Fossil Fish Knightia alta
mm = 1 inch): 125 mm in length on 162 mm by 115 mm matrix
Site: Green River Formation, Fossil Lake, Kemmerer, Wyoming
This 50 million year old, Eocene-Era fossil fish comes 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 this specimen.
particular fish is Knightia alta, a close relative of Knightia eocaena.
It is a more robust species, and is far less common than K. eocaena
in Fossil Lake. At a maximum size of 150 mm, it was just over ½
the size of K. eocaena. Knightia 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. At the top right you can see a single scale of a larger
fish, possibly of the genus Priscacara.