Many of the rock layers in Grand Staircase-Escalante National Monument were formed in the Cretaceous Period. These Cretaceous rocks hold a treasure trove of fossils, including many species of dinosaurs. In fact, in these layers of Cretaceous rocks scientists have found the most complete series of terrestrial, late Cretaceous fossils found anywhere on Earth.
Dinosaur discoveries have been made primarily in the rock layers that are 100-75 million years old (mya). Each field season more Cretaceous dinosaurs are discovered and most of these species are new to science.
Many of the rock layers in Grand Staircase-Escalante National Monument were formed in the Cretaceous Period. These Cretaceous rocks hold a treasure trove of fossils, including many species of dinosaurs. In fact, in these layers of Cretaceous rocks scientists have found the most complete series of terrestrial, late Cretaceous fossils found anywhere on Earth. 
