neither side has knock-out data or evidence on the table yet. It’s the same old frustrating cop-out, but we need more fossils, and fossils of the right sort, to resolve this. Specifically, we need early saurischians or dinosauromorphs with good skin preservation, as well as that Triassic sauropodomorph with excellent skin remains. It must be said that these animals are not generally found in fossil Lagerstätten conducive to good soft-tissue preservation, so I’m not advising anyone to hold their breath for this one. But new techniques for detecting soft-tissues and increasing awareness of soft-tissue preservation in lithologies once thought to only preserve bone are reasons to be optimistic that we'll have insight on these matters one day.

Me¹. And ‘frustrating’ is the right word here, too. It seems like dinosaur science has made sufficient headway on understanding integument evolution and predictive methodologies that a reasonable, if provisional answer to the ancestral integument of the three major clades is close. But the puzzle piece needed to get our first good look at the broad picture is still out of reach.

Awkward facial expression, bad fashion sense and a hygiene problem. No wonder no-one likes to paint early sauropodomorphs.

Me². OK, that seems like a point to end. This discussion with yourself didn't seem to go too bad, actually. Unlike that vulture-like ruff around the base of the neck in the Plateosaurus reconstruction. I mean, if you're going to paint a controversial reconstruction, at least make the animal look good.

Me¹. Pfft... Good… bad… I’m the guy with the graphics tablet.

Me². Movie quotes in scientific blog post don’t make you look clever, you know. You just cheapen the whole act.

Me¹. There is no fate but what we make for ourselves.

Me². What...? that doesn’t even fit our context.

Me¹. It wasn’t the airplanes. It was beauty killed the beast.

Me². Sigh, why do I hang around with you? I think we're done here.

So long everyone - I'm away from my computer for the next few weeks so I'm going to be pretty quiet in blog comments, social media and so on. Things will pick up again come December when we'll be addressing the sauropods in the palaeo-outreach room: has the popularity of dinosaurs above other fossil animals become a problem?

This blog post was inarguably supported by Patreon

The paintings and words featured here are sponsored by an excellent group of animals with regional variation in integument, Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. Later this month (much later - around the 28th/29th) I'll be uploading a video version of the presentation I gave over the Halloween weekend at Dinosaur Days 2016, entitled Palaeoart and the Never-Ending Quest for Accuracy. Here's the title slide to whet your appetite:

"Oh, I see you're putting movie easter eggs in this post now too. This is why no professional blogging platform will pick you up."

Whether it's a giant armoured thyreophoran like Panoplosaurus mirus (thanks to the Empress of Ankylosauria, Victoria Arbour, for advice on this restoration) or a svelte theropod like Chirostenotes pergracilis, everyone likes dinosaurs and we - palaeontologists - like using them in our outreach. But are dinosaurs really universally popular and appropriate for the wide range of outreach we use them in?

The success of dinosaurs in outreach

Exactly why dinosaurs occupy such an important and influential space in popular culture remains largely mysterious. On paper, dinosaurs are a group of extinct reptiles which are not - superficially at least - so different from other long-dead sauropsids, and yet they have somehow gained global fame and many dedicated followers. My suspicion is that dinosaurs uniquely combine obviously amazing, ‘high impact’ anatomy - large size, fantastic skeletal structures such as horns, huge teeth and so on - with bauplans that are easily understood by the general public, without being so familiar that they’re pedestrian. For instance, everyone can appreciate Allosaurus as an active, large bodied predator even if just looking at its skeleton in a museum, but - as bird-like as it is in detail - the overall form is somewhat alien and intriguing. Other fossil groups, such as ancient carnivorans or whales, are impressive enough but perhaps also too familiar to inspire our imaginations in the same way. At the other end of the spectrum are extinct creatures which are just too unusual for widespread appreciation. Perhaps their anatomy is too strange or their life histories are too obscure and difficult to relate to familiar biology. This applies to many extinct invertebrates, as well as several types of weirder vertebrates. Dinosaur biology is thus near perfect for outreach material: they’re visually impressive, anatomically and biologically accessible, but different enough to warrant interest. Whether this is the actual basis for dinosaurian appeal or not, museum staff, educators and merchandisers have realised for over 150 years that dinosaurs are an excellent way to interest the public and make money, and given them prominent roles in outreach. Aiding any intuitive draw we have to dinosaurs is a lot of social inertia, and part of the enduring appeal of dinosaurs is a long history of ingraining them into popular culture.

The success of dinosaurs in the public eye almost certainly reflects many varied influences, but their unique anatomical qualities may play an important role. Does any other fossil group combine interesting, ‘high impact’ biology, in a format that the public can easily grasp, in the way that dinosaurs do?

