Denver Formation, formed during the Paleogene / Cretaceous periods 55 million years, contains fossils and bones from dinosaurs like Tyrannosaurus rex and Triceratops. While the forests of vegetation, dinosaurs, and other organisms thrived, their reign would come to an end at the Cretaceous-Paleogene boundary (K-T boundary). In an instant, millions of species are obliterated from a meteor impact in Mexico's Yucatan Peninsula. While this extinction lead to the dinosaurs' and other organisms' demise, some life did prevail to repopulate the earth as it recovered from this tremendous disaster. The uplifted Front Range continued to constantly erode and, by 40 million years ago, the range was once again buried in its own rubble.: Related sites are: Austin Bluffs Park, Green Mountain, Palmer Park, Pulpit Rock Park, South Table Mountain