Coelophysis was a small, compact dinosaur that lived about 210 million years ago. It was a quick and agile hunter that had hollow bones and a hole-ridden skull, which helped to reduce its weight and increase its speed. Some fossils have been found with other small Coelophysis bones inside, and at first, it was thought that Coelophysis might have given birth to live young. It is now believed, however, that it was probably a cannibal that occasionally devoured its own young.