by John Conway
Mesozoic Goats— Protoceratops andrewsi Do What They Aren't Best At
Reconstructing the behaviour of extinct animals is challenging, even if we assume a good correlation between anatomy and behaviour. Unfortunately, this correlation does not always exist in the real world. Elephants are excellent at swimming, crocodiles and alligators sometimes eat fruit and leaves, juvenile iguanas sometimes jump up at the moon at night, and goats in some areas often climb trees in order to browse. Animals do what they do, not necessarily because it is what they are good at, or even because their anatomy is suited to it, but simply because they can. As a result, unexpected behaviours are commonplace.
Here, the famous ceratopsian Protoceratops is engaged in something it has no obvious adaptations or reason to do: climbing trees. Protoceratops was a boar-sized herbivore that lived during the Late Cretaceous in Mongolia. It is related to the larger horned dinosaurs of North America such as Triceratops, and is thought to have retained the general appearance of their common ancestor. Hundreds of Protoceratops skeletons are known, many preserved in spectacular and lifelike poses. One specimen is preserved locked in combat with a Velociraptor; others died in poses showing that they were struggling to dig out of the sand that buried them.
Majungasaurus Makes Like a Log
Crypsis is a theme rarely explored in palaeontological art. Many present-day animals develop complex coloration schemes to disguise themselves from predators, prey, or both. Other animals match their appearance and behavior to different, usually poisonous species and mimic them for protection. While crypsis and mimicry are seen most often in smaller creatures, large-bodied animals also exhibit strange and confusing body patterns for disguise. A tiger’s orange and black stripes might look dazzling in a zoo but, in its natural environment, they render it nearly invisible in the tall grass. Likewise, crocodiles blend in among swamps and riverbanks with their outline-breaking scutes and mottled coloration. At least some dinosaurs must have had similar camouflage schemes.
Can you see the Majungasaurus in this picture? Majungasaurus was a Cretaceous abelisaurid theropod from Madagascar, a strangely-proportioned relative of the Carnotaurus we saw earlier. Unless there is something very wrong with the fossils we have, Majungasaurus had an extremely long body, combined with very short legs and relictual arms, giving it the proportions of a bipedal, dinosaurian daschund. As you might have guessed, it is not clear how this predatory dinosaur moved about and hunted with such an atypical body plan. We imagined that camouflage, made possible by matching its pebbly scales to the texture of rocks or trees, made things easier for the strange old Majungasaurus.
A Plesiosaur Makes like Some Coral
Camouflage is not limited to land animals. Rivers, lakes and seas also contain many risks, and many opportunities for hiding. The oceans especially teem with dazzling examples of crypsis; sea dragons that mimic strands and stalks of kelp, wobbegong sharks that lie down like mats of sand and seaweed, poisonous stonefish that are dangerously invisible among stones, and so on.
We imagined what sort of animals might have camouflaged themselves in prehistoric seas, and turned to long-necked marine reptiles known as plesiosaurs , as a possible example. Plesiosaurs were not dinosaurs, and instead belonged to a major group of marine reptiles called sauropterygians. The most successful, most diverse and most long-lived sauropterygians, plesiosaurs included the previously-mentioned elasmosaurs, the big-headed, macropredatory pliosaurs as well as a number of groups that are intermediate in shape and proportions.
We pictured this particular plesiosaur as a sit-and-wait hunter, lying in shallow coral reefs and waiting for suitably sized prey to swim by. A near total absence of information on plesiosaur skin morphology means that we have no firm ideas about skin texture in these animals. It is assumed that most had a smooth skin for hydrodynamic efficiency, but we imagined this particular plesiosaur as a well-camouflaged hunter with an exceptional sit-and-wait strategy.
