All Yesterdays: Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals

by John Conway

  Triceratops horridus

  Even the most familiar of dinosaurs may hold great surprises in their life appearance. It seems that every time the soft tissue of a dinosaur is discovered, our views of that animal, and usually all of its relatives as well, are changed drastically. Such revelations show how artificial our images of even the most well-known dinosaurs can be. What we are drawing all the time may not be the "real" animals themselves, but artifacts of an artistic tradition.

  An example is Triceratops, arguably one of the most recognizable of all dinosaurs. This animal has always been seen as a sort of dinosaurian rhinoceros, with its iconic head frill, three horns and the giant, plant-cropping beak. In recent years, however, scientists have made several discoveries that may drastically revise our image of this animal. Fossil skin impressions (mentioned online in 2010, but unpublished at the time of writing) apparently reveal that Triceratops had nipple-like protuberances located within the centres of the scales that cover its back and tail: it is inferred that these structures anchored quill-like structures of some sort. Moreover, other fossils show that an earlier member of the horned dinosaur family, Psittacosaurus, had a fringe of long, spine-like filaments lining the upper surface of its tail.39 Since Psittacosaurus was close to the ancestry of all large-bodied, horned dinosaurs, it would not be unreasonable to suggest that all ceratopsians possessed some sort of spiny integument.

  Following this line of deduction, we produced this unfamiliar depiction of the very familiar Triceratops. What if the unusual dermal nipples of Triceratops were the bases of giant protective spines? While we are not suggesting that this was the definitive look of this animal, it wouldn't surprise us if Triceratops, or other, even less-expected dinosaurs bore a covering of spiky hairs.

  Everything Old is New Again: Opisthocoelicaudia

  The oldest dinosaur stereotype is that of the massively dumb, long-necked sauropod, dragging itself slowly out of a fetid swamp. Once pictured as too big to support themselves on land, sauropod dinosaurs have long since been lifted out of the marshlands. Thanks to new fossil discoveries and unbiased considerations of the anatomical and palaeoenvironmental evidence,40 we now know that most sauropods lived on land, moved about on erect legs and did not drag their tails on the ground.41

  Numerous recent discoveries have also revealed that sauropods were far more diverse and complicated than originally assumed. There were tall, long-limbed forms such as Brachiosaurus and Giraffatitan, long and lean, whiplash-tailed form such as Diplodocus, and strangely proportioned forms such as the short-necked Brachytrachelopan42 and the weird Isisaurus43 with its wide, deep neck and unusually proportioned limbs. Isolated island habitats led to the evolution of dwarf, cow-sized sauropods such as Europasaurus44.

  Within this diversity, how sure are we that sauropods were all landlubbers? As we can see from hippopotamuses and certain Asian rhinoceros species today, large herbivores don't need to be cold-blooded dimwits in order to pursue partially aquatic lifestyles. Perhaps the same was also true for members of some sauropod lineages.

  If we could bet on the possibility of a certain sauropod being at least partially aquatic, our money would be on Opisthocoelicaudia, a titanosaur from the Late Cretaceous of Mongolia. Known from a famous fossil that preserved a more-or-less complete body and limbs but, frustratingly, has no head or neck preserved, it was surprisingly rotund animal, with short legs and a massive, round body. Its tail vertebra fit together via flexible ball-and-socket joints, and its tail preserves evidence of massive ligamentous and muscular attachments. It is not difficult to imagine these adaptations as modifications for a mostly water-based mode of existence. While today's Mongolia doesn't sound like the best place to find water-dwelling dinosaurs, the area was a lush, fertile zone crossed by many rivers during the time Opisthocoelicaudia lived. At the time of writing, no technical study has properly addressed the possibility of aquatic life for Opisthocoelicaudia, but its proportions certainly recall those of fossil mammals suggested to be amphibious.45 Those who know their palaeoart will of course recognise our illustration as a homage to part of the Zallinger mural.

  All Todays

  Although the accumulation of discoveries and fossil insights have given us a more-or-less clear view of some extinct animals, many are still reconstructed with a rule-of-the thumb methodology. As we saw in the previous section, this modus operandi does not take soft tissues, integument, colour and behavioural elements into account. More recently, palaeontological artists have began to notice these shortcomings and have begun to include more lifelike (if slightly speculative) elements in their reconstructive work.

  In this section, "All Todays", we took the opposite approach and tried to highlight what some reconstructions might be missing out by "reconstructing" modern animals from their skeletal diagrams. We took the position of speculative observers with some knowledge of how vertebrate bones and muscles work, but with no information on the lifestyles or the soft tissue integument of their subjects. We applied this approach to a number of modern-day animals such as birds, ungulates, carnivores, whales and reptiles, with extraordinary and sometimes hilarious results.

  Shrink-Wrapping: How Future Artists Will Show that They Know the Anatomy

  As we have already discussed, the modern, sleek versions of dinosaurs have become a cliché. Dinosaurs have been stripped of extraneous soft tissue, with every muscle and bone ridge carefully portrayed as visible in life. It has become fashionable to reconstruct theropods with every ridge and fossa on their skulls echoed by lines of scales, with the joints between skull bones given maximum visibility.

