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True to Life?

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Species: bauri, rhodesiensis
Range: Late Triassic (Norian-Sinemurian, 221-190 MYA) from New Mexico, Arizona, Colorado, Texas, Zimbabwe, possibly Utah, Connecticut, and South Africa
Size estimate: 8-10 ft length, 40-50 lbs
Discovery: Edward Drinker Cope, 1889
Classification: dinosauria, saurischia, therapoda, coelophysoidea, coelophysidae

For such a lightly built animal, Coelophysis fossils rank among the most common dinosaurs. A site at Ghost Ranch, New Mexico preserves hundreds of their skeletons. Footprint fossils known as Grallator might belong to Coelophysis as well. If so, they and other fossils show that this animal and its relatives ranged across North America, Europe, and as far away as Africa. During the Late Triassic, the continents we now know all belonged to a giant landmass called Pangaea. A long-legged animal like Coelophysis would have no trouble spreading across a wide part of that supercontinent. Coelophysis’ long legs also made it fast. It needed all the speed it could get. Dinosaurs still coexisted with many other branches of the archosaur family tree. Many of these animals looked and acted like four-legged versions of the large theropods that would succeed them. Coelophysis would also need quick movement for catching prey. A 2009 in-depth study of Coelophysis found that thigh bones of adults thickened as they grew. Unlike mammals, which tend to slow down as they grow older, these animals stayed as swift proportionately as they were when younger. With longer strides as adults, that means they got slightly faster.

A ring of bones supported Coelophysis’ eye. Studying similar “sclerotic rings” from birds and lizards may help scientists reconstruct its visual capabilities, though time can distort them. If we can rely on such fossils, Coelophysis had a large, round eye with vision like a hawk’s. Its eyes may have functioned best in full daylight, which means its pupil likely had a round shape. Evidence from the skull itself shows the field of vision in each eye overlapped to give this animal depth perception. Predators like Coelophysis need to be able to tell how far away their prey is to catch it.

Coelophysis might be one of the few dinosaurs where scientists can tell male from female. Half the population had relatively thinner bones than the other. The thin-boned versions also had longer skulls and necks, shorter arms, and fused hip bones. The differences in hip bones have led some scientists to conclude the thinner skeletons belonged to females.

True to Life?

Since no one has ever seen a living dinosaur, and the missing pieces of the fossil record withhold important clues to their appearance, no artistic representation of a dinosaur ever gets it 100% right. On top of that, new discoveries can change our ideas of extinct creatures drastically. So, how close does this sculpture come to what we know of the original animal?
• Thanks to a massive collection of about 200 Coelophysis skeletons from Ghost Ranch, New Mexico, and decades of studying them, science has an excellent knowledge of this species’ anatomy. Some of the skeletons discovered there remained articulated, providing us with a clear guide on how to sculpt them. As a result, these sculptures rank among the most true-to-life in the Park.
• One neat detail from the skull appears in this sculpture as well. Your best view of it may come from moving to the western side of this paddock. Toward the front of the jaws, the jawline changes in the direction of its curve, leaving a slight notch. A glimpse at the Dilophosaurus, Spinosaurus, and Baryonyx statues or specimens here at the Park reveals similar and more extreme kinks in jawline. This feature alters the angle of the teeth, creating a “sweet spot” for catching small, slippery prey. The other dinosaurs mentioned here specialized in a piscivorous diet (meaning they liked their sashimi so fresh it wiggled going down), and so bore an extreme version of this notch, but Coelophysis’ slight notch suggests a more varied diet of small, quick, slippery things that might try to wriggle away from getting eaten. Sure enough, the Ghost Ranch specimens preserved the remains of lizards in some Coelophysis skeletons’ torsos. They also probably took salamander, fish, and mammal prey as well.
• One unfortunate detail of these sculptures’ heads deals with an artistic habit among paleoartists sometimes known as “shrink wrapping.” Here, it manifests as an oval on the snout outlining a hole in the skull underneath called the antorbital fenestra. In life, this detail of the skull would have been as invisible as the border between the bone and the cartilage of the human nose. Artists may include it for several reasons, many of which might be subconscious depending on the artist. One reason might deal with the artistic and scientific revolution of the 1980s and 90s dubbed the Dinosaur Renaissance. During this period, some artists started portraying dinosaurs as hyper-emaciated, partly as a rebellion against older portrayals which made dinosaurs look tubby (a look coming back into vogue in recent years). Note to paleoartists: two wrongs don’t make a right, so just learn and follow the anatomy and quit distorting your subjects in order to reflect some umbrage against other artists or some personal aesthetic preference.

