Coelophysis

Coelophysis, one of the earliest known dinosaur genera, was a theropod dinosaur genus that lived during the Late Triassic, from 216 to 196 million years ago, in the southwestern part of the today United States[1] and in southern Africa[2]. It was a small, lightly built, bipedal carnivorous dinosaur with a maximum length of 3 meters. The first fossils of this dinosaur were found by David Baldwin (he was an amateur fossil collector, and worked for Edward Drinker Cope ) in the Chinle Formation (northwestern New Mexico), in 1881[3]. The type species of the genus was originally described as Coelurus bauri by Cope in 1887[4], and later attributed to the subsequently established genus Coelophysis[5]. The name Coelophysis means ’hollow form’, referring to the hollow fossil vertebrae of the animal[5]. Later, in 1947, a large number of Coelophysis fossils were found by George Whitaker (assistant of Edwin H. Colbert) also in New Mexico, at the Ghost Ranch[6].

Coelophysis map

Known occurrences of Coelophysis fossils.

Description and anatomy

Coelophysis had an estimated weight of between 15 and 20 kilogramms[7]. It must have been a quite fast and agile runner[8]. This dinosaur possessed the ancestral characteristic of having four digits on its hands – however, one of these was not well developed, and it was embedded in the hand[5]. Nevertheless, these forelimbs were suitable for grasping prey. It had a slender and relatively long neck and tail, and the neck showed a sigmoid curve. The prezygapophysis of its caudal vertebrae forming a semi-rigid lattice probably prevented the up-down moving of the tail[9]. Some fossils have preserved the sclerotic rings, which gave protection for the eyes[10]. Its well-developed forward-facing eyes, which provided an excellent stereoscopic vision, shows that Coelophysis was a diurnal, visually oriented carnivurous dinosaur[10].


Smiley face

Coelophysis bauri. Source: By Firsfron, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1059865

Valid species

Besides C. bauri, there are two more valid species in the genus: C. rhodesiensis from Africa[11], and C. kayentakatae from the south-western pat of the United States.

Paleobiology

Coelophysis had a dentition typical for carnivorous dinosaurs; recurved, sharp, and blade-like teeth, with fine, saw-like serrations on both edges. This dinosaur probably hunted for smaller reptiles. However, it also could have the ability to hunt in packs in order to kill larger preys[12]. Earlier, based on bone fossils which were supposed to belong a juvenile Coelophysis and were found within the abdominal cavity of a mature specimen, it has been suggested that cannibalism might have occurred in case of this dinosaur[13]. However, due to more recent investigations, this theory was rejected[14]. Some evidences also suggest that Coelophysis might have been a gregarious dinosaur[7]. It is likely that Coelophysis had some degree of parental care towards its hatchlings, until they grow large enough for surviving by their own[15].


Smiley face

Coelophysis bauri in triassic environment. Source:By ABelov2014 (https://abelov2014.deviantart.com/) - https://abelov2014.deviantart.com/art/Coelophysis-Peteinosaurus-530148271, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=64765007

Smiley face

Fossilized skeleton of Coelophysis bauri. Source: wikiwand. Author: Thom Quine. License link: https://creativecommons.org/licenses/by/4.0/

Scientific references

[1] Gaines, Richard M. (2001): Coelophysis. ABDO Publishing Company. p. 4. ISBN 978-1-57765-488-9

[2] Weishampel, David B; et al. (2004): Dinosaur distribution (Early Jurassic, Africa). In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 535–536. ISBN 0-520-24209-2.

[3] Glut, D.F. (1999): Dinosaurs, the Encyclopedia, Supplement 1. McFarland & Company, Inc. p. 442. ISBN 978-0-7864-0591-6.

[4] Cope, E.D. (1887): The Dinosaurian Genus Coelurus. The American Naturalist. xxi 5: 367-369.

[5] Cope, E.D. (1889): On a new genus of Triassic Dinosauria. The American Naturalist. 23 (271): 621–633. doi:10.1086/274979.

[6] Colbert, E. (1989). "The Triassic Dinosaur Coelophysis". Museum of Northern Arizona Bulletin. 57: 160.

[7] Schwartz, H.L.; Gillette, D.D. (1994): Geology and taphonomy of the Coelophysis quarry, Upper Triassic Chinle Formation, Ghost Ranch, New Mexico. Journal of Paleontology. 68 (5): 1118–1130. doi:10.1017/S0022336000026718.

[8] Rinehart, L.F.; Lucas, S.G.; Heckert, A.B.; Spielmann, J.A., and Celesky, M.D. (2009). "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.

[9] Gay, R.J. (2001): An unusual adaptation in the caudal vertebrae of Coelophysis bauri (Dinosauria: Theropoda). PaleoBios. 21: 55.

[10] Rinehart, L.F.; Heckert, A.B.; Lucas, S.G., and Hunt, A.P. (2004): The sclerotic ring of the Late Triassic theropod dinosaur Coelophysis. New Mexico Geological Society Spring Meeting. 26: 64.

[11] Bristowe, A.; Raath, M.A. (2004): A juvenile coelophysoid skull from the Early Jurassic of Zimbabwe, and the synonymy of Coelophysis and Syntarsus.(USA). Palaeontologica Africana. 40 (40): 31–41.

[12] Paul, G.S. (1988): Predatory Dinosaurs of the World. Simon & Schuster. p. 260. ISBN 978-0-671-61946-6.

[13] Haines, T.; Chambers, P. (2007): The Complete Guide to Prehistoric Life. Firefly Books. pp. 70–71. ISBN 978-1-55407-181-4.

[14] Gay, R.J. (2010): Notes on Early Mesozoic Theropods (First ed.). Lulu press. pp. 9–24. ISBN 978-0-557-46616-0.

[15] Rinehart, L.F.; Lucas, S.G.; Heckert, A.B.; Spielmann, J.A., and Celesky, M.D. (2009): 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 and Science, A Division of the Department of Cultural Affairs Bulletin. 45: 260.