Heliobatis radians,an extinctstingray,had small teeth for crushing snails and other mollusks and barbed spines on the tail for defense. This specimen is about 35 centimetres (14 in) long, including the tail.This 1.7-meter (5 foot 6 inch)Axestemys byssinusis one of the largest turtles known from Fossil Lake.
Fossil Butte National Monumentis aUnited States National Monumentmanaged by theNational Park Service,located 15 miles (24 km) west ofKemmerer, Wyoming,United States. It centers on an assemblage ofEocene Epoch(56 to 34 million years ago) animal and plant fossils associated withFossil Lake—the smallest lake of the three great lakes which were then present in what are nowWyoming,Utah,andColorado.The other two lakes wereLake GosiuteandLake Uinta.Fossil Butte National Monument was established as a national monument on October 23, 1972.
Fossil Butte National Monument preserves the best paleontological record ofCenozoicaquatic communities in North America and possibly the world, within the 50-million-year-oldGreen 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,freshwaterbasin when the sediments accumulated, over about a 2 million-year period.[3]
Map of major Wyoming geological formations, showing Fossil Butte (lower left) far south ofYellowstone(upper left), southwest across the state fromDevils Tower(upper right).
During theEocenethis portion ofWyomingwas asub-tropicallake ecosystem. TheGreen River Lake Systemcontained three ancient lakes, Fossil Lake, Lake Gosiute, and Lake Uinta. These lakes covered parts of southwestWyoming,northeastUtahand northwesternColorado.Fossil Butte is a remnant of the deposits from Fossil Lake. Fossil Lake was 40 to 50 miles (64 to 80 km) long from north to south and 20 miles (32 km) wide. Over the two million years that it existed, the lake varied in length and width.[4]
Fossil Buttes National Monument contains only 13 square miles (8,198 acres (33,180,000 m2)) of the 900-square-mile (595,200 acres (2.409×109m2)) ancient lake. The ancient lake sediments that form the primary fossil digs is referred to as theGreen River Formation.In addition to this fossil-bearing strata, a large portion of theWasatch 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.[4]
Coal mining for the railroad led to the settlement of the nearby town ofFossil, Wyoming.[7]When the fossils were discovered, miners dug them up to sell to collectors. In particular,Lee Craigsold 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.
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.
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.
Stingray prepared by R. Lee Craig (Asterotrygon maloneyi). In the collection of Fossil Shack. Prepared circa 1920.
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 theGeological Society of Americatalk about their excavation and let children help them flake apart sedimentary deposits to discover fish fossils andcoprolites.
List of fossil species recovered at Fossil Butte National Monument
FossilSabalitessp. palmetto frond, about two metres (6.6 ft) long.[9]
Notogoneus osculus,a 53-centimetre-long (21 in) bottom-dwelling fish from Fossil Lake.
An unidentified fossil bird from FBNM, in the collections of theField Museum
A well-preservedBuprestidaebeetle (3.5 cm or 1.4 in long) from the FBNM collections. Other beetles, flies andHemipterabugs have also been found in the Fossil Lake sediments.[9]