Genus Diplomystus fossils for sale, Family Ellimmichthyidae, abundant in the Green River lacustrine formation, has also been found in Cretaceous marine deposits of southern Europe, Syria, and Brazil. 

Diplomystus dentatus (Cope 1877) is the only currently recognized Diplomystus species found in the Green River Formation.  Diplomystus is a common fossil fish in the Fossil Lake deposit but less common in Lake Gosiute and Lake Uinta strata.  Diplomystus can reach a length of 26 inches though most of the fossils found are less than 8 inches in length.

Diplomystus dentatus has the upturned mouth of a surface feeder and can be further identified by the long anal fin and deep body.