Temporal range: Late Silurian – recent
|Class:|| Actinopterygii |
Actinopterygii // (New Latin actino- ('having rays') + Greek πτέρυξ (ptérux 'wing, fins')), members of which are known as ray-finned fishes, is a clade (traditionally class or subclass) of the bony fishes.
The ray-finned fishes are so-called because their fins are webs of skin supported by bony or horny spines (rays), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii (lobe-finned fish). These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).
By species count, actinopterygians dominate the vertebrates, and they comprise nearly 99% of the over 30,000 species of fish. 8 mm (0.3 in), to the massive ocean sunfish, at 2,300 kg (5,070 lb), and the long-bodied oarfish, at 11 m (36 ft). The vast majority of Actinopterygii (~95%) are teleosts.They are ubiquitous throughout freshwater and marine environments from the deep sea to the highest mountain streams. Extant species can range in size from Paedocypris , at
Ray-finned fishes occur in many variant forms. The main features of a typical ray-finned fish are shown in the adjacent diagram. The swim bladder is the more derived structure.
Ray-finned fishes have many different types of scales; but all teleosts, the most advanced actinopterygians, have leptoid scales. The outer part of these scales fan out with bony ridges while the inner part is crossed with fibrous connective tissue. Leptoid scales are thinner and more transparent than other types of scales, and lack the hardened enamel or dentine-like layers found in the scales of many other fish. Unlike ganoid scales, which are found in non-teleost actinopterygians, new scales are added in concentric layers as the fish grows.[ citation needed ]
Ray-finned and lobe-finned fishes, including tetrapods, possessed lungs used for aerial respiration. Only bichirs retain ventrally budding lungs.
Ray-finned fish vary in size and shape, in their feeding specializations, and in the number and arrangement of their ray-fins.
In nearly all ray-finned fish, the sexes are separate, and in most species the females spawn eggs that are fertilized externally, typically with the male inseminating the eggs after they are laid. Development then proceeds with a free-swimming larval stage.However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism. In most cases this involves protogyny, fish starting life as females and converting to males at some stage, triggered by some internal or external factor. Protandry, where a fish converts from male to female, is much less common than protogyny.
Most families use external rather than internal fertilization.Of the oviparous teleosts, most (79%) do not provide parental care. Viviparity, ovoviviparity, or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction (21%) of the 422 teleost families; no care is likely the ancestral condition. The oldest case of viviparity in ray-finned fish is found in Middle Triassic species of † Saurichthys . Viviparity is relatively rare and is found in about 6% of living teleost species; male care is far more common than female care. Male territoriality "preadapts" a species for evolving male parental care.
There are a few examples of fish that self-fertilise. The mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to the fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below 19 °C (66 °F) and can fertilise eggs that are then spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred.
The earliest known fossil actinopterygian is Andreolepis hedei , dating back 420 million years (Late Silurian). Remains have been found in Russia, Sweden, and Estonia.
Actinopterygii is divided into the classes Cladistia and Actinopteri. The latter comprised subclasses Chondrostei and Neopterygii. The Neopterygii, in turn, is divided into the infraclasses Holostei and Teleostei. During the Mesozoic and Cenozoic the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts. The cladogram shows the major groups of actinopterygians and their relationship to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish.Approximate dates are from Near et al., 2012.
The polypterids (bichirs and reedfish) are the sister lineage of all other actinopterygians, the Acipenseriformes (sturgeons and paddlefishes) are the sister lineage of Neopterygii, and Holostei (bowfin and gars) are the sister lineage of teleosts. The Elopomorpha (eels and tarpons) appear to be the most basal teleosts.
|Chondrostei|| ||Chondrostei (cartilage bone) is a subclass of primarily cartilaginous fish showing some ossification. Earlier definitions of Chondrostei are now known to be paraphyletic, meaning that this subclass does not contain all the descendants of their common ancestor. There were 52 species divided among two orders, the Acipenseriformes (sturgeons and paddlefishes) and the Polypteriformes (reedfishes and bichirs). Reedfish and birchirs are now separated from the Chondrostei into their own sister lineage, the Cladistia. It is thought that the chondrosteans evolved from bony fish but lost the bony hardening of their cartilaginous skeletons, resulting in a lightening of the frame. Elderly chondrosteans show beginnings of ossification of the skeleton, suggesting that this process is delayed rather than lost in these fish. This group had once been classified with the sharks: the similarities are obvious, as not only do the chondrosteans mostly lack bone, but the structure of the jaw is more akin to that of sharks than other bony fish, and both lack scales (excluding the Polypteriforms). Additional shared features include spiracles and, in sturgeons, a heterocercal tail (the vertebrae extend into the larger lobe of the caudal fin). However the fossil record suggests that these fish have more in common with the Teleostei than their external appearance might suggest.|
|Neopterygii|| ||Neopterygii (new fins) is a subclass of ray-finned fish that appeared somewhere in the Late Permian. There were only few changes during its evolution from the earlier actinopterygians. Neopterygians are a very successful group of fishes because they can move more rapidly than their ancestors. Their scales and skeletons began to lighten during their evolution, and their jaws became more powerful and efficient. While electroreception and the ampullae of Lorenzini is present in all other groups of fish, with the exception of hagfish, neopterygians have lost this sense, though it later re-evolved within Gymnotiformes and catfishes, who possess nonhomologous teleost ampullae.|
The listing below follows Phylogenetic Classification of Bony Fisheswith notes when this differs from Nelson, ITIS and FishBase and extinct groups from Van der Laan 2016 and Xu 2021.
