Fossilized Fish (Diplomystus dentatus)

Species: Diplomystus dentatus

Age: Eocene (34 - 56 Million years ago)

Source: Green River, WY

Size: 6.5 x 3.25 inches

Diplomystus dentatus is an extinct genus of freshwater fish distantly related to modern-day herrings and sardines, found in the Green River formation in Wyoming. 

The anoxic conditions at the bottom of Fossil Lake in Wyoming slowed bacterial decomposition, prevented scavengers from disturbing corpses, and suffocated creatures that ventured into the oxygen-starved aquatic layer. This resulted in a range of perfectly preserved animal remains, including a number of these incredibly well-preserved prehistoric fish.