Size and Weight:
One of the earliest dinosaurs, Coelophysis has left a disproportionate imprint on the fossil record: thousands of Coelophysis bones have been discovered in the Ghost Ranch quarry of New Mexico, leading to speculation that these small, lithe, theropods roamed the western North American plains in pack. This pint-sized predator seems to have come in two varieties: "robust" (big and strong) and "gracile" (small and sleek), which paleontologists believe corresponded to males and females (though it's unclear if males were bigger than females, or vice versa). See also 10 Facts About Coelophysis
The 25- to 50-pound Coelophysis was characterized by its unusually large eyes (a hint that it may have hunted by night) and by its primitive wishbone, even though this dinosaur was only remotely ancestral to modern birds. In these respects, Coelophysis had some marked affinities with other theropods of the late Triassic and early Cretaceous periods, including Megapnosaurus (the dinosaur formerly known as Syntarsus) and Podokesaurus. The evolutionary relationships of these early dinosaurs is still being sorted out; suffice it to say that they were removed by a few million years from the first true dinosaurs of South America like Eoraptor and Herrerasaurus.
By the way, for years, Coelophysis was unjustly believed to be a cannibalistic dinosaur, since what seemed to be the bones of juveniles were found fossilized inside the guts of larger, adult skeletons. It now appears that these were in fact the bones of other dinosaurs that the Coelophysis specimens had recently eaten, and not juveniles of the species, though paleontologists are still debating the evidence. (As to why thousands of Coelophysis individuals have been found in the same location, that's not hard to explain; they were probably drowned in a flash flood and wound up piled together in a heap when the water receded.)