3" Brown Wyoming Fossil Fish from Fossil Lake | Artifact #G3020

Size Guide

Wyoming Fossil Fish from the Fossil Lake with Fish Identification Guide

Fifty-million years ago an ancient Fossil Lake existed in what is now southwest Wyoming. Of its estimated maximum extent of 930 square miles, approximately 500 square miles of sediments remain. The 230 square miles across the center of the ancient lake bed contain exceptionally fossiliferous sediments and associated geologic features including deltas, beaches, springs and rocks.

The unusual chemistry of Fossil Lake prevented decay and scavenging of dead organisms, while millimeter-thick layers of alternating limestone and organic matter slowly accumulated. The resulting laminated limestone contains the highest concentration of articulated fossil fish in the world. These fish, other fossilized aquatic organisms, and associated geologic features make Fossil Lake the world’s best Paleogene record of a freshwater lake ecosystem.

Since its discovery in the 1870s more than a million perfectly preserved fossil fish have been recovered. Preserved with the fish in the laminated limestone is a complete ancient aquatic ecosystem: cyanobacteria, plants, insects, crustaceans (shrimp, crayfish and ostracods), amphibians (frog and primitive salamander), alligators, turtles, birds and mammals, including the oldest pantolestid (otter-like animal). The subtropical terrestrial ecosystem surrounding the lake is also represented my rare fossils, including a horse, two snakes, lizards, two bat species, birds, an apatemid (an aboreal insectivore), a miacid (primitive carnivore), insects, and more than 325 types of leaves, seeds and flowers.

What is a Fossil?

A fossil is the prehistoric remains of a plant or animal.  Most fossils are created when a plant or animal is buried under layer after layer of sand and mud.  Under the massive pressure of hundreds of thousands of years these layers become sedimentary rock.  Minerals from the rock seep into the plant or animal, replacing them with a perfect replica in stone.

Fossils come in all shapes and sizes – they are as varied as the plants or animals they once were. The largest are dinosaur bones (which may be ten or more feet in length for a single bone) and the smallest are plant spores only a few hundredths of an inch across.

Fossils are found all over the world.  As the wind and rain erode hillsides, fossils become visible, and scientists can find and study them.  Removal of fossils from the rock is done very carefully to preserve the beauty and detail of the specimen.