Redfieldiiformes is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

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 hor ...

(actinopterygians) which lived from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...

to Early Jurassic. Redfieldiiforms were fairly typical Triassic fish in overall anatomy. They had a

fusiform Fusiform means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a b ...

(streamlined,

tuna A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max length: ...

-like) body shape with thick, ganoine-covered scales. The dorsal and anal fins were large, positioned opposite from each other, and shifted back, close to the tail. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

was hemiheterocercal, with the vertebral column and body scales extending into an upper lobe which was equal in size and shape to the lower lobe. They also had several characteristic skeletal traits, such as a hatchet-shaped preopercle, a series of fulcra (thin spiny scales) fringing the fins, a reduced number of

branchiostegal rays This glossary of ichthyology is a list of definitions of terms and concepts used in ichthyology, the study of fishes. A B C ...

(typically just one), and a snout ornamented with tubercles. The

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

has small teeth and is strongly connected to the preopercle; this would have allowed a deep gape to assist in

ram feeding Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identifi ...

. The function of the snout tubercles is uncertain; some authors have suggested that they attached to a fleshy upper lip, while others argue that they could have held sensory organs akin to the tubercles of siluriforms (

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

). Redfieldiiforms were fairly primitive 'subholostean' fish (more primitive than

holosteans Holostei is a group of ray-finned bony fish. It is divided into two major clades, the Halecomorphi, represented by a single living species, the bowfin (''Amia calva''), as well as the Ginglymodi, the sole living representatives being the gars (Le ...

such as gars or the

bowfin The bowfin (''Amia calva'') is a bony fish, native to North America. Common names include mudfish, mud pike, dogfish, grindle, grinnel, swamp trout, and choupique. It is regarded as a relict, being the sole surviving species of the Halecomorphi ...

), with uncertain relations to neopterygians. Some studies draw comparisons to ' perleidiforms' or ptycholepids, while others consider redfieldiiforms to be early neopterygians related to pholidopleuriforms. Redfieldiiforms were exclusively freshwater fish which became prominent in southern

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

(

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

, southern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

) during the Middle Triassic. By the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

they had become a major component of freshwater ecosystems in western

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...

(

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

), though they were much rarer further east (

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

, possibly

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

). The last member of the order, '' Redfieldius'', lived in the Early Jurassic of eastern North America.

Genera

* '' Atopocephala'' * '' Brookvalia'' * '' Calaichthys'' * '' Cionichthys'' * '' Daedalichthys'' * '' Denwoodichthys?'' * ''

Dictyopyge ''Dictyopyge'' is an extinct genus of prehistoric bony fish that lived during the Late Triassic epoch.Olsen, P. E., McCune, A. R. & Thomson, K. S. (1982). Correlation of the Early Mesozoic Newark Supergroup by vertebrates, principally fishes. Ame ...

'' * '' Endemichthys?'' * '' Geitonichthys'' * ''

Helichthys ''Helichthys'' is an extinct genus of prehistoric bony fish that lived during the Early Triassic epoch (geology), epoch in what is now South Africa. Although several species of ''Helichthys'' have been erected (''H. elegans'', ''H. stegopyge'', ...

'' * '' Hiascoactinus'' * ''

Ischnolepis ''Ischnolepis'' is a species of plants in the family Apocynaceae first described as a genus in 1909. It contains only one known recognized species, ''Ischnolepis graminifolia'', endemic to Madagascar.Venter, H. J. T. & R. L. Verhoeven. 1997. A tr ...

'' * '' Lasalichthys'' * '' Leighiscus?'' * '' Mauritanichthys'' * '' Molybdichthys'' * '' Pacorichthys?'' * '' Phlyctaenichthys'' * '' Redfieldius'' * '' Sakamenichthys?'' * '' Schizurichthys'' * '' Sinkiangichthys (

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

)?'' * '' Synorichthys''

References

Prehistoric ray-finned fish orders {{Triassic-fish-stub