Wyoming is globally recognized for its remarkable paleontological discoveries, preserving an extensive record of prehistoric life. Its rock formations contain ancient organisms, from microscopic bacteria to colossal dinosaurs. For millions of years, Wyoming’s landscapes have acted as natural archives, safeguarding diverse ecosystems. This rich fossil heritage draws scientists and enthusiasts, providing insights into Earth’s deep past.
Why Wyoming is a Fossil Hotspot
Wyoming’s geological history created exceptional conditions for fossilization. During the Mesozoic and Cenozoic eras, the region experienced varied environments, including inland seas, vast swamps, and expansive floodplains. These ancient landscapes allowed organisms to be rapidly buried and preserved.
Sediment deposition from rivers and lakes entombed dead organisms before decay. Anoxic, or oxygen-depleted, conditions in ancient lake bottoms also preserved soft tissues and articulated skeletons. Over time, these sediment layers compacted into rock, transforming organic remains into fossils. The subsequent uplift and erosion of the Rocky Mountains exposed these fossil-rich layers, making them accessible.
Diverse Fossil Discoveries
Wyoming’s fossil record showcases an extensive array of life forms from different geological periods. Dinosaur remains are particularly abundant, with significant finds from both the Jurassic and Cretaceous periods, including sauropods like Diplodocus and Apatosaurus, and predatory theropods such as Allosaurus and Tyrannosaurus rex.
The state is also known for its well-preserved fish fossils from the Eocene epoch, including the state fossil, Knightia. Ancient mammals, such as early horses, camels, rhinoceroses, and primates, appear in Cenozoic deposits, offering insights into mammalian evolution. Beyond vertebrates, fossilized plants, insects, and marine invertebrates like trilobites and ammonites are commonly found, revealing Wyoming’s ancient ecosystems.
Iconic Fossil Localities
Wyoming hosts several renowned fossil localities. The Green River Formation, spanning parts of Wyoming, Utah, and Colorado, is world-famous for its exceptionally preserved Eocene fish, insects, and plant fossils, dating back approximately 52 million years. These fossils are found in fine sedimentary layers, indicating calm, deep lake conditions.
The Morrison Formation, a Late Jurassic sedimentary rock sequence, is another globally recognized site for its diverse dinosaur discoveries. Historic locations like Como Bluff within the Morrison Formation yielded numerous sauropods and other dinosaur species, playing a central role in the “Bone Wars” of the late 19th century. The Hell Creek Formation, found in eastern Montana and parts of Wyoming, is significant for Late Cretaceous dinosaur fossils, including Tyrannosaurus rex and Triceratops, providing a window into the final days of the dinosaurs.
Experiencing Wyoming’s Fossil Heritage
Visitors can engage with Wyoming’s rich fossil heritage through various museums and public sites. The Wyoming Dinosaur Center in Thermopolis features over 50 mounted skeletons, including a 106-foot Supersaurus and a Tyrannosaurus rex, alongside a rare Archaeopteryx specimen. This museum also offers “Dig for the Day” programs, allowing visitors to participate in active dinosaur excavations.
The Tate Geological Museum at Casper College displays a 75-foot Apatosaurus skeleton and “Big Al,” a complete Allosaurus fossil. For in-situ viewing, Fossil Butte National Monument near Kemmerer preserves a 52-million-year-old ancient lake bed within the Green River Formation. The monument’s visitor center exhibits over 2,000 fossils, and during summer, visitors can observe paleontologists at work in the quarry.