A WELL-PRESERVED EOCENE FISH FOSSIL
The Green River Formation in Wyoming, Colorado, and Utah contains one of the world's most prolific Eocene (about 50 million years old) fossil-fish. This formation was deposited in subtropical lake(s) environment with anoxic conditions at its bottom that prevented decay. As a result, the Green River Formation shale beds contain some of the world's best preserved fish faunas (as well as leaves, freshwater stingrays, dog-sized horses, alligators, early flying bats, and an early primate).
The fish shown here (Fig. 1) is the second-most commonly preserved fish in this formation.
An example of Diplomystus (a surface feeder) from the Green River Formation.
The scale is in centimeters (note: this specimen is just under 2 inches long).
Reference
Bradley, W. H. 1964. Geology of Green River Formation and associated Eocene rocks in southwestern Wyoming and adjacent parts of Colorado and Utah. United States Geological Survey Professional Paper 497-A, 86 pp. [This publication is readily available online and for free download.]
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