Palaeonisciformes

Palaeonisciformes Temporal range: Late Silurian–Late Cretaceous PreЄ Є O S D C P T J K Pg N
File:Platysomus gibbosus.jpg
Platysomus gibbosus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Infraphylum:	Gnathostomata
Superclass:	Osteichthyes
Class:	Actinopterygii
Subclass:	Chondrostei
Order:	Palaeonisciformes
Families
Acrolepidae Birgeriidae Palaeoniscidae

The Palaeonisciformes are an extinct order of early ray-finned fishes (Actinopterygii) which began in the Early Silurian and ended in the Late Cretaceous. The name of the order is derived from the Greek words paleo (ancient) and ὀνίσκος (oniskos or woodlouse), probably pertaining to the organization of the fishes' scales, similar to the exoskeletal plating of woodlice.

Classification

File:Acropholis.jpg

Acropholis stensioei fossil at the Geological Museum in Copenhagen

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.

Timeline of genera

External links

• Palaeonisciformes at University of Bristol