8 1/4 Inch Diplomystus Fish Fossil (18 Inch Layer)

/ Inch Diplomystus Fish Fossil ( Inch Layer) #269

This is a nice large Diplomystus dentatus from the 18 inch layer of the Green River Formation. The 18 inch layer produces some spectacularly dark colored fossil fish, though they take significantly more preparation time than those from the split fish layers. This specimen is beautifully detailed, with the bone structure, backbone and fins easily seen.

It is layed out nicely on a creme colored piece of matrix. Like essentially ALL fish from the 18 inch layer, there is some minor restoration to repair small bits of scale that flaked off during prep and on some fin tips (which typically don't preserve well) This is a very aesthetic specimen of Diplomystus from the Green River Formation.

Diplomystus is an extinct genus of freshwater, ray-finned predators that are distantly related to modern herrings and sardines. Diplomystus has a distinctive jaw that protrudes aggressively outward from the mouth at an angle that allowed it to feed in surface waters and devour such prey as the smaller, schooling Knightia.

50 million years ago in the Eocene (55.8 mya to 33.8 mya), D. dentatus thrived in lakes fed by the Uinta and Rocky Mountain highlands. D. dentatus is uniquely entombed in the fine-grained lime mud of Fossil Lake.

The anoxic conditions at the bottom of Fossil Lake slowed bacterial decomposition, prevented scavengers from disturbing corpses, and, most interestingly, suffocated creatures that ventured into the oxygen-starved aquatic layer. The result is a miraculous exhibition of Eocene biota in a subtropical aquatic community within sycamore forests, teeming with creatures such as freshwater stingrays, dog-sized horses, menacing alligators, early flying bats, and one of the first primates.

By the end of the Eocene, Earth developed icehouse climate characteristics and had a change in atmospheric chemistry. The effects of bolide impacts may also have contributed to the eventual loss of flora and fauna at once verdant latitudes.

Today the wonderfully preserved fossils of Diplomystus 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, enhancing the faint signs of fish under the surface indicating underlying fossils. 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.