C. bauri (type)
C. longicollis
C. willistoni
One of the earliest known dinosaurs, Coelophysis ("hollow form") is a small, carnivorous biped from North America. It first appeared in the Late Triassic period, around 210 million years ago.
Description
Coelophysis had a spindly, delicate build, and was about 3 m long, which is small for a dinosaur. However, its long stiff tail and S-shaped neck accounted for most of this length, so it probably weighed no more than 30 kg. Coelophysis was also among the earliest dinosaurs to have hollow bones to save weight, like the later sauropods. Despite looking very similar to the ancestors of the dinosaurs, the thecodonts, Coelophysis nevertheless bore the defining mark of the dinosaurs — legs placed underneath the body rather than out to the sides.
The skull, while long, was very light since it was full of holes to save weight, and was perched on the end of a long and slender neck that had a very flexible bone structure. The minimized skull is a feature seen in all later dinosaurs. Coelophysis had many serrated teeth, for eating any number of small animals.
Each hand had four fingers, but one was too small to be functional. Coelophysis appears to be a transition between the redundant fingers of earlier dinosaurs such as the five-fingered Staurikosaurus, and later theropods which had only two or three. The three-toed feet were around four inches long, and left impressions similar in shape to those of modern birds, and indeed some preserved tracks had formerly been thought to belong to Archaeopteryx, which is almost by definition the "first bird".
Behavior
There is evidence that it ate its own young, since some bones from small Coelophysis are often found inside the body cavities of larger specimens. On the other hand, it is possible that Coelophysis gave birth to live young and these Coelophysis were being carried by mothers when both were killed. Indeed, no Coelophysis eggs have been found, though this is inconclusive because eggs are rarely preserved in the fossil record. Also, the bones recovered seem to belong to Coelophysis that are too large to have been pre-natal.
Coelophysis was also probably not above scavenging. The teeth were larger in the upper jaw and curved backwards, and the muscle arrangement in the jaw was such that the upper and lower jaws could grind against one another, similar to an electric carving knife.
The distribution of fossils suggests that it probably moved and hunted in packs, typical of later small theropods. Coelophysis would in fact have been a fast mover, being light, long-legged and with a stride length of around 75 cm, and could have moved through the upland forests and open plains of Triassic North America with ease.
Two different forms of Coelophysis have been found, a more graceful form and those of a slightly more robust build. Originally, these were thought to be different species within the genus Coelophysis, but opinion among paleontologists is now that these were female and male variants (see: sexual dimorphism) — in fact, many other dinosaurs formerly considered distinct species are now being reclassified in this fashion.
Classification
Coelophysis is a genus in the Coelophysidae (or "Podokesauridae") family, but the exact classification is open to some debate. Although it was certainly a theropod, it may have been a ceratosaur or a theropod basal to the ceratosaur-tetanuran division. Opinion among paleontologists is currently divided and no conclusion will be reached until a more accurate reconstruction can be made.
To further the confusion, the type species of Coelophysis has come under some debate. The original C. bauri may not have been the same species as those at Ghost Ranch , since the original skeletons were fragmentary to say the least. Therefore those at Ghost Ranch were given a new name, Rioarribausaurus . However, this made the confusion still worse since the Ghost Ranch material was still known as but this is now known as Coelophysis in much literature. In the end, the International Commission on Zoological Nomenclature (ICZN) voted to make one of the Ghost Ranch samples the actual type specimen for Coelophysis, and dispose of the name Rioarribasaurus altogether, thus hopefully resolving the confusion. The original Coelophysis specimen is now put in its own genus Eucoelophysis ("true Coelophysis") until it can be confidentally assigned to Coelophysis.
In a situation affecting many dinosaur genera, many specimens were originally classified as new species but were in fact species of Coelophysis. For example, Talbot originally named C. holyokensis in 1911, but this is now known as Podokesaurus holyokensis. C. posthumus, named by Friedrich von Huene in 1908, also needs reclassification and is tentatively titled Halticosaurus longotarsus at the moment. On the other hand, Edward Drinker Cope named Coelurus longicollis in 1887, two years before Coelophysis, but it is in fact a species of the latter and has now been renamed C. longicollis. Likewise, Tanystropheus willistoni is now C. willistoni.
History of discovery
Cope first named Coelophysis in 1889 during his competition to name species with Othniel Charles Marsh, known as the Bone Wars. An amateur fossil collector, David Baldwin, had found the first remains of the dinosaur in 1881. The type species, C. bauri was named for Baur, one of Cope's many fossil collectors who supplied him. However, these first finds were small and there was certainly no complete picture of this new dinosaur.
In 1947, a whole graveyard of Coelophysis fossils were found in New Mexico, at the Ghost Ranch, close to the original find. These were originally given the name Rioarribasaurus, but are now known as Coelophysis. So many fossils together were probably the result of a flash flood, which swept away the whole herd and buried it at once. In fact, it seems such flooding was commonplace during this period of the Earth's history, and indeed the Petrified Forest of nearby Arizona is caused by a preserved log jam of tree trunks caught in one such 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.
Since then, 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 has been discovered date from the late Carnian to the early Neroin faunal stages.
Trivia
Coelophysis was the second dinosaur in space. Although Maiasaura had been taken into space three years earlier, a Coelophysis skull from the Carnegie Museum of Natural History was aboard the Space Shuttle Endeavour mission STS-89 when it left the atmosphere on January 22, 1998. It was also taken onto the space station Mir before being returned to Earth.
Coelophysis is also the state fossil of New Mexico, the United States.