For those of us interested in science education, dinosaurs are one of the most important and potent tools at our disposal. We see them as not only fascinating subjects in their own right but as a way to introduce ‘bigger picture’, perhaps fundamentally more important, scientific concepts to lay audiences. Dinosaurs are gateways to discussions of evolution, adaptation, anatomy, biological diversity, extinction, geological time and the changing nature of the planet. They provide, as charismatic and fantastic creatures, perfect characters to maintain interest in discussions of these sometimes complex concepts, and well-known Mesozoic dramas - the breakup of Pangea, formation of the Deccan Trapps, the Chicxulub Impact - offer rich backgrounds to stage our conversations. Dinosaurs are more than just awesome animals: they’re public ambassadors for science, facts and intelligent thinking.

We cannot ignore the economic value of dinosaurs, too - and not just to Hollywood movie makers and toy manufacturers. Dinosaurs provide academia and its satellite industries with vital income because of their easy marketability and merchandising potential. Public interest in dinosaur news, books and artwork keeps authors and palaeoartists in work, while the pull of dinosaur exhibitions in natural history museums not only keeps turnstiles spinning but brings essential revenue - in the form of gift shop purchases, entry fees and cafe visits - to these underfunded venues. I don’t know that anyone has ever attempted to work out the net worth of dinosaurs to education, but, globally, their appeal must bring millions of pounds into venues that perform outreach every year.

Too much of a good thing?

So hurrah for dinosaurs, then, and their role as not only fascinating subjects for research and art, but as bankable, relatable and demanded elements of modern culture. But the popularity of dinosaurs does have an impact on other aspects of palaeontological PR, and in some conversations at our workshop ‘dinosaur’ almost became a bit of dirty word. No-one will deny the positive aspects of dinosaur popularity, but their dominance in popularised palaeontology influences outreach strategies, merchandising and public expectation, and not always in a positive way.

Some of the problems caused by dinosaurs were outlined in detail during talks at our workshop. We heard that a large portion of natural history museum visitors are exclusively concerned with seeing dinosaur exhibits, challenging natural history museums to use the rest of their collections in a meaningful, impactful manner. This is despite many museum goers being unable to distinguish dinosaur remains from those of other animals without the aid of helpful signage. It seems that, for some museum visitors, dinosaurs act like a brand label, or justification for interest, rather than an excuse to visit a museum for a rounded educational experience.

We also heard that bringing attention to non-dinosaur groups can be extremely difficult, and the less dinosaur-like they are, the harder it is. Groups like pre-Cenozoic synapsids, extinct invertebrates, fossil fish and so on struggle for attention and require highly creative outreach tactics to receive any interest. One of the commonest strategies - used frequently for semi-technical books on fossil animals (below) - is to make sure dinosaurs remain prominently mentioned even in those events or products which are focused on completely unrelated groups of animals. We just don’t trust most non-dinosaur clades to draw crowds or revenue on their own and have to spin them as being relevant to dinosaurs in some way. Tellingly, the only groups to escape frequent dinosaur namechecking are those which are already somewhat ‘dinosaur-like’. Giant fossil mammals, pterosaurs and Mesozoic marine reptiles share aspects of size and gross appearance with Mesozoic dinosaurs and might be seen as ‘honorary dinosaurs’ by the public, and perhaps mistakenly interpreted as the genuine article by many. Both dinosaur-targeted museum visits and our resistance to promote palaeontological topics without a dinosaurian safety net questions whether dinosaurs are a genuine ‘gateway’ to wider scientific education, and perhaps suggests a rather narrower interest in prehistoric life among the public.

Just some of the non-dinosaurian textbooks coming your way in 2017. Probably.

Our group also raised the association between dinosaur outreach and very young demographics, and the challenge this presented to educators. The problem isn’t that many children are naturally interested in dinosaurs - if anything, this is something to celebrate and encourage - but the impact this association has on older audiences. Many adults assume that anything to do with dinosaurs, and by extension any prehistoric animal, is automatically related to children, and often very young children. This becomes an issue for to those attempting to perform outreach or market palaeontologically-informed products to older audiences, and particularly outside of online venues. Experience shows that ‘real world’ dinosaur events - regardless of venue, event type or advertising theme - will be primarily stocked by children and parents expecting child-friendly media. I’ve experienced this many times in my outreach career, such as bowing to pressure for colouring-in stations at a palaeoart gallery, being asked whether a public lecture (entitled Palaeoart: the Never Ending Quest for Accuracy) was suitable for toddlers, and being invited to run art stalls and events for older audiences at dinosaur-themed events to find few interested people over 10 years of age.

