During his competition to name species with Othniel Charles Marsh, Edward Drinker Cope first named Coelophysis ("Hollow form") in 1889. 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 only - a valuable commodity in such competitive times in paleontology! 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 "Ghost Ranch", close to the original find. These were originally given the name Rioarribasaurus, but are now known as Coelophysis proper (see Classification). So many fossils together were probably the result of a flash flood, which swept away the whole herd and burried 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, from both adults and juveniles.
Coelophysis is one of the earliest known dinosaurs, having evolved in the Late Triassic period, around 210 million years ago, from around the late Carnian to early Neroin times. It had a spindly, delicate build and would have been "only" about three metres long. However, its long stiff tail and S-shaped neck accounted for most of this length so it probably weighed no more than 30kg. Coelophysis was also among the earliest dinosaurs to have bone hollows to save weight, like the later sauropods. Despite looking hardly dissimilar to the ancestors of the dinosaur, 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 minimised skull is a feature seen in all later dinosaurs. Coelophysis had many serated teeth, for eating any number of small animals. There is evidence that it ate its own young, since some bones from small Coelophyses are often found inside the body cavities of larger specimens. On the other hand, it could be that Coelophysis gave birth to live young and these Coelophyses were being carried by mothers when both were killed. Indeed, no Coelophysis eggs have been found, although such objects were fragile at the best of times. Also, the bones recovered seem to belong to Coelophyses 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 - like 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 75cm, and could have moved through the upland forests and open plains of Triassic North America with ease.
Each hand had four fingers, but one was too small to be functional. It seems Coelophysis was 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 ancient birds.
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 varients - in fact, many other dinosaurs formerly considered distinct species are now being reclassified in this fashion.
Incidentally, Coelophysis was the second dinosaur in space. Although Maiasaura had been taken into space three years earlier, a skull of Coelophysis from the Carnegie Museum of Natural History was aboard the space shuttle Endeavour when it left the atmosphere on 22nd January, 1998. It was also taken onto the Space Station Mir before being returned to Earth.
The exact classification
is open to some debate. Although it was certainly a theropod, it may have been a coelurosaur
or a ceratosaur
. 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 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 we can be sure that it belongs in 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 (perhaps they should have changed the species name at the same time, it sounds like it was named after a soap). C. posthumus, named by von Huene in 1908, also needs reclassification and is tentatively titled Halticosaurus longotarsus at the moment. On the other hand, Cope named Coelurus 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 is now C. willistoni.