Coelophysis

***Coelophysis*** (see - low - FI - sis) is a very well known early theropod dinosaur as scientists have discovered hundreds of skeletons of this meat-eater. It is the oldest dinosaur known in North America, living around 216 to 203 million years ago, during the Late Triassic Period.

*Coelophysis* could get fairly large for an early dinosaur, with adults ranging to a size of up to 3 meters (10 feet). These sizes are generally divided into two specimen types - robust andmehps

aa - and are thought to represent gender differentiation. Being a basal (one of the first) theropods, it had some characteristics which were lost on later members of the theropod family. It still had four fingers, although the fourth digit was quite small.

The remains of hundreds of individuals were found at Ghost Ranch in New Mexico, which provided scientists with an unprecedented opportunity to study the individual differences within a large herd of the same dinosaurs.

Like other early carnivores, *Coelophysis* had many small, sharp teeth. As is shown by the vast numbers of individuals at Ghost Ranch, it is evident that early dinosaurs exhibited social behavior to the extent of congregating in large herds. The exact purpose of this large gathering is not known, but some scientists feel that it may have been breeding season.

*Coelophysis* is at the base of the family tree of a great many dinosaurs including all the dilophosaurs, oviraptors, ornithomimids and the ever popular "Raptor" family which includes *Velociraptor*, *Utahraptor*, and *Deinonychus*.

Note that the original type material, which may or may not belong to the same kind of animal as those later found at Ghost Ranch, has been given its own (disputed) genus: *Eucoelophysis* ("true *Coelophysis*").

A *Coelophysis* skull became the first dinosaur fossil to be taken into space in January 1998 when the Space Shuttle "Endeavor" carried a specimen from the Carnegie Museum to the Mir Space Station.

It wasn't until in 2002 that the remains from the Ghost Ranch specimens have been re-examined, and later concluded that the "juvenile coelophysids" found in the abdominal cavities were actually from small crurotarsan reptiles such as *Hesperosuchus*. This is likely the result of the fossil of a larger individual overlapping a smaller one. With this discovery and to date, *Coelophysis* would no longer be recognized for having a cannibalistic behavior.

## Description

Coelophysis is known from a number of complete fossil skeletons of the species C. bauri, which was a lightly built dinosaur which measured up to 3 metres (9.8 feet) in length and which was more than a meter tall at the hips. Paul (1988) estimated the weight of the gracile form at 15 kg (33 lbs), and the weight of the robust form at 20 kilograms (44 lbs). Coelophysis was a bipedal, carnivorous, theropod dinosaur that was a fast and agile runner.

Recent studies on activity levels and the genus occurring in climates that could get colder than previously thought have changed opinions on the animal's integument. This revived an old hypothesis from the 1980s that *Coelophysis* was covered in feathers. The study indicated only a feathered animal of *Coelophysis* shape and size could have survived the cold so handily. Many paleontologists has thus begun returning the 1980s reconstructions for an idea of how the animal looked in life.

## Classification

Coelophysis is a distinct taxonomic unit (genus), composed of two species; C. bauri and C. rhodesiensis (the latter formerly classified as the genus Megapnosaurus). 2 additional originally described species, C. longicollis and C. willistoni, are now considered synonymous with C. bauri. C. rhodesiensis is probably part of this generic complex, and is known from the Jurassic of southern Africa.