The general expectation that dinosaur-related events or products skew towards children presents a complex set of challenges. Firstly, it can lead to older audiences deciding a priori that they cannot take anything away from dinosaur outreach because the event - whatever it is - is ‘just for kids’. I’m sure many of us have seen how ‘switched off’ parents of young dinosaur fanatics are when visiting outreach events, even though the people their children are speaking to may be expert scientists, experienced fossil hunters or world-renowned palaeoartists. Secondly, mismatched expectations of outreach events can be frustrating for both outreachers and audiences: attendees may wonder why a dinosaur event is pitched above the level of their children, while outreachers may feel over-prepared or over-invested in their activity programme when confronted with only young audiences. Perhaps the most concerning issue is that many outreachers and merchandisers use young demographics as an excuse for low scientific standards and sensationalism, promoting outdated, erroneous and sometimes idiosyncratic views of palaeontology because their audience is too young and insufficiently educated to know otherwise, or ignoring scientific data where it might curb child appeal. I am sure most readers can think of numerous examples of products - many labelled as ‘educational’ - which show evidence of this, and it’s easy to see how this attitude may play a major role in perpetuating outdated and erroneous ideas about the past.

One of our final discussion touched on perhaps another issue faced by dinosaur outreach: the schism between public and palaeontological appreciation of what dinosaurs are. For palaeontologists, dinosaurs are a constantly - and sometimes rapidly - evolving set of hypotheses and ideas, and this is what we generally try to present to the world in our outreach. But certain dinosaur concepts outgrew palaeontologist-steered media long ago and now occupy their own place in popular culture, one almost entirely divorced from developments of dinosaur science and instead orbiting their portrayals in film, TV and popular literature. Most of these products - even those produced in the last few years - stick to now long-outdated 20th century interpretations of dinosaur biology and, divorced from guiding hands of scientists, solely emphasise marketable aspects such as their size, perceived ferociousness, and unusual anatomy. The result is a public largely familiar with dinosaurs in a scientifically-distanced, simplified and monstrous form rather than the animals reconstructed through biological and geological sciences, and with little appreciation for their evolutionary context, the scientific techniques used to understand them, or their relationship to wider, ‘core themes’ of scientific outreach. Recent studies partly vindicate this view in showing that the public are generally unaware of even the most basic aspects of dinosaur science, such as the near 50-year old revision from the classic ‘tail-dragging’ posture to an elevated tail and horizontal body attitude (Ross et al. 2013). This is despite museums, artwork, documentaries and some of the most successful blockbuster movies of all time showing the latter since at least the 1990s. This being the case (and with an added caveat that the study in question was relatively small), perhaps our issue with dinosaur education is more severe than we thought: are people really engaging with dinosaur media at all, or are our subjects of research, artwork, and hallowed gateways to other sciences little more than time-fillers and distractions?

Despite the best efforts of many scientists, the public at large seem to associate dinosaurs with considerably outdated interpretations and monstrous creatures. Reviewing recent successful entries into one of the most widely-accessed sources of popular dinosaur culture - Hollywood movies - is this surprising? Perhaps the most visually progressive rendering in this set are the sparsely feathered dromaeosaurs from Pixar’s The Good Dinosaur (bottom right). However, the state of their integument still recalls dinosaur palaeoart from the mid-1990s, and not the extensive feather body covering shown by fossil evidence and now commonly restored over certain dinosaur species. Image sources, from top row down; King Kong (2005); Godzilla (2014); Transformers: Age of Extinction (2014); Toy Story (1996 - onwards); Jurassic World (2015); The Good Dinosaur (2015).

So, are dinosaurs as useful as we think for outreach purposes?

The points raise a simple but significant question: how effective is dinosaur-based outreach, really? As noted above, many decisions about outreach are shaped around dinosaur science and resources are poured into promoting dinosaur science itself. But are we right to regard dinosaur outreach as highly as we do?

Trying to balance the positive and negative points raised above, my take is yes, dinosaurs are an effective means to bringing science to people… but probably only certain people. Specifically, they seem to work very well among those who are already tuned into palaeontology, natural history and general science, an audience composed mostly of adult enthusiasts and children. Beyond this, their effect seems to tail off quickly and they may actually be a barrier to effective outreach. Audiences with preconceived expectations of dinosaur-themed content may ignore anything dinosaur related, which is a concern with us giving dinosaurs such privileged consideration in educational material. Are we limiting our promotion of other topics that could engage these uninterested people? And is one of our challenges of popularising palaeontology making dinosaurs and related topics universally attractive, and not just subjects with appeal to specialist audiences or younger people?

Of course, your opinion on this matter may differ. But even so, I think most of us would agree that our wider education about dinosaurs and related matters could be more effective, or at least more nuanced and reflective of more topics, than it currently is. I am optimistic that a groundswell of suitable movements towards this goal may already be underway. Many modern curators, scientists and artists are attuned to matters of science communication and interested in identifying outreach issues, sharing best practise, evolving public engagement methods and reaching new audiences with new topics. The fact that this article is being written as output from a workshop dedicated to popularised palaeontology is evidence of these practises actually occurring, and it feels like the right questions are being discussed. How can we, and when should we, shift focus from dinosaurs? How do we make other forms of life/parts of museum collections of wider interest? How do we more effectively impart new science to publishers, movie makers and other non-educational bodies making palaeontologically-themed media? It’s also pleasing to see more discussions about the once largely backgrounded industry practises of palaeoartistry in both scientific and popular media. Realising the important role that palaeoart has for communicating science, many involved in its production are vocally distancing themselves from the ‘popularised’ image of dinosaurs to more nuanced, scientifically-validated and interesting portrayals of dinosaurs, as well as other forms of prehistoric life. We are still on the uphill part of this journey to revising our outreach approach, but it’s reassuring to know that a body of professionals are looking critically at dinosaur outreach and its wider impact.

