Knightia Fresh water herring fish fossil from the Green River Formation.  50 million years ago. Kemmerer, Wyoming, USA.  Fossil fish in shale measures overall approx. 6 inches wide x 4.5 inches x 1/2 inch slab thickness at the thickest point. Slab thickness varies.  genuine fossil, enhanced with stain to make the fossil stand out.  Nicely defined fossil.