Fossil Butte National Monument is a United States National Monument managed by the National Park Service, located west of Kemmerer, Wyoming, United States. It centers on an assemblage of Eocene Epoch (56 to 34 million years ago) animal and plant fossils associated with Fossil Lake—the smallest lake of the three great lakes which were then present in what are now Wyoming, Utah, and Colorado. The other two lakes were Lake Gosiute and Lake Uinta. Fossil Butte National Monument was established as a national monument on October 23, 1972.

Fossil Butte National Monument preserves the best paleontological record of Cenozoic aquatic communities in North America and possibly the world, within the 50-million-year-old Green River Formation — the ancient lake bed. Fossils preserved include fish, alligators, bats, turtles, a dog-sized horse, insects, and many other species of plants and animals — suggest that the region was a low, subtropical, freshwater basin when the sediments accumulated, over about a 2 million-year period.Geologic travel guide from American Geological Institute

Geologic formations

During the Eocene this portion of Wyoming was a sub-tropical lake ecosystem. The Green River Lake System contained three ancient lakes, Fossil Lake, Lake Gosiute, and Lake Uinta. These lakes covered parts of southwest Wyoming, northeast Utah and northwestern Colorado. Fossil Butte is a remnant of the deposits from Fossil Lake. Fossil Lake was long from north to south and wide. Over the two million years that it existed, the lake varied in length and width.

Fossil Buttes National Monument contains only 13 square miles () of the 900-square-mile () ancient lake. The ancient lake sediments that form the primary fossil digs is referred to as the Green River Formation. In addition to this fossil-bearing strata, a large portion of the Wasatch Formation, river and stream sediments, is within the national monument. The Wasatch Formation represents the shoreline ecosystem around the lake and contains fossil teeth and bone fragments of Eocene mammals. Among these are early primates and horses.

History Coal mining for the railroad led to the settlement of the nearby town of Fossil, Wyoming. When the fossils were discovered, miners dug them up to sell to collectors. In particular, Lee Craig sold fossils from 1897 to 1937. Commercial fossil collecting is not allowed within the National Monument, but numerous quarries on private land nearby continue to produce extraordinary fossil specimens, both for museums and for private collectors.

Climate

Exhibits

The Fossil Butte National Monument Visitor Center features over 80 fossils and fossil casts on exhibit, including fish, a crocodile, turtle, bats, birds, insects and plants. A 13-minute video is shown about the fossils found at the site and what scientists have learned. Interactive exhibits let visitors create fossil rubbings to take home, and a computer program discusses fossils, geology and the current natural history of the monument.

Activities During the summer, lab personnel prepare fossils in public. Summer activities also include ranger programs, hikes, paleontology and geology talks, and participation in fossil quarry collections for the park.

A Junior Ranger program can be completed by children aged 5–12 (with exercises scaled to the child's age) in 3–4 hours. A highlight is hiking 3/4 mile up the butte to the dig, where interns from the Geological Society of America talk about their excavation and let children help them flake apart sedimentary deposits to discover fish fossils and coprolites.

List of fossil species recovered at Fossil Butte National Monument

Fish: Asterotrygon spp, an extinct stingray Diplomystus dentatus, an extinct ray-finned fish Knightia spp, an extinct fish related to herring and sardines Seven extinct species of perch Heliobatis radians, an extinct stingray Notogoneus spp, an extinct bottom-feeding fish Crossopholis magnicaudatus (Commons), a 1-meter (40 inches) long predatory paddlefish Asineops squamifrons, called 'mystery fish'- allocated its own family Asineopidae Two extinct species of the family Osteoglossidae Amphiplaga brachyptera, an extinct freshwater fish Two extinct species of the genus Hiodon

Amphibians:

Aleoamphiuma tetradactylum, an extinct omnivorous salamander Aerugoamnis paulus, an extinct frog

Mammals:

Coryphodon Onychonycteris finneyi and Icaronycteris index, bats Heptodon, an extinct tapir Apatemys chardini, a tree-dwelling mammal similar to the lemur Protorohippus, an early horse-like mammal Palaeosinopa didelphoides, an otter-like carnivore Hyopsodus wortmani 'tube sheep', a small omnivore L. popoagicum, an extinct odd-toed ungulate

Birds: Frigate birds Pseudocrypturus cercanaxius, an extinct shoreline bird Gallinuloides wyomingesis, an extinct land fowl Primobucco mcgrewi, an extinct roller bird Four extinct species of parrot- Cyrillavis coldurnorum, Cyrillavis olsoni, Avolatavis tenens and Tynskya eocaena

Reptiles: Afairiguana, an extinct anole Boavus idelmani, a small extinct snake Bahndwivici, Afairiguana avius and Bahndwivici ammoskius, extinct lizards Baptemys wyomingenis, an extinct river turtle Echmatemys wyomingensis, an extinct pond turtle Borealosuchus wilsoni and Tsoabichi greenriverenis, extinct crocodiles Three species of soft-shell turtles- Apalone heteroglypta, Axestemys byssinus and Hummelichelys guttata Baenidae, turtle Plants: Palm trees Cattails Gyrocarpus spp Lagokarpos Lacustris, a type of distinct 'winged fruit' plant Lagokarpos found in lake deposits Ailanthus confucii Platycerium, a staghorn fern Salvinia preauriculata, a water fern Lygodium kaulfussi 'climbing fern' Nelumbo spp Chaneya tenuis; a genus of uncertain affinities Birthwort (species unknown) Soapberry Species similar to a walnut

Arthropods:

Bechleja rostrata, an extinct species of shrimp Procambarus primaevus, an extinct species of crayfish Three unidentified species of spider Dragonflies Damselflies Crickets Other insects including bees and ants

Primary source:Green River Formation Fossils at Fossil Butte

Gallery

See also Crooked Creek National Natural Landmark Wyoming Dinosaur Center Paleontology in Wyoming Dinosaur National Monument, Colorado, Utah List of national monuments of the United States Other NPS Cenozoic Era sites in the western U.S.: John Day Fossil Beds National Monument, Oregon Hagerman Fossil Beds National Monument, Idaho Agate Fossil Beds National Monument, Nebraska Badlands National Park, South Dakota Florissant Fossil Beds National Monument, Colorado

References

External links

National Park Service: official Fossil Butte National Monument website Photo Gallery of Green River Formation Fossils from FBNM Photo tour of FBNM, from USGS Paleontology of Green River fossils, from University of California, Berkeley Geologic travel guide from American Geological Institute