Procambarus primaevus
Green River Formation
Middle Eocene
Lincoln County, Wyoming
Sold Scott Beech

Here is a part and counter-part specimen of fossil crayfish from the Fossil Butte Member of the Green River Formation in Wyoming. The fossil is 5 cm long on an 11x8 cm slab. The specimen is exactly as collected. There is no restoration of any kind and the detail is outstanding including legs and antennae.
Procambarus is an extant genus of the family Cambaridae whose species mostly prefer warm, fresh, slow-moving rivers or streams, or nearshore marsh habitat. The genus today has about 160 living species ranging through North and Central America. Some specimens of the fossil crayfish have been found with fossil ostracods in their abdominal region indicating that they may have been feeding on these. In the Green River deposits Procambarus is found mostly in the nearshore facies and are not reported from deeper water facies.