Knightia Eocaena is the most common fish in Fossil Lake and maybe the most commonly articulated vertebrate fossil in the world. It is Wyoming's State Fossil. Length: up to 25 cm (10 in).
Fifty million years ago ancient Fossil Lake existed in what is now southwest Wyoming. Of its estimated maximum extent of 930 square miles, approximately 500 square miles of sediment remains. The 230 square miles across the center of the ancient lake-bed contain exceptionally fossiliferous sediments and associated geologic features including deltas, beaches, springs, and rocks from the center and nearshore environments.