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One of the earliest known dinosaurs, '''Coelophysis''' (see-low-FYS-iss) meaning "hollow form" in reference to its hollow bones (Greek ''κοιλος''/''koilos'' meaning 'hollow' and ''φυσις''/''physis'' meaning 'form') is a small, carnivorous biped from North America. It first appeared in the Mid Triassic Period, around 228 million years ago.

Contents

Description

Paleobiology

History of discovery

Classification

Trivia

In popular culture

References

External links

Description

''Coelophysis bauri'' is the earliest dinosaur known from a number of complete fossil skeletons. ''C. bauri'' was a lightly built dinosaur, between two to three meters in length, and less than a meter tall at the hips. The name ''Coelophysis'' means "hollow form" or "hollow process", so named because of its hollow limb bones.
Despite being an early dinosaur, the evolution of the theropod body form had already advanced greatly from creatures like ''Herrerasaurus'' and ''Eoraptor''. ''Coelophysis'' had an elongated snout with large fenestrae which helped to reduce skull weight, while narrow struts of bones preserved the structural integrity of the skull. The neck had a pronounced sigmoid curve.
The torso of ''Coelophysis'' conforms to the basic theropod body shape, but the pectoral girdle displays some interesting 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, the fourth embedded in the flesh of the hand.

The pelvis and hindlimbs of ''C. bauri'' are also slight variations on the theropod body plan. It has the open acetabulum and straight ankle hinge that define the Dinosauria. The hindlimb ended in a three-toed foot (pes), with a raised hallux.
The tail of ''Coelophysis'' 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.^[1] This may have let the tail act as a rudder or counterweight when the animal was maneuvering at high speeds.
''Coelophysis'' was very slim and it could have run either on two or four legs. The neck and tail were long. The hands had only three fingers, but they were strong. ''Coelophysis'' had a long narrow head, and its sharp, jagged teeth show that it ate meat - probably the small, lizardlike animals that were found with it. Dr. Michael Benton, Dinosaur and other prehistoric animal Fact Finder, 1992.

Paleobiology

''Coelophysis'' was probably opportunistic, catching live prey and scavenging. The teeth were typical of predatory dinosaurs, blade-like and recurved with fine serrations on both anterior and posterior edges. They were rooted in the jaws in sockets, and were continually replaced throughout the animal's life.
Since our knowledge of ''Coelophysis'' comes mainly from the specimens excavated at Ghost Ranch, there is a tendency to see this massive congregation of animals as evidence for huge packs of ''Coelophysis'' roaming the land (as seen in the television series ''Walking with Dinosaurs''). There is no evidence for this. What the deposit does tell us is that large numbers of ''Coelophysis'', along with 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 spawning run of fish, then became buried in a catastrophic flash flood.
It has been suggested that ''C. bauri'' was a cannibal, based on juvenile specimens found "within" the abdominal cavities of some Ghost Ranch specimens. However, Rob Gay showed in 2002 that these specimens were misinterpreted (several specimens of "juvenile coelophysids" were actually small crurotarsan reptiles such as ''Hesperosuchus''), and there is no longer any evidence to support cannibalistic behavior in ''Coelophysis''.^[2] Gay's study was corroborated in 2006 in a subsequent study by Nesbitt ''et al.''^[3] There may be other evidence coming to light that may show stomach contents from some of these specimens, which might bring greater resolution to the subject.^[4]
Two forms of ''Coelophysis'' have been found, a more gracile form and a slightly more robust form. Opinion among paleontologists is now that these were female and male variants (''see:'' sexual dimorphism). Colbert, Edwin. (1989) "The Triassic Dinosaur ''Coelophysis''". ''Museum of Northern Arizona Bulletin''.Colbert, Edwin. 1990. ''in'' Dinosaur Systematics.Paul GS. (1988) Predatory Dinosaurs of the WorldGay, R. 2005. Sexual Dimorphism in the Early Jurassic Theropod Dinosaur ''Dilophosaurus'' and a Comparison with Other Related Forms; pp. 277-283 ''in'' K. Carpenter (ed.), The Carnivorous Dinosaurs. Indiana University Press, Bloomington, IN.

