More than 400 Green River Formation fossils are displayed in the museum. Plan time to wander through the exhibits and ask park rangers the questions these fossils are sure to inspire. Photography is welcome. In addition to the fossils displays, visitor center activities include:
Fossil Rubbing Table
Fossil Preparation Lab
Journey Through Time Exhibit
This exhibit displays the timeline of planet Earth. The display starts on the road leading up to the Visitor Center, with the formation of Earth, approximately 4.54 billion years ago. The timeline is set to scale, with every 9 inches equaling 1 million years in time. Along the road, major geologic and biologic events are displayed. At the Visitor Center, the timeline continues to wrap around the porch. It ends at present day, almost simultaneously with the appearance of recorded human history. Fossil Butte National Monument offers a place to study a small slice of time and change. We invite you to look for that small slice in time, labeled as Fossil Lake on the timeline.
The vitual aquarium provides an opportunity to look into ancient Fossil lake and see how the animals may have looked and behaved 52 million years ago. Fish can be selected by touching their fossil on the control panel or using a touchscreen to choose a different fish. A transparent OLED TV monitor displays the seleted fish as it swims across the aquarium. Inside the exhibit, there is a diorama of a nearshore lake bottom with models of plants, snails, and a stingray. Along the edges of the diorama are TV monitors which provide depth to the lake scene. A screen above the window to the aquarium provides information about that fish including how many fossils are found each year. The park hopes to add more organisms to the aquarium in the future.
27 species of fishes have been identified from Fossil Lake. This exhibit displays 14 fish species. While some of the fossils displayed in the Visitor Center are casts (exact replicas of the original fossil), all the fossils in this exhibit are originals. There are 45 fossils housed in this display, including a few mass mortality plates. The species represented in this display are:
8 species of turtles have been identified from Fossil Lake. This exhibit displays 9 fossil specimens, representing 6 species. All identified turtle species lived in aquatic or semi-aquatic habitats. The species represented in this display are:
This Borealosuchus wilsoni is a 13-foot-long cast of a fossil housed in the Chicago Field Museum. This specimen was discovered in 1984 and took almost a year to prepare for display.
Below the crocodilian is a coprolite (fossil poop). This coprolite, believed to be crocodilian coprolite, has no bone fragments in it. The lack of bone fragments suggests that B. wilsoni had an especially acidic digestive tract, similar to its modern relatives.
Plants are major indicators of climate. Paleobotanists (paleontologists who study fossil plants) use plant characteristics to understand ancient climates. Over 400 leaves, seeds, and flowers are known from Fossil Lake. All the fossils in this exhibit are original, while some other fossils in the visitor center are casts. This exhibit displays over 100 fossil leaves.
4 of the 34 species of birds identified from Fossil Lake are displayed in this case. In addition, a number of isolated feathers, feet, wings, and other body parts are displayed. The 4 species represented are:
This case displays the interactions, symbiotic (mutually beneficial) and parasitic (one organism benefits and other suffers), of plant life with other organisms. The 4 examples of plant and animal interaction displayed are:
Skeletonization (insect feeding located along the veins of leaves, often associated with larvae)
Marginal (insect feeding near the edges of leaves, may be associated with leaf-cutting insects such as bees)
Oviposition (fossilized insect eggs on leaves)
Holes in leaves
This case displays the large variety of invertebrates (animals having no backbone or spine) found from Fossil Lake. The fossils displayed include:
Procambarus primaevus (crayfish)
Bechleja rostrata (freshwater shrimp)
Biomphalaria sp. (snail)
Viviparus sp. (snail)
Plesielliptio sp. (clam)
Fry & Fingerlings Display
Fossil Lake's unique environment allowed for cartilaginous skeletons of young fish and other species to be preserved. This allows scientists to study the life cycle of species 52 million years old. The species displayed in this case are:
Ichnofossils (trace fossils) are evidence of animal activity, such as footprints or feces, that were not part of a physical organism. The trace fossils displayed in this case are:
Coprolites (fossilized feces)
Oncolites (sedimentary structures formed by cyanobacterial growth, similar to stromatolites)
Predator & Prey Display
Three examples of predator-prey interactions are displayed in this case.
Ingestion - Some fish are found with smaller fish ingested and preserved in their stomach region. Other fish are found with smaller fish preserved in their mouths.
Bite marks - One turtle is displayed with holes in its shell matching the teeth of a gar fish. Another turtle is displayed with large, widely-spaced holes, suggesting it fell prey to a crocodilian.
Regenerated fish tails - Regrown fish tails could be the result of a prey-fish escaping a predator-fish, but losing part of its tail in the process. Another possibility is that a fish had a disease that caused part of its tail to fall off.
Mass mortality plates represent a catastrophic event in Fossil Lake. These fossils can represent one of several events.
Change in water temperature - A change of 1-3 degrees fahrenheit could kill fish that require a specific water temperature to survive.
Change in lake water pH - Several volcanoes existed to the north of Fossil Lake. A volcanic eruption, resulting in volcanic ash entering the lake, could cause a sudden change in the lake water's pH. This could mean catastrophe to lake life.
Under-filled state of Fossil Lake - If the lake entered an under-filled state due to an increased period of evaporation, small pools of water could form. Fish trapped in pools would die due to starvation and suffocation.
Blue-green algal bloom - As bacteria dies, it consumes nearby oxygen from the water. This lack of oxygen rich water often causes fish to suffocate.
Overturn of lake water - If saltier water near the bottom of Fossil Lake rose to the surface, freshwater fish would die in the mix of saltwater and freshwater.
