The Palaeonisciformes, commonly known as "palaeoniscoids" are an extinct grouping of primitive ray-finned fish (Actinopterygii), spanning from the Silurian/Devonian to the Cretaceous. They are generally considered paraphyletic, but their exact relationships to living ray-finned fish are uncertain. While some and perhaps most palaeoniscoids likely belong to the stem-group of Actinopteryii, it has been suggested that some may belong to the crown group, with some of these possibly related to Cladistia and/or Chondrostei. Many palaeoniscoids share a conservative body shape and a similar arrangement of skull bones.
Dicellopyge is an extinct genus of freshwater ray-finned fish that lived during the Anisian age of the Middle Triassic epoch in what is now South Africa. It was originally named "Dicellopygae" by James Brough but the name was later corrected to Dicellopyge by Peter Hutchinson.
Amblypterus is an extinct genus of freshwater ray-finned fish that lived during the Gzhelian and Cisuralian epoch in what is now Europe and possibly India and Argentina. Potential indeterminate records stretch as far back as the early Carboniferous.
Atopocephala is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Middle Triassic epoch. It contains a single species, A. watsoni from the Karoo Supergroup of South Africa. A potential indeterminate species was known from the Timezgadiouine Formation of Morocco, but is now considered an indeterminate actinopterygian.
Australosomus is an extinct genus of prehistoric ray-finned fish that lived during the Early Triassic epoch in what is now Greenland, Kenya, Tanzania, Madagascar, South Africa and Canada.
Acrolepis is an extinct genus of prehistoric marine bony fish that lived from the Famennian stage of the Devonian to the early Triassic epoch. Some species from the Early Triassic of Tasmania are also ascribed to Acrolepis.
Cornuboniscus is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Pennsylvanian epoch (Carboniferous), and the only member of the family Cornuboniscidae. It contains a single species, C. budensis from the Bashkirian/lower Westphalian age of what is now Cornwall, England. The genus Cornubonisus was named after the island of Cornubian, and the species name refers to the coastal town of Bude in Cornwall. The type specimen is held in the town's Castle Heritage Centre.
Cheirodopsis is an extinct genus of prehistoric marine ray-finned fish that lived during the Viséan stage of the Mississippian epoch. It contains a single species, C. geikiei from what is now Glencartholm, Scotland.
Cosmoptychius is an extinct genus of freshwater and estuarine ray-finned fish that lived during the Mississippian epoch. It contains a single species, C. striatus from the Visean of Scotland. It has a wide stratigraphic range in the Wardie Shale, with many specimens known.
Watsonichthys is an extinct genus of prehistoric bony fish that lived during the Tournaisian age to possibly the Asselian age in what is now Europe and possibly Namibia. It is named after David Meredith Seares Watson.
Bendenius is an extinct genus of prehistoric marine ray-finned fish. It is known from the Early Carboniferous of Belgium. It was named after Belgian paleontologist Pierre-Joseph van Beneden.
Cyranorhis is an extinct genus of prehistoric bony fish that lived during the Serpukhovian age of the Carboniferous period in what is now Montana, United States.
Cosmolepis is an extinct genus of prehistoric marine ray-finned fish that lived during the Early Jurassic epoch. It contains a single species, C. ornatus from the Blue Lias in what is now England. It is the only member of the family Cosmolepididae.
Charleuxia is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Asselian age in what is now Burgundy, France (Autun). It may possibly belong to the genus Paramblypterus.
Bourbonnella is an extinct genus of prehistoric freshwater and coastal marine ray-finned fish that lived during the late Mississippian (Carboniferous) and Asselian in what is now Burgundy, the Czech Republik, and Utah, with other remains known from elsewhere. The genus was named by Daniel Heyler in 1967.
Challaia is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Triassic period in what is now Argentina (Mendoza). Two species are known, C. magna, most likely from the Cerro de Las Cabras Formation, and C. elongata from the Los Rastros Formation. Three other species, C. multidentata, C. striata and C.? cacheutensis, are considered nomina dubia.
Brazilichthys is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Cisuralian epoch in what is now Maranhão, Brazil. The type and only species, B. macrognathus, is known from a single partially complete skull, which was recovered from the Pedra de Fogo Formation near Pastos Bons, Maranhão, Brazil.
Pygopterus is an extinct genus of prehistoric bony fish that lived during the Wuchiapingian to Olenekian ages in what is now England, Germany, Greenland and Svalbard (Spitsbergen). It is one of the few genera of ray-finned fish known to cross the Permian-Triassic boundary.
Coccocephalus is an extinct genus of prehistoric freshwater and marine basal ray-finned fish from the Carboniferous to the early Permian period. The type species, C. wildi, lived during the Bashkirian age of the Pennsylvanian epoch in what is now Lancashire, United Kingdom. One specimen of C. wildi is notable for having the earliest known instance of fossilized brain tissue in a vertebrate.
Bluefieldius is an extinct genus of prehistoric marine ray-finned fish that lived during the Late Mississippian epoch in what is now West Virginia, United States. It is known from a single fossil collected from the late Serpukhovian or early Viséan Bluefield Formation. The type and only species (monotypy) is Bluefieldius mercerensis.
