Continued from: http://www.furaffinity.net/view/6202298/

Coelophysis is known from a great many skeletons, many of them excavated in mass from a quarry at Ghost Ranch, New Mexico. At Ghost Ranch, the bodies of hundreds of Coelophysis that were probably killed in a flood are preserved in the remains of an ancient forest whose trees often reached more than 100 feet in height. This extraordinary concentration of Coelophysis specimens is usually interpreted as evidence of gregarious, social behavior, but other interpretations are possible.

First and foremost, it is extraordinarily strange given our present understanding of small predator ecology for them to form such a large herd. This in itself is a good reason to seek other explanations, but is not conclusive proof that such herds were impossible. Still, we know that the late Triassic period was often hot and dry, or hot and dry with a cooler rainy season. It is possible that the Coelophysis specimens at Ghost Ranch were concentrated around dwindling water supplies by a drought, and then killed in a flash flood when rain finally came. The fact that the last water to be found in drought-plagued areas is often found in areas vulnerable to flash floods makes this plausible, but proves nothing. However, a bit of information supporting the hypothesis is often overlooked: At least two of the specimens at Ghost Ranch were found with the remains of juveniles in their stomachs. In normal times, such cannibalism among social groups is rare, if not unknown. However, it is not rare in stressful times such as drought. During droughts, various animals (including birds) that are not ordinarily cannibalistic will engage in cannibalism, sometimes even eating their own young.

Another possible explanation supports the idea that Coelophysis was gregarious, but did not form such large herds. For example, penguins are predators that live in groups and return year after year to the same rookeries to raise their young. In such rookeries, the ground is a thick, spongy mass of dead, decomposed penguins from many years past. (Yes, it is gross!) Thus penguins can accumulate many dead penguins in a single place in such a fashion that the total number of dead penguins exceeds the size of the live flock that produced the mass of dead penguins. In a similar fashion, repeated use of the Ghost Ranch site over a period of years could give the false impression that Coelophysis congregated in larger groups than it actually did. (Paleontologically, it is very hard to determine if all the critters in a big pile of bones died simultaneously in an instant, or sequentially over 50 or 200 years.) Thus, a pack of 10 Coelophysis with an annual mortality of 10% could produce 200 skeletons in 200 years. [Personally, I prefer the second theory.]

From the Dinosaur Walk Museum in Pigeon Forge, Tennessee.

~ harui