The fish fossils are found in an area called Fossil Lake, which is a part of the Green River Formation, the world’s largest fossil fish find. This ancient lake was located near erupting volcanoes. The fish are between 40 million and 50 million years old. Some of the fossil fish are related to modern day fish. The fossil fish come in several different types including knightia (herring), diplomystus (herring), phareodus, mioplosus (perch), and priscacara. The knightia and diplomystus may be found in the mass-mortality layers in the quarries. There are many theories that may explain why these fish died by the thousands in these particular layers. These theories include poisonous volcanic gases, temperature fluctuations, and food shortages. The fish are found in limestone. Fish fossils should never be washed under water as the limestone may weaken and break. A damp cloth should be okay, or we recommend blowing on the piece to remove the dust. Like other fossils, a lot of care goes into cleaning and preparing the pieces for display.
