These Knightia eocaena fossil fish are from the Green River Formation in Wyoming. The Green River Formation of Colorado, Utah, and Wyoming is one of the world's best locations for finding fossil fish. These Eocene fossils were preserved in intermountain lake basins while the Rocky Mountains were still growing! Knightia eocaena is an extinct genus of bony fish that lived in the fresh water lakes and rivers of North America during the Eocene epoch.