Genus Mioplosus belongs to the perch family (Percidae).

Mioplosus labracoides (Cope 1877) is frequently found in the Fossil Lake deposit but is rare in Lake Gosiute and Lake Uinta strata.  Mioplosus can be readily identified by the double dorsal fin.  The rear dorsal fin is mirrored by an anal fin.  Body depth varies greatly as is seen also in modern perch.  Mioplosus was a predator able to eat prey half it's own length.  Knightia have been found preserved as stomach contents of Mioplosus fossils.