Minor victories in recent palaeontological outreach involve effectively communicating to certain, interested audiences that Deep Time was not a dinosaur theme park, and that fossil creatures did not spend all their time battling and roaring at one another. Evidence that this message has hit home with at least some audiences is reflected in the broadening depth and nuance of palaeoart being posted across the internet. Shown here: my take on Jurassic stem-mammals, a gorgonopsian, gliding drepanosaurs, a goniopholidid crocodyliform, Cretaceous albanerpetontid, erythrosuchids, and... Longisquama, whatever the heck that is. Not shown here: dinosaurs in premier view, or roaring. The challenge is getting scenes like this, and subjects like this, to wider audiences.

Most of the discussions and innovation in dinosaur/palaeontolgical outreach are taking place online, and transferring these to ‘real-world’ outreach, where the necessity of resource investment makes change risky, may be our greatest upcoming challenge. Again, however, there are signs of this sort of thing happening, such as the famous (or infamous?) decision to replace the Natural History Museum’s famous Diplodocus cast with a blue whale skeleton. This logic of moving this famous attraction has been questioned by some, but I admire the museum for putting a very relevant and symbolically significant specimen in their most prominent location. In doing so, they’re making a clear statement about what they consider to be important, and what they want the public to engage with. Whether you agree with the controversial reorganisation of the natural history museum or not, the idea of outreachers taking initiative with their educational agenda is something I feel we should echo when popularising prehistoric animals. If our outreach is primarily reaching pre-interested audiences anyway, then why not have faith in their interest and tell them what we - as researchers, artists and curators - think is fascinating and exciting about our field, whether it’s related to dinosaurs or not? It would seem a diverse array of outreach topics is more likely to spread out from palaeo-primed audiences and into broader public interest than one largely revolving around a single, perhaps somewhat over-familiar topic. Perhaps cutting palaeontological outreach’s umbilical chord with dinosaurs would benefit us outreachers too, allowing us to freshen and rethink our approach to popularising neglected groups and focus on their own selling points, instead of using them to greater contextualise dinosaurs.

The risk of failure is what prevents many of us, and our employers, from straying too far from tried and tested means of outreach. And yes, if we’re talking paleontology with the public, dinosaurs are an obvious safety net. But we should take advantage of the fact that we’re more enabled than any previous generation of educators to cooperate, create and promote the subjects we feel are important with only a little inventive thinking and technological knowhow. Individuals can now develop significant outreach resources without the need for expensive designers and developers; online promotion can be essentially free; and the increasing accessibility of printing - both 2D and 3D materials - is lowering the financial risks tied into ‘real world’ outreach events. Any public enterprise involves a level of investment and risk, but resourceful thinking and shouldering the brunt of development ourselves can minimise these.

In closing, I want to stress that I’m not wailing on dinosaurs. As may be evident from my own output, I think they’re fantastically interesting animals with an important role to play in outreach. But for dinosaur outreach to be successful and support, not restrict, other outreach efforts we have to realise their limitations, as well as their strengths, as public ambassadors.

This piece of outreach was supported by Patreon

The paintings and words featured here are sponsored by folks who are certainly very popular in my house, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, and in return you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post we'll be looking at my new angry nodosaur painting, discussing ankylosaurs in palaeoart and why they're so darned challenging to render well. Sign up to Patreon to be part of the discussion!

Reference

• Ross, R., Duggan-Haas, D. and Allmon, W. (2013). The posture of Tyrannosaurus rex: Why do student views lag behind the science? Journal of Geoscience Education, 61, 145-160

In an ideal world, all blog posts would start with images like this one. (Edited talk title slide I used back at SVPCA 2013 - we've been working on the project discussed below for a while now.)

In the last year we've spoken at great length about the giant azhdarchid pterosaurs, those toothless, tube-necked, 10 m wingspan behemoths that awesomed their way into existence at the end of the Cretaceous Period (if you need more of an introduction, check out these posts). Of the three named giant species, we've discussed what is really known of Quetzalcoatlus northropi and outlined why their least famous representative - Arambourgiania philadelphiae - is worthy of greater attention. But we've yet to tackle the most recently named and, in some respects, intriguing giant of them all: the heavily built, giant-headed Romanian behemoth Hatzegopteryx thambema.

