View source for Coelophysis

{{short description|Genus of theropod dinosaurs from the late Triassic}}
{{Use dmy dates|date=March 2025}}
{{Automatic taxobox
| fossil_range = [[Late Triassic]] (middle [[Norian]] to [[Rhaetian]]), {{fossil range|215|201.4}}
| image = Coelophysis bauri mount.jpg
| image_caption = Mounted skeleton at the [[Cleveland Museum of Natural History]]
| taxon = Coelophysis
| authority = [[Edward Drinker Cope|Cope]], [[1889 in paleontology|1889]]<ref name="cope1889"/>
| type_species = {{extinct}}'''''Coelophysis bauri'''''
| type_species_authority = (Cope, [[1887 in paleontology|1887a]])<ref name="cope1887"/>
| synonyms =
{{collapsible list|bullets = true|title=<small>Genus synonymy</small>
|''Longosaurus'' {{small|[[Samuel P. Welles|Welles]], [[1984 in paleontology|1984]]}}<ref name="welles1984"/>
|''Rioarribasaurus'' {{small|Hunt & [[Spencer G. Lucas|Lucas]], [[1991 in paleontology|1991]]}}<ref name="hunt1991"/>
}}
{{collapsible list|bullets = true|title=<small>Synonyms of ''C. bauri''</small>
|''[[Coelurus]] bauri'' {{small|Cope, 1887a}}
|''[[Tanystrophaeus]] bauri'' <br/>{{small|(Cope, 1887a) Cope, 1887b}}<ref name="cope1887b"/>
|''Rioarribasaurus colberti'' <br/>{{small|Hunt & Lucas, 1991}}
|''Syntarsus colberti'' <br/>{{small|(Hunt & Lucas, 1991) [[Gregory S. Paul|Paul]], [[1993 in paleontology|1993]]}}<ref name="paul1993"/>
}}
{{collapsible list|bullets = true|title=<small>Dubious species designations</small>
|''Coelurus longicollis'' {{small|Cope, 1887a}}
|''Tanystrophaeus longicollis'' <br/>{{small|(Cope, 1887a) Cope, 1887b}}
|''Coelophysis longicollis'' <br/>{{small|(Cope, 1887a) Cope, 1889}}
|''Longosaurus longicollis'' {{small|Welles, 1984}}
|''Tanystrophaeus willistoni'' {{small|Cope, 1887b}}
|''Coelophysis willistoni'' <br/>{{small|(Cope, 1887b) Cope, 1889}}
}}
}}

'''''Coelophysis''''' ({{IPAc-en|s|ɛ|ˈ|l|ɒ|f|ɪ|s|ɪ|s}} {{respell|se|LOF|iss|iss}} [[Traditional English pronunciation of Latin|traditionally]]; {{IPAc-en|ˌ|s|ɛ|l|oʊ|ˈ|f|aɪ|s|ᵻ|s}} {{respell|SEL|oh|FY|siss}} or {{IPAc-en|ˌ|s|iː|l|oʊ|ˈ|f|aɪ|s|ᵻ|s}} {{respell|SEE|loh|FY|siss}}{{efn|Paleontologist Benjamin Creisler, author of pronuciation guides for dinosaurs, argued for this pronunciation in the late 1990s.<ref>{{cite web |title=RE: Afrovenator pronunciation |url=http://dml.cmnh.org/1999Nov/msg00569.html |website=dml.cmnh.org |access-date=26 May 2019 |archive-date=24 February 2012 |archive-url=https://web.archive.org/web/20120224011455/http://dml.cmnh.org/1999Nov/msg00569.html }}</ref>}}) is an extinct [[genus]] of [[coelophysid]] [[Theropoda|theropod]] dinosaurs that lived [[Approximation|approximately]] 215 to 201.4 [[million years ago]] during the late [[Triassic]] [[Period (geology)|period]] from the middle [[Norian]] to [[Rhaetian]] age in what is now the southwestern United States. ''[[Megapnosaurus]]'' was once considered to be a species within this genus, but this interpretation has been challenged and the genus ''Megapnosaurus'' is now considered valid.

''Coelophysis'' was a small, slenderly built, ground-dwelling, [[bipedal]] [[carnivore]] that could grow up to {{Convert|3|m|ft|1|abbr=on}} long. It is one of the earliest known dinosaur genera. Scattered material representing similar animals has been found worldwide in some [[Late Triassic]] and [[Early Jurassic]] formations.

The [[type species]] '''''C. bauri''''', originally given to the genus ''[[Coelurus]]'' by [[Edward Drinker Cope]] in 1887, was described by the latter in 1889. The names ''Longosaurus'' and ''Rioarribasaurus'' are synonymous with ''Coelophysis''. ''Coelophysis'' is one of the most specimen-rich dinosaur genera.

== History of discovery ==
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|image1=Euskelosaurus Coelophysis Huene.png |alt1=
|image2=Coelophysis hindlimb Huene.png |alt2=
|image3=Coelophysis Hortalotarsus Huene.png |alt3=
|footer=Original materials of the ''Coelophysis'' species (excluding ''[[Euskelosaurus]]'' femur in top left and ''[[Hortalotarsus]]'' limb bones bottom right)
}}
In April of [[1887 in paleontology|1887]] American paleontologist [[Edward Drinker Cope]] first described vertebrate remains from the [[Triassic]] of [[New Mexico]] as new species of the genus ''[[Coelurus]]'', including nearly all parts of the skeleton except the [[skull]] and [[teeth]]. While ''Coelurus'' had been considered by its describer [[Othniel Charles Marsh]] as an uncertain type of reptile, the new material described by Cope demonstrated that it was a [[dinosaur]], and likely closely related to ''Megadactylus'' (now ''[[Anchisaurus]]'') from the Triassic of [[Massachusetts]]. Cope chose to name two new species from his collection of New Mexican material, the first being ''Coelurus longicollis'' for multiple {{dinogloss|vertebrae}} and a {{dinogloss|femur}},{{efn|[[American Museum of Natural History|AMNH]] 2701 ({{dinogloss|cervical vertebra}}), 2715 ({{dinogloss|dorsal vertebra}}, 2702 ({{dinogloss|caudal vertebra}}), and 2704 (femur)<ref name="padian1986"/>}} while the second was ''Coelurus bauri'', named after German paleontologist [[Georg Baur]], included the same regions of the skeleton.{{efn|AMNH 2717 (cervical vertebra), 2722 ({{dinogloss|sacrum}}), and 2725 (partial femur)<ref name="padian1986"/>}}<ref name="cope1887"/> Following this description, Cope reclassified his New Mexican material in July 1887 from ''Coelurus'' to the German taxon ''[[Tanystrophaeus]]'' based on the similarities of the vertebrae, creating the [[new combination]]s ''Tanystrophaeus longicollis'' and ''Tanysteophaeus bauri''. Cope described additional material of both ''T. longicollis''{{efn|AMNH 2735 (caudal), 2708 ({{dinogloss|ilium}}), 2705 (ilium), 2706 ({{dinogloss|pubis}}), 2716 ({{dinogloss|ischium}}), 2707 ({{dinogloss|phalanx}}), and 2703 ({{dinogloss|ungual}})<ref name="padian1986"/>}} and ''T. bauri''{{efn|AMNH 2720 (cervical), 2723 (dorsal), 2724 (partial pubis), 2719 (partial ischium), 2718 (partial ischium), and 2721 ({{dinogloss|tibia}})<ref name="padian1986"/>}} to cover more of the anatomy of both species, and he also named the new species ''Tanystrophaeus willistoni'' for a partial [[pelvis]] even smaller than both other species, named after American paleontologist [[Samuel Wendell Williston]].{{efn|AMNH 2726 (ilium), and 2727 (dorsal)<ref name="padian1986"/>}}<ref name="cope1887b"/> Following this, Cope came to the realization that the vertebrae of ''Tanystrophaeus'' he considered similar to the New Mexican species were not definitively caudal vertebrae, and as a result the species were in need of a new [[genus name]]. As a result, in [[1889 in paleontology|1889]] Cope named ''Coelophysis'' for ''C. longicollis'', ''C. bauri'', and ''C. willistoni'', with the name as a combination of the [[Ancient Greek]] words κοῖλος (''koilos''), "hollow", and φύσεις (''fysis''), "form".<ref name="cope1889"/><ref name="lucas2016"/>

The original material of ''Coelophysis'' described by Cope was all collected by David Baldwin in 1881 from three localities of [[Rio Arriba County, New Mexico]], with the only surviving collection information being labels written by Baldwin associated with the specimens, indicating a provenance of {{cvt|400|ft|m}} below a [[gypsum]] layer at "Arroyo Seco" and "Gallina Canyon". The layer of gypsum identified by Baldwin is now known as part of the [[Middle Jurassic]] [[Todilto Formation]] that overlies the [[Chinle Formation]] within the region of [[Ghost Ranch]] that "Arroyo Seco" (Arroyo Canjilon or Canjilon Creek) flows past, so while no other information on the area Baldwin collected can be known for certain, he must have collected from within a {{cvt|3|mi|km}} region around Ghost Ranch where the river cuts through the Chinle Formation below the Todilto gypsum layer.<ref name="colbert1989"/><ref name="sullivan1996"/> Williston and [[Ermine Cowles Case]] believed they located the area of Baldwin's collecting in a 1912 visit to the region where they located fragments they assigned to ''Coelophysis'' on the surface.<ref name="williston1912"/>
{{multiple image
|perrow=2
|align=right
|total_width=300
|image1=Coelophysis longicollis vertebrae Huene.png|alt1=
|image2=Coelophysis longicollis appendicular Huene.png|alt2=
|image3=Coelophysis bauri Huene.png|alt3=
|image4=Coelophysis bauri willistoni Huene.png|alt4=
|footer=Illustrations of ''C. longicollis'' (top), ''C. bauri'' (bottom), and ''C. willistoni'' (bottom right) fossils by Huene
}}
German paleontologist [[Friedrich von Huene]] revisited the material and taxonomy of ''Coelophysis'' in a 1906 [[review article|review]] of Triassic dinosaurs, following the species identifications of Cope and illustrating the material for the first time, with the additional description of elements of the hand of ''C. longicollis'' and vertebrae of ''C. bauri'' that Cope had not described.{{efn|AMNH 2730 ({{dinogloss|metacarpal}} III of ''C. longicollis''), and 2744 (dorsal of ''C. bauri'')<ref name="padian1986"/>}} Huene did not see justification in considering ''Coelophysis'' a close relative of ''[[Anchisaurus]]'' (a replacement name for ''Megadactylus''), instead classifying the genus within [[Coeluridae]].<ref name="huene1906"/> In a further 1915 review limited to the New Mexican collection of Cope, Huene separated the specimens into the three species differently from previously, assigning bones based on size with ''C. longicollis'' as the largest species and ''C. willistoni'' as the smallest and suggesting that more than three species may be present.<ref name="huene1915"/> No [[type species]] for ''Coelophysis'' was designated by Huene, nor were specimen numbers identified, complicating the assignment of material to the species. In 1986 American paleontologist [[Kevin Padian]] revisited the type material of ''Coelophysis'' and identified which material was referred to which species by Cope and Huene in their studies, and identified some material in the Cope collection that had yet to be described.{{efn|AMNH 2732, 2742-43, 2746-2748, and 2753, all fragments<ref name="padian1986"/>}}<ref name="padian1986"/>

