Macrosemiiformes is an extinct order of ray-finned fish with one family, Macrosemiidae. The group evolved during the Late Triassic and disappeared during the Late Cretaceous. The group has been found in rock formations in Africa, Australia, Eurasia and North America. They members of Ginglymodi, meaning that their closest living relatives are gars, with them either being placed as the most basal members of the clade, or as nested within the Semionotiformes. Many members of the family have elongated dorsal fins, often associated with adjacent area of skin which was free of scales. These fins were likely undulated for use in precision swimming. Their body morphology suggests that they were slow swimmers that were capable of maneuvering around complex topography, such as reef environments.

Taxonomy

†Order Macrosemiiformes
†Family Macrosemiidae, Thiollière, 1858
 Genus †Eosemionotus
 Genus †Aphanepygus 
 Genus †Disticholepis
 Genus †Enchelyolepis
 Genus †Orthurus
 Genus †Petalopteryx
 Genus †Neonotagogus
 Genus †Histionotus
 Genus †Legnonotus
 Genus †Macrosemius
 Genus †Propterus
Incetae sedis
 Genus †Uarbryichthys
 Genus †Voelklichthys

Timeline of genera

References

 

 
Prehistoric ray-finned fish orders