Ichthyodectiformes is an extinct order of marine stem-

teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tele ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

. The order is named after the genus '' Ichthyodectes'', established by Edward Drinker Cope in 1870. Ichthyodectiforms are usually considered to be some of the closest relatives of the teleost crown group. They were most diverse throughout the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period, though basal forms like '' Thrissops, Occithrissops'' and '' Allothrissops'' are known from the Middle-

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

of Europe and North America. Most ichthyodectiforms ranged between 1 and 5 meters (3–15 ft) in length. Most of known

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

were

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s, feeding on smaller fish; in several cases, larger ichthyodectiforms preyed on smaller members of the order. Some

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

had remarkably large teeth, though others, such as '' Gillicus arcuatus'', had small ones and sucked in their prey. '' Heckelichthys preopercularis'' is a rare example of non-predatory ichthyodectiform, more likely to be microphagous, fed on small particles. There is evidence that at least one species, '' Xiphactinus audax'', may have been

endotherm An endotherm (from Greek ἔνδον ''endon'' "within" and θέρμη ''thermē'' "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions inst ...

ic ("warm-blooded").

Systematics

The basal phylogeny is badly resolved, leading to many ichthyodectiforms that are simply known to be rather primitive, but where nothing certain can be said about their precise relationships. Ichthyodectiformes * '' Africathrissops'' Taverne, 2010 * '' Allothrissops'' Nybelin, 1964 * '' Altamuraichthys'' Taverne, 2016 * '' Antarctithrissops'' Arratia ''et al.'', 2004 * '' Ascalabothrissops''? Arratia, 2000 * '' Capassoichthys'' Taverne, 2015 * '' Dugaldia'' Lees, 1990 * '' Faugichthys'' Taverne & Chanet, 2000 * '' Furloichthys'' Taverne & Capasso, 2018 * '' Garganoichthys'' Taverne, 2009 * '' Occithrissops'' Schaeffer & Patterson, 1984 * '' Ogunichthys'' Alvarado-Ortega & Brito, 2009 * '' Pachythrissops''? Woodward, 1919 * '' Prymnetes'' Cope, 1871 * '' Thrissops'' Agassiz, 1843 * '' Sultanuvaisia'' Nesov, 1981 * '' Verraesichthys'' Taverne, 2010 * Chuhsiungichthyidae Yabumoto, 1994 ** '' Chuhsiungichthys'' Lew, 1974 ** '' Jinjuichthys'' Kim ''et al.'', 2014 ** '' Mesoclupea'' Ping & Yen, 1933 * Bardackichthyidae Hacker & Shimada, 2021 ** '' Amakusaichthys''? Yabumoto ''et al.'', 2020 ** '' Bardackichthys'' Hacker & Shimada, 2021 ** '' Heckelichthys''? Taverne, 2008 * Cladocyclidae Maisey, 1991 ** ''

Aidachar ''Aidachar'' (named for Aydahar, a mythical Kazakh dragon) is an extinct genus of ichthyodectiform teleost ray-finned fish from the Late Cretaceous of Kyzyl Kum, central Asia. It was named by Lev Nesov in 1981. At first, he tentatively describ ...

'' Nesov, 1981 ** '' Chirocentrites'' Heckel, 1849 ** '' Chiromystus'' Cope, 1885 ** '' Cladocyclus'' Agassiz, 1841 ** '' Eubiodectes'' Hay, 1903 * Ichthyodectidae Crook, 1892 ** '' Cooyoo'' Bartholomai & Less, 1987 ** '' Ghrisichthys'' Cavin ''et al.'', 2013 ** '' Ichthyodectes'' Cope, 1870 ** '' Postredectes'' Kaddumi, 2009 ** ''

Xiphactinus ''Xiphactinus'' (from Latin and Greek for " sword-ray") is an extinct genus of large (Shimada, Kenshu, and Michael J. Everhart. "Shark-bitten Xiphactinus audax (Teleostei: Ichthyodectiformes) from the Niobrara Chalk (Upper Cretaceous) of Kansas. ...

'' Leidy, 1870 * Saurodontidae

Cope The cope (known in Latin as ''pluviale'' 'rain coat' or ''cappa'' 'cape') is a liturgical vestment, more precisely a long mantle or cloak, open in front and fastened at the breast with a band or clasp. It may be of any liturgical colour. A c ...

, 1870 Cope, E. D. (1870). On the Saurodontidæ. ''Proceedings of the American Philosophical Society'' 11:529-538 Cope, E. D. (1873). On two new species of Saurodontidae. ''Proceedings of the Academy of Natural Sciences of Philadelphia'' 25:2-339 ** '' Amakusaichthys''? Yabumoto ''et al.'', 2020 ** ''

Gillicus ''Gillicus'' was a relatively small, 2-metre long ichthyodectiform fish that lived in the Western Interior Seaway, in what is now central North America, during the Late Cretaceous. Description Like its larger relative, ''Ichthyodectes ctenodon ...

'' Cope, 1875 ** '' Gwawinapterus'' Arbour & Currie, 2011Vullo, R., Buffetaut, E. and Everhart, M.J. (2012). "Reappraisal of ''Gwawinapterus beardi'' from the Late Cretaceous of Canada: a saurodontid fish, not a pterosaur." ''Journal of Vertebrate Paleontology'', 32(5): 1198-1201. ** '' Heckelichthys''? Taverne, 2008 ** '' Prosaurodon'' Stewart, 1999 ** '' Saurocephalus'' Harlan, 1824 ** '' Saurodon'' Hay, 1830 ** '' Unamichthys'' Alvarado-Ortega, 2004 ** '' Vallecillichthys'' Blanco & Cavin, 2003

References

Prehistoric ray-finned fish orders Late Jurassic first appearances Late Cretaceous extinctions {{paleo-rayfinned-fish-stub