Description: This 50 million year old, Eocene-Era fossil fish death assemblage contains OVER FORTY complete and partial examples, and comes from one of the world's famous Laggerstatten, the Green River Formation in Wyoming. The Green River system consisted of 3 lakes: Lake Uinta in Colorado and Utah, along with Lake Gosiute and Fossil Lake in Wyoming. A small portion of the fish fossils from Green River exhibits such fine preservation. The significant extent of soft-tissue preservation that makes the site famous is evident in this specimen.

This particular fish is Gosiutichthys parvus that was thought to be a species of Knightia until it was assigned to a new genus in the early 1980’s. With a maximum langth of about 70 mm and a more common 50 mm length, the derivation of the species name parvus (small) is easy to understand. It was a schooling fish which is sometimes found in mass mortality layers confined to a single plane, indicative of a single event. Theories as to the reasons include stratified water turnovers as well as poisoning due to blooms of blue-green algae. The modern-day Alewife is known to do so in the Great Lakes of the US.