As an air-breather, the dive time of our camouflaged lurker would be limited, but could theoretically still be long enough to allow fruitful hunting in areas of rich prey density. The dorsoventrally compressed body shape present in at least some plesiosaurs31 renders it possible that they could lie on the seafloor; intriguingly, the shallow-bodied Jurassic form Tatenectes also has particularly dense, heavy bone located on its underside and near its midline, suggested that it was using bone as a form of ballast to stay near (or on?) the seafloor. We speculate that some bottom-hugging plesiosaurs may have used their long necks for suction feeding: they would open their mouths and lunge up when a small fish or marine reptile wandered by. The rush of water filling the animal's long throat cavity would create a brief vacuum effect, helping it capture its victim.
Ouranosaurus : I'm Not Fat, it's the Spines!
Nothing quite says "prehistoric" like an animal with a skin sail running down its back. This is possibly due to the "reptilian" nature of such baroque accessories: the only animals with sails on their backs today are cold-blooded, "exotic" lizards such as basilisks. Whatever its cause, this trend is so entrenched in popular culture that Dimetrodon, a sail-backed animal that lived millions of years before dinosaurs and was more closely related to mammals, is frequently lumped in with the ruling reptiles in children's books and toy sets. Even within dinosaurs, the popular desire to have ridge-backed monsters manifests itself with depictions of exaggerated skin sails in species with extended vertebral spines, such as the herbivorous ornithopod Ouranosaurus.
Tall vertebral spines on dinosaurs are usually interpreted as having supported "sails", with little flesh covering the bones. However, it is possible that these spines supported other tissues, such as fat deposits or humps. This is exactly the case in large herbivores today such as bison, camels and rhinoceroses. Indeed, palaeontologist Jack Bailey published some reconstructions in 1997 in which he made Ouranosaurus and Spinosaurus look more 'hump-backed' than 'sail-backed'.32 Perhaps, however, this approach is wrong and tall-spined reptiles like chameleons, with narrow ridges that are neither sails nor a humps, provide better models for dinosaurs.33 Nevertheless, this area remains understudied and we decided to reconstruct one of the more popular "sail-backed" dinosaurs with an armored hump on its back. Behold Ouranosaurus in its hump-backed glory.
Ouranosaurus was a large iguanodontian ornithopod that inhabited northern Africa during Early Cretaceous times. Several other distantly related dinosaurs from the same location also have elongated vertebral spines, including the enormous theropod Spinosaurus and the sauropod Rebbachisaurus. So perhaps, instead of just Ouranosaurus, the region was inhabited by an entire cast of unusual, hump-backed dinosaurs in real life. The reason for such unusually synchronized convergent evolution, and indeed the very nature of these spines in life, remains unknown. Perhaps climactic factors or sexual selection could have played a role. Display is certainly a likely purpose-and certainly fits with the general idea that dinosaurs were flamboyant, social animals.
Parasaurolophus walkeri the Porker and Lambeosaurus magnicristatus the Flapper
Since the old view of dinosaurs as lumbering and shapeless piles of stocky lard was discarded, palaeontological artists have been keen to portray most dinosaurs as slim, sleek animals where every contour of the limbs, every muscle and even every bone can be clearly discerned. No living mammal, reptile or bird has such a “visible” anatomy. Living animals are replete with skin flaps, fat and saggy bits that obscure the exact lines of their bones and musculature.
Parasaurolophus skeletal
The famous “duck-billed dinosaurs” known as hadrosaurs have provided us with some of the best demonstrations of the fact that dinosaurs were not walking anatomical diagrams. Remarkable mummified hadrosaur specimens provide us with an unprecedented amount of information on hadrosaur soft tissue anatomy, and one of the most interesting features of these fossils is a series of vertical “shoulder folds” that cover the upper arm and shoulde
r region. Greg Paul has argued that these were evidently present in life, and must always be depicted in life reconstructions of these animals.34 Here, however, we explore the possibility that these are actually artifacts of desiccation, and that they supported a heavy padding of fat and muscles in real life. Behold our fat Parasaurolophus and the solidly-built Lambeosaurus with a flap-like throat pouch.