===Ghost Ranch discoveries===
During the summer of 1946, American paleontologist [[Edwin H. Colbert]] began searching for Triassic fossils in the [[Petrified Forest National Park]] of northern [[Arizona]], under the employment of the [[American Museum of Natural History]]. This exploration continued the following year, where Colbert planned to stop at Ghost Ranch on the way to Petrified Forest, where many skulls of [[phytosaurs]] had been found. Colbert, along with George Simpson, Bill Fish, George Whitaker, and Tom Ierardi, were the field crew for the 1947 season, with Simpson and Fish focusing on [[Eocene]] mammals of northern New Mexico while Colbert, Whitaker, and Ierardi would continue to northern Arizona for Triassic reptiles. On 21 June, Colbert, Whitaker and Ierardi began exploring the sediments of the Chinle Formation in the area near Ghost Ranch, uncovering a complete phytosaur skull, and on 22 June Whitaker discovered some fragments including a claw that Colbert identified as ''Coelophysis'', from a [[talus slope]] above an intermittent [[stream]]. Upon excavating bones on the surface and removing some of the talus, a fossil layer was found containing numerous ''Coelophysis'' bones. After several more days of excavations, it was understood that the fossil layer contained hundreds of skeletons of ''Coelophysis'' in a single concentration, and upon the return of Simpson and Fish to the locality the former stated that "this was the greatest find ever made in the Triassic of North America".<ref name="colbert1995a"/>

[[File:Ghost Ranch Coelophysis Quarry.jpg|left|thumb|The famed ''Coelophysis'' quarry of [[Ghost Ranch]], as it appeared in 2019]]

Excavations of the Ghost Ranch ''Coelophysis'' quarry were continued throughout 1947 and 1948 by the crew of the AMNH, which also included Carl Sorensen after arrival from [[New York City]], assisted by the landowners [[Arthur Newton Pack|Arthur and Phoebe Pack]] and farm hand Herman Hall. Seven large blocks were excavated, each containing numerous skeletons, numbered I to VI for identification of location when transported back to the AMNH. Around 105 smaller blocks were also collected, created by the channels excavated to separate the larger blocks. A further 6 blocks, VII to XIII, were excavated as the quarry expanded to several meters in diameter, with the blocks being distributed amongst the AMNH, [[Museum of Northern Arizona]], [[New Mexico Museum of Natural History]], and [[Yale Peabody Museum]].<ref name="colbert1995c"/> All of the excavations at Ghost Ranch took place within the upper [[sandstone]] level of the Chinle Formation, believed to be [[Norian]] in age at the time and making the expanse of ''Coelophysis'' one of the longest deposits within the Chinle despite being one of the earliest known dinosaurs. Colbert believed that the original material of ''Coelophysis'' may have been collected from the surface in a similar method to Whitaker's discovery, as part of the same fossil layer that was excavated by the AMNH.<ref name="colbert1989"/><ref name="colbert1995b"/>

Upon completion of the AMNH excavations at Ghost Ranch at the end of 1948 the quarry was abandoned, with the hillside above slumping down to cover the dig site, and the land itself gifted to the [[Presbyterian Church (USA)|Presbyterian Church]]. After 32 years in this state, American paleontologist David Berman of the [[Carnegie Museum of Natural History]] approached Reverend Jim Hall of Ghost Ranch to propose reopening of the dinosaur quarry with the intention of collecting a specimen for display in the museum. Hall agreed to reopen the quarry on the condition that Colbert and the recently opened [[New Mexico Museum of Natural History]] would both participate, with the MNA, YPM and [[University of Toronto]] additionally contributing to the efforts. The quarry was worked from 1981 to 1982, with 16 large blocks of {{cvt|6|to|10|short ton|tonnes}} excavated, and all but one block being removed. The last block remained at the site until 1985 when it was moved by American paleontologist [[David Gillette]] to the new Ruth Hall Museum of Paleontology at Ghost Ranch. Blocks from both collections were distributed by the primary institutions through trades and sale to be distributed across all of North America, and eventually even other continents.<ref name="colbert1995c"/>

[[File:Coelophysis bauri.jpg|thumb|right|Two Ghost Ranch specimens preserved together, AMNH 7223 and 7224]]

A [[monograph]] on ''Coelophysis'' was then published by Colbert in 1989, focusing primarily on the material collected by him at the AMNH but supplemented by material in various other institutions. Under the belief that the material of Baldwin was found near at the same locality as the dinosaur quarry, Colbert diagnosed ''Coelophysis'' using the anatomy of the complete skeletons he had excavated, and considered ''C. bauri'' the [[senior synonym]] of ''C. longicollis'' and ''C. willistoni'', with the partial sacrum AMNH 2722 as the [[lectotype]] of the species.<ref name="colbert1989"/> ''C. longicollis'' had been believed by American paleontologist [[Samuel P. Welles]] to be a different genus than ''Coelophysis'', which he had named ''Longosaurus'' in 1984 after American paleontologist Robert A. Long.<ref name="welles1984"/> All of the Ghost Ranch material was thus described as part of a single species known from hundreds of individuals of various ages and sizes, with some additional variation in proportions of individuals at the same size that gave the suggestion of a "robust" and "gracile" morph.<ref name="colbert1989"/> While Colbert considered ''Coelophysis'' to be diagnostic, this opinion was not shared in other reviews of early theropods, where Padian instead considered it a "metataxon" or otherwise lacking unique characteristics of its own and having anatomy primitive to [[Theropoda]]. Padian believed that as ''Coelophysis'' was founded in scrappy and incomplete material, it is difficult to justify the referrals of additional material to the taxon. He still considered ''Coelophysis'' a useful taxonomic entity, being characterized by the lack of more derived traits common to other theropods, and as a result a partial skeleton from Petrified Forest, and the theropods ''[[Avipes]]'', ''Podokesaurus'', ''Procompsognathus'', and ''[[Trialestes]]'' could be considered referrable to ''Coelophysis''.<ref name="padian1986"/>

[[File:Hayden Quarry.png|thumb|left|Stratigraphic section around Ghost Ranch showing the level of the ''Coelophysis'' Quarry (CoQ) relative to other localities]]

American paleontologists [[Adrian P. Hunt]] and [[Spencer G. Lucas]] went further than Padian, declaring ''Coelophysis'' a ''[[nomen dubium]]'' as its type material could not be distinguished from other theropods. As a result, they determined that a new taxon was required for the very complete specimens from Ghost Ranch (what they referred to as the Whitaker Quarry), for which they named ''Rioarribasaurus colberti''. The genus name referred to the Rio Arriba County where the fossils were discovered, while the species name was in honor of Colbert for his work excavating and describing the material. Hunt and Lucas also designated a lectotype for ''C. longicollis'' as the specimen chosen by Welles as its type was invalid, identifying that the cervical AMNH 2701 should be used to identify the species. A lectotype was also designated for ''C. willistoni'', the partial ilium AMNH 2726. None of the material of the three species was believed by Hunt and Lucas to bear any unique characteristics that could support their synonymy to ''C. bauri'' or any other theropod. The complete skeleton AMNH 7224, mounted on display at the museum, was selected as the [[holotype]] of ''Rioarribasaurus'', and all the Ghost Ranch specimens collected from 1947 to 1982 were referred to the taxon as they lacked differences beyond sexual or growth-related variation.<ref name="hunt1991"/>

In a following study in 1996, Hunt and Lucas as well as American paleontologists [[Robert M. Sullivan]] and Andrew Heckert established that the locality where Baldwin collected ''Coelophysis'' was not the same deposit or level as the dinosaur quarry as Colbert had believed. The color and [[concretions]] attached to the bones Baldwin collected differs from those of the specimens named ''Rioarribasaurus'', but was instead identical to material found at a separate cluster of sites along Arroyo Seco {{cvt|400|ft|m}} below the Todilto Formation. The Baldwin localities would therefore be from the region of Orphan Mesa {{cvt|3|km|mi|order=flip}} southeast of the dinosaur quarry, and from older deposits equivalent to the Canjilon Quarry and aetosaur quarry where ''[[Pseudopalatus]]'' and ''[[Typothorax]]'' are known. According to the stratigraphy of Sullivan, Lucas and colleagues, ''Coelophysis'' would therefore be from the [[Revueltian]]-age [[Petrified Forest Formation]], with ''Rioarribasaurus'' from the [[Apachean]]-age [[Rock Point Formation]]. Additional collected material{{efn|Partial skeletons, isolated bones, and fragments [[New Mexico Museum of Natural History|NMMNH]] P-22298, [[State Museum of Pennsylvania|SMP]] VP-453, 456, 462, 465, 469, 476, 478, 487, and 491<ref name="sullivan1996"/>}} from these relocated sites was used as justification for ''Coelophysis'' being a distinct taxon separated from ''Rioarribasaurus'', showing differences in the pubis, femur, and metatarsals.<ref name="sullivan1996"/> The stratigraphic divisions of Lucas for the Chinle are not supported by other paleontologists, who instead place the ''Coelophysis'' quarry within a "siltstone member" of the Chinle Formation with a [[Rhaetian]] age, with the Baldwin sites as part of the [[Petrified Forest Member]] radiometrically dated to 211.9±0.7 [[million years ago]] in the late [[Norian]].<ref name="irmis2011"/><ref name="marsh2020"/>

Since the numerous well-preserved Ghost Ranch specimens were used as ''Coelophysis'' in most of the scientific literature as well as public mentions, the introduction of ''Rioarribasaurus'' would have caused much confusion. As such, Colbert and other paleontologists petitioned to the [[International Commission on Zoological Nomenclature]] to replace the lectotype of ''Coelophysis bauri'' with AMNH 7224 as a [[neotype]], thereby making ''Coelophysis bauri'' and ''Rioarribasaurus colberti'' objective synonyms, giving ''Coelophysis'' a much better type specimen, and preserving the use of ''Coelophysis'' for the Ghost Ranch material as it had been since its discovery in 1947. They emphasised their belief that the Ghost Ranch quarry was from approximately the same level and place as the original collection, as well as that the lectotype sacrum of ''C. bauri'' belonged to the same taxon as AMNH 7224 as justification for the neotype.<ref name="colbert1992">{{cite journal|last1=Colbert|first1=E.H.|author-link1=Edwin H. Colbert|last2=Charig|first2=A.J.|author-link2=Alan Jack Charig|last3=Dodson|first3=P.|author-link3=Peter Dodson|last4=Gillette|first4=D.D.|author-link4=David Gillette|last5=Ostrom|first5=J.H.|author-link5=John Ostrom|last6=Weishampel|first6=D.B.|author-link6=David B. Weishampel|year=1992|title=''Coelurus bauri'' Cope, 1887 (currently ''Coelophysis bauri''; Reptilia, Saurischia): Proposed replacement of the lectotype by a neotype|journal=Bulletin of Zoological Nomenclature|volume=49|issue=4|pages=276–279}}</ref> The petition was met with opposing comments by Hunt, Lucas, and Sullivan, as well as Welles, George Olshevsky, and Philip Huber, on the grounds of stratigraphic and possibly anatomical differences between the original material and more complete specimens, and that the synonymy of ''Rioarribasaurus'' and ''Coelophysis'' should be established through anatomy rather than by ruling, while it was supported by paleontologists including [[Hans-Dieter Sues]], [[Thomas R. Holtz Jr.]], [[Farish Jenkins]], [[Ralph Molnar]], [[Elizabeth Nicholls]], [[Louis L. Jacobs]], who presented views of the common use of ''Coelophysis'', the potential that the stratigraphic and anatomical differences suggested were invalid, and the belief that a replacement of the type by a better specimen helps with the continued use of taxa over time even when originally diagnostic material is later shown to be inadequate.<ref name="tubbs1993"/><ref name="schwartz1993"/><ref name="gillette1993"/><ref name="welles1994"/><ref name="huber1994"/><ref name="lucas1994"/><ref name="sullivan1995"/> American [[paleoartist]] [[Gregory S. Paul]] also published in 1993 the opinion that ''Coelophysis'' was indeterminate, but that ''Rioarribasaurus'' and ''[[Syntarsus rhodesiensis|Syntarsus]]'' belonged to the same genus, creating the combination ''Syntarsus colberti''.<ref name="paul1993"/> In the end, the ICZN voted in 1996 to designate the complete specimen AMNH 7224 as the neotype of ''Coelophysis'' and disposed of the name ''Rioarribasaurus'', declaring the latter a ''nomen rejectum'', or "rejected name". The name ''Coelophysis'' became a ''nomen conservandum'' ("conserved name"), and thus the confusion and uncertainty surrounding the status of ''Coelophysis'' was resolved.<ref name="iczn1996"/>

