Green River Formation Identification help

[WildwoodWizard]

Hey there, this is my first post and my second big trip to go fossil hunting. Attached are what I think these fish are identified as, but I think I will need a bit of help seeing as I still have novice eyes. Any help on identifying or noticing differences between differe nt species would be incredibly helpful. These were found in Kemmerer Wyoming at one of the split quarries. Thanks!

[Sagebrush Steve]

The Diplomystus look correct.  I always have difficulty separating Knightia eocaena from Alta.  The primary difference is the ratio of length to width, with Alta being fatter.  (I can look up the formula, if you want.) Some of your Alta might be eocaena, but let’s wait for the real experts to chime i n.

[Sagebrush Steve]

And by the way, you have lots of nice specimens!

[Fossildude19]

Your ID's are mostly right.

I believe that the Knightia are all K. eocaena, however.

Knightia alta are very deep bodied.

 

I think you would have to check the different counts in the table below to be sure.

 

[Sagebrush Steve]

Here’s a page from Lance Grande’s paper, “A Revision of the Fossil Genus Knightia” from 1982 that describes the differences between alta and eocaena.  I think the easiest diagnostic feature to measure is body depth, as the preservation quality of specimens from the split fish layer may not be good enough to make accurate counts of fin rays.