These 50 million year old, Eocene-Era fossil fish come from one
of the world's famous Laggerstatten, the Green River Formation
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 these specimens.
particular fish are Knightia eocaena, the State Fossil of Wyoming.
In Fossil Lake, these fish reach their maximum size of 25 cm,
but averages roughly half that. Knightia was a schooling fish
that 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.
Order Clupeifomes; Family: Clupeidae; Knightia eocaena
Location: Green River Formation, Fossil Lake, Kemmerer, Wyoming