Eocene Green River Knightia
Knightia eocaena
Green River Formation
Middle Eocene
Lincoln County, Wyoming
This is an fine example of the species from the Fossil Butte Member of the Green River Formation. It displays excellent preservation of bones, scales, and fins. The slab is from the 18 inch layer. The fish is 19.5 cm. and slab is 31 x 31 cm.
Knightia eocaena is the most important and most common fish species in the Fossil Lake early Eocene. It formed immense schools that sometimes were killed en masse and are found preserved in mass-mortality layers in this famous lagerstatten. Sudden changes in water temperature or chemistry are suspected to cause the mass die-offs. Their schooling behavior persisted throughout their lives as evidenced by mortality layers of both juvenile and adult fishes. This species was a keystone of the food web in Fossil Lake. It fed on algae and zooplankton and in turn was prey for a wide variety of predatory fish.