Osteichthyes, popularly referred to as the bony fish, is a diverse taxonomic group of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilage. The vast majority of fish are members of Osteichthyes, which is an extremely diverse and abundant group consisting of 45 orders, and over 435 families and 28,000 species. It is the largest class of vertebrates in existence today. The group Osteichthyes is divided into the ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii). The oldest known fossils of bony fish are about 420 million years old, which are also transitional fossils, showing a tooth pattern that is in between the tooth rows of sharks and bony fishes.
The Amiiformes order of fish has only one extant species, the bowfin. These Amiiformes are found in the freshwater systems of North America, in the United States and parts of southern Canada. They live in freshwater streams, rivers, and swamps.
Semionotiformes is an order of primitive, ray-finned, primarily freshwater fish from the Triassic to the Cretaceous. The best-known genus is Semionotus of Europe and North America.
Actinopteri is the sister group of Cladistia in the class Actinopterygii.
Neopterygii is a subclass of ray-finned fish (Actinopterygii). Neopterygii includes the Holostei and the Teleostei, of which the latter compromise the vast majority of extant fishes, and over half of all living vertebrate species. While living holosteans include only freshwater taxa, teleosts are diverse in both freshwater and marine environments. Many new species of teleosts are scientifically described each year.
The superorder Elopomorpha contains a variety of types of fishes that range from typical silvery-colored species, such as the tarpons and ladyfishes of the Elopiformes and the bonefishes of the Albuliformes, to the long and slender, smooth-bodied eels of the Anguilliformes. The one characteristic uniting this group of fishes is they all have leptocephalus larvae, which are unique to the Elopomorpha. No other fishes have this type of larvae.
The Syngnathiformes are an order of ray-finned fishes that includes the pipefishes and seahorses.
Holostei is a group of ray-finned bony fish including gars and bowfins. There are eight living species divided among two orders: the Amiiformes, represented by a single living species, the bowfin ; and the Lepisosteiformes, the gars, represented by seven living species in two genera. Further species are to be found in the fossil record. Fossil species included, the Amiiformes belong to the clade Halecomorphi, whereas Lepisosteiformes are part of Ginglymodi.
Acanthopterygii 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 is often given to the class Actinopterygii as a whole.
The Palaeonisciformes are an extinct order of early ray-finned fishes (Actinopterygii) which began in the Late Silurian and ended in the Late Cretaceous. The name of the order is derived from the Greek words paleo (ancient) and ὀνίσκος, probably pertaining to the organization of the fishes' scales, similar to the exoskeletal plating of woodlice.
Acanthomorpha is an extraordinarily diverse taxon of teleost fishes with spiny-rays. The clade contains about one third of the world's modern species of vertebrates: over 14,000 species.
Pachycormiformes is an extinct order of marine ray-finned fish known from Mesozoic deposits from Eurasia, the Americas and Antarctica. They were characterized by having serrated pectoral fins, reduced pelvic fins and a bony rostrum. Their exact relations with other fish are unclear, but they are generally though to be more closely related to teleosts than to Amiiformes. Pachycormiformes are morphologically diverse, containing both tuna-like carnivorous and edentulous suspension-feeding forms, the latter including the largest ray finned fish known to have existed, Leedsichthys.
Saurichthyiformes is an extinct order of ray-finned fish which existed in Asia, Africa, Australia, Europe and North America, during the late Permian to early Middle Jurassic. Saurichthyiiformes comprise two families, Saurichthyidae and Yelangichthyidae. Whereas Yelangichthyidae is monotypic, Saurichthyidae includes at least two genera, Saurorhynchus and the very speciose Saurichthys. Additionally, the subgenera Costasaurichthys, Eosaurichthys, Lepidosaurichthys, and Sinosaurichthys are frequently used to group species. Saurichthyiforms were highly successful predators, and with Yelangichthys possibly even included durophagous forms. Species are known from both marine end freshwater deposits. They had their highest diversity during the Early and Middle Triassic.
Crossognathiformes is an extinct order of ray-finned fish that lived from the Late Jurassic to the Eocene. Its phylogenetic placement is disputed; some authors have recovered it as part of the teleost stem group, while others place it in a basal position within crown group Teleostei.
Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The sole living Halecomorph is the bowfin, but the group contains many extinct species in several families in the order Amiiformes, as well as the extinct orders Ionoscopiformes, Panxianichthyiformes, and Parasemionotiformes. The fossil record of halecomorphs goes back at least to the Early Triassic epoch.
Percomorpha is a large clade of ray-finned fish that includes the tuna, seahorses, gobies, cichlids, flatfish, wrasse, perches, anglerfish, and pufferfish.
Otocephala is a clade of ray-finned fishes within the infraclass Teleostei that evolved some 230 million years ago. It is named for the presence of a hearing (otophysic) link from the swimbladder to the inner ear. Other names proposed for the group include Ostarioclupeomorpha and Otomorpha.
Stomiati is a group of teleost fish belonging to the cohort (group) Euteleostei, which is a group of bony fishes within the infra-class Teleostei that evolved ~240 million years ago. Teleostei is a group of ray-finned fishes with the exception of primitive bichirs, sturgeons, paddlefishes, freshwater garfishes, and bowfins. The cohort of Euteleostei is divided into two smaller groups: the Protacanthopterygii and the Neoteleostei. Stomiati happen to be descendants of the Protacanthopterygii, and contains the order of Osmeriformes and Stomiiformes.
Amia, commonly called bowfin, is a genus of bony fish related to gars in the infraclass Holostei. They are regarded as taxonomic relicts, being the sole surviving species of the order Amiiformes, which dates from the Jurassic to the Eocene, persisting to the present. There is one living species in Amia, Amia calva, and a number of extinct species which have been described from the fossil record.
The Trachichthyiformes are an order of ray-finned fishes in the superorder Acanthopterygii.