FISH FOSSILS
Green River Formation,
Kemmerer, Wyoming
Class actinopterygii, the ray-finned bony fishes, comprise almost half of all known species of vertebrates, some 20,000 extant species. There are numerous locations worldwide that are noted for wondrous preservation of bony fishes, and the Green River formation which covers some 25,000 square miles of SW Wyoming, west Colorado and east Utah is one of them. The formation is one of the largest lacustrine (i.e., lake) sedimentary accumulations in the world, averages some 2,000 feet thick, and spans the period 40 to 50 million years ago during the Eocene Epoch of the Cenozoic Era.