A quick primer for those of you who aren't familiar with Hatzegopteryx. The first fossils of this Romanian, Maastrichtian pterosaur were announced in 1991 but, on account of their considerable size and robustness, they were interpreted as belonging to a large theropod, not a pterosaur. Eric Buffetaut and colleagues reassessed these bones some years later and made their azhdarchid pterosaur identity apparent (Buffetaut et al. 2002, 2003). As with all giant azhdarchids, only scraps of Hatzegopteryx are known. Bits of skull and a broken humerus from the Densuș Ciula Formation form the holotype, and a large femoral shaft from the same formation may belong to this animal as well. All these elements are remarkable for their size - wingspan estimates of 10-12 m seem sensible (Buffetaut et al. 2003; Witton and Habib 2010) - as well as an unusual degree of internal reinforcement. In addition to thick bone walls (4-6 mm, which doesn't seem much, but is impressive for a pterodactyloid pterosaur), both Haztegopteryx humeral and jaw elements possess large amounts of coarse spongiose bone. This reinforcement may be related to the evolution of some very substantial anatomy. Buffetaut et al. (2003) were able to make a compelling case for a 50 cm wide jaw for this animal, and even conservative extrapolation of that figure suggests Hatzegopteryx was among the longest-jawed non-marine tetrapods to have ever lived (Witton 2013). Such an unusual pterosaur seems fitting for its provenance, the Densuș Ciula Formation representing part of the ancient and peculiar 'Hateg Island' ecosystem. This setting will be familiar to many as an ancient, large Cretaceous island well-separated from the rest of Europe by deep seas, and populated by archaic, sometimes dwarfed or otherwise peculiar dinosaur lineages (e.g. Benton et al. 2010).

Since Hatzegopteryx was named in 2002 several Romanian sites of equal age and palaeoenvironmental setting have provided new fossils of giant pterosaurs. Some of them have a real Hatzegopteryx flavour (Vremir 2010; Vremir et al. 2013) and, although a complete specimen remains far from realised, a crude picture of this giant pterosaur is slowly being put together. These specimens are being worked on by different teams and, hopefully soon, we'll have a lot of new Haztegopteryx (or at least large azhdarchid) material to play with.

But that's not to say there's nothing new about Hatzegopteryx to discuss here. In fact, today Darren Naish and I published a new, open-access peer-reviewed form-function assessment of a Hatzegopteryx vertebra which takes us a step closer to understanding this enigmatic animal (Naish and Witton 2017). Long-term readers of this blog or Tetrapod Zoology will know that Darren and I team up semi-regularly to write about azhdarchid palaeobiology and may have played a role in shaping modern interpretations of these pterosaurs (Witton and Naish 2008, 2013). Our work this time focuses on a remarkable pterosaur bone known as EME 315, a giant azhdarchid cervical briefly described by Vremir (2010) and likely representing the first described axial element of Hatzegopteryx*. Our ideas about the proportions, structural properties and surrounding musculature of this bone are quite different to what has previously been said about Hatzegopteryx and other azhdarchids and, if we were sensible people, we would have kept quiet until today. However, our enthusiasm for the project and as well as a long, complex writing process has made for a particularly leaky embargo (artwork of our new interpretation of Hatzegopteryx made it into my art book, Recreating an Age of Reptiles, of instance) and many readers may be aware of our punchline: Hatzegopteryx may have a been a particularly powerful and 'short necked' azhdarchid, and maybe even a dominant predator of the topsy-turvy island ecosystem of ancient Hațeg. With the cat already somewhat out of the bag, let's take a look at our substantiation for what is a bold, counter-intuitive claim: could a pterosaur, even a giant azhdarchid, have been a formidable arch predator?

*EME 315 is from the Sebeș Formation, and thus not from the same formation as the H. thambema type, and does not overlap with our existing thambema inventory. However, it has the same characteristically thick bone walls, spongiose internal texture and stupendous size that we can recognise in the Hatzegopteryx type specimen. This, and its extremely close geographic and chronostratigraphic (Maastrichtian) occurrence, make referral to Hatzegopteryx reasonable, although we hedge our bets a little in not referring it to H. thambema itself. We settled on H. sp.

Mighty EME 315 as presented in our paper. The scale bar represents 100 mm - for a pterosaur vertebra, this is a massive bone. Note the graph at the base of the image - for its size, EME 315 is a clear outlier to other azhdarchid cervical specimens. That's the Arambourgiania type cervical V for contrast. From Naish and Witton (2017).

