Knightia

Name Meaning:  For Knight
Location Found:  Wyoming (Green River Formation)
Estimated Range:  Modern North America
Geologic Era:  Eocene
Size:  Between 6 and 25 cm long (most on the smaller end)
Extinction Date:  Eocene

Not one, but 6 Knightia fish are present here, with four being complete and the other two partial.  There may even be a tiny bit of a seventh in the top right corner of the specimen (maybe part of a tail fin).  The background stone is typical of Green River Formation rock, a little bit soft and easily scraped with a fingernail.  The fish themselves are very well preserved, clearly showing vertebral columns, ribs, and skulls.

Knightia is classified as a herring-like fish, and appears to have traveled in large schools.  It is not uncommon to find Knightia in large clusters such as this one.  In fact, Knightia is one of the most commonly traded fossils on the market, with thousands of individuals being recovered.  Most of the commonly available specimens are small (under 10 cm long), but many show the fine preservation that our specimen does. 

Knightia would have been an important part of the food chain in the lakes that they lived in, with specimens being found in the mouths and stomachs of larger fish such as Diplomystous and Mioplosus. Knightia itself probably fed on small organisms such as fish fry or plankton.  The only defenses Knightia would have had against predators would be speed and safety in numbers. 

Image Credits:

Life Reconstruction:  By Nobu Tamura (http://spinops.blogspot.com) – Own work, CC BY 3.0, $3