TORONTO, Oct. 7 (UPI) -- Dinosaurs did not spread throughout the world by fiercely overpowering other species but by a more stealthy and patient advance, North American scientists say.
Canadian and U.S. researchers say a previously unknown species of dinosaur discovered in Arizona suggests dinosaurs were opportunists, taking advantage of a natural catastrophe that wiped out their competitors, a University of Toronto release said.
One of the five great mass extinction events in Earth's history happened at the end of the Triassic Period -- about 200 million years ago -- wiping out many of the potential competitors to dinosaurs.
Evidence from the newly identified dinosaur, named Sarahsaurus, and two other early dinosaur species suggests each migrated into North America from South America in separate waves long after the extinction and that no such dinosaurs migrated there before the extinction.
"Until recently, we've viewed dinosaurs as very successful animals that out-competed other species wherever they went," Robert R. Reisz, professor of biology at the University of Toronto Mississauga, says. "But this study puts dinosaurs in a very different light -- that they were more opportunistic creatures that moved into North America only when a mass extinction event made eco-space available to them."
