Museum Exhibits

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:

  • Video Programs
  • Fossil Rubbing Table
  • Fossil Preparation Lab
  • Ranger Programs
Earth's timeline exhibit on visitor center porch, displaying Fossil Lake
Visitor Center Timeline

NPS / Elizabeth Bargdill

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.
A look inside a virtual aquarium with a gar fish Atractosteus simplex swimming past. Above a screen provides information about the fossil fish. Below is a control panel where fossil replicas can be touched and a touch screen allows for additional choices.
A computer animated Atractosteus simplex swims through the virtual aquarium.

Chase Studio

Fossil Lake in a Box, a Virtual Aquarium

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.
Over 30 fossil fish of various shapes and sizes on display
Fossil fish exhibit

NPS Photo / Jamie Kennedy

Fish Wall

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:
  • Knightia eocaena
  • Knightia alta
  • Diplomystus dentatus
  • Phareodus encaustus
  • Phareodus testis
  • Mioplosus labracoides
  • Hypsiprisca hypsacantha
  • Hypsiprisca sp.
  • Cockerellites liops
  • Priscacara serrata
  • Amphiplaga brachyptera
  • Aesineops squamifrons
  • Hiodon falcatus
  • Notogoneus osculus
Learn more about fish fossils.
Dark brown fossil turtle facing right on tan stone. The fossil has all 4 feet extended and a tail that is as long as its shell.
Chisternon undatum fossil. Cast of private specimen.

NPS Photo

Turtle Wall

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:
  • Axestemys sp.
  • Chisternon undatum
  • Echmatemys sp.
  • Oliveremys uintaenis
  • Plastomenus thomasii
  • Baptemys wyomingensis
Learn more about reptile fossils.
11 fishes in an exhibit including 3 stingrays and 3 gars with scales visible.
The primitive fishes exhibit is located right in front of the front door to the visitor center.

NPS photo / Jamie Kennedy

Primitive Fish Case

8 species of primitive fishes can be found in this exhibit. All fish fossils in the museum are original fossils. The species represented in this display are:
  • Lepisosteus bemisi
  • Atractosteus simplex
  • Masillosteus janei
  • Amia pattersoni
  • Cyclurus gurleyi
  • Heliobatis radians
  • Asterotrygon maloneyi
  • Crossopholis magnicaudatus
Learn more about fish fossils.
5 plants in an exhibit case. 3 leaf structures, one with seeds on a stem, and one with a stem and curly branches coming off.
Fossils that associate different parts of plants, like leaves with seeds, are easier to scientifically describe.

NPS photo / Jamie Kennedy

Plant Structures Case

This case features 5 plant structures including leaves associated with seeds or roots and a palm inflorescene (flowering structure).

Learn more about plant fossils.
An alligator-looking fossil facing down in a tall, thin case. Fossilized poop is at the bottom of the case.
Crocodilian, cast of FMNH PR1674, a specimen on display in the Field Museum in Chicago.

NPS Photo / Jamie Kennedy

Crocodilian Case

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.

Learn more about reptile fossils.

Exhibit with mammals and reptile fossils including a lizard, caiman, and several snakes.
Mammal and reptile fossils exhibit.

NPS Photo / Jamie Kennedy

Mammal & Reptile Display

10 species of mammals and 15 species of reptiles (including 7 turtles) have been identified from Fossil Lake. This exhibit displays 11 fossils, representing 9 species. The reptiles displayed are:
  • Tsoabichi greenriverensis (caiman)
  • Boavus idelmani (small snake)
  • Saniwa ensidens (lizard)
  • Bahndwivici ammoskius (lizard)
Learn more about reptile fossils.

The mammals displayed are:
  • Protorohippus venticolus (horse)
  • Hyopsodus wortmani (rodent-like mammal)
  • Paleosinopa didelphoides (otter-like mammal)
  • Onychonycteris finneyi (bat)
  • Icaronycteris index (bat)
Learn more about mammal fossils.
An exhibit of around 100 fossil plants. A palm frond is in the foreground on the left with the exhibit case spreading to the right at an angle.
Plant Wall

NPS Photo / Jamie Kennedy

Plant Wall

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.

Learn more about plant fossils.
Exhibit with a mural of birds in the center and surrounded by bird or feather fossils
The bird exhibit showcases some of the many birds of Fossil Lake.

NPS Photo / Jamie Kennedy

Bird Wall

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:
  • Pseudocrypturus cercanaxius (shoreline bird)
  • Eoxygodactylus americanus (early songbird)
  • Primobucco mcgrewi (roller)
  • Gallinuloides wyomingenis (land fowl)
Learn more about bird fossils.
Fossil leaves with holes
Fossil leaves with evidence of insects.