Estimating the neck length of Hatzegopteryx

sp. has a neck of equal size - 1.49 m long (below). By contrast, the giant holotype cervical of Arambourgiania, which probably also represents a gigantic animal of 10 m(ish) wingspan, gives a reconstructed cervical III-VII length of 2.65 m. So EME 315 has a neck no longer than that of a pterosaur with perhaps half its wingspan, and much shorter than that of at least one other giant species. We thus suggest that, for its size, Hatzegopteryx had an abbreviated neck skeleton. Of course, this is not the first time the potential of short-necks in azhdarchids has been raised - it's not even the first time Darren and I have discussed it in a peer-reviewed paper (Vremir et al. 2015). But Naish and Witton (2017) is the first time this hypothesis has been outlined in detail and substantiated with a dataset of neck bone measurements, so it feels that we've elevated the idea to something that can be discussed and challenged more legitimately.

Neck lengths in large and giant azhdarchids. A and B show Hatzegopteryx in lateral and dorsal aspect (B shows EME 315 and the holotype jaw bones only, but gives you an idea how chunky its neck was); C, shows Arambourgiania (known bones in white) with a reconstructed neck (grey elements); D and E, Quetzalcoatlus sp., lateral skeletal and dorsal view of skull and neck. From Naish and Witton (2017).

A short-necked azhdarchid may not seem like a big deal, but they're potentially important for at least two reasons. The first is that azhdarchids are in part classified by their super-elongate neck bones, but our data indicates that this may not be a universal trait. We used our neck bone dataset to predict that the longest bone in the EME 315 neck - cervical V - would have only just exceed 400 mm, which makes its length less than twice the width of EME 315. By contrast, a typical azhdarchid cervical V is 5-8 times longer than wide. We need to find a complete Hatzegopteryx neck without hypertrophied mid-series cervicals to confirm our calculations, and have little idea how common this 'short necked' variant might be within Azhdarchidae as a whole (we helped describe another proportionally short Romanian azhdarchid vertebra, R.2395, which could be a second 'short necked' species a few years back - Vremir et al. 2015), but - if verified - a 'short necked' morph could complicate how we characterise Azhdarchidae.

Secondly, and perhaps of more general interest, this calculation adds to increasing evidence that azhdarchids may have differed rather dramatically in overall proportions. A number of workers have criticised the concept of azhdarchid anatomical uniformity in recent years (Vremir et al. 2012, 2013, 2015; Witton 2013), and our new paper adds further force to that argument: data for skulls, wing morphologies and now necks hint at a range of bauplans within the group. Their categorisation may not be as simple as 'robust' and 'gracile' forms as I've previously suggested (Witton 2013), but it's increasingly difficult to view Azhdarchidae as a parade of Quetzalcoatlus clones. This is of interest to not only researchers - differing forms might indicate differing behaviours and ecologies - but is something for artists to take note of too.

Arambourgiania vs. Hatzegopteryx: Neck Wars

Just how does our new 'short-necked'Hatzegopteryx compare to a regular, long-necked giant form? Something like this. That's our Industry Standard 5.8 m tall male Masai giraffe on the left, the Disacknowledgement centre left, Arambourigania centre right, and Captain SuperChunk on the right. As restored here, Hatzegopteryx is nowhere near as tall as Arambourgiania, but the bulk of its skull and neck likely made it a more formidable animal.

Being interested in azhdarchid ecology, we wondered how the different proportions and internal anatomy of giant azhdarchid cervicals might influence their ability to withstand neck stresses caused by foraging, supporting their heads and so on. We performed a range of bending strength assessments on both the robust and thick-walled EME 315 and the elongate, slender-walled tube that is the giant holotype Arambourgiania cervical V. There are too many variants of the experiments to report all the results here (again, see the paper for details), but the TL;DR version is that the performance difference was consistently huge. OK, no-one was expecting the long, gracile Arambourgiania vertebra to outperform EME 315 in a bone strength competition, but the difference between the two is significant enough to indicate very different neck functions. Even comparing Arambourgiania's best bending performance against EME 315's worst, the latter is ten times stronger. We extrapolated our data to assess bending strength in the longest (and therefore weakest) neck bone in the Hatzegopteryx skeleton (a hypothetical cervical V) and it still outperformed its counterpart in Arambourgiania by several biomechanical miles. A larger cross-section, shorter vertebral body and thicker bone walls all contribute to EME 315's stellar bending performance, and we identify several additional aspects of reinforcement and strengthening of EME 315 in our paper.

It's therefore clear that the neck structure of Hatzegopteryx was in a different biomechanical league to that of Arambourgiania, and this implies vastly different neck functions in these species. We expect that one factor in this distinction is the wide, presumably heavy head ascribed to Hatzegopteryx, and infer that the weaker neck bones of Arambourgiania would require a narrower, gracile variant of the azhdarchid skull (maybe something a bit Q. sp-like). But the strength of the Hatzegopteryx neck seems high even accounting for its likely skull size, and we postulate that additional loads - big prey items, violent uses of the head and beak during foraging - may have contributed to its boosted structural properties.