That said, another reason may deal with instincts associated with iconography. Since no one has seen a living dinosaur but we do have their fossils, dead dinosaurs seem more familiar to us than living ones. If an artist sets out to portray a living dinosaur but needs to make its character seem less alien or more sympathetic or familiar, including the antorbital fenestra may seem like a natural fit. After staring at skulls in detail for hours on end, the anatomy of a living dinosaur may seem alien to the artist, prompting the inclusion of the antorbital fenestra as a way of coping with the cognitive dissonance. Then again, shrink-wrapping the eye sockets and postorbital fenestrae don’t show up quite as often, so maybe the snout just looks boring without it. Whatever the reason, it doesn’t belong on a portrayal of the living animal.
• These sculptures’ main departure from the original animal’s anatomy deals with their arms. For many years, artists and scientists alike assumed a more human-like posture for the arms of small theropods and many other dinosaurs. Recent studies in dinosaurian forelimb range of motion have found more limits to their movement than previously thought. With little exception, they could not turn their palms to face the ground, as shown here, without jutting their elbows out at an extreme angle, as if they were doing the chicken dance. Some enthusiasts call the posture of these sculptures’ forelimbs “bunny paws syndrome.”
• While these sculptures do get the forelimb posture wrong, it’s worth noting here that a recent trend portrays an opposite sort of wrong, especially with small theropods like Coelophysis. Artists who follow the trend pose their forelimbs as if they employed the same joints as birds, ignoring how the joints of bird limbs took tens of millions of years to develop the specializations necessary for folding their forearms like the wings of modern birds. Since they descend from flight-capable ancestor species, even flightless birds bear forelimbs with radical design differences from early dinosaurs. Regardless of their shared lineage, it helps to think of dinosaurs and birds as two separate groups in order to grasp (har!) this point.

Starting at the shoulder, the general differences are as follows: bird shoulders allow their forelimbs to reach above the level of their spines, whereas dinosaur shoulders limited movement to directly below the chest and out to the sides a little with few exceptions (gliding dinosaurs could stick their arms perpendicular to their torsos, but not very far up from there; a couple of dinosaurs, Rahonavis and Overoraptor, might have achieved powered flight, but like Archaeopteryx, they probably employed a rather unbirdlike flight stroke due to dinosaurian limitations on their forelimb movement). Movement at the elbow allows birds to fold their forearms against their upper arms not unlike humans; some dinosaurs like the raptors developed this kind of folding, but more basal theropods employed more restrictive elbows and could not fold their arms as tightly as a result. This last point correlates with the length of dinosaur arms: long-armed ‘raptors needed to fold those limbs away in order to run efficiently, whereas other theropods simply shortened their arms and maybe folded them towards their bellies to get them out of the way.

The wrists get especially interesting: do you remember the quarry scene in Jurassic Park where Alan Grant explains why he considers dinosaurs birdlike? He mentions a half-moon-shaped bone in the wrist “just like a bird” which helps define the maniraptoran group of dinosaurs. That roughly half-moon shape of this wrist bone, called the “radiale” because it attaches to the radius bone of the forearm, developed in order to cause the wrist to fold in such a way that the little finger of the hand could approach the bottom of the forearm. In modern birds, their fused fingers can normally form a highly acute angle with their ulnae, but the closest any classic dinosaur could get between fingers and forearm was slightly over 90 degrees (Hagryphus, portrayed in the Stewart Museum, could achieve this extreme). Most dinosaurian maniraptors other than oviraptorosaurs could achieve a roughly 150 degree obtuse angle with the forearm, a range comparable to humans (try it!).

As a much more basal theropod, Coelophysis could fold its palms inward and outward to a great degree, not too different from our own wrist range of motion. When it comes to up-and-down movement, though, they could barely wiggle. The joints of the wrist performed functions which required a sacrifice of range of motion in certain planes in favor of greater strength and/or stability. This means that if only Coelophysis could cross its radius over its ulna mammal-style, the bunny paws posture shown here would be plausible. On the other hand, folding its forelimbs like bird wings would dislocate shoulder, elbow, and wrist alike.
• Despite the quality of the Ghost Ranch Coelophysis skeletons, neither they nor any other Coelophysis specimen preserves any skin data. We must therefore use indirect means to deduce the likely look of their skin. Contrary to hypothetical claims that feathers evolved only once in the common ancestor of pterosaurs and dinosaurs, and that small dinosaurs needed fuzz or feathers as insulation, a 2015 study found that most dinosaurs, including the ancestral dinosaur and its close descendants, bore scales. To draw this conclusion, it used statistical analysis of known dinosaur skin impressions to calculate the likelihood of fuzz or feathers in any given dinosaur group. The authors of the study then repeated it with new data, publishing their new findings in 2020, and found an even greater likelihood of scales in the common ancestor of dinosaurs and in early dinosaurs. Though it remains possible that early dinosaurs bore feathers, fuzz, or some other skin covering, the betting odds remain vastly in favor of scales. It may be hard to see from a distance with their current color scheme, but these sculptures employ a scalation somewhat similar to the Carnotaurus sculpture on the far east side of the Park.
• Scale patterns on dinosaur feet generate some controversy among scientists, with some favoring a more crocodilian scalation and some a birdlike scalation. One carnivorous dinosaur fossil, from a relative of Allosaurus and Giganotosaurus with a sharklike fin over its hips and called Concavenator, preserves the birdlike condition on its feet and shins. This specimen does weigh the accuracy-o-meter in favor of these sculptures, but since Concavenator succeeds Coelophysis in the fossil record, it may have inherited an innovation that postdates Coelophysis. All told, the birdlike scales shown here are plausible, if a bit of a Schroedinger’s Cat.