Semionotiformes is an order of primitive, ray-finned, primarily freshwater fish from the Middle Triassic (Anisian) to the Late Cretaceous (Maastrichtian). The best-known genus is Semionotus of Europe and North America. Their closest living relatives are gars (Lepisosteidae), with both groups belonging to the clade Ginglymodi within the Holostei. Classification Order †Semionotiformes Arambourg & Bertin 1958 sensu López-Arbarello 2012 Genus ?†Orthurus Kner 1866 Genus †Sangiorgioichthys Tintori & Lombardo 2007 Genus †Luoxiongichthys Wen et al. 2011 Genus †Aphanepygus Bassani 1879 Genus †Placidichthys Brito 2000 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 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 Timeline of genera References Prehistoric ray-finned fish orders Lopingian first appearances Late Cretaceous extinctions