===Formerly assigned material and taxa===
[[File:Replica of coelurosaur bone casts from Middletown, Connecticut.jpg|thumb|right|Bone impression BSNH 13656 referred to ''Coelophysis'' and then ''Podokesaurus'']]

In 1922 Case described the first supposed material of ''Coelophysis'' from outside New Mexico with the referral of a series of vertebrae he collected in 1921 from [[Dockum Formation]] of [[Crosby County, Texas]]. The specimen, [[University of Michigan Museum of Paleontology|UMMP]] No. 7507, was considered by Case as an indeterminate species of ''Coelophysis'', with similarities in the elongation to both ''Coelophysis'' and ''Anchisaurus''.<ref name="case1922"/> Huene did not agree with the referral by case, naming the new coelurosaur genus ''[[Spinosuchus]]'' for the material. The greatest difference from ''Coelophysis'' was in the elongate neural spines, but he also referred a partial braincase from the same region that shows differences from the only other comparable braincase, that of ''[[Thecodontosaurus]]''.<ref name="huene1932"/> Redescription of ''Spinosuchus'' in 2009 showed that it was separate from ''Coelophysis'' and not even a theropod, being a member of the early [[archosauriform]] group [[Trilophosauridae]].<ref name="spielmann2009"/>

Following the rediscovery of a specimen containing the bone impressions of an early dinosaur by Colbert and Donald Baird in 1958, ''Coelophysis'' was first compared to ''Podokesaurus'' as potentially synonymous. [[Boston Society of Natural History|BSNH]] No. 13656 was found in the in 1864 from possibly-Triassic sediments of [[Connecticut]], probably the [[Portland Formation]], and remained undescribed until the work of Colbert and Baird.<ref name="colbert1958"/> ''Podokesaurus'' had been named in 1911 by American paleontologist [[Mignon Talbot]] for a partial skeleton from the Portland Formation with the only species ''P. holyokensis'', the same deposits which bore the BSNH specimen.<ref name="talbot1911"/><ref name="colbert1958"/> Comparisons between the BSNH specimen, ''Podokesaurus'', and ''Coelophysis'' showed that they all differed minimally in the limb material in common, with Colbert and Baird assigning BSNH 13656 to an indeterminate ''Coelophysis'' species and suggesting that ''Podokesaurus'' may not be valid.<ref name="colbert1958"/> This was followed up by Colbert in 1964 where he proposed that ''Podokesaurus'' should be considered a [[junior synonym]] of ''Coelophysis'' and created the new combination ''C. holyokensis'', to which he also referred the BSNH specimen.<ref name="colbert1964"/> In his 1989 monograph, Colbert no longer followed this synonymy, finding that the shared similarities were widespread throughout podokesaurids;<ref name="colbert1989"/> though some later authors considered ''Podokesaurus'' a synonym, most now consider it as an indeterminate or potentially undiagnostic taxon.<ref name="bristowe2004"/><ref name="galton2025"/>

In 1983 another partial skeleton of a theropod was found from the Orphan Mesa region where it is possible Baldwin collected the original ''Coelophysis'' material, at a site named Cross Quarry after its discoverer Robert Cross. The specimen, [[New Mexico Museum of Natural History and Science|NMMNH]] P-22298 and known informally as the "Orphan Mesa theropod", was an incomplete skeleton of an immature theropod, preserving several {{dinogloss|vertebrae}}, the {{dinogloss|scapulacoracoid}}, parts of the {{dinogloss|pelvis}} and most of the hindlimb. Following the designation of AMNH 7224 as the neotype of ''Coelophysis bauri'', ''C. longicollis'', ''C. willistoni'', and the specimens named ''C. bauri'' by Cope lacked a genus and species, so the NMMNH P-22298 as well as material previously assigned to ''C. willistoni'' (AMNH 2706) were named ''[[Eucoelophysis]]'' by Sullivan and Lucas in 1999. When originally named, Sullivan and Lucas placed ''Eucoelophysis'' within [[Ceratosauria]] as a close relative of ''Coelophysis'', ''[[Syntarsus rhodesiensis]]'', and ''[[Syntarsus kayentakatae]]''.<ref name="sullivan1999"/> American paleontologists Andrew Heckert and colleagues in 2000 referred further theropod material to ''Eucoelophysis'' (as ''E.'' sp.) from the Snyder Quarry elsewhere in the [[Chinle Formation]], suggesting it may belong to a new species, which they reiterated in 2003.<ref name="heckert2000"/><ref name="heckert2003"/> These referrals and the identify of ''Eucoelophysis'' was reevaluated in 2006 by Argentine paleontologist [[Martín Ezcurra]] who identified that many of the features used by Sullivan and Lucas to support the identity of ''Eucoelophysis'' were instead shared amongst all early dinosaurs, with ''Eucoelophysis'' instead appearing more similar to the non-dinosaur ''[[Silesaurus]]''. Neither the Snyder Quarry specimens nor the material originally assigned to ''C. longicollis'' were found to share features with ''Eucoelophysis'' by Ezcurra, who identified them instead as indeterminate [[coelophysoids]].<ref name="ezcurra2006"/> An articulated skeleton ([[Royal Tyrrell Museum of Paleontology|TMP]] 1986.63.33) from the ''Coelophysis'' quarry previously considered a specimen of ''Coelophysis'' was moved to ''Eucoelophysis'' by American paleontologist Larry Rinehart and colleagues in 2009, but it was returned to ''Coelophysis'' in 2018 by American paleontologist Chris Griffin.<ref name="rinehart2009"/><ref name="griffin2018"/> The identification of ''Eucoelophysis'' as a [[silesaurid]], distant from ''Coelophysis'' and the Baldwin material, was upheld by independent work by American paleontologists [[Sterling Nesbitt]], Randall Irmis and William Parker in 2007.<ref name="nesbitt2007"/>

[[File:Snout and front teeth of Coelophysis and Syntarsus.jpg|thumb|right|Snout and front teeth of ''C. bauri'' and ''C.? kayentakatae'']]

While the [[Zimbabwe]]an genus ''[[Syntarsus rhodesiensis|Syntarsus]]'' was first described by South African paleontologist Michael A. Raath as a separate genus of podokesaurid, it was compared very favourably to ''Coelophysis'' by both Raath and Colbert, with differences in bone fusion and the pelvis separating the two taxa.<ref name="raath1969"/> The similarity between the two genera was extended upon by American paleontologist [[Gregory S. Paul]] in 1984, who considered ''Syntarsus'' a species of ''Coelophysis'', ''C. rhodesiensis'', as well as finding ''Halticosaurus'' to be a probable synonym.<ref name="paul1984"/> ''Syntarsus'' and ''Coelophysis'' were distinguished by Padian in 1986 despite his referral of many other Triassic theropods lacking unique features to ''Coelophysis'', but Paul maintained the synonymy of the two genera in 1988 and 1993, including assigning ''Rioarribasaurus colberti'' to ''Syntarsus'' as ''S. colberti'' under the belief that ''Coelophysis'' was undiagnostic but the Ghost Ranch specimens were not.<ref name="paul1993"/><ref name="padian1986"/><ref name="paul1988"/> American paleontologist Timothy B. Rowe kept ''Syntarsus'' and ''Coelophysis'' separate in his 1989 description of the new species ''[[Syntarsus kayentakatae]]'', but in 2000 American paleontologist Alex Downs reiterated the opinion of synonymy between ''Coelophysis'' and ''Syntarsus'', crediting the poor description of some features of ''Coelophysis'' by Colbert to previous misinterpretations.<ref name="rowe1989"/><ref name="downs2000"/> Downs also found that the theropod ''[[Camposaurus]]'' could not be distinguished from ''Coelophysis'', and considered it undiagnostic, but it was reidentified as a distinct coelophysid by Ezcurra and American paleontologist [[Stephen Brusatte]] in 2011.<ref name="downs2000"/><ref name="ezcurra2011"/>

Further complications with ''Syntarsus'' occurred when it was recognized that the genus name had been [[preoccupied]] by a [[Colydiinae|colydiine]] beetle named in 1869, which prompted American and Polish entomologists Michael Ivie, Adam Ślipiński, and Piotr Węgrzynowicz to provide the new replacement name ''[[Megapnosaurus]]'' for the theropod in 2001, with ''M. rhodesiensis'' becoming its type.<ref name="ivie2001"/> Many paleontologists did not like the naming of ''Megapnosaurus'', partially because taxonomists are generally expected to allow original authors of a name to correct any mistakes in their work. Raath was aware of the homonymy between the dinosaur ''Syntarsus'' and beetle ''Syntarsus'', but the group who published ''Megapnosaurus'' have claimed that they believed Raath was deceased and unable to correct his mistake, so they proceeded accordingly. American paleontologist Mickey Mortimer pointed out that "Paleontologists might have reacted more positively if the replacement name (''Megapnosaurus'') hadn't been facetious, translating to "big dead lizard".<ref name="mortimer2012"/> In 2024, it has been petitioned to the ICZN that ''Syntarsus'' be retained for the name of the theropod.<ref name="iczn2024"/> In the interim, Bristowe and Raath (2004) first proposed the synonymy of both species of ''Syntarsus'' with ''Coelophysis'', though they were uncertain whether ''S. kayentakatae'' belonged to this genus, referring it to as ?''C. kayentatakatae''.<ref name="bristowe2004"/> Multiple authors in the 2000s provisionally considered ''S. rhodesiensis'' to be a species of ''Coelophysis'', while ''S. kayentakatae'' has been identified as belonging to a separate genus and in need of a new name.<ref name="tykoski2004"/><ref name="yates2005"/><ref name="ezcurra2007"/><ref name="ezcurra2007b"/> [[Phylogenetic]] analyses of Coelophysidae have found that ''S. rhodesiensis'' is not the sister taxon to ''Coelophysis'', so the name ''Megapnosaurus'' has been used in those cases.<ref name="ezcurra2017"/><ref name="barta2018"/><ref name="spiekman2021"/>

== Description ==
[[File:Coelophysis size.jpg|thumb|right|Size of ''C. bauri'' compared to a human]]

