Eocene Period- C. 50 Million Years Ago

Order to which the fossil belongs:   Ellimmichthyformes
Name of which the family belongs: Ellimmichthyidae
Informal name of the fossil: Herring

The typical length of a Diplomystus is 21cm and comes from one of the world’s famous Laggerstatten, the Green River Formation in Wyoming.  It has a deep body, single dorsal and anal fins, a homocercal tail and an upturned mouth, which is typical of a surface-water feeder.
A nice example of a Diplomystus on a matrix of sub-oolitic limestonewith crisp definition.
Matrix: 191mm x 220mm length
Diplomystus: 132mm length