Wyoming Fossil Fish

Limited Availability: We acquire these specimens directly from Wyoming craftsmen who are passionate about these creatures. It takes a significant amount of time to prepare them and as such supply is limited.

Above: The front of the specimen card.

Fifty-million years ago, a system of large lakes covered hundreds of square miles across the modern-day intersection of Utah, Colorado, and Wyoming. Known to geology as the Green River formation, this vibrant, Eocene Epoch landscape was home to alligators, bats, turtles, and all manner of flora. It was also home to an incredible variety of fish, including Wyoming’s state fossil: Knightia eocaena.

Above: Fossil Butte National Monument part of what was once home to a large system of wetlands and lakes. Our fish come from private land near Kemmerer, Wyoming.

This specimen is a meticulously prepared Knightia eocaena from Wyoming’s Fossil Lake. This freshwater ecosystem lasted for about two million years during the warmest period of the Cenozoic and today serves as a basis for research on future climate change.

Above: Wilford Brimley voiceover with stories about fly fishing and fossils not included.  Also, if you’re interested, the book on the bottom is John McPhee’s legendary Annals of the Former World. If you love Geology and personal narratives, you’ll love this Pulitzer Prize winner.

Each fossil comes with a small, acrylic stand. Use of the stand is optional but when we tried it out at MMHQ we knew we had to send it along.

Please Note: Each fossil is prepared by local craftsmen in Wyoming and no two are alike. Roughly speaking, the fossils measure 2-4″ wide but as you can see below the shape can vary. The matrix surrounding and protecting the fossil is a bit too large for our regular cases, and frankly they are best displayed in the open. So, we’ve opted to carefully wrap each fish and ship them in sturdy containers for protection. A small information card is also included.

Above: Two examples of our Wyoming Fossil Fish.

About Knightia and the Fossil Lake of Wyoming

“At prominent places in my office, I have several small slabs of rock containing Knightia, my modest hymn to evolution. Fish, after all, are the ancestors of all four-legged creatures.” – M. Dane Picard, Geologist.

Knightia were small, schooling fish with K. eocaena reaching up to 10 inches (25 cm). They were related to modern day herrings and sardines and evidence suggests a similar diet of algae and insects, though they were also known to eat tiny fish.

Above: An artist’s rendition of Knightia and the Fossil Lake ecosystem. (Source: Mini Museum)

In the fossil beds of Wyoming’s Fossil Lake, Knightia specimens often appear in large clusters known as mass mortality plates. These clusters can contain up to 100 fish per square meter and suggest the Knightia had a high sensitivity to changes in its environment which could lead to sudden death. Many larger fish have been found fossilized with Knightia in their stomachs and even between their jaws. Their abundance and fine articulation is attributed to the unique properties of Fossil Lake.

Above: Fossilized in mid-swallow from Paleontology of the Green River Formation, with a Review of the Fish Fauna. This Knightia proved to be too large to swallow and the larger fish died as a result.[PDF]

Roughly fifty miles long and two miles wide, Fossil Lake was the smallest of the three major lakes in the Green River formation. The other lakes, Lake Gosiute and Lake Uinta, were orders of magnitude larger, with Gosiute estimated to be 120 miles (200 km) wide and Uinta at 185 miles (300 km) wide. Comparative geochemical studies suggest that the waters of Fossil Lake lacked the oxygen needed to sustain scavengers. Without scavengers, decaying bodies were less likely to be picked apart for meat and left undisturbed. It is also theorized that microbial mats would drift over the corpses of fish, keeping the skeletons articulated underneath a layer of pressure.

Above: Map of the Fossil Lake and the other Eocene lakes in the area imposed over a modern state and city map. The red square marks the survey area in the source reference. Green marks areas elevated during Eocene. (Source: Meacham, Amanda L., 2017, Unique Preservation of Fossil Ghost Fish in Green River Formation, MS Thesis Loma Linda University)

Above: The back of the specimen card.