Above is an image of a fish fossil called Diplomystus dentatus (Cope, 1877). This fish fossil dates to the Eocene Epoch between 54.8 and 33.7 million years ago. It was found Fossil Lake, Wyoming, USA. The genus Diplomystus was named by Edward Drinker Cope (1840-1897) in 1877. It is an extinct herring like fish.
The fossil was on display in the Evolving Planet section of The Field Museum of Natural History in Chicago Illinois, USA as of August 2020. Accession number is PF12501. They have an extensive collection of Fossil Lake fish fossils at the exhibit including holotypes.