6 ago 2012
The evolution of new dinosaur species may have surged due to the rise of the Rocky Mountains and the emergence of a prehistoric inner sea in North America, researchers say. Duck-billed and horned dinosaurs flourished in North America, reaching a peak about 75 million years ago, a time known as the Campanian. For instance, one Campanian region known as the Dinosaur Park formation in what is now Canada saw seven different duck-billed dinosaur species and five horned dinosaur species emerge. A comparable region known as the Hell Creek formation in the United States from the Maastrichtian, the time that led up to the end of the Age of Dinosaurs 65 million years ago, saw only a single duck-billed dinosaur species and maybe three horned dinosaur species at most. PHOTOS: Evolution Before Your Eyes "The reason for this discrepancy in dinosaur diversity has never been adequately explained," said researcher Terry Gates, a vertebrate paleontologist at Ohio University.
Dinosaurs and geology
To help solve the mystery behind this pattern of evolution, Gates and colleagues analyzed the ancient geology of western North America, since environmental alterations often influence evolution. After focusing on trends in mountain and ocean formation 70 million to 80 million years ago, they found the landscape experienced profound changes back then that may have influenced dinosaur evolution. During the early to middle Cretaceous, geological forces lifted the western United States, creating a huge mountain range known as the Sevier Mountains. This extended in a line from the American southwest through Alberta, Canada. Later, one of the tectonic plates under North America's crust shifted, building another mountain range farther east — the Laramide Orogeny, the infant stage of the modern-day Rocky Mountains. (The World's Tallest Mountains) The area just to the east of the new Sevier Mountains dipped downward, creating a shallow inner sea known as the Western Interior Seaway that flooded the continent from the Canadian Arctic to the Gulf of Mexico. This seaway divided the continent into three large islands to the north, east and west that were densely populated with dinosaurs.
The wild west
The dinosaurs of the west
dwelled on an island called Laramidia. "Western North America has been a
hotbed for dinosaur discoveries for more than a century, but the recent
explosion of new dinosaur species coming out of Utah
is sending waves through the paleontological community and
revolutionized our understanding of dinosaur evolution on the
continent," researcher Lindsay Zanno said in a statement. Zanno is the
director of the Paleontology and Geology Research Laboratory at the
Nature Research Center of the North Carolina Museum of Natural Sciences...
