In Depth
Coelophysis is frequently used as an example of the early dinosaurs. Its bipedal stance from two legs that supported its body from underneath as opposed to sticking out to the sides, smaller arms and head mounted on an ‘S curved’ neck give it the distinctive theropod look. Coelophysis also had sharp recurved teeth that were serrated on the front and back edges, making them perfect for slicing.
Inside, the limb bones were hollow making Coelophysis very light. This combined with the long legs mean that Coelophysis would have been able to easily cover a greater distance in the search for prey, suggesting that Coelophysis most probably lived the life of an opportunistic carnivore in that not only did it hunt for small animals, it may have actively sought out carrion as well.
It was long assumed that Coelophysis was cannibalistic. This view was based upon the remains of smaller creatures found in what would have been the gut of Coelophysis. Although upon first glance they appeared to be Coelophysis juveniles, later study in 2002 by Rob Gay proved that they were the bones of reptiles that belonged to the crurotarsan group. These reptiles were common during this time of the Triassic, and the evidence now points to the crurotarsan reptiles forming a key part of the diet of Coelophysis, at least in this fossil location.
Coelophysis remains can be sub divided into robust and gracile forms, and it is now thought that these represent males and females of the species. This sexual dimorphism is also clearly seen in group concentrations of Coelophysis remains, and shows that they would at times cluster together. It is still unknown if this is evidence of an established pack, or just a number of individuals taking advantage of an abundant food source like can be seen with bears fishing for salmon in rivers today. The most famous group concentration of Coelophysis comes from the Ghost Ranch deposit discovered in 1947. It is thought by many that the Coelophysis individuals deposited there were killed by a flash flood, something that is considered to have been a frequent occurrence during this time. The specimens recovered from this deposit were in a much better state of preservation than the early fossils that had been described by Cope in 1889, and because of this, the phylogenetic position of Coelophysis would need to be shuffled around.
The original type specimen was in a very poor state of preservation, so poor in fact, some were uncertain about the legitimacy of assigning the Ghost Ranch specimens to the name Coelophysis. In 1991 the new name of Rioarribasaurus was assigned to these specimens but quickly contested on the grounds that the majority of the knowledge, written material and reconstruction of Coelophysis was based upon the Ghost Ranch fossils. Considering the arguments of the petition the ICZN voted to restore the name Coelophysis, and also decreed that a new type specimen of Coelophysis be taken from the Ghost Ranch deposits so that new specimens may be referred against more complete material. A consequence of this decision was Rioarribasaurus becoming a nomen rejectum (meaning ‘rejected name’), and has since been placed as a synonym to Coelophysis.
Further to the above, some palaeontologists also think that a later dinosaur named Megapnosaurus is actually a late surviving Coelophysis. Support for this comes from striking similarities between the two dinosaurs. If it can be proven that Megapnosaurus is a synonym, the temporal range of Coelophysis would extend beyond the Norian and well into the early Jurassic.
Further Reading
– Podokesaurus holyokensis, a new dinosaur from the Triassic of the Connecticut Valley. – American Journal of Science. 4 31: 469–479. – M. Talbot – 1911. – The Triassic dinosaur genera Podokesaurus and Coelophysis. – American Museum Novitates 2168: 1–12. – E. Colbert – 1964. – Rioarribasaurus, a new name for a Late Triassic dinosaur from New Mexico (USA). – Pal�ontologische Zeitschrift. 65 (1/2): 191–198. – A. P. Hunt & S. G. Lucas – 1991. – Coelurus bauri Cope, 1887 (currently Coelophysis bauri; Reptilia, Saurischia): Proposed replacement of the lectotype by a neotype. – Bulletin of Zoological Nomenclature. 49 (4): 276–279. – E. H. Colbert, A. J. Charig, P. Dodson, D. D. Gillette, J. H. Ostrom & D. B. Weishampel – 1992. – Geology and taphonomy of the Coelophysis quarry, Upper Triassic Chinle Formation, Ghost Ranch, New Mexico. – Journal of Paleontology 68 (5): 1118–1130. – Hilde L. Schwartz, David D. Gillette – 1994. – Opinion 1842: Coelurus bauri Cope, 1887 (currently Coelophysis bauri; Reptilia, Saurischia): lectotype replaced by a neotype. – Bulletin of Zoological Nomenclature 53 (2): 142–144. – International Commission on Zoological Nomenclature – 1996. – 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 Paleontology19. – R. M. Sullivan & S. G. Lucas – 1999. – An unusual adaptation in the caudal vertebrae of Coelophysis bauri (Dinosauria: Theropoda). – PaleoBios 21: 55. – R. J. Gay – 2001. – Forelimb bio-mechanics of non-avian theropod dinosaurs in predation. – Senckenbergiana Lethaea 82: 59–76. – K. Carpenter – 2002. – The myth of cannibalism in Coelophysis bauri. – Journal of Vertebrate Paleontology 22 (3): 57A. – R. J. Gay – 2002. – Preliminary statistical analysis defining the juvenile, robust and gracile forms of the Triassic dinosaur Coelophysis. – Journal of Vertebrate Paleontology 21: 93. – L. F. Rinehart, S. G. Lucas & A. B. Heckert – 2004. – A juvenile coelophysoid skull from the Early Jurassic of Zimbabwe, and the synonymy of Coelophysis and Syntarsus. – Palaeontologia Africana 40: 31–41. – A. Bristowe, & M. A. Raath – 2004. – The sclerotic ring of the Late Triassic theropod dinosaur Coelophysis. – New Mexico Geological Society Spring Meeting 26: 64.- L. F. Rinehart, A. B. Heckert, S. G. Lucas & A. P. Hunt – 2004. – Prey choice and cannibalistic behaviour in the theropod Coelophysis. – Biology Letters. 22 2 (4): 611–614. – S. J. Nesbitt, A. H. Turner, G. M. Erickson & M. A. Norell – 2006. – Furculae in the Late Triassic theropod dinosaur Coelophysis bauri. – Pal�ontologische Zeitschrift 81 (2): 174–180. – L. F. Rinehart, S. G. Lucas & A.P. Hunt – 2007. – A critical re-evaluation of the Late Triassic dinosaur taxa of North America. – Journal of Systematic Palaeontology 5 (2): 209–243. – S. J. Nesbitt, R. B. Irmis & W. G. Parker – 2007. – The paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block. – New Mexico Museum of Natural History & Science, a division of the Department of Cultural Affairs Bulletin 45: 260. – L. F. Rinehart, S. G. Lucas, A. B. Heckert, J. A. Spielmann & M. D. Celesky – 2009.