History of discovery

Edward Drinker Cope first named ''Coelophysis'' in 1889^[5] during his competition to name species with Othniel Charles Marsh, known as the "Bone Wars". An amateur fossil collector, David Baldwin, had found the first remains of the dinosaur in 1881. The type species, ''C. bauri'' was named for Baur, one of the many fossil collectors who supplied Cope. However, these first finds were too poorly preserved to give a complete picture of this new dinosaur.
In 1947, a substantial 'graveyard' of ''Coelophysis'' fossils was found in New Mexico, at the Ghost Ranch, close to the original find. So many fossils together were probably the result of a flash flood, which swept away a large number of ''Coelophysis'' and buried them quickly and simultaneously. In fact, it seems such flooding was commonplace during this period of the Earth's history and, indeed, the Petrified Forest of nearby Arizona is caused by a preserved log jam of tree trunks that were caught in one such flood. Edwin H. Colbert made a comprehensive study Colbert, Edwin. (1989) "The Triassic Dinosaur ''Coelophysis''".'' Museum of Northern Arizona Bulletin''. of all the fossils found up to that date, and it is from him that we take most of our information about ''Coelophysis''. The Ghost Ranch specimens were so numerous, including many well-preserved specimens, that one of them has since become the diagnostic, or type specimen, for the entire genus, replacing the original, poorly preserved specimen (see Classification below).
Since the Ghost Ranch specimens were discovered, more skeletons have been found in Arizona, New Mexico and an as-yet unconfirmed specimen from Utah, including both adults and juveniles. The deposits where ''Coelophysis'' has been discovered date from the late Carnian to the early Norian faunal stages of the Triassic Period.

Classification

''Coelophysis'' is a distinct taxonomic unit (genus), composed of a single species, ''C. bauri''. Two additional species were originally described in addition to ''C. bauri'', ''C. longicollis'', and ''C. willistoni'', however they are not diagnostic and are considered synonymous with ''C. bauri''. ''C. rhodesiensis'' is probably part of this generic complex, and is known from the Jurassic of southern Africa (see below for more). In phylogenetic taxonomy, ''Coelophysis'' is treated as a clade within the Coelophysidae.
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. Some paleontologists were of the opinion that the original specimens were not diagnostic beyond themselves and, therefore, that the name ''C. bauri'' could not be applied to any additional specimens. They therefore applied a different name, ''Rioarribasaurus'',^[6] to the Ghost Ranch quarry specimens.
Since the numerous well-preserved Ghost Ranch specimes were used as ''Coelophysis'' in most of the scientific literature, the use of ''Rioarribasaurus'' would have been very inconvenient for researchers, so a petition was given to have the type specimen of ''Coelophysis'' transferred from the poorly-preserved original specimen to one of the well-preserved Ghost ranch specimens. In the end, the International Commission on Zoological Nomenclature (ICZN) voted to make one of the Ghost Ranch samples the actual type specimen for ''Coelophysis'' and dispose of the name ''Rioarribasaurus'' altogether (declaring it a ''nomen rejectum'', or "rejected name"), thus resolving the confusion. The name ''Coelophysis'' therefore became a ''nomen conservandum'' ("conserved name").
Sullivan & Lucas (1999) suggested that the original type specimen was referable to what they thought was a newly discovered coelophysid, ''Eucoelophysis baldwini''.^[7] However, subsequent studies have shown that ''Eucoelophysis'' was misidentified, and is actually a primitive, non-dinosaurian ornithodiran closely related to ''Silesaurus''. Therefore, the original type specimen of ''Coelophysis'' cannot be considered a specimen of ''Eucoelophysis''.^[8]
In addition to all of this, there is a competing controversy with another coelophysoid, ''Megapnosaurus'', which many regard to be congeneric with ''Coelophysis''.Downs, Alex. 2000. in "Dinosaurs of New Mexico," ''New Mexico Museum of Natural History Bulletin''.Paul GS. (1988) Predatory Dinosaurs of the World To make matters more confusing, Paul^[9] suggested that ''Coelophysis'' should be placed in ''Megapnosaurus'' (then known as ''Syntarsus'') to get around the above-mentioned taxonomic confusion.
In a situation affecting many dinosaur genera, many specimens were originally classified as new species but were in fact species of ''Coelophysis''. For example, Prof. Mignon Talbot's 1911 discovery^[10] which she labeled ''Podokesaurus holyokensis,'' may be related to (or is) ''Coelophysis''. In addition, ''C. posthumus'', named by Friedrich von Huene in 1908, also needs reclassification and is tentatively titled ''Halticosaurus longotarsus'' at the moment.