''Coelophysis'' is known from a number of complete fossil skeletons of the species ''C. bauri''. This lightly built dinosaur measured up to {{convert|3|m|ft}} long<ref name="SchwartzGillette">{{cite journal| last = Schwartz| first = Hilde L.|author2=Gillette, David D.| title = Geology and taphonomy of the ''Coelophysis'' quarry, Upper Triassic Chinle Formation, Ghost Ranch, New Mexico| journal = Journal of Paleontology| volume = 68| issue = 5| pages = 1118–1130| year = 1994| doi = 10.1017/S0022336000026718| jstor = 1306181| bibcode = 1994JPal...68.1118S| s2cid = 130635216}}</ref> and was more than a meter tall at the hips. [[Gregory S. Paul]] (1988) estimated the weight of the gracile form at {{Convert|15|kg|lb|0|abbr=on}} and the weight of the robust form at {{Convert|20|kg|lb|0|abbr=on}},<ref name="paul88" /> but later presented a higher estimate of {{Convert|25|kg|lb|0|abbr=on}}.<ref>{{cite book|last=Paul|first=Gregory S.|year=2010|chapter=Theropods|title=The Princeton Field Guide to Dinosaurs|pages=67–162|publisher=Princeton: Princeton University Press|doi=10.1515/9781400836154.67b|isbn=978-1-4008-3615-4}}</ref> ''Coelophysis'' was a bipedal, carnivorous, theropod dinosaur and a fast, agile runner.<ref name="rinehart2009"/> Despite its basal position within [[Theropoda]], the [[bauplan]] of ''Coelophysis'' differed from those of other basal theropods, such as ''[[Herrerasaurus]]'', showing more derived traits common in theropods that superseded it. The torso of ''Coelophysis'' conforms to the basic theropod bauplan, but the [[pectoral girdle]] displays some special characteristics. ''C. bauri'' had a [[furcula]] (wishbone), the earliest known example in a dinosaur. ''Coelophysis'' also preserves the ancestral condition of possessing four digits on the hand (manus). It had only three functional digits, with the fourth being embedded in the flesh of the hand.<ref name="rinehart2007">{{cite journal|year=2007|title=Furculae in the Late Triassic theropod dinosaur ''Coelophysis bauri''|journal=Paläontologische Zeitschrift|volume=81|issue=2|pages=174–180|doi=10.1007/bf02988391|last1=Rinehart|first1=Larry F.|last2=Lucas|first2=Spencer G.|last3=Hunt|first3=Adrian P.|bibcode=2007PalZ...81..174R |s2cid=129076419}}</ref>

''Coelophysis'' had narrow hips, arms adapted for grasping prey, and narrow feet.<ref name="tykoski2004"/> Its neck and tail were long and slender.<ref name=RMG01>{{cite book |first=Richard M.|last=Gaines|title=Coelophysis|year=2001 |publisher= ABDO Publishing Company|page= 4|isbn= 978-1-57765-488-9}}</ref> The [[pelvis]] and hindlimbs of ''C. bauri'' are also slight variations on the theropod body plan. It has the open [[Acetabulum#Perforate Acetabulum|acetabulum]] and straight ankle hinge that define Dinosauria. The leg ended in a three-toed foot ([[pes (zoology)|pes]]) with a raised dewclaw ([[hallux]]). The tail had an unusual structure within its interlocking [[prezygapophysis]] of its vertebrae, which formed a semi-rigid lattice, apparently to stop the tail from moving up and down.<ref name="gay2001">{{cite journal|author=Gay, R.J.|year=2001|title=An unusual adaptation in the caudal vertebrae of ''Coelophysis bauri'' (Dinosauria: Theropoda)|journal=PaleoBios|volume=21|page=55}}</ref>

[[File:Coelophysis neotype skull.jpg|thumb|left|Skull of the ''C. bauri'' neotype]]

''Coelophysis'' had a long and narrow head (approximately {{Convert|270|mm|ft|1|abbr=on}}), with large, forward-facing eyes that afforded it [[stereoscopy|stereoscopic]] vision and, as a result, excellent depth perception. Rinehart et al. (2004) described the complete [[sclerotic ring]] found for a juvenile ''Coelophysis bauri'' (specimen NMMNH P-4200) and compared it to data on the [[sclerotic rings]] of reptiles (including birds), concluding that ''Coelophysis'' was a [[Diurnality|diurnal]], visually oriented predator.<ref name="rinehart2004">{{cite journal|author1=Rinehart, L.F. |author2=Heckert, A.B. |author3=Lucas, S.G. |author4=Hunt, A.P. |year=2004|title=The sclerotic ring of the Late Triassic theropod dinosaur ''Coelophysis''|journal=New Mexico Geological Society Spring Meeting|volume=26|page=64}}</ref> The study found that the vision of ''Coelophysis'' was superior to most lizards' vision and ranked with that of modern birds of prey. The eyes of ''Coelophysis'' appear to be the closest to those of eagles and hawks, with a high power of [[Accommodation (vertebrate eye)|accommodation]]. The data also suggested poor night vision, which would mean this dinosaur had a round pupil rather than a split pupil.<ref name="rinehart2009"/>

''Coelophysis'' had an elongated snout with large [[Fenestra (anatomy)|fenestrae]] that helped to reduce skull weight, while narrow struts of bones preserved the structural integrity of the skull. The neck had a pronounced [[wikt:sigmoid|sigmoid]] curve. The braincase is known in ''Coelophysis bauri'', but little data could be derived because the skull was crushed.<ref name="tykoski2004"/> Unlike some other theropods, the cranial ornamentation of ''Coelophysis'' was not located at the top of its skull. 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]].<ref name="colbert1989"/>

=== Distinguishing anatomical features ===

[[File:Coelophysis skeleton.jpg|thumb|right|Reconstructed skeleton]]

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also [[Autapomorphy|autapomorphies]]. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group.

According to Ezcurra (2007) and Bristowe and Raath (2004), ''Coelophysis'' can be distinguished based on the absence of an offset rostral process of the maxilla, the quadrate being strongly caudally, a small external mandibular fenestra (which is 9–10% of the mandibular length<ref name="ezcurra2007"/>), and the anteroposterior length of the ventral lacrimal process is greater than 30% of its height.<ref name="bristowe2004"/>

Several paleontologists consider ''Coelophysis bauri'' to be the same dinosaur as ''Megapnosaurus rhodesiensis'' (formerly ''Syntarsus''). However, this has been refuted by many paleontologists. Downs (2000) concluded that ''C. bauri'' differs from ''C. rhodesiensis'' in cervical length, proximal and distal leg proportions, and proximal caudal vertebral anatomy.<ref name="downs2000"/> Tykoski and Rowe (2004) concluded that ''C. bauri'' differs from ''M. rhodesiensis'' in that it lacks a pit at the base of the nasal process of the premaxilla.<ref name="tykoski2004" /> Bristowe and Raath (2004) concluded that ''C. bauri'' differs from ''M. rhodesiensis'' in having a longer maxillary tooth row.<ref name="bristowe2004" /> Barta et al. (2018) concluded that ''C. bauri'' differed from ''M. rhodesiensis'' in that it bears its 5th metacarpal.<ref name="barta2018" /> Griffin (2018) concluded that ''C. bauri'' differs from ''M. rhodesiensis'' in several differences in the musculature of the limbs.<ref name="griffin2018"/>

== Classification ==
[[File:Coelophysis sp skull Harvard.jpg|thumb|Skull of ''Coelophysis'' specimen MCZ 4327 from Ghost Ranch]]
When first described, Cope believed that ''Coelophysis'' was a member of the carnivorous dinosaur group [[Goniopoda]], as a relative of ''Anchisaurus'', ''Coelurus'' and at times ''Tanystropheus''.<ref name="cope1887"/><ref name="cope1887b"/><ref name="cope1889"/> Huene, in his 1906 reevaluation of Triassic dinosaurs, found that ''Coelophysis'' differed significantly from the families [[Plateosauridae]] and [[Thecodontosauridae]] (which included ''Anchisaurus''), and that ''Tanystropheus'' was an intermediate early reptile and not a dinosaur. Huene believed that ''Coelophysis'' represented the earliest, and first Triassic, member of the [[theropod]] family Coeluridae, as a relative of the [[Jurassic]] taxa ''Coelurus'', ''[[Compsognathus]]'', and ''[[Ornitholestes]]'' and also later [[Cretaceous]] members.<ref name="huene1906"/> Huene maintained a similar classification later in 1914 and then 1915, but had changed his opinion on the status of Dinosauria following the suggestion of British paleontologist [[Harry Govier Seeley]] that was not a natural group, with [[Saurischia]] and [[Ornithischia]] replacing it. From this, Huene created the new subgroups of Saurischia, [[Pachypodosauria]] for large carnivores and [[sauropod]]s, and [[Coelurosauria]] for slender carnivores. Triassic coelurosaurs were separated into two families, the [[Hallopoda]] and the [[Podokesauridae]], the latter of which included the Triassic genera ''Coelophysis'', ''[[Halticosaurus]]'', ''[[Podokesaurus]]'', ''[[Procompsognathus]]'', ''[[Saltopus]]'' and ''[[Tanystropheus]]''. From podokesaurids, ''Podokesaurus'' was believed to give rise to the Jurassic and Cretaceous [[Compsognathidae]] while ''Coelophysis'' was believed to give rise to Jurassic-only Coeluridae.<ref name="huene1914"/><ref name="huene1915"/>

The placement of ''Coelophysis'' as a coelurosaur continued to be followed by Huene and Hungarian paleontologist [[Franz Nopcsa]], though its classification amongst coelurosaurs was variable.<ref name="huene1921"/><ref name="nopcsa1928"/><ref name="huene1932"/><ref name="huene1956"/> In 1921 Huene moved ''Coelophysis'' into the Coeluridae from the Podokesauridae alongside ''Halticosaurus'', while he would retain it within Podokesauridae later in 1932 and 1956.<ref name="huene1921"/><ref name="huene1932"/><ref name="huene1956"/> Other podokesaurids were also reclassified during this time into the families [[Procompsognathidae]] or [[Halticosauridae]] of Huene, or the subfamilies [[Coelophysinae]] and [[Podokesaurinae]] named by Nopcsa, with ''Coelophysis'' by 1956 only considered a close relative of ''Podokesaurus'', ''Saltopus'', ''[[Lukousaurus]]'' and ''[[Spinosuchus]]''.<ref name="nopcsa1928"/><ref name="huene1956"/> A taxonomic scheme based on the work of Huene was followed by American paleontologists including [[Alfred Sherwood Romer]] and Colbert with modifications. Romer found in 1956 that Podokesauridae included ''Coelophysis'' and almost all Triassic coelurosaurs, and Colbert in 1964 believed that ''Coelophysis'' was the best-known podokesaurid, both differing from Huene by treating Coelurosauria as an early branch of Theropoda and not recognizing Pachypodosauria.<ref name="romer1956"/><ref name="colbert1964"/>

The family [[Coelophysidae]] was first recognized by American paleontologist [[Samuel P. Welles]] in 1984 who described ''[[Dilophosaurus]]'' and reviewed early theropods. Welles advocated for abandoning Coelurosauria as a [[paraphyletic]] group that gave rise to later theropods, and instead recognized many families of Triassic and Jurassic theropods of uncertain interrelationships. ''Coelophysis bauri'' was placed along with ''[[Sarcosaurus]]'' as coelophysids, while ''C. longicollis'' (as ''Longosaurus'') was placed as a halticosaurid alongside ''Dilophosaurus'', ''Halticosaurus'' and ''[[Liliensternus]]''. The family Procompsognathidae was also recognized to include Triassic genera, while ''Podokesaurus'' was unable to be classified due to its incompleteness and Podokesauridae was abandoned.<ref name="welles1984"/> Colbert did not follow this during his 1989 description of the Ghost Ranch specimens, recognising ''Coelophysis'', ''Halticosaurus'', ''Podokesaurus'', ''Procompsognathus'' and ''[[Syntarsus rhodesiensis|Syntarsus]]'' as podokesaurids,<ref name="colbert1989"/> but American paleontologist [[Thomas R. Holtz Jr.]] in 1994 followed Welles, using Coelophysidae for ''Coelophysis'' and its relatives, considering ''Podokesaurus'' indeterminate, and naming the new clade [[Coelophysoidea]] to unite coelophysids with ''[[Dilophosaurus]]''.<ref name="holtz1994"/>

