Paleontology and geology

Triassic limestones in the western half of Utah were deposited in marine waters. The eastern half of the state contains red sandstones and shales deposited along the shoreline and on the floodplains of rivers further inland. Fossils in the limestones include marine organisms such as snails, clams, brachiopods, and ammonoids, while the terrestrial deposits yield the remains of freshwater sharks, bony fish, amphibians, and reptiles (lizards and the earliest dinosaurs) that lived in and along rivers, lakes, and marshes. Fossilized footprints of dinosaurs are also abundant.