Protacanthopterygii is a

superorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

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 ...

. They inhabit both marine and

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s. They appear to have

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

or perhaps late

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

, originating probably roughly 150

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

;

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of them and the closely related Otocephala are known from throughout the Cretaceous.Encyclopædia Britannica Online (2009): Annotated classification – Superorder Protacanthopterygii. ''In:'
Fish
Version of 2009-APR-22. Retrieved 2009-SEP-28.

Characteristics and origin

The Protacanthopterygii contain a number of moderately advanced

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

Anatomical Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

and other traits commonly found in this superorder are: more than 24

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

, epicentral

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

s, one supraorbital bone, and a mesocoracoid, an

adipose 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 b ...

, and (often prominent) glossohyal

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

. However, they usually lack a protrusible

upper jaw 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 maxillar ...

, a gular plate, and

proximal Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

forking of the intermuscular bones. Most members of this taxon are rather specialized mid-sized to larger

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s of smaller animals. As a group, they prefer

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

waters and are far more diverse in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

than in the Southern. Some are

anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...

migrants and many are quite

euryhaline Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the short-finned molly, '' Poecilia sphenops'', which can live in fresh water, brackish water, or salt water. The green crab ('' Carcinus m ...

. Thus, they likely originated in nearshore or

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

waters of the Northern Hemisphere – theoretically the original protacanthopterygian might have been a

catadromous Fish migration is animal migration, mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few ...

migrant inhabiting fresh water, but given that the basal Otocephala were very likely marine, this seems not so likely. Given that they are widespread in the

Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...

but reached the Southern Hemisphere in the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

region, it is more likely than not that they originated in general region of the Turgai Strait and the nearby

Tethys Sea The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...

– perhaps towards the Eastern Tethys as they never seem to have settled Africa or Atlantic

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Systematics

As mentioned initially, one of the closest relatives of the Protacanthopterygii are the Otocephala, which include such different fishes as

carp The term carp (: carp) is a generic common name for numerous species of freshwater fish from the family (biology), family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized game fish, quarries and a ...

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 ...

, and

herring Herring are various species of forage fish, belonging to the Order (biology), order Clupeiformes. Herring often move in large Shoaling and schooling, schools around fishing banks and near the coast, found particularly in shallow, temperate wate ...

s in superorders

Clupeomorpha Clupeomorpha is a superorder of ray-finned fish which belongs to the clade Otocephala. Represented today only by the diverse, economically-important order Clupeiformes (containing herrings, anchovies and allies), it was formerly even more diverse ...

and

Ostariophysi Ostariophysi is the second-largest superorder of fish. Members of this superorder are called ostariophysians. This diverse group contains 10,758 species, about 28% of known fish species in the world and 68% of freshwater species, and are present ...

. While the core of the present superorder has always consisted of three orders, additional taxa are likely to belong here, but are more disputed.Diogo, Rui (2008): On the cephalic and pectoral girdle muscles of the deep sea fish ''Alepocephalus rostratus'', with comments on the functional morphology and phylogenetic relationships of the Alepocephaloidei (Teleostei). '' Anim. Biol.'' 58(1): 23-29. In recent times, a trend exists to

split Split(s) or The Split may refer to: Places * Split, Croatia, the largest coastal city in Croatia * Split Island, Canada, an island in the Hudson Bay * Split Island, Falkland Islands * Split Island, Fiji, better known as Hạfliua Arts, enter ...

the

Osmeriformes The Osmeriformes are an order (biology), order of ray-finned fish that includes the true or freshwater smelts and allies, such as the noodlefishes; they are also collectively called osmeriforms. They belong to the teleost superorder Protacanthopt ...

in two, as their supposed

suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

s do not seem to be particularly closely related among the Protacanthopterygii. The resultant order Argentiniformes contains a number of peculiar

deep sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low tempe ...

forms. And as it seems, the superorders Cyclosquamata and

Stenopterygii Stenopterygii are a superorder of ray-finned fish in the infraclass Teleostei. Their validity is somewhat doubtful, as the group was established to separate, out of a large group of closely related Teleostei, a mere two rather peculiarly autapom ...

, which contain some bizarre

apomorph In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ha ...

ic forms, are so closely related to the "traditional" Protacanthopterygii as to be included therein. Alternatively, the unranked

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

name Euteleostei has been proposed for the whole group, but that would require splitting up the Protacanthopterygii lest they become

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

. Thus, up to seven orders might be included here:Myers, P.; Espinosa, R.; Parr, C.S.; Jones, T.; Hammond, G.S. & Dewey, T.A. (2008):

Animal Diversity Web The Animal Diversity Web (ADW) is a non-profit group that hosts an online database site that collects natural history, classification, species characteristics, conservation biology, and distribution information on species of animals. The website ...

&ndash
Protacanthopterygii
Nelson, Joseph S. (2006): ''

Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...

'' (4th ed.). John Wiley & Sons, Inc. pp.189-207 The placement of the Myctophiformes, traditionally held to be close relatives of the

Aulopiformes Aulopiformes is a diverse order (biology), order of Marine (ocean), marine ray-finned fish consisting of some 15 Extant taxon, extant and several prehistoric family (biology), families with about 45 genera and over 230 species. The common names ...

and separated in a superorder "Scopelomorpha", as well as the

Lampriformes Lampriformes is an order (biology), order of Actinopterygii, ray-finned fish. Members are collectively called lamprids (which is more properly used for the Opah, Lampridae) or lampriforms, and unite such open-ocean and partially Deep sea, deep-s ...

(the monotypic superorder Lampridiomorpha, and putative relatives of the "Stenopterygii") consequently warrants further study. However, these two seem to be somewhat more advanced and closer to the

Paracanthopterygii Paracanthopterygii is a superorder of fishes. Members of this group are called paracanthopterygians. The oldest members are known as fossils from the Cenomanian. It includes five orders: * † Sphenocephaliformes * Percopsiformes ( trout-perche ...

. More dubiously, the Cetomimiformes and " Ctenothrissiformes" are sometimes placed here. While they are indeed of uncertain relationships, the former are widely assumed to belong to superorder

Acanthopterygii Acanthopterygii (meaning "spiny-finned one") is a superorder of teleost, bony fishes in the class Actinopterygii. Members of this superorder are sometimes called ray-finned fishes for the characteristic sharp, bony rays in their fins; however th ...

and be closely related to the

Stephanoberyciformes The Stephanoberycoidei is a suborder of marine ray-finned fishes, consisting of about 68 species, the majority (61) of which belong to the ridgehead family (biology), family (Melamphaidae). They were formerly placed as their own order, the Stepha ...

. Thus, it is rather unlikely that they are correctly placed here. As regards the latter, it is an entirely

group and may well be an invalid paraphyletic assemblage of ancient

Teleostei Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

, and in part may indeed belong in the Protacanthopterygii ''

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

''. The supposed family "Macristiidae" was sometimes considered the only extant member of the "Ctenothrissiformes". But actually these are

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e of certain Aulopiformes, as was already suspected when the first "macristiid" was scientifically studied. They were subsequently split as a distinct family and placed in the Osmeriformes. This is interesting in the light of the modern view that these two orders are not nearly as distantly related as they were believed throughout most of the 20th century.Taylor, Christopher (2009): ''Catalogue of Organisms'' &ndash
Living Larvae and Fossil Fish
Version of 2009-FEB-05. Retrieved 2009-SEP-28.

Phylogeny

The

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

is based on Betancur-Rodriguez et al. 2016.

References

* * {{Taxonbar, from=Q149091 Euteleostei Fish superorders Extant Late Jurassic first appearances