Semionotiformes

Semionotiformes is an order of ray-finned fish known from the Middle Triassic (Anisian) to the Late Cretaceous (Maastrichtian). Their closest living relatives are gars (Lepisosteidae), with both groups belonging to the clade Ginglymodi within the Holostei. The group includes both freshwater (Semionotidae) and marine (Callipurbeckiidae, Macrosemiidae) adapted forms. 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.

== 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 †Austrolepidotes Bocchino, 1974 Genus †Corunegenys Wade, 1942 Genus †Placidichthys Brito 2000 Family ?†Hadrodontidae Thurmond and Jones, 1981 (alternately considered a pycnodont) 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) 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