By Katherine J. Wu/Smithsonianmag.com
About 145 million to 200 million years ago during the Jurassic Period, Earth’s creatures had to contend with one of the most powerful, ferocious predators that ever lived—a clawed, flesh-eating, sharp-toothed behemoth of a dinosaur that stalked the floodplains of what would become Western North America.
Despite what Hollywood might have you think, we’re not talking about Tyrannosaurus rex, which wouldn’t appear until the Cretaceous, the period immediately following the Jurassic. But as researchers reported last week in the journal PeerJ, a newly-described species called Allosaurus jimmadseni, which lived some 70 million years before its more famous carnivorous cousin, certainly made for a worthy opening act. A. jimmadseni roamed the North American continent between 152 million years ago and 157 million years ago, making it the oldest species of Allosaurus discovered so far, reports George Dvorsky for Gizmodo.
Like other members of the Allosaurus genus, A. jimmadseni boasted a suite of truly terrifying features. Study co-authors Mark Loewen, a paleontologist at the Natural History Museum of Utah, and Daniel Chure, a paleontologist at the Dinosaur National Monument in Utah, estimate that A. jimmadseni weighed up to 4,000 pounds and reached 26 to 29 feet in length at full size. ……