Arthropods are invertebrate animals (having no backbone or spine) with a hard external skeleton known as an exoskeleton. They also have segmented bodies with jointed appendages. This case displays insects, rare arthropods to find from Fossil Lake. Insect fossils from Fossil Lake exist only as very thin carbon stains on the rock. These soft-bodied organisms are difficult to preserve and are not visible beneath the limestone (unlike fossil vertebrates (having no backbone or spine). The insects displayed in this case are:
The Green River Formation produces a variety of angiosperm (flowering plant) fossils. Monocots (Liliopsida) are the most common flowers found from Fossil Lake. They usually have have parts in multiples of 3 parallel-veined leaves. Dicots (Magnoliopsida) are not as common to find fossilized.
Winged seeds are more common to find fossilized from the sediments of Fossil Lake than non-winged seeds. Non-winged seeds appear as black ovals or small flecks, making them more difficult to recognize in the collecting process.
Winged seeds displayed include:
Ailanthus lesquereuxi (Tree of Heaven)
Non-winged seeds displayed include:
unidentified seed resembling a walnut
This dense jungle-like landscape represents the forests and marshlands surrounding Fossil Lake. Over 400 species of fossil plants have been discovered in the sediments of Fossil Lake. Fossil grasses are rare, but woody flowering plants, similar to those found today in Asia, are abundant. A great diversity of bird species have also been found. These fossils and more help scientists understand what the greater ecosystem of Fossil Lake looked like. The temperate forest and humid climate are depicted in this diorama with multiple species. In the background mural, a giant Borealosuchus wilsoni (crocodilian) eyes a group of tapirs in shallow water.
Species displayed include:
This diorama depicts Fossil Lake's shallow shoreline, swarming with life. Fish swim among turtles and crayfish. Crayfish feed on dead shrimp. On the water's surface, water skimmers glide between giant lotus leaves. Damselflies fill the air, while the otter-like sinopa species emerges from a burrow. A giant, hippo-like corophydon wades along the shore through horsetails. In the background, crocodilians eye the scene hungrily. Species displayed include:
10 arthropods including: snails, crayfish, damselflies, water striders, shrimp
10 plants including: horsetails, ferns, flowers, seeds, trees
1 bird species: Accipitridae (early raptor)
1 reptile species: Chisternon undatum (turtle)
3 mammal species
Icaronycteris index (bat)
Coryphodon sp. (hippo-like herbivore)
Palaeosinopa didelphoides (otter-like carnivore)
Rocks Talk Display
The rocks of the Green River Formation tell the story of Fossil Lake. Above and below the Green River Formation, rocks of the Wasatch Formation tell the story of rivers and floods in the forest surrounding Fossil Lake. The rock types, rock structures, and fossils found within help scientists understand the ecosystem of Fossil Lake and its surrounding environment.
The 10 Rock Types of the Green River Formation
Chert - Hyper-saline period of Fossil Lake as evaporation dominates.
Kerogen-poor Laminated Micrite - Laminated limestone beds indicate freshening of Fossil Lake water. Fossil fish Asineops squamifrons is abundant.
Dolomicrite (evaporative) - Evaporation exceeds fresh-water entering the lake. Magnesium carbonate precipitates from lake water and forms mud layers on lake bottom. This mud layer eventually hardens into dolomicrite.
Dolomicrite - Water dissolves exposed limestone, causing calcium and bicarbonate to flow into Fossil Lake through rivers. This higher concentration of ions nearshore results in increased precipitation and a smaller quantity of kerogen. This creates soft, light-colored limestone.
K-spar Tuff - Volcanic ash falls from the air and makes a layer across the entire bed of Fossil Lake. These K-spar Tuff beds have been radiometrically dated at 51.98 million years old.
Kerogen-rich Laminated Micrite - Microbial mats separated by thin layers of carbonate mud, in contrast to thicker mud layers in nearshore rock. These thin layers of mud indicate this kerogen-rich laminated micrite is from the deep-waters of Fossil Lake.
Siltstone - Silt particles carried into Fossil Lake by streams. Siltstone indicates a shallow, nearshore environment close to a delta.
Sandstone - Fast moving river water moves large particles like sand or gravel. As rivers and streams enter Fossil Lake, sand settles at the river mouth. Sandstone is also present along the Fossil Lake shoreline, where wave energy washed away finer particles and left sand-sized grains.
Massive Limestone - Nearshore, shallow water is oxygenated by wave action and inflowing streams.
Claystone - Sediment around Fossil Lake is deposited by streams. Particles are carried away from streams by flood water and deposited on the forest floor. This eventually creates purple, red, and tan rock layers consisting of clay and silt.
The Green River Formation is made up of sediment from Fossil Lake. The sediment has been divided into 3 units, known as members. The middle unit, the Fossil Butte Member (FBM), represents the deepest and freshest state of Fossil Lake. This is the layer famous for producing an abundance of well preserved fossils.
The 4 Layers Within the Fossil Butte Member (FBM)
Gastropod Beds - In this layer, are an abundance of 3-D snails preserved.
Mini-fish Bed - Several bedding planes with an abundance of small fish, primarily Knightia eocaena, are indicators of catastrophic events capable of causing a mass die off of schooling fish. Chemical traces in the rock suggest red algae blooms may be a culprit.
18-inch Layer - Thin limestone laminae and high kerogen content in this layer cause fossil bones to create visible bumps under the sediment. Because of this, fossils are found and removed fully covered. They are prepared under a microscope and are exceptionally well preserved.
Sandwich Beds or "Split-Fish" Layer - 2 pairs of ash layers create "sandwiches" with limestone in the middle. The low kerogen content of this layer causes rock to split along fish fossils.
Fossil Quarry Display
The earliest fossil discoveries from ancient Fossil Lake were collected and sold to scientists, museums, and collectors around the world. This tradition continues today on private and state-owned land. This exhibit displays a quarry diorama and a timeline of fossil collecting and scientific discovery from Fossil Lake.