Paleontology and geology
During the Triassic, erosion lowered the Ancestral Rockies, burying them in their own debris. Extensive red beds formed adjacent to a shallow seaway that lay to the north in Wyoming, and Colorado hosted its first dinosaur. Other Triassic fossils include armored aetosaurs, crocodile-like phytosaurs, large amphibians, conifers, and the very enigmatic plant known as Sanmiguelia. Portions of the Triassic section near Denver were formed in a coastal environment and contain abundant limestone stromatolites.