Fish fossil millions of years old on a limestone surface - a rare museum item of its quality

Fish fossil millions of years old on a limestone surface - a rare museum item of its quality
The item dates back 48-55 million years.

Dimensions: 15x11 cm, thickness 11 mm, weight 430 g.

"Knightia alta fossil fish from the Green River Formation near Kemmerer, Wyoming. It was found at the Warfield Quarry, one of several commercial fossil quarries in the area. The specimen is nicely centered on a piece of irregularly shaped matrix that is well displayed on the included stand. All scales, bones, and fins are preserved well.

Knightia is an extinct genus of finned, spindle-like, bony housefish that shares a family with herrings and sardines. They lived in the freshwater (lacustrine) environments of North America and were eaten by almost anything that was larger. They ate insects and smaller fish, and used gill rakers to feast on plankton. Knightia eocena is the largest of the three species of Knightia, with a typical length of about 15 centimeters. This is Wyoming's state fossil.

The Green River Formation is an Eocene-age geologic formation that records the deposition of a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The Eocene spanned about 55.8 to 33.8 million years. This formation has a distinct stratigraphy showing alternating light and dark layers representing seasonal erosion and deposition.

Freshwater basins, fed by the Uinta Mountains on the Wyoming-Utah border, contained a vast representation of taxa. The beginning of the Eocene was characterized by warm upper latitudes, a greenhouse atmosphere rich in methane and carbon dioxide, and a local climate stabilized by large lakes inhabited by creatures such as crocodiles. Fossil Lake in Wyoming, which includes the Green River Formation, is known for its well-preserved warm lacustrine ecology."

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