The spurt in evolution is similar to the rise of mammals after the extinction of dinosaurs. Mammals, no larger than small dogs during the age of dinosaurs, diversified into tigers, elephants, whales and people after the reptilian competition died away.
The success of the dinosaurs after the Triassic-Jurassic extinction may be why they did not survive the second extinction.
"Small animals always do better in catastrophic situations," Dr. Olsen said, "because they can survive on smaller amounts of food."
He also pointed out that scientists now believe the small dinosaurs did survive. "We just call them birds," he said.
I'm a evolution buff (is that a real word?) who finds discoveries like this totally fascinating.