Knightia eocaena (fish fossil)

Knightia eocaena is an extinct species of small, schooling freshwater fish related to modern herrings. Living roughly 40 to 50 million years ago during the Eocene epoch, they are exclusively found in the remarkably preserved limestone deposits of the Green River Formation in Wyoming, Colorado, and Utah.

Size: Averaging 10 to 15 centimeters (4 to 6 inches) in length, K. eocaena is the largest of the three known Knightia species, capable of growing up to 25 centimeters.Diet: They fed on plankton, insects, and tiny fish, using their gill rakers and small conical teeth.Ecosystem Role: As a highly abundant schooling fish, they served as the primary food source for larger Eocene predators like Diplomystus, Mioplosus, and Phareodus.

Green River Formation, Fossil Lake safari quarry, Wyoming