Palaeonisciformes is an extinct order of primitive ray-finned fishes. They possessed additional supraorbitals and had a keystone-shaped dermosphenotic. Andreolepis hedei has proven so far to be the earliest-known Actinopterygiian, living around 420 million years ago (Late Silurian in Russia, Sweden, Estonia, and Latvia. The group diversified during the Carboniferous. The Palaeonisciformes survived into the Mesozoic, and became extinct during the early Cretaceous.