December 2010 lesson

Coelophysis, a bipedal dinosaur that was generally 6 to 10 feet (1.8 to 3 meters) long, was among the best known of all late Triassic theropods (Colbert, 1989). The Triassic world, beginning about 230 million years ago, marked the beginning of the Age of Dinosaurs and was very different than today. The continents of the Triassic Earth were joined together into one huge continent called Pangaea. The central region of this enormous landmass was a vast and inhospitable desert with a dry and harsh climate. Coelophysis inhabited this super continent during very uninviting times.



The death curve pose of this Coelophysis is caused by body tissues and neck tendons stiffening and shortening. This post-mortem action bends the head back. Note the sharp-clawed fingers used to grab small prey. Image © by S. Veatch, May, 2006

These slightly built predatory dinosaurs, first named by the famous paleontologist Edward Drinker Cope, had long jaws with sharp and serrated teeth (Cope, 1889). Coelophysis was a quick and agile dinosaur that hunted prey in packs, bringing other animals down with the fearsome claws of their three-fingered hands (Paul, 1989). They held their long tails high above their backs for balance.

Many hypotheses about Coelophysis behavior are based on interpretations of the remarkable accumulation of hundreds of well-preserved skeletons found at Ghost Ranch, New Mexico. George Whitaker discovered skeletons of Coelophysis bauri at Ghost Ranch in the summer of 1947, approximately 38 miles northwest of the town of Española, New Mexico (Colbert, 1995).

The Whittaker quarry preserves the full range of growth of both genders of Coelophysis—from juveniles to fully grown adults. When juvenile Coelophysis bones were found in the rib cage of a large Coelophysis, it was thought that Coelophysis was cannibalistic (Colbert, 1995). Why so many Coelophysis died at once at the Ghost Ranch location is a puzzle—predators typically do not congregate in the high density seen at Ghost Ranch unless there is an exceptionally rich food source. There is nothing to suggest there was such a prey concentration at the Ghost Ranch locality. The Coelophysis skeletons at the Whittaker quarry are well-preserved (about 25% are articulated or complete) and show no signs of scavenging. This is consistent with the leading hypothesis that these animals were killed by a flood, washed into a low spot or pond, and were then quickly buried (Colbert, 1995).

New discoveries of Coelophysis fossils are continuing to be made at Ghost Ranch. Each new discovery of these fossils yields more information about these remarkable dinosaurs.

References Cited:

Colbert, E. H., 1989, The Triassic Dinosaur Coelophysis: Museum of Northern Arizona Bulletin 57, 160 p.

Colbert, E.H., 1995, The Little Dinosaurs of Ghost Ranch: Columbia University Press, New York, 247 pp.

Cope, E. D., 1889, On a New Genus of Triassic Dinosauria: American Naturalist xxiii; 626.

Paul, G. S., 1988, Predatory Dinosaurs: New York Academy of Sciences, 464 p