Temporal range: Upper Triassic–Lower Jurassic, 216.5–189.6 mya
|Mounted skeleton cast at the Cleveland Museum of Natural History|
Coelophysis was a small fast running carnivorous dinosaur. It is one of the earliest known genera of dinosaur. Coelophysis was found in Upper Triassic strata dated to about 215 million years age. It lived in what is now the southwestern United States. Similar dinosaurs are found all over the world at that time.
Coelophysis walked on two legs (as did all theropods). It was no more than about three feet (1 meter) tall at the hips but because of a long tail could be almost 10 feet (3 meters) long. There is some evidence that these animals hunted in packs, from the large numbers found together at the Ghost Ranch fossil site in New Mexico.
Two different sizes of this species have been found in the fossil record. At first paleontologists (scientists who study the fossil remains of dinosaurs) thought that they were two different species, but most now think that this is because Coelophysis males were larger than the females. This trait, known as sexual dimorphism, is often seen today in many species, including humans (although it is much less extreme in humans than in, for example, elephant seals).
For a while, it was thought that Coelophysis were cannibalistic, because what looked like Coelophysis babies were seen in the stomach of an adult Coelophysis. However, Rob Gay in 2002 showed that that these specimens were misinterpreted. Several specimens of "juvenile coelophysids" were actually small crurotarsan reptiles such as Hesperosuchus. In some cases bigger individuals were crushed on top of smaller ones). There is no longer any evidence to support cannibalistic behavior in Coelophysis.
History of discovery [change]
Edward Drinker Cope first named Coelophysis in 1889. This was during the "Bone Wars" with Othniel Charles Marsh. An amateur fossil collector, David Baldwin, found the first remains of the dinosaur in 1881. The type species, C. bauri was named after him. These first finds were too poorly preserved to give a complete picture of the new dinosaur.
In 1947, a substantial 'graveyard' of Coelophysis fossils was found in New Mexico, at Ghost Ranch, close to the original find. So many fossils together were probably the result of a flash flood, which swept away a large number of Coelophysis and buried them quickly and simultaneously. It seems such flooding was commonplace during this period of the Earth's history; the Petrified Forest of nearby Arizona was caused by a preserved log jam of tree trunks caught in a flood. Edwin H. Colbert made a comprehensive study of all the fossils found up to that date, and it is from him that we take most of our information about Coelophysis. The Ghost Ranch specimens were so numerous, including many well-preserved specimens, that one of them has since become the type specimen for the entire genus, replacing the original, poorly preserved specimen.
Since the Ghost Ranch specimens were discovered, more skeletons have been found in Arizona, New Mexico and an as-yet unconfirmed specimen from Utah, including both adults and juveniles. The deposits where Coelophysis was discovered date from the late Triassic, bur similar specimens have been found in the Lower Jurassic elsewhere in the world.
In 1998, a Coelophysis skull from the Carnegie Museum of Natural History was taken into space on the Space Shuttle Endeavour. It also spent some time on the space station Mir before being returned to Earth.
Coelophysis is the state fossil of New Mexico.
- Gay, Robert J. 2002. The myth of cannibalism in Coelophysis bauri. Journal of Vertebrate Paleontology 22(3); 57A
- Gay, Robert 2010. Evidence related to the cannibalism hypothesis in Coelophysis bauri from Ghost Ranch, New Mexico. In: Notes on early Mesozoic theropods. Lulu Press, 9-18. ISBN 978-0-557-46616-0
- Cope E.D. 1889. On a new genus of Triassic Dinosauria. American Naturalist. 23, 626
- Colbert, Edwin 1989. The Triassic dinosaur Coelophysis. Museum of Northern Arizona Bulletin.
- Colbert, Edwin H. (1965). The Age of Reptiles. W.W. Norton. p. 97. ISBN 0-486-29377-7.