Supporting this hypothesis are features indicative of large soft-tissue volumes around the neck of Haztegopteryx. Classically, the reduced features of azhdarchid neck vertebrae have seen them regarded - and depicted - with minimised cervical musculature and ligaments. We regard this view as problematic for a number of reasons. The first is that complete azhdarchid necks show that only the mid-series vertebrae lack complex anatomy indicative of muscle and ligament attachment. The complexity of their neck skeleton as a whole is not far off that of a 'normal' tetrapod, where the anterior and posterior vertebrae are relatively complicated to allow for greater volumes and intricacies of soft-tissues in these regions. Yes, azhdarchids do reduce their vertebral complexity further than most species, but not so far that we should assume their in vivo necks were little more than bony tubes covered in skin.

Reconstructed cervical series and associated azhdarchid specimens show that their necks were not just made of bony tubes, but variably complicated bones in a pattern structurally typical of other long-necked tetrapods. What might this mean for soft-tissue development? One obvious implication is that at least the anterior and posterior neck regions were likely fleshier than often considered. From Naish and Witton (2017).

Furthermore, assuming azhdarchid neck muscles and ligaments were basically homologous to those of living reptiles, some attachment sites must be regarded as expanded, not shrunken. These include particularly deep shoulder blades (for anchoring neck elevators and lateral flexors) and deep basins at the back of the cranium (for anchoring neck-skull extensors). While famously lacking vertebral processes on their mid-series cervicals, a suite of scars along the dorsal surfaces of azhdarchid cervicals betray long muscle or ligament attachments, while the vertebrae at the extremes of the neck have well-developed neural spines. Most startlingly, the expansion of their zygagpophyses take on new significance when we realise that these structures anchor numerous neck muscles in living sauropsids. So yes, azhdarchids certainly lost and reduced some areas of neck muscle attachment, but others were enhanced. The peculiar cervical anatomy of azhdarchids likely reflects an economising, rather than all-round loss, of neck soft-tissues.

Bringing this discussion of soft-tissue back to the giants, we have to look at Arambourgiania and Hatzegopteryx as once again reflecting very different types of animals. Our Arambourgiania cervical has much smaller areas for soft-tissue attachment compared to EME 315, which has immense, complicated anatomy in all the areas we associate with cervical soft-tissues in living sauropsids. This may partly be explained by EME 315 and the holotype Arambourgiania cervical being from different parts of the neck, but complete azhdarchid necks suggest these bones provide some general sense of neighbouring cervical skeleton anatomy - it would be weird if the Arambourgiania cervical V was juxtaposed with a massive, EME 315-type bone, for instance. We take this to indicate that EME 315 was not only a strong bone in a robust neck, but that the cervical skeleton of this animal was perhaps wrapped in large, powerful muscles and ligaments - exactly the sort of soft-tissues that can deliver those demands hinted at by our bending strength tests, and would be needed to wield that enormous head.

Ecological diversity of giant azhdarchids

These results get most interesting when we plug them into the bigger picture of giant azhdarchid anatomy and lifestyles, because there seem to be a couple of different stories being hinted at here. For example, we can take the long neck, relatively low cervical bending strength and lessened areas of muscle attachment in Arambourgiania as placing restrictions on prey size as well as precluding violent, dynamic foraging strategies and other behaviours that would impart high stresses on its neck anatomy. Assuming the 'terrestrial stalker' model for azhdarchid lifestyles (Witton and Naish 2008, 2015) applies to the giants, we might imagine Arambourgiania as preferring smaller prey and relatively lightweight foodstuffs: smallish animals, the eggs of larger reptiles and birds, and generally anything that wouldn't put up too much of a fight. These would still be formidable animals - remember that they stand 4-5 m tall - but all indications are that they represent the 'lightweight' end of the azhdarchid palaeoecology spectrum, and likely behaved accordingly.

Giant azhdarchid pterosaurs, diet edition. What we know of Arambourgiania implies they preferred smaller prey, such as diminutive dinosaurs, which may have been caught using relatively undemanding means.From Naish and Witton (2017).

The emerging picture is rather different for Hatzegopteryx. Here, we can plug our results of a relatively short, strong neck and high fractions of cervical musculature into its overall robust construction, reinforced bones, massive and wide jaws, and stupendous size. Collectively, this paints an image of a far more solidly built and powerful animal than Arambourgiania. If - as most of us now seem to think - azhdarchids were 'terrestrial stalkers', we can imagine Hatzegopteryx as as a giant azhdarchid turned up to 11: a prairie-roaming giant with elevated maximum prey size and capacity for violent and forceful foraging tactics. Given how dangerous we know modern azhdarchid-like birds can be, and armed with a powerful neck and giant, reinforced skull, we might even imagine Hatzegopteryx using powerful bites, bludgeoning blows of its head and stabbing motions to tackle prey too large to swallow whole. If we're right, Hatzegopteryx was both a truly awesome, but also entirely terrifying animal. There is not exact modern analogue for this sort of creature, but if you imagine a giant mix of a shoebill stork, a ground hornbill, and the Terminator you might be pretty close.