[[File:Coelophysis cast.jpg|thumb|right|Cast of the neotype specimen AMNH FR 7224, [[Redpath Museum]]]]
[[File:Coelophysis Jeff Martz.jpg|thumb|Restoration showing hypothetical [[Wattle (anatomy)|wattle]] and feathers]]

{{clade| style=font-size:85%;line-height:80%
|1={{clade
|label1= [[Theropoda]]
   |1={{clade
      |1=''[[Tawa hallae]]''
      |2=''[[Chindesaurus]]'' }}
   |2={{clade
      |1=''[[Eodromaeus]]''
      |2={{clade
          |label1= [[Neotheropoda]]
           |1={{clade
               |label1= [[Coelophysoidea]]
               |1={{clade
                  |1=''[[Liliensternus]]''
                  |2=''[[Dracoraptor]]''
                  |3={{clade
                     |1=''[[Coelophysis kayentakatae|"Syntarsus" kayentakatae]]''
                     |2={{clade
                        |1=''[[Panguraptor]]''
                        |2={{clade
                          |1=''[[Powellvenator]]''
                          |2={{clade
                             |1=''[[Procompsognathus]]''
                             |2={{clade
                               |2={{clade
                                 |1=''[[Camposaurus]]''
                                 |2=''[[Lucianovenator]]''
                                 |3=''[[Megapnosaurus]]''
                                 |4=''[[Segisaurus]]'' }}
                               |1={{clade
                                 |1='''''Coelophysis'''''
                                 |2=''[[Lepidus praecisio|Lepidus]]''}} }} }} }} }} }} }}
               |2={{clade
                  |1=''[[Zupaysaurus]]''
                  |2={{clade
                    |1=''[[Gojirasaurus]]''
                    |2={{clade
                      |1=''[[Cryolophosaurus]]''
                      |2={{clade
                        |1=''[[Dilophosaurus]]''
                        |2={{clade
                          |1=''[[Sarcosaurus]]''
                          |2={{clade
                            |1=''[[Tachiraptor]]''
                            |2=[[Averostra]]}} }}
		     }}
		  }}
               }}
            }}
         }}
      }}
   }}
}}
}}

{{center|
<small>Theropod [[cladogram]] based on the [[phylogenetics|phylogenetic analyses]] conducted by Ezcurra et al. (2020)</small><ref name="ezcurra2020">{{Cite journal|last1=Ezcurra|first1=Martín D|last2=Butler|first2=Richard J|last3=Maidment|first3=Susannah C R|last4=Sansom|first4=Ivan J|last5=Meade|first5=Luke E|last6=Radley|first6=Jonathan D|date=1 January 2021|title=A revision of the early neotheropod genus Sarcosaurus from the Early Jurassic (Hettangian–Sinemurian) of central England|url=https://academic.oup.com/zoolinnean/article/191/1/113/5861188|journal=Zoological Journal of the Linnean Society|language=en|volume=191|issue=1|pages=113–149|doi=10.1093/zoolinnean/zlaa054|issn=0024-4082|hdl=11336/160038|hdl-access=free|archive-date=12 November 2021|access-date=4 May 2022|archive-url=https://web.archive.org/web/20211112004559/https://academic.oup.com/zoolinnean/article/191/1/113/5861188|url-status=live}}</ref><small>.</small>}}

''Coelophysis'' is a distinct taxonomic unit (genus), composed of the single species ''C. bauri.'' Two additional originally described species, ''C. longicollis'' and ''C. willistoni'', are now considered dubious and undiagnostic.<ref name="hunt1991" /> ''M. rhodesiensis'' was referred to ''Coelophysis'' for several years, but it is likely its own genus<ref name="barta2018" /><ref name="ezcurra2017" /> and is known from the early Jurassic of southern Africa. A third possible species is ''Coelophysis kayentakatae'', previously referred to the genus ''Megapnosaurus,'' from the [[Kayenta Formation]] of the southwestern US. 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.<ref name="griffin2018" /><ref name="ezcurra2017" /><ref name="marsh2020b">{{Cite journal|last1=Marsh|first1=Adam D.|last2=Rowe|first2=Timothy B.|date=July 2020|title=A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria, Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona|journal=Journal of Paleontology|language=en|volume=94|issue=S78|pages=1–103|doi=10.1017/jpa.2020.14|s2cid=220601744 |issn=0022-3360|doi-access=free|bibcode=2020JPal...94S...1M }}</ref>

== Paleobiology ==

=== Feeding ===
[[File:Coelophysis with crocodylomorph bones AMNH.jpg|thumb|left|Bones in a skeleton of ''C. bauri'' at the [[American Museum of Natural History]], now interpreted as those of a [[crocodylomorph]]]]

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 (anatomy)|posterior]] edges. Its dentition shows that it was carnivorous, probably preying on the small, lizard-like animals that were discovered with it.<ref name="benton1993">{{Cite book|author=Benton, M.|year=1993|title=Dinosaur and other prehistoric animal Fact Finder|publisher=Kingfisher Books Ldt.|isbn=978-0-86272-949-3|page=256}}</ref> It may also have hunted in packs to tackle larger prey.<ref name="paul88">{{cite book|title=Predatory Dinosaurs of the World|last=Paul|first=Gregory S.|author-link=Gregory S. Paul|publisher=[[Simon & Schuster]]|year=1988|isbn=978-0-671-61946-6|page=[https://archive.org/details/predatorydinosau00paul/page/260 260]|url=https://archive.org/details/predatorydinosau00paul|url-access=registration}}</ref> ''Coelophysis bauri'' has approximately 26 teeth on the maxillary bone of the upper jaw and 27 teeth on the dentary bone of the lower jaw.<ref name="colbert1989"/> Kenneth Carpenter (2002) examined the bio-mechanics of theropod arms and attempted to evaluate their usefulness in predation. He concluded that the arm of ''Coelophysis'' was flexible and had a good range of motion, but its bone structure suggested that it was comparatively weak. The "weak" arms and small teeth in this genus suggested that ''Coelophysis'' preyed upon animals that were substantially smaller than itself. Rinehart et al. agreed that ''Coelophysis'' was a "hunter of small, fast-moving prey".<ref name="rinehart2009" /> Carpenter also identified three distinct models of theropod arm use and noted that ''Coelophysis'' was a "combination grasper-clutcher", as compared to other dinosaurs that were "clutchers" or "long armed graspers".<ref name="carpenter2002">{{cite journal|author=Carpenter, K.|year=2002|title=Forelimb bio-mechanics of non-avian theropod dinosaurs in predation|journal=Senckenbergiana Lethaea|volume=82|pages=59–76|doi=10.1007/bf03043773|s2cid=84702973}}</ref>

It has been suggested that ''C. bauri'' was a [[Cannibalism (zoology)|cannibal]], based on supposed juvenile specimens found "within" the abdominal cavities of some Ghost Ranch specimens.<ref name="haines2007" /> However, [[Robert J. Gay]] showed in 2002 that these specimens were misinterpreted. Several specimens of "juvenile coelophysids" were actually small [[Crurotarsi|crurotarsan reptiles]], such as ''[[Hesperosuchus]]''.<ref name="gay2002">{{cite journal|author=Gay, R.J.|year=2002|title=The myth of cannibalism in ''Coelophysis bauri''|journal=Journal of Vertebrate Paleontology|volume=22|issue=3|page=57A}}</ref> Gay's position was lent support in a 2006 study by Nesbitt et al.<ref name="nesbittetal2006">{{cite journal|year=2006|title=Prey choice and cannibalistic behaviour in the theropod ''Coelophysis''|journal=Biology Letters|series=22|volume=2|issue=4|doi=10.1098/rsbl.2006.0524|pages=611–614|pmc=1834007|pmid=17148302|last1=Nesbitt|first1=S. J.|last2=Turner|first2=A. H|last3=Erickson|first3=G. M|last4=Norell|first4=M. A}}</ref> 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.''<ref name="rinehart2009" />

In 2010, Gay examined the bones of juveniles found within the thoracic cavity of AMNH 7224 and calculated that the total volume of these bones was 17 times greater than the maximum estimated stomach volume of the ''Coelophysis'' specimen. Gay observed that the total volume would be even greater when considering that there would have been flesh on these bones. This analysis also noted the absence of tooth marks on the bones as would be expected in defleshing and the absence of expected pitting by stomach acids. Finally, Gay demonstrated that the alleged cannibalized juvenile bones were deposited stratigraphically below the larger animal that had supposedly cannibalized them. Taken together, these data suggested that the ''Coelophysis'' specimen AMNH 7224 was not a cannibal and that the bones of the juvenile and adult specimens were found in their final position as a result of "coincidental superposition of different sized individuals.<ref name="gay2010">{{cite book|author=Gay, R.J.|year=2010a|title=Notes on Early Mesozoic Theropods (First ed.)|publisher=Lulu press|pages=9–24|isbn=978-0-557-46616-0}}</ref>

=== Pack behavior ===

[[File:CMNH Coelophysis Block.jpg|thumbnail|The [[Cleveland Museum of Natural History]]'s ''Coelophysis'' block, originally [[American Museum of Natural History]] block XII collected by [[Edwin H. Colbert|Colbert]] in 1948<ref name="rinehart2009" />]]

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.<ref name="schwartz1994">{{cite journal|author1=Schwartz, H.L. |author2=Gillette, D.D. |year=1994|title=Geology and taphonomy of the Coelophysis quarry, Upper Triassic Chinle Formation, Ghost Ranch, New Mexico|journal=Journal of Paleontology|volume=68|issue=5|pages=1118–1130|jstor=1306181|doi=10.1017/S0022336000026718|bibcode=1994JPal...68.1118S |s2cid=130635216 }}</ref> There is a tendency to see this massive congregation of animals as evidence for huge packs of ''Coelophysis'' roaming the land.<ref name="haines2007" /> No direct evidence for flocking exists because the deposits only indicate that large numbers of ''Coelophysis'', along with various other Triassic animals, were buried together. Some of the evidence from the [[taphonomy]] of the site indicates that these animals may have been gathered together to feed or drink from a depleted water hole or to feed on a [[Spawn (biology)|spawning]] run of fish, being later buried in a catastrophic [[flash flood]]<ref name="haines2007" /><ref name="schwartz1994" /> or a drought.<ref name="haines2007" />

With 30 specimens of ''C. rhodesiensis'' found together in Zimbabwe, some palaeontologists have suggested that ''Coelophysis'' was indeed gregarious. Again, there is no direct evidence of flocking in this case and it has also been suggested that these individuals were also victims of flash flooding as it appears to have been commonplace during this period.<ref name="raath1969" /><ref name=Bond,_1965>G. Bond, 1965. Some new fossil localities in the Karroo System of Rhodesia. Arnoldia, Series of Miscellaneous Publications, National Museum of Southern Rhodesia 2(11):1–4</ref><ref name="raath1977">M. A. Raath, 1977. The Anatomy of the Triassic Theropod Syntarsus rhodesiensis (Saurischia: Podokesauridae) and a Consideration of Its Biology. Department of Zoology and Entomology, Rhodes University, Salisbury, Rhodesia 1–233</ref>

