The Palaeonisciformes (Palaeoniscida) are an extinct order of early ray-finned fishes. Palaeonisciformes sensu lato first appeared in the fossil record in the Late Silurian and last appeared in the Late Cretaceous. The name is derived from the Ancient Greek words παλαιός (palaiós, ancient) and ὀνίσκος (oniskos, 'cod-fish' or woodlouse), probably pertaining to the organization of the fishes' scales, similar to the exoskeletal plating of woodlice.

• Order †Palaeonisciformes Hay, 1902 sensu stricto [Palaeoniscida Moy-Thomas & Miles, 1971]
  • Family †Palaeoniscidae Vogt, 1852
    • Genus ?†Agecephalichthys Wade, 1935
      • Species †Agecephalichthys granulatus Wade, 1935
    • Genus ?†Atherstonia Woodward, 18989 [Broometta Chabakov, 1927]
      • Species †Atherstonia scutata Woodward, 1889 [Atherstonia cairncrossi Broom, 1913; Amblypterus capensis Broom, 1913; Broometta cairncrossi Chabakov, 1927]
      • Species †Atherstonia minor Woodward, 1893
    • Genus ?†Cryphaeiolepis Traquair, 1881
      • Species †Cryphaeiolepis scutata Traquair, 1881
    • Genus ?†Cteniolepidotrichia Poplin & Su, 1992
      • Species †Cteniolepidotrichia turfanensis Poplin & Su, 1992
    • Genus †Dicellopyge Brough, 1931
      • Species †Dicellopyge macrodentata Brough, 1931
      • Species †Dicellopyge lissocephalus Brough, 1931
    • Genus ?†Duwaichthys Liu et al., 1990
      • Species †Duwaichthys mirabilis Liu et al., 1990
    • Genus ?†Ferganiscus Sytchevskaya & Yakolev, 1999
      • Species †Ferganiscus osteolepis Sytchevskaya & Yakolev, 1999
    • Genus †Gyrolepis Agassiz, 1833 non Kade, 1858
      • Species †G. albertii Agassiz, 1833
      • Species †G. gigantea Agassiz, 1833
      • Species †G. maxima Agassiz, 1833
      • Species †G. quenstedti Dames, 1888
      • Species †G. tenuistriata Agassiz, 1833
    • Genus †Gyrolepidoides Cabrera, 1944
      • Species †G. creyanus Schaeffer, 1955
      • Species †G. cuyanus Cabrera, 1944
      • Species †G. multistriatus Rusconi, 1948
    • Genus ?†Palaeoniscinotus Rohon, 1890
      • Species †P. czekanowskii Rohon, 1890
    • Genus †Palaeoniscum de Blainville, 1818 [Palaeoniscus Agassiz, 1833 non Von Meyer, 1858; Palaeoniscas Rzchak, 1881; Eupalaeoniscus Rzchak, 1881; Palaeomyzon Weigelt, 1930; Geomichthys Sauvage, 1888]
      • Species †P. angustum (Rzehak, 1881) [Palaeoniscas angustus Rzehak, 1881]
      • Species †P. antipodeum (Egerton, 1864) [Palaeoniscus antipodeus Egerton, 1864]
      • Species †P. antiquum Williams, 1886
      • Species †P. arenaceum Berger, 1832
      • Species †P. capense (Bloom, 1913) [Palaeoniscus capensis Bloom, 1913]
      • Species †P. comtum (Agassiz, 1833) [Palaeoniscus comtus Agassiz, 1833]
      • Species †P. daedalium Yankevich & Minich, 1998
      • Species †P. devonicum Clarke, 1885
      • Species †P. elegans (Sedgwick, 1829) [Palaeoniscus elegans Sedgwick, 1829]
      • Species †P. freieslebeni de Blainville, 1818 [Eupalaeoniscus freieslebeni (de Brainville, 1818); Palaeoniscus freieslebeni (de Brainville, 1818)]
