page_title: Palaeonisciformes
section_title: Classification
hierarchical_section_title: Palaeonisciformes / Classification
caption_attribution_description: Acropholis stensioei fossil at the Geological Museum in Copenhagen
context_page_description: The Palaeonisciformes are an extinct order of early ray-finned fishes which began in the Late Silurian and ended in the Late Cretaceous. The name of the order is derived from the Greek words paleo and ὀνίσκος, probably pertaining to the organization of the fishes' scales, similar to the exoskeletal plating of woodlice.
context_section_description: It is not a natural group, but is instead a paraphyletic assemblage of the early members of several ray-finned fish lineages. It has traditionally encompassed most Paleozoic actinopterygians, except those that exhibit strange body forms (such as the deep-bodied Platysomoidea, or those assigned definitively to any of the living groups of ray-finned fishes.
  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. Actinopterygians underwent an extensive diversification during the Carboniferous, after the end-Devonian Hangenberg extinction.
caption: Acropholis stensioei fossil at the Geological Museum in Copenhagen
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