Coelophysis, was one of the early Dinosaurs that represented a medium sized predator within the ecosystems in which it lived. Coelophysis means, 'hollow form' in Latin. This refers to the lightweight nature of the animal and the bone structure built for speed and agility. Coelophysis is arguably the best known Triassic Dinosaur, due to the sheer number of high quality skeletal remains discover. Ghost Ranch, Arizona, is very famous within Triassic Palaeontology, being the site of a large assemblage of fossilised Coelophysis, in varying degrees of preservation and articulation, as well as varying ages and sizes. Hundreds of individuals are known from this site alone. All this adds up to a very well known animal. Coelophysis often provides a keystone example for representing the early stages of Theropod Dinosaur evolution, with certain features that can be regarded as primitive overall (but for its time rather revolutionary) when compared with later forms. However, Coelophysis was far more advanced than the mammal like reptiles which had already existed long before Coelophysis. Many Palaeontologists think that Coelophysis would have been a grouping predator, moving as a swarm, or flock, of sharp eyed hunters. Fully grown Coelophysis attained sizes of 2-3 metres in length, and a height of over 1-2 metres. This was large enough to terrorise many small-medium sized animals, and perhaps due to sheer weight of numbers if they did flock, even large enough to threaten large prey items. However, older Rauischian Archosaurs, cousins of the Dinosaurs, such as the deadly 6 metre long Postosuchus, and the 5 metre long Prestosuchus, would have been more than fearsome and powerful enough to fend off even flocks of Coelophysis - though maybe not if badly injured or ill. These older reptiles, would have been the predators of Coelophysis itself, but they probably didn't attempt to for one good reason; Coelophysis was fast. Too fast for these quadrepedal reptiles, which would do far better hunting slow herbivores such as the Dicynodontid, Placerias. Bipedal and lightly built, with a long balancing tail and efficient circulatory, digestive (particularly impressive water processing and conservation) and respiratory systems, as well as having superbly evolved legs which where 'springy' and muscular, this little Dinosaur would have been fast, agile and to many animals, dangerous as a consequence. For its day, Coelophysis may have been the most intelligent reptile (or any other animal for that matter) on Earth. Coelophysis belongs to the primitive Coelurosaurid Theropod Dinosaurs.