Fossil Fish (Diplomystus)

A fossil fish from the Green River Formation. This is a nice Diplomystus featuring lots of great detail.

The Green River Formation, spanning parts of Colorado, Utah, and Wyoming, is a famous Eocene-age geologic formation (about 53 to 48 million years old) known for its exceptionally preserved fossils. Formed from ancient lake systems, it features fine-grained sedimentary rocks like limestone and shale, preserving fish, plants, insects, and even early mammals in stunning detail. Notable for its lagerstätten—sites of exceptional fossil preservation—it offers a window into North America’s ecosystem after the dinosaurs, with species like the fish Knightia and early horse ancestors often found there. It’s also a key source of oil shale and fossil specimens for collectors.    

The fish comes with an acrylic display stand and a small card featuring the specimen name, region it was found and age.

This is genuine fossil. All the specimens we offer come with a lifetime authenticity guarantee.

Condition: Good | Size of fish: 5.63 inch | Age: 50 Million Years | Found: Kemmerer, Wyoming (Green River Formation)