NPS Photo

Interaction Display

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
Tan spiraled snail shell fossil on a darker brown stone.
Goniobasis sp., a fossil snail.

NPS Photo

Invertebrate Display

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)
  • Goniobasis (snail)
  • Plesielliptio sp. (clam)
4 juvenile fossil fish on various sized and colored rocks. It is labeled Knightia eocaena.
Juvenile fossil fish.

NPS Photo

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:
  • Phareodus encaustus (bony-tongue fish)
  • Knightia eocaena (freshwater herring)
  • Diplomystus dentatus (freshwater herring)
  • Notogoneus osculus (beaked sandfish)
  • Amphiplaga brachyptera (trout perch)
  • Asterotrygon maloneyi (stingray)
  • Mioplosus labracoides (perch-like fish)
  • Amia pattersoni (bowfin)
  • Hiodon falcatus (mooneye)
Learn more about fish fossils.
Fossil fish feces, labeled coprolite, forming a c-shape.
Coprolites, fossil fish feces.

NPS Photo

Trace Fossils Display

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:
  • Burrows
  • Footprints
  • Coprolites (fossilized feces)
  • Nematode trails
  • Oncolites (sedimentary structures formed by cyanobacterial growth, similar to stromatolites)
  • Swimming traces
Fossil turtle whose shell has several holes
Fossil turtle with bite marks on the shell.

NPS Photo

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.
4 dark brown oval-shaped fish on a speckled tan rock. One fish is alone near the top, the three fish at the bottom overlap each other slightly.
Cockerellites liops mortality.

NPS Photo

Catastrophe Display

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.
A variety of fossil insects on various sized rocks.
Fossil arthropods on display in the visitor center.

NPS Photo

Arthropods Display

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:
  • Lepidoptera (moth)
  • Buprestidae (jewel beetle)
  • Plecia pealei (march fly)
  • Hemiptera (true bug)
  • Odonata (damselfly)
  • Gerridae (water strider)
  • Hymenoptera (wasp)
  • Tipulidae (crane-fly)
  • Arachinida (spider)
  • Diplopoda (millipede)
Learn more about arthropod fossils.
11 fossil flowers on various sized rocks in an exhibit.
Fossil flowers on display in the museum.

NPS Photo

Flowers Display

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.
10 fossil seeds on varying sizes of rock.
Fossil seeds on display in the museum.

NPS Photo

Seeds Display

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:
  • Lagokarpos lacustris
  • Deviacer wolfei
  • Junglandaceae
  • Sapindaceae
  • Ailanthus lesquereuxi (Tree of Heaven)
Non-winged seeds displayed include:
  • Menispermaceae
  • unidentified seed resembling a walnut
Diorama of a lush forest with 2 fossils at the front, a mural to the left, and examples of leaves and bugs on the right.
Forest diorama with the plants and animals labeled in the display on the right.

NPS Photo / Jamie Kennedy

Forest Diorama

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:
  • 22 arthropods including: beetles, spiders, flies, moths, crickets, wasps
  • 24 plants including: trees, seeds, ferns, ivy, nettle
  • 3 bird species
    1. Gallinuloides wyomingenis (land fowl)
    2. Pseudocrypturus cercanaxius (tinamu-like bird)
    3. Eozygodactylus americanus (perching bird)
  • 1 mammal species: Onychonycteris finneyi (clawed bat)
  • 4 reptile species
    1. Echmatemys wyomingenus (pond turtle)
    2. Afairiguana avius (anole lizard)
    3. Bahndwivici ammoskius (crocodile lizard)
    4. Boavus idelmani (small snake)
Diorama a shoreline showing above and underwater including a stingray, an otter, and a bird hovering. A guide to the plants and animals is to the left.
Diorama of Fossil Lake's shoreline.

NPS Photo / Jamie Kennedy

Shoreline Diorama
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
    1. Icaronycteris index (bat)
    2. Coryphodon sp. (hippo-like herbivore)
    3. 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
  1. Chert - Hyper-saline period of Fossil Lake as evaporation dominates.
  2. Kerogen-poor Laminated Micrite - Laminated limestone beds indicate freshening of Fossil Lake water. Fossil fish Asineops squamifrons is abundant.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. Siltstone - Silt particles carried into Fossil Lake by streams. Siltstone indicates a shallow, nearshore environment close to a delta.
  8. 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.
  9. Massive Limestone - Nearshore, shallow water is oxygenated by wave action and inflowing streams.
  10. 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)
  1. Gastropod Beds - In this layer, are an abundance of 3-D snails preserved.
  2. 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.
  3. 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.
  4. 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.
A mannequin with a peg leg uses a hammer and chisel on rock.
A mannequin of Robert Lee Craig in the quarry diorama.

NPS Photo

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.

Last updated: September 23, 2022

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