5.6" Fossil Fish (Knightia & Mioplosus) Mortality Plate - Wyoming

This is a 5.6" wide fossil fish plate collected from the "gastropod layer" of the Clear Creek Quarry at the Green River Formation of Wyoming. The shale contains multiple partial fossil fish (Knightia eocaena & Mioplosus labracoides) that are naturally associated with each other and bear red-brown and black preservation. Further prep could be done to expose some of the fish and potentially some unseen fish within the shale.

This specimen is accompanied by a display stand.

About Knightia

Knightia is an extinct genus of small, schooling, ray-finned fish related to modern herrings and sardines. Abundant in the warm freshwater lakes of the Eocene Green River Formation, they fed on insects, plankton, and tiny fish, while serving as prey for nearly every larger predator in the ecosystem. The most common species, Knightia eocena, reached about 15 cm in length and is celebrated today as the state fossil of Wyoming.

These streamlined fish are recognized by their heavy scales, small conical teeth, and rows of dorsal and ventral scutes along the body. Their fossils are among the most iconic from the Green River Formation—an exceptional 48-million-year-old lake deposit in Wyoming, Colorado, and Utah known for preserving a remarkably detailed snapshot of ancient life in a warm, lake-rich Eocene landscape.

Mioplosus is a genus of large extinct perciform fish that lived through the Eocene epoch. This genus is easily distinguished by an elongate fusiform body, double dorsal fins, and forked tail. Mioplosus was a solitary predator with large teeth: a few fossil specimens have been collected with other, smaller fish lodged in their throats. Most fossils of this genus are from the Tertiary-aged Green River Formation in Wyoming, though relatives of this genus are known to range throughout Asia and New Zealand. Mioplosus is also believed to be related to the modern pike-perch of the genus Sander (Stizostedion).

About Fossil Lake

50 million years ago, in the Eocene epoch, these fish thrived in Fossil Lake, which was fed by the Uinta and Rocky Mountain highlands. The anoxic conditions at the bottom of Fossil Lake slowed bacterial decomposition, prevented scavengers from disturbing corpses, and, most interestingly, suffocated creatures that ventured into the oxygen-starved aquatic layer. The result is a miraculous exhibition of Eocene biota: a subtropical aquatic community within sycamore forests, teeming with creatures such as freshwater stingrays, dog-sized horses, menacing alligators, early flying bats, and one of the first primates.

A view of one of the commercial quarries where fossils from the Green River Formation are collected.
A view of one of the commercial quarries where fossils from the Green River Formation are collected.
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DETAILS
SPECIES
Knightia eocaena & Mioplosus labracoides
LOCATION
Clear Creek Quarry, Kemmerer, Wyoming
FORMATION
Green River Formation, "Gastropod Layer"
SIZE
Shale: 5.6 x 5.1"
CATEGORY
ITEM
#257176
GUARANTEE
We guarantee the authenticity of all of our specimens.