The Priscacara serrata fossil fish displaying fine detail whilst exhibiting subtle and delicate palettes throughout. The fish is incredibly well preserved in the calcite bearing shale which was once the mud of an exotic prehistoric lagoon. The plate has been created by lifting the shale which is now part of the Rocky Mountain range in Wyoming. Once lifted the shales are split in an attempt to recover these rare occurrences of preserved fish skeletons. This particular fish is complete and displays excellent morphology for study. While also creating a superb and beautiful display, now encased in an oak frame and ready to hang.
A fine fish fossil, displaying the defensive dorsal and anal spines typical of this genus of the perch family of fishes, sometimes referred to as a sunfish shaped body. The soft tissues have resulted in the darker patches in the mineralised shale, the darker patches of the body of the fish-particularly around the intestinal area [stomach area] exhibit the interesting bonus of the fishes fossil scales, laid in articulated rows, an excellent and rare feature of this type. A superb specimen plate.
The lower Eocene deposits of Green River formation was thought to be a large freshwater lake or lagoon which often suffered from falls of volcanic ash smothering the lagoon and creating an anoxic environment. This reduction of oxygen suffocated the inhabitants of the lake, this circumstance preserved exceedingly well the fishes and fauna of this region, a unique occurrence in the fossil record. The lack of oxygen gave little chance for bacteria to quickly establish and decay the fishes, flora and other fauna deposited in the muds at the bottom of the lake which would eventually be transformed into soft calcite bearing shale. The calcite would be absorbed by the remains of the fish, transforming their bones into a hard mineralised deposit in the slightly softer and lighter coloured limestone shales.
The fossil formation was described by Edward Drinker Cope in 1877 an American palaeontologist and comparative anatomist. In the last quarter of the nineteenth-century fossil collecting was so popular a personal feud between two great palaeontologists grew in momentum, Cope and another palaeontologist Othniel Charles Marsh became intensely competitive in discovering new dinosaur fossils, this led to a race of collecting termed the bone wars!
The Paleogene system of fossil lakes between Utah, Colorado and Wyoming existed for around 15 million years. The oldest lake known to exist today is lake Tanganyika at around 10 million years! The fish deposits represent about 5 million years of deposition. From approximately 53.5 m.y.a. to 48.5 m.y.a.
The eighteen-inch layer is a lower Eocene varve layer, is not fissile laminae and therefore much more difficult to split and work successfully, older in the fossil lakes system containing fish which have been preserved which calcite mineralisation. The mineralisation is caused by absorption of localised mineral elements being absorbed by the process of osmosis. Water coursing through the mud layers at the time of deposition deposited minerals in the tissues of the fish, in this case, its skeletal elements, bones teeth and cartilaginous parts. In this 18 inch layer, this exhibits in a dark calcite skeleton encapsulated in light coloured limestone of the Lagerstätte fossil varved lime muds. The mineral preserves every fine detail of this particular fossil bed, a very rare occurrence indeed.
Genus: Priscacara serrata sp.
Age: Paleogene period, Lower to middle Eocene epoch, 53.5 to 48.5 million years ago.
Origin: The Rocky mountains, Lake Gosiute, The Green River Formation, Wyoming, United States of America.
Priscacara serrata measurements.
Height: 19.5 cm
Width: 33.5 cm
Thickness: 1.5 cm
Approximate weight: 1,767 g