=== Growth and sexual dimorphism ===

Rinehart (2009) assessed the [[ontogeny|ontogenic]] [[Developmental biology|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.<ref name="rinehart2009" /> ''Coelophysis'' likely reached sexual maturity between the second and third year of life and reached its full size, just above 10 feet in length, by its eighth year. This study identified four distinct growth stages: 1-year, 2-year, 4-year, and 7+ year.<ref name="rinehart2009" /> It was also thought that, as soon as they were hatched, they would have to fend for themselves.<ref name="haines2007" />

Two "morphs" of ''Coelophysis'' have been identified. One is a more [[gracility|gracile]] form, as in specimen AMNH 7223, and the other is a slightly more robust form, as in specimens AMNH 7224 and NMMNH P-42200. Skeletal proportions were different between these two forms.<ref name=GSP10>{{cite book|last=Paul|first=Gregory S.|title=The Princeton Field Guide to Dinosaurs|url=https://archive.org/details/princetonfieldgu0000paul|url-access=registration|year=2010|publisher=Princeton University Press|isbn=978-0-691-13720-9|page=[https://archive.org/details/princetonfieldgu0000paul/page/74 74]}}</ref> The gracile form has a longer skull, a longer neck, shorter arms, and has [[sacrum|sacral]] neural spines that are fused. The robust form has a shorter skull, a shorter neck, longer arms, and unfused sacral neural spines.<ref name="colbert1989" /> Historically, many arguments have been made that this represents some sort of dimorphism in the population of ''Coelophysis'', probably [[sexual dimorphism]].<ref name="paul1988" /><ref name="colbert1989"/><ref name="carpenter1990" /><ref name="Gay05">Gay, R. (2005). "Sexual Dimorphism in the Early Jurassic Theropod Dinosaur ''[[Dilophosaurus]]'' and a Comparison with Other Related Forms": In: {{cite book|editor=Carpenter, K.|title=The Carnivorous Dinosaurs|publisher=Indiana University Press|location=Bloomington|isbn=978-0-253-34539-4|pages=277–283|year=2005}}</ref> Raath agreed that dimorphism in ''Coelophysis'' is evidenced by the size and structure of the arm.<ref name="carpenter1990">{{cite book |author1=Carpenter, K. |author2=Currie, P.J. |year=1990 |title=Dinosaur Systematics: Approaches and Perspectives |location=Cambridge|publisher=Cambridge University Press|pages=91–105|isbn=978-0-521-43810-0}}</ref> Rinehart et al. studied 15 individuals, and agreed that two morphs were present, even in juvenile specimens, and suggested that sexual dimorphism was present early in life, prior to sexual maturity. Rinehart concluded that the gracile form was female and the robust form was male based on differences in the sacral vertebrae of the gracile form, which allowed for greater flexibility for egg laying.<ref name="rinehart2009" /> Further support for this position was provided by an analysis showing that each morph comprised 50% of the population, as would be expected in a 50/50 sex ratio.<ref name="rinehart2001">{{cite journal |author1=Rinehart, L.F. |author2=Lucas, S.G. |author3=Heckert, A.B. |s2cid=220414868 |year=2001 |title=Preliminary statistical analysis defining the juvenile, robust and gracile forms of the Triassic dinosaur ''Coelophysis'' |journal=Journal of Vertebrate Paleontology |volume=21 |page=93A |doi=10.1080/02724634.2001.10010852}}</ref>

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. This indicates that the supposed presence of distinct morphs is simply the result of individual variation. This highly variable growth was likely ancestral to dinosaurs but later lost and may have given such early dinosaurs an evolutionary advantage in surviving harsh environmental challenges.<ref name="griffin2016">{{cite journal | title = Anomalously high variation in postnatal development is ancestral for dinosaurs but lost in birds | first1 = C.T. | last1 = Griffin | first2 = S.J. | last2 = Nesbitt | date = 2016 | journal = Proceedings of the National Academy of Sciences of the United States of America | doi = 10.1073/pnas.1613813113 | pmid = 27930315 | pmc = 5187714 | volume = 113 | issue = 51 | pages=14757–14762| bibcode = 2016PNAS..11314757G | doi-access = free }}</ref>

=== Reproduction ===

[[File:Coelophysis skeletons.jpg|thumb|Two ''C. bauri'' casts mounted at the [[Denver Museum of Nature and Science]]]]

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. It was estimated that average egg of ''Coelophysis'' was 31–33.5 millimeters across its minor diameter and that each female would lay between 24 and 26 eggs in each clutch. 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. ''Coelophysis bauri'' invested as much energy in reproduction as other extinct reptiles of its approximate size.<ref name="rinehart2009" /><ref name="glut2012">{{cite book|author=Glut, D.F.|year=2012|title=Dinosaurs, the Encyclopedia, Supplement 7|publisher=McFarland & Company, Inc.|page=866|isbn=978-0-7864-4859-3}}</ref>

=== Paleopathology ===
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.<ref name="rothschild-dino">Rothschild, B.; Tanke, D.H. & Ford, T.L. (2001). "Theropod stress fractures and tendon avulsions as a clue to activity": In: {{cite book|editor1-last=Tanke|editor1-first=D. H.|editor2-last=Carpenter|editor2-first=K.|title=Mesozoic Vertebrate Life|publisher=Indiana University Press|pages=331–336|isbn=978-0-253-33907-2|year=2001}}</ref>

In ''C. rhodesiensis'', healed fractures of the [[tibia]] and [[metatarsus]] have been observed, but are very rare. "[T]he supporting butresses of the second sacral rib" in one specimen of ''Syntarsus rhodesiensis'' showed signs of fluctuating asymmetry. Fluctuating [[asymmetry]] results from developmental disturbances and is more common in populations under stress and can therefore be informative about the quality of conditions a dinosaur lived under.<ref name="molnar-pathology">Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363.</ref>

== Ichnology ==
[[File:PSM V66 D145 Carnivorous dinosaur tracks in high relief preserved in stone.png|thumb|''Grallator'' from [[Middletown, Connecticut]]]]

Edwin H. Colbert has suggested that the theropod footprints referred to the [[ichnotaxon|ichnogenus]] ''[[Grallator]]'', located in the [[Connecticut River Valley]] across Connecticut and Massachusetts, may have been made by ''Coelophysis''.<ref name="colbert-ageofreptiles">{{cite book|title=The Age of Reptiles|url=https://archive.org/details/ageofreptiles00colb|url-access=registration|last=Colbert|first=Edwin H.|author-link=Edwin H. Colbert|publisher=[[W. W. Norton & Company]]|year=1965|isbn=978-0-486-29377-6|page=[https://archive.org/details/ageofreptiles00colb/page/97 97]}}</ref> The footprints are from the Late Triassic to Early Jurassic aged Newark Supergroup. They clearly show digits II, III, and IV, but not I or V. That condition is strange for footprints of their age. The digits I and V were presumed to be stubby and ineffective, not touching the ground when the dinosaur was walking or running. They have been thought to be from an unidentified, primitive saurischian similar to ''Coelophysis'' by David B. Weishampel and L. Young more recently.<ref name="weishampel&young1998">{{cite book|title=Dinosaurs of the East Coast|year=1998|publisher=Johns Hopkins University Press|isbn=978-0-8018-5217-6|author1=Weishampel, D.B  |author2=Young, L.}}</ref> Skeletal remains resembling ''Coelophysis'' have also been found in the valley, supporting the idea that a species similar to ''Coelophysis'' is responsible for the footprints.<ref>{{cite web |url = http://www.nashdinosaurtracks.com/learn-about-local-dinosaurs.php |title = Dinosaur footprints of the Connecticut River Valley |publisher = Nash Dinosaur Track Site and Rock Shop |access-date = 16 June 2015 |archive-date = 1 January 2017 |archive-url = https://web.archive.org/web/20170101184852/http://www.nashdinosaurtracks.com/learn-about-local-dinosaurs.php }}</ref>

== Paleoenvironment ==

[[File:Postosuchus, Coelophysis, and Placerias.jpg|thumb|left|Restoration of ''Coelophysis'' and contemporary animals]]

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<ref name="rinehart2009" /> 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,<ref name="irmis2011"/><ref name="haines2007">{{cite book|author1=Haines, T. |author2=Chambers, P. |year=2007|title=The Complete Guide to Prehistoric Life|publisher=Firefly Books|pages=[https://archive.org/details/isbn_9781554071258/page/70 70]–71|isbn=978-1-55407-181-4|url=https://archive.org/details/isbn_9781554071258|url-access=registration}}</ref> but Thomas Holtz Jr. interpreted that it was during the [[Rhaetian]] stage from approximately 204 to 201.6 million years ago.<ref name="Holtz2012">Holtz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' [http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf Winter 2011 Appendix.] {{Webarchive|url=https://web.archive.org/web/20170812011954/http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf |date=12 August 2017 }}</ref>

''C. rhodesiensis'' has been recovered in the [[Upper Elliott Formation]] in the [[Cape Province|Cape]] and [[Free State Province|Free State]] provinces of South Africa, as well as the Chitake River bonebed quarry at the [[Forest Sandstone Formation]] in Zimbabwe.

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. The discovery indicates that the two groups lived together during the early Triassic period 235&nbsp;million years ago.<ref name="donna2007">{{cite web|last=Braginetz|first=Donna|year=2007|title=A new species of dinosauromorph (lower left) was among the mixed assemblage of dinosaurs and dinosauromorphs found at Hayden Quarry in Ghost Ranch, N.M.|url=http://www.amnh.org/our-research/science-news/2007/new-find-at-ghost-ranch.-new-mexico-shows-dinosaurs-coexisted-with-their-predecessors-for-15-to-20-million-years|publisher=American Museum of Natural History|access-date=31 March 2013|archive-date=17 February 2013|archive-url=https://web.archive.org/web/20130217082040/http://www.amnh.org/our-research/science-news/2007/new-find-at-ghost-ranch.-new-mexico-shows-dinosaurs-coexisted-with-their-predecessors-for-15-to-20-million-years|url-status=live}}</ref>

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. There was a great deal of competition during drier times when animals struggled for water in riverbeds that were drying up.<ref name="therrien2000">{{cite journal|year=2000|title=Paleoenvironments of early theropods, Chinle Formation (Late Triassic), Petrified Forest National Park, Arizona|journal=PALAIOS|volume=15|issue=3|series=3|pages=194–211|doi=10.1669/0883-1351(2000)015<0194:POETCF>2.0.CO;2|last1=Therrien|first1=F.|last2=Fastovsky|first2=D. E.|url=https://digitalcommons.uri.edu/cgi/viewcontent.cgi?article=1015&context=geo_facpubs|bibcode=2000Palai..15..194T|s2cid=130468695|archive-date=27 April 2019|access-date=25 January 2019|archive-url=https://web.archive.org/web/20190427233952/https://digitalcommons.uri.edu/cgi/viewcontent.cgi?article=1015&context=geo_facpubs|url-status=live}}</ref>

