SPECIES: Cockerellites (Priscacara) liops
AGE: Eocene (~48 million years)
FORMATION: Green River Formation
This is a fossil fish (Cockerellites) from the famous 18-inch layer of the Green River Formation. It's 5” long and is incredibly well preserved on a slab of shale that has been framed for easy hanging and display. Unfortunately for it, it also has preserved coprolite (poop) on it. It beautifully shows bone and fin rays. It was self-collected and prepped in May, 2018.
Priscacara is an extinct genus of perch from the Eocene (55.8-33.8 mya) Fossils of these fish are commonly found in the Green River Formation in Wyoming. Priscacara probably darted about freshwater streams and lakes, snatching at small creatures like snails, crabs, prawns, and tadpoles.
They varied in size; for example, P. liops is a smaller species, never exceeding 150 mm, whereas the larger P. serrata has been found up to 375 mm. Priscacara means, “Primitive head”. These tough looking, ray-finned fish packed a punch if something dared to swallow it. The genus is known for its protective dorsal and anal spines.
50 million years ago, Priscacara thrived in lakes fed by Uinta and Rocky Mtn. highlands. This plucky genus of perch, possibly related to modern-day Cichlids, is now entombed in the fine-grained, lime mud of Fossil Lake. Priscacara eventually went extinct by the end of cooler and drier Miocene (23-5.2 mya).
Today the wonderfully-preserved fossils of Priscacara and other Fossil Lake fauna are collected in several private quarries around Kemmerer, Wyoming. The best preserved fish fossils come from the coveted 18 inch layer. This layer is collected at night under high-powered lights allowing the faint signs of fish under the surface to be more easily observed. These “ghosted” fish then must go through many hours of manual preparation to remove the overlying rock and reveal the Green River fauna in all of its glory.
It comes from the coveted 18 inch layer of the Green River Formation which produces darker and more detailed fish than the majority on the market. The rock from this layer is much harder and more durable. This layer is typically collected at night using low angle light to see the bump in the rock that the back bone creates. They then cut these fish out and take them to a lab where the fish which may be up to an inch under the surface of the rock are meticulously extracted under microscope with hand tools.