DINOSAURS may have come in with a bang as well as gone out with one. Just below rocks that contain the earliest footprints of large meat-eating dinosaurs are the hallmarks of an asteroid impact and a mass extinction. The discovery suggests that the ecological stage was suddenly cleared at the beginning of the Jurassic period, leaving room for these giant beasts.
The first small dinosaurs evolved about 230 million years ago, and competed with many other reptiles until the Triassic period ended around 202 million years ago. In the Jurassic period that followed, most of the competitors vanished. Dinosaurs grew…