In the upper sections of the Chinle Formation where ''Coelophysis'' is found, dinosaurs were rare. So far, only ''[[Chindesaurus]]'' and ''[[Daemonosaurus]]''<ref name="sues2011">{{Cite journal | last1 = Sues | first1 = H. -D. | last2 = Nesbitt | first2 = S. J. | last3 = Berman | first3 = D. S. | last4 = Henrici | first4 = A. C. | title = A late-surviving basal theropod dinosaur from the latest Triassic of North America | doi = 10.1098/rspb.2011.0410 | journal = Proceedings of the Royal Society B: Biological Sciences | volume = 278 | issue = 1723 | pages = 3459–64 | year = 2011 | pmid =  21490016| pmc = 3177637}}</ref> are known, the terrestrial fauna being dominated instead by other reptiles like the [[rhynchocephalia]]n ''[[Whitakersaurus]]'',<ref name="Heckert et al. 2008">{{cite journal|last1=Heckert|first1=A.B.|last2=Lucas|first2=S.G.|last3=Rinehart|first3=L.F.|last4=Hunt|first4=A.P.|title=A new genus and species of sphenodontian from the Ghost Ranch ''Coelophysis'' Quarry (Upper Triassic: Apachean), Rock Point Formation, New Mexico, USA|journal=Palaeontology|date=2008|volume=51|issue=4|pages=827–845|doi=10.1111/j.1475-4983.2008.00786.x|doi-access=free|bibcode=2008Palgy..51..827H }}</ref> the [[pseudosuchian]] ''[[Revueltosaurus]]'', the [[aetosaur]]s ''[[Desmatosuchus]]'', ''[[Typothorax]]'' and ''[[Heliocanthus]]'', the [[Crocodylomorpha|crocodilomorph]] ''[[Hesperosuchus]]'', the "[[rauisuchia]]ns" ''[[Shuvosaurus]]'',<ref name="irmis2005">Irmis, R.B. (2005). "The vertebrate fauna of the Upper Triassic Chinle Formation in northern Arizona": In: {{cite journal |editor1-last=Nesbitt |editor1-first=S.J. |editor2-last=Parker |editor2-first=W.G. |editor3-last=Irmis |editor3-first=R.B. |title=Guidebook to the Triassic formations of the Colorado Plateau in northern Arizona: Geology, Paleontology, and History |url=http://ist-socrates.berkeley.edu/~irmisr/chinlerev.pdf |journal=Mesa Southwest Museum Bulletin |volume=9 |pages=63–88 |archive-url=https://web.archive.org/web/20121004035942/http://ist-socrates.berkeley.edu/%7Eirmisr/chinlerev.pdf |archive-date=4 October 2012 |access-date=2 January 2014}}</ref> ''[[Effigia]]'',<ref name="benson2012">{{cite book|author1=Benson, R.J. |author2=Brusatte, S. |author3=Clack, J. |author4=Anderson, J. |author5=Dennis-Bryan, K. |author6=Hone, D. |author7=Duffin, C. |author8=Johanson, Z. |author9=Milner, A. |author10=Naish, D. |author11=Parsons, K. |author12=Prothero, D. |author13=Xu, X. |year=2012|title=Prehistoric Life|publisher=Dorling Kindersley|location=London|isbn=978-0-7566-9910-9|pages=214–215}}</ref> and ''[[Vivaron]]'',<ref name="Lessner2016">{{cite journal |author1=Emily J. Lessner |author2=Michelle R. Stocker |author3=Nathan D. Smith |author4=Alan H. Turner |author5=Randall B. Irmis |author6=Sterling J. Nesbitt |year=2016 |title=A new rauisuchid (Archosauria, Pseudosuchia) from the Upper Triassic (Norian) of New Mexico increases the diversity and temporal range of the clade |journal=PeerJ |volume=4 |article-number=e2336 |doi=10.7717/peerj.2336 |pmid=27651983 |pmc=5018681 |doi-access=free }}</ref> along with other rare components like the [[dinosauriformes|dinosauriform]] ''[[Eucoelophysis]]''<ref name="weishampeletal2004">{{cite book|author1=Weishampel, D.B. |author2=Dodson, P. |author3=Osmólska, H. |year=2004|title=The Dinosauria (Second ed.)|location=Berkeley|publisher=University of California Press|pages=518–521|isbn=978-0-520-24209-8}}</ref> and the [[amniote]] ''[[Kraterokheirodon]]''. In the waterways there are the [[phytosaur]] ''[[Machaeroprosopus]]'', the [[Archosauromorpha|archosauromorph]] ''[[Vancleavea]]'', the amphibians ''[[Apachesaurus]]''<ref name="irmis2005" /> and ''[[Koskinonodon]]'',<ref name="mueller2007">{{cite journal|author=Mueller, B.D.|year=2007|title=''Koskinonodon'' Branson and Mehl, 1929, a replacement name for the preoccupied temnospondyl ''Buettneria'' Case, 1922|journal=Journal of Vertebrate Paleontology|volume=27|issue=1|page=225|doi=10.1671/0272-4634(2007)27[225:KBAMAR]2.0.CO;2|s2cid=85763026 }}</ref> and the fishes ''[[Reticulodus]]'', ''[[Arganodus]]'', and ''[[Lasalichthyes]]''.<ref name="irmis2005" />

=== Taphonomy ===

[[File:Coelophysis block.jpg|thumb|right|Specimen block, [[New Mexico History Museum|New Mexico Museum]]]]

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. In fact, it seems that such flooding was commonplace during this period of the [[History of Earth|Earth's history]] and, indeed, the [[Petrified Forest National Park|Petrified Forest]] of nearby [[Arizona]] is the result of a preserved log jam of tree trunks that were caught in one such flood. Whitaker quarry at Ghost Ranch is considered a monotaxic site because it features multiple individuals of a single taxon. The quality of preservation and the ontogenic (age) range of the specimens helped make ''Coelophysis'' one of the best known of all genera.<ref name="glut2006">{{cite book|author=Glut, D.F.|year=2006|title=Dinosaurs, the Encyclopedia, Supplement 4|publisher=McFarland & Company, Inc.|page=749|isbn=978-0-7864-2295-1}}</ref> 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."<ref name="rinehart2009" />

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.<ref name="raath1969" /><ref name="Bond,_1965" /><ref name="raath1977" />

== Cultural significance ==
''Coelophysis'' was the second dinosaur in space, following ''[[Maiasaura]]'' ([[STS-51-F]]).<ref name=dinosinspace>{{cite web|author=Chure, D.|year=2009|title=dino bones in space – was it a PR thing|url=http://dml.cmnh.org/2009Oct/msg00664.html|publisher=Cleveland Museum of Natural History|access-date=12 November 2011|archive-date=8 November 2011|archive-url=https://web.archive.org/web/20111108075202/http://dml.cmnh.org/2009Oct/msg00664.html}}</ref> 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. It was also taken onto the space station [[Mir]] before being returned to Earth.<ref name="dinosinspace" /><ref name=steveparker>{{cite book|last=Parker|first=Steve|title=Dinosaurs: the complete guide to dinosaurs|year=2003|publisher=Firefly Books|isbn=978-1-55297-772-9}}</ref>

Since the discovery of ''Coelophysis'' fossils more than 100 years ago, it is one of the best-known dinosaurs in literature. It was designated as the official [[List of New Mexico state symbols#Geology|state fossil of New Mexico]] in 1981 and is now the logo of the New Mexico Museum of Natural History.<ref name="colbert1992" /><ref>{{cite magazine |url=https://geoinfo.nmt.edu/publications/periodicals/earthmatters/17/n2/em_v17_n2.pdf |title=''Coelophysis'', the New Mexico state fossil |access-date=12 March 2022 |magazine=geoinfo.nmt.edu/ |publisher=New Mexico Bureau of Geology and Mineral Resource |archive-date=7 November 2017 |archive-url=https://web.archive.org/web/20171107031601/https://geoinfo.nmt.edu/publications/periodicals/earthmatters/17/n2/em_v17_n2.pdf |url-status=live }}</ref>

