Fossil Butte National Monument - Fossils

The fossil record preserved within the Eocene Green River Formation of Fossil Basin is world-renowned. Over 100 years of intensive collecting has revealed a wide diversity of fossil fish, reptiles, birds, mammals, insects, and plants. Discoveries of new fossil species from the ancient lake sediments continue to expand understanding of the paleoecosystem.

Most notably, the quality of fossil preservation is extraordinary, nearly unparalleled in the fossil record. The quiet-water, fine-grained lake sediments, and water conditions that excluded scavengers combined to preserve articulated skeletons (all bones are in place rather than scattered). Delicate fossils, rarely preserved elsewhere, yield valuable scientific data.

Fossils from Fossil Basin are located in museums around the world. Intensive commercial fossil collecting from areas surrounding the national monument yields tens-of-thousands to hundreds-of-thousands of fossil fish each year. These fossil fish represent perhaps the most common articulated fossil vertebrates for sale anywhere in the world.

Today less than 1.5% of Fossil Lake is protected and managed by the National Park Service. Fossil Butte National Monument is a site that promotes the protection of this world-class paleontological heritage.