  Perhaps palaeontological artists of the future will give modern animals the same treatment. They will want to flaunt their knowledge of mammalian anatomy by faithfully portraying every limb bone, every finger, every indentation in the skulls. Some will be bolder than the rest, and will decorate their creations with a light sprinkling of hairs, or apply garish color schemes. To be honest, it won’t be easy to blame them, since there is only the most tenuous of correlations between bone textures and actual soft tissue in living animals.

  Can you guess what the animals in the following pages are? The answers, as explained by the unknown scientists that will discover and depict them in the future, are visible next to each image.

  "The killer stare of the Cat , a vicious, pack-dwelling hunter. This dangerous predator brandished a set of not one, but FIVE switchblade claws on each forefoot. Its fossils are usually found in the concrete nests of long-limbed, bipedal Humans , suggesting that the killer Cats wandered into their lairs before slaughtering their hapless victims."

  "Only the skull of the Hippopotamus is known, yet even that is enough to tell that this apex predator was the most dangerous hunter of its time. Its long teeth and heavy jaws were strong enough to chew right through the metallic armor of Cars ."

  "The Cow was a lithe, graceful herbivore that despite its size, could easily outrun pursuing hunters."

  "With its extraordinary skin sail, the Rhinoceros was among the strangest of the Holocene herbivores. Researchers suggest that this organ might have helped it shed excess heat."

  "Many theories have been suggested to explain the unusual, single-digit feet of equid perissodactyls. It was likely that these animals bore muscular pads on their hands and feet to support their stance."

  "The Spider Monkey was a small, possibly arboreal species of Human with extraordinarily long fingers and big eyes. Unlike its cursorial relatives, the Spider Monkeys were efficient, stealthy predators."

  "A Toad ambles merrily along the Holocene forest floor. This reconstruction is now considered to be erroneous since their longer hindlimbs indicate that Toads were possibly bipedal."

  Covering Up is not so Easy: the Integument Problem

  If no feathers are preserved in the fossil record, will future palaeontologists guess at their presence? It seems unlikely. They will
possibly recognise that birds had wings, but fill them in the simplest way: a membrane of skin. What about the other way around? Will errors of preservation, or of phylogenetic bracketing, lead to mistaken assumptions of furry body covering? Only time will tell.

  "This reconstruction of the Vulture reflects our latest theories about the wing membrane extensions in Flying Birds ,those mysterious beings which appeared suddenly on the skies of our planet a hundred million years ago."

  "Two Casque-Headed Hornbills duel for dominance. These strange beaked animals grew elaborate head horns for competition among during the mating season."

  "Two Swans are seen with their long, scythe-like forelimbs, which they must have used to spear small prey items. One of them has just caught a Tadpole , one of the mysterious fish of the past."

  "Unlike many others, this reconstruction of the Iguana is fully up-to-date. Impressions of a furry integument have been discovered around the skeletons of Rats a few years ago. It is likely that all small vertebrates had such body coverings to protect against the cool Holocene climate."

  The Biomechanics of Rabbits

  Palaeontology is an imperfect and difficult science. Many methodologies are brought to bear, and many contingencies must be considered. Since 1999, Kent Stevens and colleagues have argued that the vertebral joints of sauropod dinosaur necks can be effectively modelled in digital space using a specially designed piece of software called Dinomorph. The overriding conclusions from this work are that neck flexibility in sauropods was rather restricted, and that sauropod habitually held their necks in a more or less horizontal pose.46 However, other researchers have argued that this work fails to take proper account of the soft tissue anatomy present in animals. It ignores, for example, the substantial contribution that cartilage makes to neck flexibility, nor is it informed by the fact that virtually all living terrestrial amphibians, reptiles, birds and mammals habitually hold their necks in an elevated pose relative to the long axis of the dorsal vertebrae.47

  Perhaps, not realizing that neck posture in living animals is not properly reflected in the way neck bones fit together, future palaeontologists will model such living animals as rabbits in the same way, concluding that they, too, held their necks horizontally. This illustration thus serves as a warning against overly mechanistic approaches to anatomy.

  The Unknown Unknowns: Too Conservative, Too Cautious?

  Fossils are rarely complete, and naturally enough, we tend to fill in the missing bits with conservative parts from the closest relatives whenever we can. The problem is, the defining anatomical features of many living animals are entirely composed of soft tissue, which is hard to predict, even with educated guesswork. How daring and how correct will the palaeontologists of tomorrow be?

  "A Python rears up in a colorful, defensive body display. We know this strange animal from fragmentary remains only, but it is likely that it supported its long body with stubby legs, much like those of closely related Lizards ."

  "A solitary Manatee is shown grazing in its mountain home. We only know the skull of this enigmatic herbivore."

  "A bull Elephant , one of the gigantic mammals of ancient Africa, is shown here inflating its balloon-like facial sac. Some fanciful reconstructions depict Elephants with even longer muscular appendages projecting from their faces, but this is unlikely since no modern mammals have such organs."

