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Semionotiformes; Temporal range: Anisian–Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
	Fossil specimen of Macrosemimimus fegerti
	Fossil of Macrosemius
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Clade:	Ginglymodi
Clade:	Neoginglymodi
Order:	†Semionotiformes; Arambourg & Bertini 1958 sensu López-Arbarello 2012
Type genus
	†Semionotus; Agassiz, 1843
Families
	Callipurbeckiidae; Macrosemiidae; Pleurolepididae; Semionotidae;
Synonyms
	Macrosemiiformes Grande & Bemis 1998

Semionotiformes is an order of ray-finned fish known from the Middle Triassic (Anisian)^[1] to the Late Cretaceous (Maastrichtian).^[2] Their closest living relatives are gars (Lepisosteidae), with both groups belonging to the clade Ginglymodi within the Holostei.^[1] The group includes both freshwater (Semionotidae) and marine (Callipurbeckiidae, Macrosemiidae) adapted forms.^[3] Many members of the family Macrosemiidae (which are usually included in Semionotiformes but sometimes placed in their order), had elongated dorsal fins, often associated with an adjacent area of skin which was free of scales. These fins were likely undulated for use in precision swimming. The body morphology of macrosemiids suggests that they were slow swimmers who were capable of maneuvering around complex topography, such as reef environments.^[4]

Classification

Order †Semionotiformes Arambourg & Bertin 1958 sensu López-Arbarello 2012^[5]^[6]^[7]^[8]
- Genus ?†Orthurus Kner 1866
- Genus †Sangiorgioichthys Tintori & Lombardo 2007
- Genus †Luoxiongichthys Wen et al. 2011
- Genus †Aphanepygus Bassani 1879
- Genus †Austrolepidotes Bocchino, 1974
- Genus †Corunegenys Wade, 1942
- Genus †Placidichthys Brito 2000
- Family ?†Hadrodontidae Thurmond and Jones, 1981 (alternately considered a pycnodont)^[9]
  - Genus ?†Hadrodus Leidy, 1857 (alternately considered a pycnodont)
- Family †Pleurolepididae Lütken 1871
  - Genus †Pleurolepis Agassiz 1863 non Quenstedt 1852
- Family †Macrosemiidae Wagner 1860a corrig. Cope 1889 sensu Murray & Wilson 2009 [Macrosemii Wagner 1860a]
  - Genus †Eusemius Vetter 1881
  - Genus †Blenniomoeus Costa 1850 [Calignathus Costa 1853]
  - Genus †Enchelyolepis Woodward 1918
  - Genus †Palaeomacrosemius Ebert, Lane & Kolbl-Ebert 2016
  - Genus †Voelklichthys Arratia & Schultze 2012
  - Genus †Notagogus Agassiz 1833-1844 [Neonotagogus Bravi 1994]
  - Genus †Agoultichthys Murray & Wilson 2009
  - Genus †Histionotus Egerton 1854
  - Genus †Propterus Agassiz 1833-1844 [Rhynchoncodes Costa 1850]
  - Genus †Macrosemiocotzus González-Rodríguez, Applegate & Espinosa-Arrubarrena 2004
  - Genus †Legnonotus Egerton 1853
  - Genus †Macrosemius Agassiz 1833-1844
- Family †Semionotidae Woodward 1890 sensu López-Arbarello 2012
  - Genus †Semionotus Agassiz 1832 (Usually considered a wastebasket taxon)^[3]
  - Genus †Sargodon Plieninger 1847
- Family †Callipurbeckiidae López-Arbarello 2012 [Paralepidotidae Hadding 1919 ex Lund 1920]
  - Genus †Occitanichthys López-Arbarello & Wencker 2016
  - Genus †Semiolepis Lombardo & Tintori 2008
  - Genus †Paralepidotus Stolley 1919
  - Genus †Macrosemimimus Schröder, López-Arbarello & Ebert 2012
  - Genus †Tlayuamichin López-Arbarello & Alvarado-Ortega 2011
  - Genus †Callipurbeckia López-Arbarello 2012