A new species of flatfish (Pleuronectiformes) is described from early Oligocene deposits of the Keasey Formation near Mist, Oregon, USA. The rare preservation of an articulated fish in the Mist crinoid lagerstätte is likely because the specimen represents a relatively pelagic immature individual that had not yet settled into the typical benthic lifestyle of adult flatfishes. The new species is included in a phylogenetic analysis; although it is lacking many characters, it is recovered as an early diverging lineage, sister to the extant members of the superfamily Pleuronectoidea. This phylogenetic position fits well with the age of this fossil and conforms with the origin of flatfishes occurring in the early Cenozoic, followed by diversification and radiation throughout the Eocene, Oligocene and Miocene epochs.
