Asteroid May Have Given Rise to Dinosaurs

An asteroid may have wiped out the dinosaurs 65 million years ago, but an earlier one probably allowed the rise of the giant creatures, which dominated the planet for 135 million years, says a team from Rutgers University in New Jersey.

Piecing together evidence from footprints, fossils and a dusting of a rare metal found in asteroids, the researchers reported in the May 17 issue of Science that a huge impact wiped out most of the plants and crocodilian creatures that ruled the world during the Triassic era.

That opened the way for the age of the dinosaurs in the Jurassic era, just as the later asteroid allowed mammals to evolve. Looking at footprints and fossilized bones from nearly 80 sites, the team concluded that it only took about 50,000 years for dinosaurs to start growing really big.

Before the Jurassic, the biggest dinosaur around was probably something like plateosaurus, a long-necked, two-legged plant-eater 20 feet long. Afterward, giant carnivores such as Tyrannosaurus rex and gigantosaurus reached lengths of 41 feet and more.