Trivia

''Coelophysis'' was the second dinosaur in space. Although ''Maiasaura'' had been taken into space three years earlier, a ''Coelophysis'' skull from the Carnegie Museum of Natural History was aboard the Space Shuttle Endeavour mission STS-89 when it left the atmosphere on January 22, 1998. It was also taken onto the space station Mir before being returned to Earth.
''Coelophysis'' is also the state fossil of New Mexico.

In popular culture

''Coelophysis'' were featured in the BBC television series ''Walking with Dinosaurs'', and in ''When Dinosaurs Roamed America'', in which they are depicted hunting insects. The 1974 children's television series ''Land of the Lost'' also featured a ''Coelophysis'', nicknamed "Spot".

References

1. Gay, Robert J. 2001. "An unusual adaptation in the caudal vertebrae of ''Coelophysis bauri'' (Dinosauria: Theropoda)." ''PaleoBios'' 21: supplement to number 2. Page 55.
2. Gay, Robert J. 2002. "The myth of cannibalism in ''Coelophysis bauri''." ''Journal of Vertebrate Paleontology'' 22(3); 57A
3. Nesbitt, S.J., Turner, A.H., Erickson, G.M., and Norell, M.A. (2006). "Prey choice and cannibalistic behaviour in the theropod ''Coelophys''." ''Biology Letters'', First Cite Early Online Publishing doi:10.1098/rsbl.2006.0524.
4. Rinehart, L., Hunt, A., Lucas, S., Heckert, A., and Smith, J. (2005). "New evidence of cannibalism in the Late Triassic (Apachean) dinosaur, ''Coelophysis bauri'' (Theropoda: Ceratosauria)." ''Journal of Vertebrate Paleontology'', '25'(105A).
5. Cope ED.(1889) "On a new genus of Triassic Dinosauria". ''American Naturalist'' xxiii p. 626
6. Hunt and Lucas, (1991). "''Rioarribasaurus'', a new name for a Late Triassic dinosaur from New Mexico (USA)''. ''Paläontol. Z.'' 65 p. 191-198.
7. Sullivan and Lucas (1999). "''Eucoelophysis baldwini'', a new theropod dinosaur from the Upper Triassic of New Mexico, and the status of the original types of ''Coelophysis''". ''Journal of Vertebrate Paleontology'' 19(1): 81-90
8. R. B. Irmis, S. J. Nesbitt, and W. G. Parker. (2005). "A critical review of the Triassic North American dinosaur record." In A. W. A. Kellner, D. D. R. Henriques, & T. Rodrigues (eds.), ''II Congresso Latino-Americano de Paleontologia de Vertebrados, Boletim de Resumos''. Museum Nacional/UFRJ, Rio de Janeiro 139.
9. Paul GS. (1993) in ''New Mexico Museum of Natural History Bulletin''.
10. Talbot M (1911). "''Podokesaurus holyokensis'', a new dinosaur from the Triassic of the Connecticut Valley." ''Amer. Jour. Sci.'' 4 469-479

External links

★ ''Coelophysis'' in the Dino Directory

★ ''Coelophysis'' at DinoData