Significant fossil fish discoveries have been made in Lebanon, Germany, Brazil, Canada and China. The Green River Formation in Wyoming, Colorado and Utah is known to be the best place to find fish fossils on earth. The first noticeable characteristics of this area are the cliffs of marly limestone and pink shale. The finely bedded shale settled in a lake and contains many fossil fish. The sandstone at the top of the cliffs was deposited by a river. The limestone here is famous for its abundant and well-preserved fossil fish.

Most of the fish found here have evolved a body plan somewhere in between the Placoderms and the bony fish of the class Osteichthyes.

Fossils were first found here on the banks of the Green River in Wyoming and it was soon realized that an enormous amount of fossil fish diversity could be located in this deposit. Many types of rare and extinct fossil fish have been found here including the extremely rare Mooneye fish fossil, Dogfish fossil, Sand Fish fossil, Gar fish fossil and Paddlefish fossil. The Stingray fossil, or Heliobatis, is a very valuable fossil also found in this area.

Relatively rare fossils found in the Green River Area in Wyoming are the Priscacara fish, the Phareodus fish, and the Amphiplaga fish. The most common fish fossil found is the Knightia, a small and extinct herring.