Diplomystus
The Diplomystus is a member of the herring family. It was a surface feeder. The Diplomystus is related to the Knightia but it has a finer bone structure. I once saw a large one with the remains of 5 small fish in its digestive tract.
A great 20 inch Diplomystus on an 28x 27x 1 inch slab $1700 ppd.
A very nice 2 inch Diplomystus on a 2 x 3.5 x .2 inch slab $ 20 ppd.

A very good 8 inch Diplomystus on a 7.25 x 9.5 x 1 inch slab $ 80
A good 6.25 inch Diplomystus on a 4.5 x 8 inch slab $ 65 ppd
The smallest Diplomystus are less than an inch long. The really big ones are about 26 inches. I don't think I've ever found one that size.
I have Diplomystus from an inch long to about 21 inches long. Prices range from $10 to $1000
Frontier Fossils 307-742-2079