Where to find fish

Frequently asked questions

Where can I find fossil fish?

The Green River Formation in southwest Wyoming (Eocene, approximately 50 Ma) is the most accessible site for complete fossil fish that collectors can legally keep. Two commercial quarries near Kemmerer — American Fossil Quarry and Ulrich's Fossil Gallery — allow visitors to split limestone and keep whatever fish they find. The most common species is Knightia, a small herring-like fish typically 5 to 15 centimetres long; larger Diplomystus and Mioplosus also occur. Fossil Butte National Monument, adjacent to the commercial quarries, is the non-collecting counterpart where fish are viewable in situ. The Fur Formation in Denmark (Eocene, approximately 55 Ma) preserves complete fish in grey-green moler clay; the Fur Museum on Fur Island runs fee-based collecting day-trips. In the UK, the Eocene London Clay on the Isle of Sheppey produces fish teeth, ear bones (otoliths), and occasional vertebrae, though complete fish are rare.

What is the most common fossil fish?

Knightia eocaena from the Green River Formation in Wyoming is often described as the most abundant vertebrate fossil in the world — millions of specimens have been commercially recovered. It was a small schooling fish similar in lifestyle to modern herrings, typically 5 to 15 centimetres long. Its abundance reflects both its ecological dominance during its lifetime (approximately 48 to 52 million years ago) and the exceptional preservation conditions of the Green River lake system, where oxygen-poor bottom waters slowed decay and prevented scavenging. Complete Knightia specimens with clear scale impressions and fin rays are the most commonly sold fossil fish globally. Isolated shark teeth are more common across all fossil sites worldwide, but Knightia is remarkable for producing complete articulated skeletons in commercial volume.

How are fish fossils preserved?

Fish fossilize most readily as articulated impressions in fine-grained sediment when a carcass sinks to an anoxic (oxygen-poor) lake or sea floor. In these conditions bacterial decay slows, sediment covers the body before it disarticulates, and soft tissue gradually mineralizes or leaves a carbonaceous film. This process is most effective in stratified lake systems with permanently anoxic bottoms — which explains why the Green River Formation and the Jurassic Solnhofen lagoons of Bavaria produce such complete specimens. In higher-energy marine environments, fish are typically represented only by their hardest parts: teeth, otoliths (ear bones), and scales, which are dense enough to survive transport and dissolution. Complete articulated fish are a relatively rare outcome requiring unusual burial conditions, which is why they command premium prices from commercial collectors.