==Notes==
{{notelist}}

== References ==
{{Reflist|2|refs=
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<ref name="cope1887b">{{cite journal|last=Cope|first=E.D.|author-link=Edward Drinker Cope|year=1887|title=A Contribution to the History of the Vertebrata of the Trias of North America|journal=Proceedings of the American Philosophical Society|volume=24|issue=126|pages=209–228}}</ref>
<ref name="cope1889">{{cite journal|last=Cope|first=E.D.|author-link=Edward Drinker Cope|year=1889|title=On a new genus of Triassic Dinosauria|journal=The American Naturalist|volume=23|issue=271|page=626|doi=10.1086/274979}}</ref>
<ref name="huene1906">{{cite journal|last=Huene|first=F.F.v.|author-link=Friedrich von Huene|year=1906|title=Über die Dinosaurier der aussereuropäischen Trias|journal=Geologische und Paläontologische Abhandlungen|volume=8|issue=2|pages=97–156}}</ref>
<ref name="talbot1911">{{cite journal|last=Talbot|first=M.|author-link=Mignon Talbot|year=1911|title=''Podokesaurus holyokensis'', a new dinosaur from the Triassic of the Connecticut Valley|journal=American Journal of Science|series=4|volume=31|issue=186|pages=469–479|doi=10.2475/ajs.s4-31.186.469|bibcode=1911AmJS...31..469T }}</ref>
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<ref name="huene1914">{{cite journal|last=Huene|first=F.F.v.|author-link=Friedrich von Huene|year=1914|title=Das natürliche System der Saurischia|journal=Centralblatt für Mineralogie, Geologie und Paläontologie|volume=1914|pages=154–158}}</ref>
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<ref name="paul1993">{{cite journal|last=Paul|first=G.S.|author-link=Gregory S. Paul|year=1993|title=Are ''Syntarsus'' and the Whitaker Quarry Theropod the same genus?|journal=New Mexico Museum of Natural History Bulletin|volume=3|pages=397–402}}</ref>
<ref name="welles1994">{{cite journal|last1=Welles|first1=S.P.|author-link1=Samuel P. Welles|last2=Olshevsky|first2=G.|last3=Nicholls|first3=E.L.|author-link3=Elizabeth Nicholls|last4=Jacobs|first4=L.L.|author-link4=Louis L. Jacobs|last5=Glut|first5=D.F.|author-link5=Donald F. Glut|last6=Ricqlès|first6=A.de|last7=Tubbs|first7=P.K.|year=1994|title=Comments on a proposed neotype for ''Coelophysis bauri'' (Cope, 1887) (Reptilia, Saurischia) (Case 2840; see BZN 49: 276-279; 50: 147-151, 236-239, 291-294)|journal=Bulletin of Zoological Nomenclature|volume=51|issue=1|pages=48–51}}</ref>
<ref name="huber1994">{{cite journal|last1=Huber|first1=P.|year=1994|title=Comments on a proposed neotype for ''Coelophysis bauri'' (Cope, 1887) (Reptilia, Saurischia) (Case 2840; see BZN 49: 276-279; 50: 147-151, 236-239, 291-294; 51: 48-51)|journal=Bulletin of Zoological Nomenclature|volume=51|issue=2|pages=156–158|doi=10.5962/bhl.part.7182 |doi-access=free}}</ref>
<ref name="lucas1994">{{cite journal|last1=Lucas|first1=S.G.|author-link1=Spencer G. Lucas|last2=Hunt|first2=A.P.|year=1994|title=Comments on a proposed neotype for ''Coelophysis bauri'' (Cope, 1887) (Reptilia, Saurischia) (Case 2840; see BZN 49: 276-279; 50: 147-151, 236-239, 291-294; 51: 48-51, 156-158)|journal=Bulletin of Zoological Nomenclature|volume=51|issue=2|pages=265–266|doi=10.5962/bhl.part.7213 |doi-access=free}}</ref>
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<ref name="sullivan1995">{{cite journal|last1=Sullivan|first1=R.M.|author-link1=Robert M. Sullivan|year=1995|title=Comments on a proposed neotype for ''Coelophysis bauri'' (Cope, 1887) (Reptilia, Saurischia) (Case 2840; see BZN 49: 276-279; 50: 147-151, 236-239, 291-294; 51: 48-51, 156-158, 265-266)|journal=Bulletin of Zoological Nomenclature|volume=52|issue=1|pages=76–77|doi=10.5962/bhl.part.6734 |doi-access=free}}</ref>
<ref name="colbert1995a">{{cite book|last=Colbert|first=E.H.|author-link=Edwin H. Colbert|year=1995|chapter=The Discovery|title=The little dinosaurs of Ghost Ranch|publisher=Columbia University Press|pages=1–21|isbn=0-231-08236-3}}</ref>
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<ref name="sullivan1996">{{cite journal|last1=Sullivan|first1=R.M.|author-link1=Robert M. Sullivan|last2=Lucas|first2=S.G.|author-link2=Spencer G. Lucas|last3=Heckert|first3=A.|last4=Hunt|first4=A.P.|year=1996|title=The type locality of ''Coelophysis'', a Late Triassic dinosaur from north-central New Mexico (USA)|journal=Paläontologische Zeitschrift|volume=70|issue=1/2|pages=245–255|doi=10.1007/BF02988281 |bibcode=1996PalZ...70..245S }}</ref>
<ref name="iczn1996">{{cite journal|author=[[International Commission on Zoological Nomenclature]]|year=1996|title=OPINION 1842: ''Coelurus bauri'' Cope, 1887 (currently ''Coelophysis bauri''; Reptilia, Saurischia): lectotype replaced by a neotype|journal=Bulletin of Zoological Nomenclature|volume=53|issue=2|pages=142–144}}</ref>
<ref name="sullivan1999">{{cite journal|last1=Sullivan|first1=R.M.|author-link1=Robert M. Sullivan|last2=Lucas|first2=S.G.|author-link2=Spencer G. Lucas|year=1999|title=''Eucoelophysis baldwini'', a new theropod dinosaur from the Upper Triassic of New Mexico, and the status of the original types of ''Coelophysis''|journal=Journal of Vertebrate Paleontology|volume=19|issue=1|pages=81–90|doi=10.1080/02724634.1999.10011124 |bibcode=1999JVPal..19...81S }}</ref>
<ref name="downs2000">{{cite journal|last=Downs|first=A.|year=2000|title=''Coelophysis bauri'' and ''Syntarsus rhodesiensis'' compared, with comments on the preparation and preservation of fossils from the Ghost Ranch ''Coelophysis'' quarry|journal=New Mexico Museum of Natural History Bulletin|volume=17|pages=33–37}}</ref>
<ref name="heckert2000">{{cite journal|last1=Heckert|first1=A.B.|last2=Zeigler|first2=K.E.|last3=Lucas|first3=S.G.|author-link3=Spencer G. Lucas|last4=Rinehart|first4=L.F.|last5=Harris|first5=J.D.|year=2000|title=Preliminary description of coelophysoids (Dinosauria:Theropoda) from the Upper Triassic (Revueltian:Early-Mid Norian) Snyder Quarry, North-Central New Mexico|journal=New Mexico Museum of Natural History and Science Bulletin|volume=17|pages=27–32}}</ref>
<ref name="heckert2003">{{cite journal|last1=Heckert|first1=A.B.|last2=Zeigler|first2=K.E.|last3=Lucas|first3=S.G.|author-link3=Spencer G. Lucas|last4=Rinehart|first4=L.F.|year=2003|title=Coelophysids (Dinosauria:Theropoda) from the Upper Triassic (Revueltian) Snyder Quarry|journal=New Mexico Museum of Natural History and Science Bulletin|volume=24|pages=127–133}}</ref>
<ref name="ivie2001">{{cite journal|last1=Ivie|first1=M.A.|last2=Ślipiński|first2=S.A.|last3=Węgrzynowicz|first3=P.|year=2001|title=Generic homonyms in the Colydiinae (Coleoptera: Zopheridae)|journal=Insecta Mundi|volume=15|pages=63–64}}</ref>
<ref name="bristowe2004">{{cite journal|last1=Bristowe|first1=A.|last2=Raath|first2=M.A.|year=2004|title=A juvenile coelophysoid skull from the Early Jurassic of Zimbabwe, and the synonymy of ''Coelophysis'' and ''Syntarsus''|journal=Palaeontologica Africana|volume=40|pages=31–41|url=https://scispace.com/pdf/a-juvenile-coelophysoid-skull-from-the-early-jurassic-of-4wm08weqxr.pdf}}</ref>
<ref name="tykoski2004">{{cite book|last1=Tykoski|first1=R.S.|last2=Rowe|first2=T.B.|year=2004|chapter=Ceratosauria|pages=47–70|editor-last=Weishampel|editor-first=D.B.|editor2-last=Dodson|editor2-first=P.|editor3-last=Osmólska|editor3-first=H|title=[[The Dinosauria]]|edition=2nd|publisher=University of California Press|isbn=978-0-520-24209-8}}</ref>
<ref name="yates2005">{{cite journal|last=Yates|first=A.M.|year=2005|title=A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods|journal=Palaeontologia Africana|volume=41|pages=105–122}}</ref>
<ref name="ezcurra2006">{{cite journal|last=Ezcurra|first=M.D.|author-link=Martín Ezcurra|year=2006|title=A review of the systematic position of the dinosauriform archosaur ''Eucoelophysis baldwini'' Sullivan & Lucas, 1999 from the Upper Triassic of New Mexico, USA|journal=Geodiversitas|volume=28|issue=4|pages=649–684}}</ref>
<ref name="nesbitt2007">{{cite journal|last1=Nesbitt|first1=S.J.|author-link=Sterling Nesbitt|first2=R.B.|last2=Irmis|first3=W.G.|last3=Parker|year=2007|title=A critical re-evaluation of the Late Triassic dinosaur taxa of North America|journal=Journal of Systematic Palaeontology|volume=5|issue=2|pages=209–243|doi=10.1017/S1477201907002040|bibcode=2007JSPal...5..209N }}</ref>
<ref name="ezcurra2007">{{cite journal|last1=Ezcurra|first1=M.D.|author-link=Martín Ezcurra|year=2007|title=The cranial anatomy of the coelophysoid theropod ''Zupaysaurus rougieri'' from the Upper Triassic of Argentina|journal=Historical Biology|volume=19|issue=2|pages=185–202|doi=10.1080/08912960600861467|bibcode=2007HBio...19..185E|s2cid=129449572}}</ref>
<ref name="ezcurra2007b">{{cite journal|last1=Ezcurra|first1=M.D.|author-link=Martín Ezcurra|last2=Novas|first2=F.E.|author-link2=Fernando Novas|year=2007|title=Phylogenetic relationships of the Triassic theropod ''Zupaysaurus rougieri'' from NW Argentina|journal=Historical Biology|volume=19|issue=1|pages=35–72|doi=10.1080/08912960600845791|bibcode=2007HBio...19...35E }}</ref>
<ref name="rinehart2009">{{cite journal|last1=Rinehart|first1=L.F.|last2=Lucas|first2=S.G.|author-link2=Spencer G. Lucas|last3=Heckert|first3=A.B.|last4=Spielmann|first4=J.A.|last5=Celesky|first5=M.D.|year=2009|title=The paleobiology of ''Coelophysis bauri'' (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block|journal=New Mexico Museum of Natural History and Science Bulletin|volume=45|pages=1–260}}</ref>
<ref name="spielmann2009">{{cite journal|last1=Spielmann|first1=J.A.|last2=Lucas|first2=S.G.|author-link2=Spencer G. Lucas|last3=Heckert|first3=A.B.|last4=Rinehart|first4=L.F.|last5=Richards|first5=H.R. III|year=2009|title=Redescription of ''Spinosuchus caseanus'' (Archosauromorpha: Trilophosauridae) from the Upper Triassic of North America|journal=Palaeodiversity|volume=2|pages=283–313}}</ref>
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<ref name="ezcurra2011">{{cite journal|last1=Ezcurra|first1=M.D.|author-link1=Martín Ezcurra|last2=Brusatte|first2=S.L.|author-link2=Stephen Brusatte|year=2011|title=Taxonomic and phylogenetic reassessment of the early neotheropod dinosaur ''Camposaurus arizonensis'' from the Late Triassic of North America|journal=Palaeontology|volume=54|issue=4|pages=763–772|doi=10.1111/j.1475-4983.2011.01069.x|bibcode=2011Palgy..54..763E}}</ref>
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<ref name="marsh2020">{{cite journal|last1=Marsh|first1=A.D.|last2=Parker|first2=W.G.|year=2020|title=New dinosauromorph specimens from Petrified Forest National Park and a global biostratigraphic review of Triassic dinosauromorph body fossils|journal=PaleoBios|volume=37|pages=1–56|doi=10.5070/P9371050859|doi-access=free}}</ref>
<ref name="spiekman2021">{{cite journal|last1=Spiekman|first1=S.N.|last2=Ezcurra|first2=M.D.|author-link2=Martín Ezcurra|last3=Butler|first3=R.J.|author-link3=Richard J. Butler|last4=Fraser|first4=N.C.|last5=Maidment|first5=S.C.R.|year=2021|title=''Pendraig milnerae'', a new small-sized coelophysoid theropod from the Late Triassic of Wales|journal=Royal Society Open Science|volume=8|issue=10|pages=1–27|doi=10.1098/rsos.210915|pmid=34754500|pmc=8493203|bibcode=2021RSOS....810915S }}</ref>
<ref name="iczn2024">{{cite journal|author=[[International Commission on Zoological Nomenclature]]|year=2024|title=Notice of New Applications to the Commission (Cases 3885–3900)|journal=Bulletin of Zoological Nomenclature|volume=81|issue=1|pages=2–3|doi=10.21805/bzn.v81.a002}}</ref>
<ref name="galton2025">{{cite journal|last1=Galton|first1=P.M.|author-link=Peter M. Galton|last2=Regalado-Fernández|first2=O.R.|last3=Farlow|first3=J.O.|year=2025|title=Bones of dinosaurs and other reptiles from the Triassic-Jurassic of the Connecticut Valley: Over 200 years of published history|journal=Revue de Paléobiologie|volume=44|issue=2|pages=1–45|doi=10.5281/zenodo.14793416}}</ref>
}}

== External links ==
{{Commons}}
{{Wikispecies|Coelophysis}}
*[http://internt.nhm.ac.uk/jdsml/nature-online/dino-directory/detail.dsml?Genus=Coelophysis ''Coelophysis''] {{Webarchive|url=https://web.archive.org/web/20060925132430/http://internt.nhm.ac.uk/jdsml/nature-online/dino-directory//detail.dsml?Genus=Coelophysis |date=25 September 2006 }} in the Dino Directory

{{Theropoda|N.}}
{{Geology of South Africa|paleontology}}
{{Taxonbar|from=Q309392}}
{{Portal bar|Paleontology|Dinosaurs}}

[[Category:Coelophysoidea]]
[[Category:Dinosaur genera]]
[[Category:Rhaetian dinosaurs]]
[[Category:Chinle fauna]]
[[Category:Fossil taxa described in 1889]]
[[Category:Taxa named by Edward Drinker Cope]]
[[Category:Dinosaurs of the United States]]