4.55" Fossil Fish (Phareodus) - Green River Formation, Wyoming

Phareodus is a genus of predatory freshwater fish found in the famous Fossil Lake deposits of the Green River Formation in Wyoming. It had a mouthful of sharp pointy teeth, making it a voracious lake predator. In fact, the name Phareodus actually means "to have teeth". Spines from other fish such as Mioplosus and Priscacara have frequently been found preserved in their stomachs.

50 million years ago, in the Eocene, these fish thrived in Fossil Lake, which was fed by the Uinta and Rocky Mountain highlands. The anoxic conditions at the bottom of Fossil Lake slowed bacterial decomposition, prevented scavengers from disturbing corpses and, most interestingly, suffocated creatures that ventured into the oxygen-starved aquatic layer. The result is a miraculous exhibition of Eocene biota: a subtropical aquatic community within sycamore forests, teeming with creatures such as freshwater stingrays, dog-sized horses, menacing alligators, early flying bats, and one of the first primates.