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Fossil fish occur within the beds of what was once the ancient lake Uinta, now part of the Green River Shale formation of western Wyoming. Sometime during the Eocene Epoch of geologic time (50,000,000 years ago) volcanic or climatic changes probably occurred which disrupted the lake’s ecology and resulted in massive fish mortality. When quarried today, the shale reveals impressions and actual bones of several species.
Knightia and Diplomystus are both herring, closely related to the modern herring Clupea. Diplomystus is easily distinguished from Knightia by it’s proportionately longer anal fin base.
Phareodus is a beautiful fossil fish that makes up about 5% of the fish in the Wyoming fossil beds.
Mioplosus is a member of the perch family, which today inhabit freshwater lakes, rivers and streams throughout the northern hemisphere.
While the Priscacara can reach a maximum size of 14 inches, the average size is 4-5 inches. It is identifiable by its sunfish-like form, including 10 to 11 hard spines in the dorsal fin.
