[12] David Baldwin, an amateur fossil collector working for Cope, had found the first remains of the dinosaur in 1881 in the Chinle Formation in northwestern New Mexico.

In 1947, a substantial "graveyard" of Coelophysis fossils was found by George Whitaker, the assistant of Edwin H. Colbert, in New Mexico, at Ghost Ranch, close to the original find.

American Museum of Natural History paleontologist Edwin H. Colbert conducted a comprehensive study[16] of all the fossils found up to that date and assigned them to Coelophysis.

[17] In the early 1990s, there was debate over the diagnostic characteristics of the first specimens collected, compared to the material excavated at the Ghost Ranch Coelophysis quarry.

[21][22] The specimen consists of sandstone casts of a pubis, tibia, three ribs, and a possible vertebra that probably originated in a quarry in Middletown, Connecticut.

[23] Sullivan & Lucas (1999) referred one specimen from Cope's original material of Coelophysis (AMNH 2706) to what they thought was a newly discovered theropod, Eucoelophysis.

[24] However, subsequent studies have shown that Eucoelophysis was misidentified and is actually a silesaurid, a type of non-dinosaurian ornithodiran closely related to Silesaurus.

Mortimer (2012) pointed out that "Paleontologists might have reacted more positively if the replacement name (Megapnosaurus) hadn't been facetious, translating to "big dead lizard".

[44] Coelophysis had a long and narrow head (approximately 270 mm (0.9 ft)), with large, forward-facing eyes that afforded it stereoscopic vision and, as a result, excellent depth perception.

Low, laterally raised bony ridges were present on the dorsolateral margin of the nasal and lacrimal bones in the skull, directly above the antorbital fenestra.

[37] Tawa hallae Chindesaurus Eodromaeus Liliensternus Dracoraptor "Syntarsus" kayentakatae Panguraptor Powellvenator Procompsognathus Coelophysis Lepidus Camposaurus Lucianovenator Megapnosaurus Segisaurus Zupaysaurus Gojirasaurus Cryolophosaurus Dilophosaurus Sarcosaurus Tachiraptor Averostra Coelophysis is a distinct taxonomic unit (genus), composed of the single species C. bauri.

In recent phylogenetic analyses, "Syntarsus" kayentakatae has been shown to be distantly related to Coelophysis and Megapnosaurus, suggesting that it belongs to its own genus.

[48][29][51] The teeth of Coelophysis were typical of predatory dinosaurs, as they were blade-like, recurved, sharp, jagged, and finely serrated on both the anterior and posterior edges.

[54] Gay's position was lent support in a 2006 study by Nesbitt et al.[55] In 2009, new evidence of cannibalism came to light when additional preparation of previously excavated matrix revealed regurgitate material in and around the mouth of Coelophysis specimen NMMNH P-44551.

This material included tooth and jaw bone fragments that Rinehart et al. considered "morphologically identical" to a juvenile Coelophysis.

[56] The discovery of over 1,000 specimens of Coelophysis at the Whitaker quarry at Ghost Ranch has suggested gregarious behavior to researchers like Schwartz and Gillette.

[26][58][59] Rinehart (2009) assessed the ontogenic growth of this genus using data gathered from the length of its upper leg bone (femur) and concluded that Coelophysis juveniles grew rapidly, especially during the first year of life.

[63] However, more recent research has found that C. bauri and C. rhodesiensis had highly variable growth between individuals, with some specimens being larger in their immature phase than smaller adults were when completely mature.

[64] Through the compilation and analysis of a database of nearly three dozen reptiles (including birds) and comparison with existing data about the anatomy of Coelophysis, Rinehart et al. (2009) drew the following conclusions.

The evidence suggested that some parental care was necessary to nurture the relatively small hatchlings during the first year of life, where they would reach 1.5 meters in length by the end of their first growth stage.

[40][65] In a 2001 study conducted by Bruce Rothschild and other paleontologists, 14-foot bones referred to Coelophysis were examined for signs of stress fracture, but none were found.

[70] Specimens of Coelophysis have been recovered from the Chinle Formation of New Mexico and Arizona, more famously at the Ghost Ranch (Whitaker) quarry in the Rock Point member[40] among other quarries in the underlying Petrified Forest member, the sediments of which have been dated to approximately 212 million years ago, making them part of the middle Norian stage of the Late Triassic,[71][15] but Thomas Holtz Jr. interpreted that it was during the Rhaetian stage from approximately 204 to 201.6 million years ago.

Ghost Ranch was located close to the equator over 200 million years ago, and had a warm, monsoon-like climate with heavy seasonal precipitation.

Hayden Quarry, a new excavation site at Ghost Ranch, New Mexico, has yielded a diverse collection of fossil material that included the first evidence of dinosaurs and less-advanced dinosauromorphs from the same time period.

[73] Therrien and Fastovsky (2001) examined the paleoenvironment of Coelophysis and other early theropods from Petrified Forest National Park in Arizona and determined that this genus lived in an environment that consisted of floodplains marked by distinct dry and wet seasons.

So far, only Chindesaurus and Daemonosaurus[75] are known, the terrestrial fauna being dominated instead by other reptiles like the rhynchocephalian Whitakersaurus,[76] the pseudosuchian Revueltosaurus, the aetosaurs Desmatosuchus, Typothorax and Heliocanthus, the crocodilomorph Hesperosuchus, the "rauisuchians" Shuvosaurus,[77] Effigia,[78] and Vivaron,[79] along with other rare components like the dinosauriform Eucoelophysis[80] and the amniote Kraterokheirodon.

[77] The multitude of specimens deposited so closely together at Ghost Ranch was probably the result of a flash flood that swept away a large number of Coelophysis and buried them quickly and simultaneously.

[82] In 2009, Rinehart et al. noted that in one case the Coelophysis specimens were "washed into a topographic low containing a small pond, where they probably drowned and were buried by a sheet flood event from a nearby river.

"[40] The 30 specimens of C. rhodesiensis found together in Zimbabwe was also probably the result of a flash flood that swept away a large number of Coelophysis and buried them quickly and simultaneously as well.

[83] 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 22 January 1998.