This beautifully preserved fish thrived in warm, shallow, ancient lakes that covered parts of Colorado, Utah, and Wyoming over 30 million years ago. Phareodus is one of many species of fish and other vertebrate animals (including the oldest known bat!) preserved in the Green River Formation. The Science Museum of Minnesota Paleontology collection includes over 100 specimens of Green River Formation fish fossils, including several type specimens (specimens upon which new species are based).

I chose this fossil because it represents one of our most important collections, and is a great example of the science of taphonomy. Taphonomy is the study of how fossils get preserved – in other words – what happens to an animal after it dies, before it gets buried, and during its entombment. Since dead fish usually float, it is unusal to find such intact skeletons preserved on the bottom of lakes, and untouched by scavengers. The preservation of these specimens helps reveal that the lakes of the Green River Formation were deep, with little oxygen at the deepest parts. A lack of oxygen prevents scavengers from feeding on carcasses, leaving them well-preserved by the gentle settling of fine-grained sediment from the water column over time.
– Kristi Curry Rogers, Curator of Paleontology