Fossils in Utah Show Progression of How Dinosaurs Became Extinct

A trove of 100-million-year-old fossils found in Utah has filled a giant gap in the history of dinosaurs and sheds light on how some of them may have become extinct, scientists reported Tuesday in the Proceedings of the National Academy of Sciences. The bones and other fossils were found at Cedar Mountain in central Utah, and show that the long-necked treetop browsers had already died out in favor of animals who could munch ground cover.

Richard Cifelli of the University of Oklahoma and colleagues at Brigham Young University say they also found the oldest-yet remains of a Gila monster--a stocky lizard that still roams U.S. deserts today--a snake and a very early marsupial mammal. The dinosaurs they found included the earliest tyrannosaur, a velociraptor, a boneheaded ankylosaur and a duck-billed hadrosaur.