      • Species †P. hassiae (Jaekel, 1898) [Galeocerdo contortus hassiae Jaekel, 1898; Palaeomyzon hassiae (Jaekel, 1898)]
      • Species †P. kasanense Geinitz & Vetter, 1880
      • Species †P. katholitzkianum (Rzehak, 1881) [Palaeoniscas katholitzkianus Rzehak, 1881]
      • Species †P. landrioti (le Sauvage, 1890) [Palaeoniscus landrioti le Sauvage, 1890]
      • Species †P. longissimum (Agassiz, 1833) [Palaeoniscus longissimus Agassiz, 1833]
      • Species †P. macrophthalmum (McCoy, 1855) [Palaeoniscus macrophthalmus McCoy, 1855]
      • Species †P. magnum (Woodward, 1937) [Palaeoniscus magnus Woodward, 1937]
      • Species †P. moravicum (Rzehak, 1881) [Palaeoniscas moravicus Rzehak, 1881]
      • Species †P. promtu (Rzehak, 1881) [Palaeoniscas promtus Rzehak, 1881]
      • Species †P. reticulatum Williams, 1886
      • Species †P. scutigerum Newberry, 1868
      • Species †P. vratislavensis (Agassiz, 1833) [Palaeoniscus vratislavensis Agassiz, 1833]
    • Genus †Palaeothrissum de Blainville, 1818
      • Species †P. elegans Sedgwick, 1829
      • Species †P. macrocephalum de Blainville, 1818
      • Species †P. magnum de Blainville, 1818
    • Genus ?†Shuniscus Su, 1983
      • Species †Shuniscus longianalis Su, 1983
    • Genus ?†Suchonichthys Minich, 2001
      • Species †Suchonichthys molini Minich, 2001
    • Genus ?†Trachelacanthus Fischer De Waldheim, 1850
      • Species †Trachelacanthus stschurovskii Fischer De Waldheim, 1850
    • Genus ?†Triassodus Su, 1984
      • Species †Triassodus yanchangensis Su, 1984
    • Genus ?†Turfania Liu & Martínez, 1973
      • Species †T. taoshuyuanensis Liu & Martínez, 1973
      • Species †T. varta Wang, 1979
    • Genus ?†Turgoniscus Jakovlev, 1968
      • Species †Turgoniscus reissi Jakovlev, 1968
    • Genus ?†Weixiniscus Su & Dezao, 1994
      • Species †Weixiniscus microlepis Su & Dezao, 1994
    • Genus ?†Xingshikous Liu, 1988
      • Species †Xingshikous xishanensis Liu, 1988
    • Genus ?†Yaomoshania Poplin et al., 1991
      • Species †Yaomoshania minutosquama Poplin et al., 1991

This list includes families that at one time or another were placed in this order.

• †Acropholidae Kazantseva-Selezneva, 1977
• †Atherstoniidae Gardiner, 1969
• †Brazilichthyidae Cox & Hutchinson, 1991
• †Centrolepididae Gardier, 1960
• †Coccolepididae Berg, 1940 corrig.
• †Commentryidae Gardiner, 1963
• †Cryphiolepididae MoyThomas, 1939 corrig.
• †Dwykiidae Gardiner, 1969
• †Holuridae Moy-Thomas, 1939
• †Igornichthyidae Heyler, 1977
• †Irajapintoseidae Beltan, 1978
• †Monesedeiphidae Beltan, 1989
• †Moythomasiidae Kazantseva, 1971
• †Rhabdolepididae Gardiner, 1963
• †Stegotrachelidae Gardiner, 1963
• †Thrissonotidae Berg, 1955
• †Tienshaniscidae Lu & Chen, 2010
• †Turseodontidae Bock, 1959 corrig.
• †Uighuroniscidae Jin, 1996
• †Urosthenidae Woodward, 1931

• Acentrophorus
• Palaeoniscidae

1. "Palaeonisciformes". Paleobiology Database. Retrieved November 17, 2012.