Parasaurolophus and Lambeosaurus are familiar duckbilled dinosaurs, recognisable by their spectacular head crests. Duckbilled dinosaurs, or hadrosaurs, were the dominant plant-eaters of the Late Cretaceous, and had evolved one of the most advanced chewing mechanisms seen in vertebrates. Their crests were hollow and almost certainly would have been used to create loud honking sounds for communication.
Lambeosaurus magnicristatus
Mountain of Feathers— Therizinosaurus
Some dinosaurs suffer from looking too exciting de-fleshed, leading artists to depict them in exciting and garish ways. If one group of dinosaurs could be singled out for their strangeness, the mystifying, long-clawed therizinosaurs would win hands (or claws) down.
Therizinosaurs are a such a bizarre group of dinosaurs that, for a long time, it was not possible to discern what they were, let alone what they looked like. Originally they were known only from a set of giant, mystifying claws, the longest of which were more than 70 centimeters long. These claws prompted a whole range of theories and hypothetical identities. Early ideas were that therizinosaurs might be gigantic, turtle-like beasts or vast, vicious predators which slashed open the bellies of sauropods and other large dinosaurian prey. Better remains led to suggestions that therizinosaurs were plant eaters: perhaps late-surviving prosauropods or relatives of early ornithischians, or even a completely unique lineage of dinosaurs distinct from any other group. With newer discoveries and the rise of cladistic methodology, it became clear that they were, in fact, aberrant herbivorous theropods, reasonably closely related to birds.
The skeleton of Nothronychus mckinleyi shows the strange anatomy of therizinosaurs
Even after scientists established what they were, depictions of therizinosaurs maintained a strong claw-based fetish. Therizinosaurus – shown here in our life reconstruction – was one of the later, more advanced forms. It was a large, elephant-sized animal with tremendously wide hips and (presumably) enormous guts. To be fair, it is difficult to ignore the sheer weirdness of these majestic animals; in real-life, however, exciting skeletons, claws and bellies are all covered up in a great big mounds of feathers, fur, or fat. Silhouettes are the most distinctly recognizable visual attributes of large animals today. As a result, our Therizinosaurus are not brandishing their meter-long claws in the viewer’s face. Our opinion on palaeoart is that subtle references and hints of anatomical features are more realistic, more in line with what we see in living animals. Portrayed with style and in an appropriate setting, they can leave a more distinct effect on the viewer.
Heterodontosaurus tucki the Goes the Whole (Hedge)Hog
Small ornithischians, the quintessential "harmless herbivores" of the prehistoric world, have had one of the greatest image changes of the dinosaur renaissance in the recent years. Traditionally, these animals were usually portrayed as smaller versions of their larger relatives. Unlike the meat-eating theropods, whose feathery integument is becoming more-or-less common knowledge thanks to dozens of new well-preserved fossil discoveries, artists and scientists were reluctant to dress small ornithischians in feathers or "dinofuzz."
When illustrated, these generic, naked herbivores were mostly shown running, either away from a more interesting predator, or simply scampering across the landscape with no purpose or aim. However, recent discoveries have shown that there is far more to small ornithischians than previously assumed. To begin with, they are no longer naked: dermal quills are now thought to be present in almost all small ornithischians after the discovery of the Chinese heterodontosaurid Tianyulong (preserved with a covering of spike-like body hairs35) and of the early ceratopsian Psittacosaurus (one specimen is preserved with bristle-like structures on its tail36). Another exciting discovery, this time of an ornithopod called Oryctodromeus, has revealed that at least some small ornithischians had burrowing habits, spending at least part of their time sheltering together in dens.37 It seems that these dens were inhabited by family units. Taken altogether, these discoveries paint a very different picture of small ornithischians. No longer are they defenseless bipedal ‘lizards’, but an unique group of animals with their own extraordinary adaptations and social behavior.
