Redfieldiiformes is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

(actinopterygians) which lived from the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic� ...

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

fusiform Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...

(streamlined,

tuna A tuna (: tunas or 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 bul ...

-like) body shape with thick,

ganoine Ganoine or ''ganoin'' is a glassy, often multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes, such as gars and bichirs, as well as lobe-finned coelacanths. It is composed of ...

-covered scales. The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

and

anal Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving ...

fins were large, positioned opposite from each other, and shifted back, close to the tail. The

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

was hemiheterocercal, with the vertebral column and body scales extending into an upper lobe equal in size and shape to the lower lobe. They also had several characteristic skeletal traits, such as a hatchet-shaped

preopercle The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. Anatomy The opercular series contains four bon ...

, 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 In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

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 (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

). 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 the single living genus, '' Amia'' with two species, the bowfins (''Amia calva'' and ''Amia ocellicauda''), as well as the Ginglymo ...

such as

gar Gars are an ancient group of ray-finned fish in the family Lepisosteidae. They comprise seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine waters of eastern North America, Central America and Cuba ...

s or the

bowfin The ruddy bowfin (''Amia calva'') is a ray-finned 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 one of only two surviving species ...

), 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, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

(

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, southern

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

) 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 a ...

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 Pa ...

(

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

and

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

). However, they were much rarer further east (

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

, possibly

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

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

Taxonomy

The following families and genera are known: * Order Redfieldiiformes ** Genus '' Calaichthys'' ** Genus '' Denwoodichthys?'' ** Genus ''

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

'' ** Genus '' Hiascoactinus'' ** ''Genus

Pacorichthys ''Pacorichthys'' ("Pacor fish") is an extinct genus of Palaeonisciformes, palaeoniscoid Actinopterygii, ray-finned fish from Switzerland. It is currently only known from the Meride Limestone, a part of the Monte San Giorgio palaeontological Lage ...

?'' ** Genus '' Sakamenichthys?'' ** Genus '' 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 ...

)?'' ** Family Brookvaliidae *** Genus ''

Atopocephala ''Atopocephala'' is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Middle Triassic epoch. It contains a single species, ''A. watsoni'' from the Karoo Supergroup of South Africa. A potential indeterminate species ...

'' *** Genus ''

Brookvalia ''Brookvalia'' is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Middle Triassic epoch (Anisian stage). It contains four species, all known from the Hawkesbury Sandstone near Brookvale, New South Wales, Australi ...

'' *** Genus ''

Ischnolepis ''Ischnolepis'' is a species of plants in the family Apocynaceae first described as a genus in 1909.Venter, H. J. T. & R. L. Verhoeven. 1997. A tribal classification of the Periplocoideae (Apocynaceae). Taxon 46: 705–720. It contains two speci ...

'' *** Genus '' Phlyctaenichthys'' *** Genus '' Schizurichthys'' (formerly placed in the family Schizurichthyidae) **Family

Redfieldiidae Redfieldiiformes is an extinct Order (biology), order of ray-finned fish (actinopterygians) which lived from the Early Triassic to Early Jurassic. Redfieldiiforms were fairly typical Triassic fish in overall anatomy. They had a fusiform (streamli ...

*** Genus '' Cionichthys'' *** Genus '' Endemichthys?'' *** Genus ''

Daedalichthys ''Daedalichthys'' is an extinct genus of prehistoric freshwater ray-finned fish that lived during the Early Triassic epoch. It contains a single species, ''D. formosa'' (=''D. higginsi'' Warren, 1936) from the Olenekian-aged ''Cynognathus'' Assem ...

'' *** Genus ''

Dictyopyge ''Dictyopyge'' is an extinct genus of prehistoric freshwater ray-finned fish that inhabited eastern North America during the early part of the Late Triassic. Two species are recognized, both from the early Carnian-aged Doswell Formation in what ...

'' *** Genus '' Geitonichthys'' *** Genus '' Lasalichthys'' (=''Synorichthys'') *** Genus '' Mauritanichthys'' *** Genus '' Molybdichthys'' *** Genus '' Redfieldius''

References

Prehistoric ray-finned fish orders {{Triassic-fish-stub Induan first appearances Sinemurian extinctions