9x12x5/8" thick slab of rock contains a 9" long fossil of Mioplosis, an extinct genus of prehistoric bony fish that lived from the early to middle Eocene Period. This fish was the ancestor of the modern day bass and perch. Mioplosus is distinguished by its double dorsal fin and pointed teeth. It is thought to have been a solitary predator often attacking fish up to half of its own size. Mioplosus range from 2" to 20" but anything over 16" inches is very rare. This fossil was excavated in Lincoln County, WY. and dates to 55 million years ago. During the Eocene, large inland seas covered much of what is now the Western United States. The most well-preserved Eocene fish fossils come from this region. The example we are offering is nicely preserved, w/more than half of the vertebrae present and tiny teeth still visible in the fish's jaws.