0.5 Detailed Fossil March Fly Insect Green River FM Uintah County UT Eocene Age
Location: Uintah County, Utah
Weight: 0.5 Ounces
Dimensions: 1.8 Inches Long, 1.7 Inches Wide, 0.2 Inches Thick (Plate)
Insect Dimensions: 0.5 Inches Long, 0.5 Inches Wide
The item pictured is the one you will receive.
50 million years old, Eocene age
March Fly Insect
About 50 million years ago, during the Eocene Epoch, Fossil Lake occupied what is now southwestern Wyoming. At its greatest extent, the lake covered approximately 930 square miles; today, around 500 square miles of sediment remain. The central 230 square miles of this ancient lake bed contain exceptionally fossil-rich layers and diverse geological features—including deltas, beaches, springs, and deposits from both deep-water and nearshore environments.
The lake’s unique chemical composition inhibited decay and scavenging, allowing organisms to settle undisturbed on the lake floor. Over time, millimeter-thick layers of alternating limestone formed, preserving even the most delicate details of ancient life. These laminated limestones contain the highest concentration of fossil fish known anywhere in the world.
Since their discovery in the 1870s, countless exquisitely preserved specimens have been uncovered, making Fossil Lake the most complete Paleogene record of a freshwater lake ecosystem. Beyond fish, the site preserves a rich array of aquatic life, including cyanobacteria, plants, insects, crustaceans (shrimp, crawfish, and ostracods), amphibians (frogs and primitive salamanders), alligators, turtles, birds, and mammals, such as the oldest known pantolestid—an early otter-like creature.
The surrounding subtropical landscape also contributed to this remarkable fossil record. Rare terrestrial fossils include early horses, snakes, lizards, bats (two species), birds, arboreal insectivores (apatemyids), primitive carnivores (miacids), diverse insects, and over 325 species of leaves, seeds, and flowers—a breathtaking snapshot of Eocene biodiversity.
