This Knightia fish skeleton was preserved by sediments dating around 50 million-years-ago during the sub-tropical to temperate Eocene Epoch when a large inland lake located near Kemmer, Wyoming, part of the Green River Formation, dried up. It was discovered by splitting the sandy layers of shale to expose it, then trimming and preparing it. The final step was to darken the skeleton and put a preservative on it to keep the skeleton from flaking off.

Extinct Knightia Fish Interesting Facts

Thousands of specimens of the small 6 to 10 inch (15 to 25 cm) long, prehistoric fish, Knighta, have been discovered in Wyoming’s Green River formation and in fact, Knightia, is Wyoming’s official state fossil. In life, the fish assembled in vast schools throughout the fresh water lakes and rivers of Eocene North America, and placed near the bottom of the aquatic food chain. The scarcer and larger Diplomytus and Mioplosus, mentioned below, were likely sustained by Knightia’s abundance, evident from stomach analysis. Befitting its small size, Knightia fed on tiny marine organisms such as plankton, insect larvae and diatoms.

I may have been a little too imaginative when I color penciled what I thought my fossil fish may have looked like in life, but I like how it turned out, anyway. At least the basic shape is accurate including its forward lower jaw and forked tail!

The Green River Formation

The following species are some of the most common extinct fish from the Green River Formation of Wyoming including, Knightia, similar to present day herring; Diplomystus, a large rib caged fish; Prisacara, a sun fish type fish; Mioplosus, a fierce bass like fish and Phareodus, a toothy piranha like fish. You can get a picture of all of these doing an internet search, very cool!

About the Green River Formation: Class Actinopterygii, the ray-finned bony fishes, comprise almost half of all known species of vertebrates, some 20,000 extant species. There are numerous locations worldwide that are noted for wondrous preservation of bony fishes, and the Green River formation that covers some 25,000 square miles of SW Wyoming, west Colorado and east Utah is one of the premier examples. The formation is one of the largest lacustrine (growing in lakes) sedimentary accumulations in the world, and spans the period from 40 to 50 million years ago during the Eocene Epoch.