Knightia has the distinction of being the vertebrate fossil most often found completely
articulated _ that is, with its structural parts still attached or aligned as in life. A herring and
relative of Diplomystus (see opposite), it can be distinguished from the latter by its smaller
size, shorter anal fin and slender body. Knightia is frequently found in mass mortality 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. Its 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 probably fed on
plankton. Its phenomenal abundance in the Green River Formation rocks (see opposite) has
led to it being appointed as Wyoming's state fossil.