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Coelophysis bauri

Two hundred twenty five million years ago a pack of Coelophysis dinosaurs wandered the Late Triassic floodplains of Western North America. The pack numbered in the hundreds; males females, juveniles and hatchlings, gathered together to do their dinosaur business. Perhaps the group stopped for a moment, all raising their heads, looking right, then left, and listening. Hearing, but not understanding their peril, until it was too late. They died together, all at once. Many millions of years later, paleontologists would wonder and then speculate about what really happened, and how these hundreds of Coelophysis were collected in a single mass grave. Perhaps it was a flash flood that gathered the struggling creatures in its furious currents, and carried them away to a watery end. Whatever the event, it has provided us with a unique and detailed look at one of the earliest dinosaurs. These hundreds of complete skeletons were found at a single site on Ghost Ranch in northern New Mexico.

Coelophysis bauri was a small dinosaur, growing up to 3 meters (10 ft.) long. It ran swiftly on its hind legs and its pointed snout was lined with tiny, dagger-like teeth. Long, three-clawed arms dangled from strong shoulders and its tail stretched out behind. It was a predator, about as tall as a coyote (or medium-sized dog), but with its neck and tail, much longer.

Taxonomy
Coelophysis is one of the best known early theropods. Its skeleton shows all the distinguishing characteristics of this group including clawed hands, hollow bones, and a bipedal stance. Most theropod dinosaurs fall into three subgroups: the more primitive ceratosaurs, the carnosaurs, and the bird-like coelurosaurs. Coelophysis is ceratosaur and within the ceratosaur group, it is assigned to its own family (Coelophysidae).

Two of the features that characterize ceratosaurs from other theropods are noticeable on the skull. First, the end of the snout has a notch or gap between the fourth and fifth teeth. This gap forms where the maxilla joins the premaxilla. With other theropods, this bone joint is a smooth one. Second, is a single, large triangular opening in front of the eye. This antorbital fenestra exceeds 25% of the length of the skull in Coelophysis. In more advanced theropods this opening is smaller and a second opening is also found.

Coelophysis can have up to 50 teeth in the upper jaw and another 50 on the bottom. This "hundred tooth bite" was probably used to capture a variety of prey that may have included heterodontosaurs, as well as, small lizards, insects and amphibians. The excavations at the mass grave on Ghost Ranch have uncovered some specimens that showed evidence of cannibalism. The fossilized remains of their last meal were revealed to be hatchling-sized members of their own species!

The Ghost Ranch site is so rich in Coelophysis materials that scientists have been able to establish that male and female Coelophysis. differed in size and body structure. Both robust (larger, stouter) and gracile (slender, lightweight) forms have been found.

[ Dinosauria -> Saurischia -> Theropoda -> Ceratosauria-> Coelophysidae ]

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