Priscacara & Knightia Fossil Fish Pair, from Green River Formation, Wyoming USA (No.83)

£ 150.00
Priscacara & Knightia Fossil Fish Pair, from Green River Formation, Wyoming USA (No.83)

Priscacara & Knightia Fossil Fish Pair  SOLD
from, Green River Formation, Wyoming USA
50 Million Years, Eocene Period

Measurements Approx Whole Matrix Size.
Height - 1.6 cm
Width - 28.3 cm
Length - 25.4 cm

Measurements Approx Fish Size.
Length - 11.5 cm - 5 cm (Priscacara)
Length - 9.2 cm - 2.2 cm (Knightia)

Priscacara is an extinct genus of perch from the Middle Eocene. It is characterized by a sunfish-like body and its stout dorsal and anal spines. The fish is best known from the Green River Shales of Wyoming, Utah and Colorado. Mass deaths of Priscacara suggest it formed schools

Two species are recognised, of which the smaller species, P. liops is the most common.

P. serrata, the second of the two species of Priscacara differs from the P. Liops by number of dorsal and anal fin rays as well as possibly a coarser serrated rear edge of the preopercle in P. serrate.

P. liops also has small conical teeth on the pharyngeal jaw, whereas P. serrata has large grinding toothplates, suggesting a diet of snails and crustaceans.

Knightia has the distinction of being the vertebrate fossil most often found completely articulated - this is, with it's structural parts still attached or aligned as in life. It can be distinguished from it's relative  Diplomystus by it's smaller size, shorter anal fin and slender body.
Knightia is frequently found in mass morality layers, in which thousands of individuals have died virtually simultaneously. This clearly suggests shoaling or schooling, but often the cause of death remains unclear - perhaps sudden temperature changes, or water stagnation with falling oxygen content, or rising levels of toxins due to algal blooms. It's small size, and common presence in the jaws  or guts of larger fish, suggest that Knightia was near the beginning of the food chains and it self probably fed on plankton.
It's phenomenal abundance in the Green River Formation rocks have led to it being appointed as Wyoming's state fossil.




                        Bottom Fish Knightia                                             Top Fish Priscacara