Description: This 50 million year old, Eocene-Era fossil fish comes from one of the world's famous Laggerstatten, the Green River Formation in Wyoming. A small portion of the fish fossils from Green River exhibits such fine preservation.

Amphiplaga is one of the more rare of the Green River fish fossils, making up some 1% of the total from Fossil Lake, its only known location. Named by the famous 19th Century paleontologist E.D. Cope, the name Amphiplaga is thought to mean "ambiguous wound", pointing to the fact that the holotype specimen was headless.. Shaped rather like a cross between a trout and a perch, the Percopsidae are colloquially termed “trout perches”. Fossil percopsids are only known from North America, the current home of the extant genus Percopsis. With a maximum total length of 150 mm and an average of 100 mm this is an average-sized adult specimen of this rarely-offered taxon.