About Coelophysis
| Scientific Name (Genus) | Coelophysis |
| Meaning of Name |
Hollow form
koilos(hollow)[Ancient Greek]-physis(form)[Ancient Greek] |
| Classification | Saurischia, Theropoda (Coelophysoidea) |
| Total Length | Approx. 2.8 - 3.0m |
| Weight | 15 - 25kg |
| Diet | Carnivorous |
| Period | Late Triassic (Carnian - Rhaetian) |
| Sub-classification / Species Name |
Coelophysis bauri
(* C. longicollis, which was once classified, is now considered a synonym) |
| Year of Paper Publication | 1889 |
| Genus Name Publication |
On a new genus of Triassic Dinosauria.
The American Naturalist. 23. by Cope, E.D. 1889. |
Basic Structure of Early Theropods
Coelophysis is an early theropod (carnivorous dinosaur) that appeared in the Late Triassic period (about 228 to 201.3 million years ago).
With a total length of about 2.8 to 3.0 meters and a weight of about 15 to 25 kilograms, it was a bipedal predator with an extremely lightweight and slender build.
Its forelimbs were relatively short and flexible, with four digits. However, only three digits had claws that functioned to catch prey, while the fourth was a vestigial organ buried in the flesh. It is thought to have functioned as a "grasper-clutcher" (grabbing and holding down) to quickly snatch small prey.
In addition, it had a "furcula" (wishbone) formed by the fusion of the left and right clavicles in its chest. This is the oldest clear evidence in the dinosaur fossil record, indicating that the important skeletal structure to which the flight muscles of later birds attach already existed in the Triassic period.
Coelophysis' Excellent Vision and Biomechanics
It had excellent vision and was a diurnal hunter.
Not only did it have "hollow bones," from which its name is derived, but the sides of its long, narrow skull had multiple large cavities called antorbital fenestrae, reducing the overall weight of its skeleton to the absolute limit.
What is noteworthy is its excellent visual ability. It had extremely high accommodation and depth perception, comparable to modern birds of prey such as hawks and eagles. It is thought to have been a diurnal hunter that relied on its vision, with round pupils.
Furthermore, biomechanical research using the latest computer simulations has revealed the important role of Coelophysis' "tail." Until now, the long, heavy tails of dinosaurs were thought to be simply "static weights" to balance the body's center of gravity.
However, it was found that when running at top speed, the tail swings from side to side (lateral bending) perfectly synchronized with the movement of the hind legs. This played the same mechanical role as humans "swinging their arms" when running, and was a revolutionary mechanism that significantly saved energy consumption during walking.
The latest biomechanical research has proven that dinosaur tails were not mere weights, but important organs for driving the entire body.
Growth Patterns and Dietary Changes
It was once believed that there were two body types in Coelophysis populations: a "gracile" type with a long, robust neck, and a "robust" type with a short neck and small build, and that this represented sexual dimorphism (differences between males and females).
However, recent "osteohistological" studies examining growth lines inside the bones have completely overturned this theory. The differences in physical build were not differences between males and females, but simply "severe individual variations in growth rates." It is thought that they flexibly changed their growth speed depending on the amount of food available to prevent starvation in the harsh environment of the Late Triassic.
In addition, the shape of their teeth changed dramatically as they grew. Young, immature individuals used flat, knife-like teeth to scrape meat off large carcasses. On the other hand, it is known that mature individuals transitioned to a feeding style where their teeth were replaced by backward-curving conical teeth, allowing them to firmly grasp small prey they had hunted themselves with their fangs and swallow them whole.
The Ghost Ranch Mass Death Assemblage
Indispensable to elucidating the ecology of Coelophysis is the great discovery at Ghost Ranch (Whitaker quarry) in New Mexico, USA. Here, hundreds to thousands of complete skeletons of Coelophysis at all stages of growth were excavated densely packed together.
Discovered at the Chinle Formation-Ghost Ranch (Whitaker) quarry in New Mexico, USA.
This mass death is thought to have been formed in an instant by a single catastrophic event, rather than a long-term accumulation of bones. Prominent theories suggest that the entire flock was swallowed by a sudden flash flood accompanying a localized downpour, or that animals gathered at the last watering hole during a severe drought exhausted their strength and were washed away to a single location by a subsequent flood. This fossil group is important evidence supporting the possibility that Coelophysis was highly social and acted in flocks.
The Truth of the "Cannibalism" Controversy
A widely accepted theory about Coelophysis was that it was a "dinosaur that routinely cannibalized." This is because, in the 1980s and 90s, skeletons of small reptiles were found in the abdomens of adults, and these were concluded to be the "bones of juvenile Coelophysis." Museum exhibits also recreated scenes of them eating their own young.
However, dramatic counter-evidence from the latest science in 2006 refuted this cannibalism theory. As a result of a detailed analysis of the bones in the stomach contents, the shape of the pelvis and femur completely matched those of early crocodylomorphs (such as Hesperosuchus). In other words, what the adult Coelophysis had eaten last was not a Coelophysis child, but a small crocodylomorph that lived in the same area.
The theory of routine cannibalism has been refuted, but later fossils have shown that under extreme environmental stress such as extreme starvation, they very rarely preyed opportunistically on young individuals, similar to modern reptiles and birds.
History of Discovery and Naming
The first fossils were discovered in New Mexico in 1881 by fossil collector David Baldwin. The renowned paleontologist Edward Drinker Cope described these specimens as a species of the genus Coelurus in 1887, but later formally established "Coelophysis" as an independent new genus in 1889.
At the time of discovery, there were only fragmentary fossils and confusion regarding its classification continued for a long time, but the complete skeletons (AMNH 7224) discovered at Ghost Ranch in 1947 were designated as the neotype (new type specimen), and currently the scientific name is stable and unified as Coelophysis bauri.
Closely Related Species and the Mystery of the Ecosystem
"Megapnosaurus" (formerly Syntarsus), a dinosaur extremely closely related to Coelophysis, has been discovered in Zimbabwe, Africa. At one time, there was a theory that these belonged to the same genus as Coelophysis, but the latest anatomical analysis proved that there are decisive differences in the depressions of the nasal bones and the proportions of the hind legs, and they are now treated as a separate genus.
Furthermore, the excavation results at Ghost Ranch denied the "rapid replacement hypothesis" regarding dinosaurs. The early dinosaurs to which Coelophysis belongs did not immediately drive out older archosaurs such as crocodylomorphs and dominate the ecosystem as soon as they appeared. In reality, it is known that they coexisted with more primitive dinosauriforms and early crocodylomorphs for tens of millions of years. The history of dinosaurs is one of adaptive radiation to the top of the ecosystem after undergoing dramatic environmental changes through the mass extinction at the end of the Triassic period.
The Dinosaur That Traveled to Space
Coelophysis is known as a dinosaur that reached not only the Earth but also outer space.
On January 22, 1998, a Coelophysis skull fossil from the Carnegie Museum of Natural History in the United States traveled to space aboard the Space Shuttle "Endeavour" (STS-89 mission). After docking with the Russian space station "Mir," this fossil safely returned to Earth.
It is a story transcending time and space, where a dinosaur that ran around the Triassic Earth went to space about 200 million years later.
Coelophysis Stamp and Fossil Gallery