  "The enigmatic Whales were some of the largest animals to swim in the ancient oceans. Here, we can see a couple of predatory Sperm Whales looking for prey.

  "Another dangerous predator, the elongated, serpentine Bowhead Whale, is visible swimming through a tangled underwater forest. This extremely derived predator fed on animals as big as itself, which it trapped with its gigantic, extensible jaws."

  Strange Hypotheses

  Modern palaeontology has its fair share of strange and outlandish hypothesis floating around, and these frequently find their way into artworks and illustrations. What kinds of strange and uninformed hypotheses might be formulated about present day animals?

  Venomous Baboons

  Lacking any and all knowledge of the thick woolly coats and brightly coloured, naked skin patches and large guts of living baboons, it seems plausible that these lightly built, long-muzzled, fanged primates would be reconstructed as gracile terrestrial predators. Furthermore, those giant fangs have grooves running down their sides - a feature normally regarded as as key signature of the ability to produce venom, and inject it into the tissues of other animals. Perhaps the complicated nasal sinuses of baboons might be interpreted as spaces for venom glands.

  The skull of Sinornithosaurus.

  Baboons, of course, are not venomous, and quite why they have fang grooves isn’t entirely clear. Knowing this, suggestions of venomosity sound more than a little preposterous. However, it will be surprising to know that very similar theories have been proposed for quite a few fossil animals: the most notorious recent example concerning the bird-like theropod dinosaur Sinornithosaurus.48 This hypothesis was later rebuked by a number of experts, but not before it had been reported by a number of media sources as a legitimate discovery. Thus, this case also illustrates the importance of proper science reporting in facilitating or limiting the spread of untrue or unproven ideas.

  Hummingbird Parasites

  The future will no doubt have its fair share of bizarre and poorly supported hypotheses, and not all unusual ideas are equal. Would it be obvious that the slender, tubular (and sometimes serrated) bills of hummingbirds were used to probe deep into flowers and feed on nectar, or would alternative hypotheses be entertained? There is much reason to think so. A hummingbird's skeleton is among the strangest in the animal kingdom. Their wings are tiny, in fact shorter than their legs. The large, strongly curved foot claws hint at a lifestyle involving clinging and climbing, as do small curved claws on the distinctive elongate hands.

  Combine all of these features with a lack of evidence for their true lifestyle, and we imagine that future palaeontologists could misinterpret hummingbirds entirely. Vampiric hummingbirds sound unlikely, but similar theories have been proposed about vampiric pterosaurs. In 2003, researcher David Peters claimed that he had discovered “rattlesnake fangs” and other indications of a blood- and egg-sucking lifestyle in a small anurognathid pterosaur known as Jeholopterus. However, Peters’ controversial research methods involved relying on manipulated images on a computer to discern features that no other observer can see. Both this methodology and Peters’ hypothesis of vampiric pterosaurs were consequently disproved by other scientists.

  An Ending and Self-reflection: Homo diluvii

  Having shown you a fair share of speculations, oddities and unusual theories, we conclude our tour with perhaps the oldest "wrong reconstruction" of them all. Behold Homo diluvii: the Man of the Deluge. Described in 1726 by the Swiss Scholar Johann Jakob Scheuchzer from giant salamander remains, the creature was thought to be an actual human being, fossilized after drowning in the mythical deluge of the Bible.

  This mistake seems so obvious now that even children could realize that the skeleton was not that of a human being. But Homo diluvii shows us how we take scientific reasoning and our repository of evidence and theories for granted. Science was still at its infancy at the time this fossil was discovered. People didn't understand what fossils were and tried to explain them with concepts they had at hand, which invariably came from religious myths at the time. Scholars were incapable of even conceiving that animals could leave their remains as fossils in rock, or that different animals and plants lived at different times, or that organisms could go extinct. Thus, a salamander ended up a man in their worldview.

  Over the centuries, we have come a long way from Homo diluvii.We now know what fossil animals are, and can reliably formulate their relationships to living beings today. Almost with each passing day, new discoveries are providing us with insi
ghts into their lifestyles, forms, colour, diversity and evolutionary relationships. Indeed, our repository is growing faster than we can assimilate and get used to its implications. It is possible, though unlikely, that paradigm shifts may one day make our current view of extinct animals as odd and dated as Homo diluvii itself.

  This is why we prepared this collection: to show you some of our mistakes, and hint at what we might be missing on the way. We don't pretend to have any conclusive answers-the only solid statement we can offer in this work is that no one should "rest easy" with the facts on hand. Our picture of the past is constantly evolving, and it will continue to evolve as new discoveries change or sweep old certainties away. We hope you enjoyed your ride with us through All Yesterdays and All Todays.

  Notes and References

  1 A minor note on terminology. Some people argue that the term palaeoart (or 'paleoart' if you're American) should best be applied to art produced during prehistoric times, and that artwork depicting prehistoric times and prehistoric organisms therefore needs a new name. However, the only word yet on the cards-palaeontography-has yet to catch on.