This picture shows a family group of Heterodontosaurus near the entry of their collective burrow. Taking the latest discoveries into account, we reconstructed them with a full set of porcupine-like quills for defence. Heterodontosaurus was a small, basal ornithischian from the Early Jurassic of South Africa. Its name ("differing tooth lizard") refers to its unusual dentition. Heterodontosaurus had the beak and chewing teeth common to most ornithischian dinosaurs, but it also had large "canines" and two other types of teeth that helped it chew its food efficiently. Scientists still aren't sure if Heterodontosaurus was purely herbivorous, or if it supplanted its diet with small animals as well.
Let's get fluffy: Leaellynasaura amicagraphica
As seen before with Hypsilophodon, many small plant-eating dinosaurs will have their popular images greatly revised thanks to new discoveries of social behaviour and integument. Instead of looking like two-legged iguanas, these animals will have to be re-imagined with the extra possibilities offered by furry bodies and communal living habits.
Here is one more small ornithischian re-interpretation, this time featuring Leaellynasaura. This dinosaur was discovered in Australia, where it lived during Early Cretaceous times, about one hundred and ten million years ago. At that time, Australia was located close to the Earth's geographic south pole. Although its climate was possibly not as cold as today's Antarctic, the axial tilt of our planet meant that Cretaceous Australia did not receive direct sunlight for long periods of time, and almost certainly experienced sub-zero temperatures.
Aside from being a polar dinosaur, Leaellynasaura was also extraordinary for its immensely long tail, which was almost three times as long as its body. Nobody knows why Leaellynasaura had such a long tail, or what it used it for. Theories range from the tail being used as a climbing aid, a sexual and social display feature, or a long, shaggy “scarf” that the dinosaur wrapped around itself as protection from the cold. It has even been suggested that the tail aided the animal in swimming!
Drawing on these facts, we reconstructed Leaellynasaura as a rotund furball that scurried peacefully about in the polar forests of Australia's past. We imagined its long tail as a thin, signalling "flagpole" that helped it identify and keep close to members of its herd. No doubt some people will find this reconstruction preposterous, and perhaps they will be right. However, we felt that not enough dinosaurs were reconstructed as "cute" beasts, whereas in nature, polar animals can look quite pulchritudinous under layers of fat, muscle, fur and other insulation.
Microraptor gui
Almost twenty years of fossil discoveries have firmly established that certain small, meat-eating dinosaurs were covered in feathers, to such a degree that even popular science books routinely depict these animals with some sort of integument. Yet many palaeoartists, it seems, still have difficulty picturing such small, feathered theropods as bird-like creatures. Instead of picturing the coherent, well-rounded forms that are found in nature, most artists over-focus on certain features or details of preservation found in a single fossil, and repeat and exaggerate them to picture "little monsters" that look more like film creatures than real animals. When examined in detail, this typecasting can tell us a lot about trends in palaeoart.
The small theropod Microraptor is a case to the point. This small, possibly flying relative of Velociraptor and Archaeopteryx was described in 2003 as a "four-winged dinosaur"38 amid much med
ia hype. Since then, almost every reconstruction of this animal has depicted it as a strange, dragon-like feathered glider with a reptilian face. In almost every picture, Microraptor is virtually always shown spreading its arms and legs, all lined with feathers that stick out as visibly as possible, as if to prove to the viewer that it really had “four wings.” Such illustrations might be educational, but they also help popularize an image of the animal that was not real. It’s as if artists are unable to conceive of dinosaurs that don’t look abnormal and “alien” in some way.
When illustrating Microraptor, we wanted to “filter out” all popular repetitions and approach it from scratch. The animal was indeed remarkable for having wing-feather-like structures on its rear legs, but we know from observations of living animals that flying species rarely have their wings fully visible when resting. Our result looks far more naturalistic, and far less like the spread-eagled fantasy creature that popular audiences have come to associate with Microraptor.
On a side note, we gave our Microraptor s a nest in order to add depth to their story. The nesting behaviour of dinosaurs is a complex issue that deserves further discussion and speculation: it seems likely that this varied immensely, just as it does in modern birds.
