Knightia & Diplomystus Fossil Fish, from Wyoming U.S.A. (No.34)

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Knightia & Diplomystus Fossil Fish, from Wyoming U.S.A. (No.34)Knightia & Diplomystus Fossil Fish
from Green River, Kemmerer, Wyoming U.S.A.
50 Million Years, Eocene Period

Measurements Approx. Knightia Fish Size
Width - 4 cm
Length - 13.4 cm

Measurements Approx. Diplomystus Fish Size
Width - 3.5 cm
Length - 10.5 cm

Measurements Approx. Whole Size
Height - 1.5 cm
Width - 23.7 cm
Length - 30.1 cm

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.


Diplomystus Dentatus
The genus was first named and described by American palaeontologist, Edward Drinker Cope in 1877. D. dentatus  is well known from lower Eocene deposits from the Green River Formation in Wyoming. Specimens size ranges from larval size to around 50-65 cm, which are more commonly found in the centre of the lake.