Prehistoric Planet Store - Replica fossils including dinosaurs like T. rex, Triceratops, and more!

Diplomystus is a representative of a primitive group of herring-like fishes known only from the fossil record. Some Diplomystus fossils have been found that date back to the Late Cretaceous Period, 80 million years ago. This species, Diplomystus dentatus is from the Eocene Epoch and is about 55 million years old. It is found in southwestern Wyoming in the world famous Green River Formation fossil beds. In these beds, layers of fine grained limestone yield well preserved fossils that offer the world's most complete look at an ancient fresh water lake environment. The Green River Formation contains an abundant and diverse flora and fauna including plants, insects, fish, and the other inhabitants of the lake environment.

The Green River Formation was a system of three ancient fresh water lakes that covered parts of Utah, Colorado, and Wyoming. These Lakes covered an area of about 25,000 square miles. Lake Uinta was the longest lived, spanning nearly 18 million years. Lake Gosiute existed for about 6 million years, and Fossil Lake, the shortest lived, existed for about 2 million years. During the Eocene Epoch this area of the United States had a subtropical climate similar to today's Florida Everglades.

Diplomystus dentatus is easily identified by its unique body shape and upturned mouth. The upturned mouth was used to prey upon fish and other organisms that lived near the lake's surface. Many Diplomystus specimens are less than eight inches long, but some have been found as long as twenty-six inches.