Green River Formation
Osteichthyes
Phareodus encaustus (fish skeleton)
Tertiary
Wyoming
The Green River Formation is composed of sedimentary rocks located in western Colorado, eastern Utah, and southwestern Wyoming (see map). During the Eocene Epoch (55-37 million years ago) the Green River sediments were being deposited at much the same latitude as they are found today, but a series of three lakes (Fossil Lake, Lake Gosiute, and Lake Uinta) extended across the region. At the bottom of these lakes, plant and animal remains were buried by sediment and fossilized as the sediment was compacted and cemented into rock. Vertebrate, insect, and plant fossils are found within the Green River Formation, and these fossils indicate that the region's climate during the Eocene was subtropical.
Osteichthyes
Knightia (fish skeletons)
Tertiary
Wyoming
The distribution of fossils varies within the sedimentary rocks of the formation. At least fourteen genera of fish fossils have been found in the Green River Formation, most from Fossil Lake, which was the deepest of the three lakes. Found in this display are samples of the five most common fish genera found in the formation: Knightia, Mioplosus, Diplomystus, Priscara, and Phareodous. A variety of plant, mammal, stingray, alligator, turtle, bird, and insect fossils have also been found within the formation's rocks, though these fossils are rare in comparison to the fish fossils.
Osteichthyes
Mioplosus labracoides (fish skeleton)
Tertiary
Wyoming
The Green River Formation's fossil record provides
clues to the region's past climate. Fossil distribution within the formation
indicates that the lakes existed for just over 20 million years, forming about
sixty million years. Climate change caused the lakes to dry up, and many of
the plants and animals living in the region became extinct.
Osteichthyes
Diplomystus dentatus (fish skeleton)
Tertiary
Wyoming
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