A fossil of Priscacara clivosa, a species of the extinct genus of perch (Percidae family), which are characterized by their stout dorsal and anal spines. Here seen in a slab of Eocene limestone (some 50 million years old) from the Green River formation in Wyoming, USA. Certain particular locations in this formation, notably the marls at Fossil Lake, provide a wide variety of exceptionally well-preserved fossils, such as this one