Protacanthopterygii is a

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 ...

taxon 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 ...

ranked as a

superorder Order ( la, ordo) 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 ...

of the

infraclass In biological classification, class ( la, classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. It is a group of related taxonomic orders. Other well-known ranks in descending order of size are life, domain, kingdo ...

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

. 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. Although the term specifically excludes seawater and brackish water, it does include ...

habitat In ecology, the term habitat summarises the array of resources, physical and 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 ...

s. They appear to have

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

in 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 th ...

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 Mya. The J ...

, originating probably roughly 150

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

;

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 preserved ...

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 (; 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. Tel ...

Anatomical Anatomy () is the branch of biology concerned with the study of the 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 science, having it ...

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

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

, epicentral

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

s, one supraorbital bone, and a mesocoracoid, an

adipose 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 s ...

, and (often prominent)

glossohyal The glossohyal, in fish anatomy, is the tongue and hyoid bone. It is the Tongue, lingual plate, which is a dermal toothed bone that covers or fuses with the basihyal. The glossohyal changes its proportions when the fish increases in size. Reference ...

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 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 ...

, a

gular Gular is of or pertaining to the throat In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebrae. It contains the pharynx and larynx. An important section of it is the epiglottis, separatin ...

plate, and

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

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

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 of smaller animals. As a group, they prefer

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

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 as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

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 thousan ...

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 molly (''Poecilia sphenops'') which can live in fresh water, brackish water, or salt water. The green crab (''Carcinus maenas'') is an e ...

. 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 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 thousan ...

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 region ...

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 definition, to Antarctica) in the south, and is bounded by the continen ...

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 ( el, Τηθύς ''Tēthús''), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean that covered most of the Earth during much of the Mesozoic Era and early Cenozoic Era, located between the ancient continents ...

– 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 relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

Systematics

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

carp Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...

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, ...

, and

herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...

s in superorders Clupeomorpha 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, enterta ...

the

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

in two, as their supposed suborders do not seem to be particularly closely related among the Protacanthopterygii. The resultant order

Argentiniformes The Argentiniformes are an order of ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes (typical smelt and allies) as suborder Argentinoidei. That term refers only to ...

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 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

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 have ...

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

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

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

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

. 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 Animal Diversity Web (ADW) is an online database that collects the natural history, classification, species characteristics, conservation biology, and distribution information on thousands of species of animals. The website includes thousands ...

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

Fishes of the World ''Fishes of the World'' by the American ichthyologist Joseph S. Nelson (1937–2011) is a standard reference for fish systematics. Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the ...

'' (4th ed.). John Wiley & Sons, Inc. pp.189-207 The placement of the

Myctophiformes The Myctophiformes are an order of ray-finned fishes consisting of two families of deep-sea marine fish, most notably the highly abundant lanternfishes (Myctophidae). The blackchins (Neoscopelidae) contain six species in three genera, while t ...

, traditionally held to be close relatives of the

Aulopiformes Aulopiformes is a diverse order of marine ray-finned fish consisting of some 15 extant and several prehistoric families with about 45 genera and over 230 species. The common names grinners, lizardfishes and allies, or aulopiforms are someti ...

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

Lampriformes Lampriformes is an order of ray-finned fish. Members are collectively called lamprids (which is more properly used for the Lampridae) or lampriforms, and unite such open-ocean and partially deep-sea Teleostei as the crestfishes, oarfish, opah ...

(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. It includes five orders: * † Sphenocephaliformes * Percopsiformes ( trout-perches & allies) * Zeiformes (dories) * Stylephoriformes ( Tube ...

. More dubiously, the

Cetomimiformes The Cetomimiformes or whalefishes are an order of small, deep-sea ray-finned fish. Some authoritiesE.g. Nelson (2006) include the whalefishes as part of the order Stephanoberyciformes, within the superfamily Cetomimoidea. Their sister order, the ...

and "

Ctenothrissiformes Ctenothrissiformes is an extinct order of prehistoric ray-finned fish. Timeline of genera ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-145.5 till:-65.5 TimeA ...

" 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 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 this name i ...

and be closely related to the

Stephanoberyciformes The Stephanoberyciformes are an order of marine ray-finned fishes, consisting of about 68 species, the majority (61) of which belong to the ridgehead family (Melamphaidae). The Stephanoberyciformes are mostly uncommon deep-sea species with litt ...

. 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

, 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 (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

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 ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

is based on Betancur-Rodriguez et al. 2016.

References

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