The Hatzapocalypse: a group of foraging Hatzegopteryx find a chunky, subadult rhabdodontid Zalmoxes. Rather than pursuing baby sauropods or raiding nests, our interpretation of Hatzegopteryx implies it was a dangerous predator of mid-sized or larger animals. Whether it used the catchphrase "Hatze la vista, baby" after each successful hunt remains a matter of debate among scientists. From Naish and Witton (2017).

It is significant to this hypothesis that no large theropods are known from the same sediments as Hatzegopteryx. We can never say never with negative evidence, but the Maastrichtian sediments of Romania have been sampled for centuries and not a single large predatory dinosaur bone has been found - not even a single tooth. These are the only sediments in the world where you stand a better chance of finding a giant pterosaur than a large theropod, and it's hard not to look at that as intriguing. Hatzegopteryx is the only carnivorous animal we know of from this time and place which was large enough, and robust enough, to tackle good-sized prey, and we postulate that it may have taken the 'arch predator' niche occupied by theropods elsewhere in the world.

Further work on new Romanian pterosaur fossils, as well as new discoveries, will show if this view is correct or not. Moreover, they'll help answer the many, many questions that remain concerning giant azhdarchid anatomy, evolution and palaeobiology. For me, among the most significant of these questions is what Hatzegopteryx signifies in the context of Late Cretaceous pterosaur disparity, ecological diversity and their eventual extinction. The latter is something we discuss briefly in our paper, as we've classically interpreted Maastrichtian pterosaurs as a biologically conservative group living on borrowed time. But our new work on Hatzegopteryx, as well as the potential recovery of a small-bodied pterosaur from Campanian sediments of Canada (Martin-Silverstone et al. 2016), and ongoing work on non-azhdarchid pterosaurs found near to the K/Pg boundary from Morocco (these being presented at SVPCA 2016 by Nick Longrich and colleagues) complicates that picture. It's looking more and more likely that our perception of the last pterosaurs as a low diversity, dying group has been distorted by sampling biases, and they may have actually been doing just fine until the end of the Mesozoic. Perhaps pterosaur extinction was a more significant event than previously realised.

But these questions will have to wait. For now, it's satisfying to finally be talking about these new data on what was clearly one of the coolest animals in the pterosaur canon. I'll leave you with a thought echoed from our paper: whether the ideas discussed here are right or wrong, the fact we can discuss 'the Hatzegopteryx arch predator hypothesis' without laughing is a real sign that interpretations of azhdarchids - and pterosaurs generally - have moved on considerably. Could our colleagues of 50-60 years ago have imagined pterosaurs - considered lame, underweight, creaky-winged gliding things - would be discussed in this sort of context? I imagine not.

(We're not done with pterosaurs, or new papers, at the blog just yet: stay tuned for more pterosaur news in the very near future.)

This paper, blog post and paintings are made possible by Patreon

The content featured here is sponsored by another group of short-necked tetrapods, my Patreon backers. Supporting my blog from $1 a month helps me produce researched and detailed articles with paintings to accompany them, as well as peer-reviewed papers on which to base them. In return for being a Patreon backer you get access to bonus blog content: additional commentary, in-progress sneak-previews of paintings, high-resolution artwork, and even free prints. For this post, we'll be looking the four years of development that went into the Hatzegopteryx painting shown above, revealing the earliest versions up to the final, published version. Sign up to Patreon to get access to this and the rest of my exclusive content!

References

A few years ago I wrote about how the 21st century is a terrific interval for palaeoart because of the wealth of information, discussion of palaeoart theory and diversity of talent we presently enjoy. Never before has so much data on this topic been available to practitioners of the trade, to scientists and historians, or to curious members of the public. The increase in palaeoart talent, a movement of artists exploring the outer regions of palaeoart science and artistry, and hints of wider interest in art of fossil animals are all traceable to these recent developments.

Any palaeoartist you speak to will tell you that there are honed practises and processes that should be applied when executing a palaeoart study. Several decades worth of influential artwork and writing by the likes of Knight, Hallett, Paul, Antón, Conway et al. and others send a unified message: reconstructions of fossil animals should be produced through close study of animal anatomy, both fossil and modern. They demonstrate that palaeoartworks must pass some basic, almost objective tests to be considered scientifically credible, successful examples of the medium.

• The proportions of the subject should be accurate to those indicated by its fossil remains
• The skeleton of the subject should fit within the restored soft-tissue volume
• Depicted poses should conform to predictions of joint motion
• The soft-tissue volume should - at minimum - be informed by predictions of muscle bulk derived from fossil remains as well as relevant data from modern, related species
• Soft-tissues restoration should be informed where possible by fossil data, or else via robust predictive techniques, such as phylogenetic bracketing