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. 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 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.
Anatomy of a typical ray-finned fish (cichlid
−gall bladder, Q
−internal sex organs (ovaries or testes), S
−tail (caudal fin
). Possible other parts not shown: barbels
, adipose fin
, external genitalia (gonopodium
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.
Ray-finned and lobe-finned fishes, including tetrapods, possessed lungs used for aerial respiration. Only bichirs retain ventrally budding lungs.
Ray-finned fish are very varied in size and shape, and in the number of their ray-fins and the manner in which they arrange them.
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. Viviparity is relatively rare and is found in about 6% of 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.
Actinopterygia is divided into the 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 (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 (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.
Skeleton of the angler fish, Lophius piscatorius
. The first spine of the dorsal fin of the anglerfish is modified so it functions like a fishing rod with a lure
Skeleton of another ray-finned fish, the lingcod
The listing below follows Phylogenetic Classification of Bony Fishes with notes when this differs from Nelson, ITIS and FishBase and extinct groups from Van der Laan 2016 and Xu 2021.
- Order †?Asarotiformes Schaeffer 1968
- Order †?Discordichthyiformes Minikh 1998
- Order †?Paphosisciformes Grogan & Lund 2015
- Order †?Scanilepiformes Selezneya 1985
- Order †Cheirolepidiformes Kazantseva-Selezneva 1977
- Order †Paramblypteriformes Heyler 1969
- Order †Rhadinichthyiformes
- Order †Palaeonisciformes Hay 1902
- Order †Tarrasiiformes sensu Lund & Poplin 2002
- Order †Ptycholepiformes Andrews et al. 1967
- Order †Haplolepidiformes Westoll 1944
- Order †Aeduelliformes Heyler 1969
- Order †Platysomiformes Aldinger 1937
- Order †Dorypteriformes Cope 1871
- Order †Eurynotiformes Sallan & Coates 2013
- Subclass Cladistii Pander 1860
- Clade Actinopteri Cope 1972 s.s.
- Order †Elonichthyiformes Kazantseva-Selezneva 1977
- Order †Phanerorhynchiformes
- Order †Saurichthyiformes Berg 1937
- Subclass Chondrostei
- Subclass Neopterygii Regan 1923 sensu Xu & Wu 2012
- Order †Pholidopleuriformes Berg 1937
- Order †Redfieldiiformes Berg 1940
- Order †Platysiagiformes Brough 1939
- Order †Polzbergiiformes Griffith 1977
- Order †Perleidiformes Berg 1937
- Order †Louwoichthyiformes Xu 2021
- Order †Peltopleuriformes Lehman 1966
- Order †Luganoiiformes Lehman 1958
- Order †Pycnodontiformes Berg 1937
- Infraclass Holostei Muller 1844
- Division Halecomorpha Cope 1872 sensu Grande & Bemis 1998
- Division Ginglymodi Cope 1871
- Clade Teleosteomorpha Arratia 2000 sensu Arratia 2013
- Order †Prohaleciteiformes Arratia 2017
- Division Aspidorhynchei Nelson, Grand & Wilson 2016
- Infraclass Teleostei Müller 1844 sensu Arratia 2013
- Order †?Araripichthyiformes
- Order †?Ligulelliiformes Taverne 2011
- Order †?Tselfatiiformes Nelson 1994
- Order †Pholidophoriformes Berg 1940
- Order †Dorsetichthyiformes Nelson, Grand & Wilson 2016
- Order †Leptolepidiformes
- Order †Crossognathiformes Taverne 1989
- Order †Ichthyodectiformes Bardeck & Sprinkle 1969
- Teleocephala de Pinna 1996 s.s.
- Megacohort Elopocephalai Patterson 1977 sensu Arratia 1999 (Elopomorpha Greenwood et al. 1966)
- Megacohort Osteoglossocephalai sensu Arratia 1999
- Supercohort Osteoglossocephala sensu Arratia 1999 (Osteoglossomorpha Greenwood et al. 1966)
- Supercohort Clupeocephala Patterson & Rosen 1977 sensu Arratia 2010
- Cohort Otomorpha Wiley & Johnson 2010 (Otocephala; Ostarioclupeomorpha)
- Subcohort Clupei Wiley & Johnson 2010 (Clupeomorpha Greenwood et al. 1966)
- Subcohort Alepocephali
- Subcohort Ostariophysi Sagemehl 1885
- Section Anotophysa (Rosen & Greenwood 1970) Sagemehl 1885
- Section Otophysa Garstang 1931
- Order Cypriniformes Bleeker 1859 sensu Goodrich 1909 (barbs, carp, danios, goldfishes, loaches, minnows, rasboras)
- Order Characiformes Goodrich 1909 (characins, pencilfishes, hatchetfishes, piranhas, tetras, dourado / golden (genus Salminus) and pacu)
- Order Gymnotiformes Berg 1940 (electric eels and knifefishes)
- Order Siluriformes Cuvier 1817 sensu Hay 1929 (catfishes)
- Cohort Euteleosteomorpha (Greenwood et al. 1966) (Euteleostei Greenwood 1967 sensu Johnson & Patterson 1996)
- Subcohort Lepidogalaxii
- Subcohort Protacanthopterygii Greenwood et al. 1966 sensu Johnson & Patterson 1996
- Subcohort Stomiati
- Subcohort Neoteleostei Nelson 1969
- Infracohort Ateleopodia
- Infracohort Eurypterygia Rosen 1973
- Section Aulopa [Cyclosquamata Rosen 1973]
- Section Ctenosquamata Rosen 1973
- Subsection Myctophata [Scopelomorpha]
- Subsection Acanthomorpha Betancur-Rodriguez et al. 2013
- Division Lampridacea Betancur-Rodriguez et al. 2013 [Lampridomorpha; Lampripterygii]
- Division Paracanthomorphacea sensu Grande et al. 2013 (Paracanthopterygii Greenwood 1937)
- Division Polymixiacea Betancur-Rodriguez et al. 2013 (Polymyxiomorpha; Polymixiipterygii)
- Division Euacanthomorphacea Betancur-Rodriguez et al. 2013 (Euacanthomorpha sensu Johnson & Patterson 1993; Acanthopterygii Gouan 1770 sensu])
- Subdivision Berycimorphaceae Betancur-Rodriguez et al. 2013
- Subdivision Holocentrimorphaceae Betancur-Rodriguez et al. 2013
- Subdivision Percomorphaceae Betancur-Rodriguez et al. 2013 (Percomorpha sensu Miya et al. 2003; Acanthopteri)
- Series Ophidiimopharia Betancur-Rodriguez et al. 2013
- Series Batrachoidimopharia Betancur-Rodriguez et al. 2013
- Series Gobiomopharia Betancur-Rodriguez et al. 2013
- Series Scombrimopharia Betancur-Rodriguez et al. 2013
- Series Carangimopharia Betancur-Rodriguez et al. 2013
- Subseries Anabantaria Betancur-Rodriguez et al. 2014
- Subseries Carangaria Betancur-Rodriguez et al. 2014
- Subseries Ovalentaria Smith & Near 2012 (Stiassnyiformes sensu Li et al. 2009)
- Series Eupercaria Betancur-Rodriguez et al. 2014 (Percomorpharia Betancur-Rodriguez et al. 2013)
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- ^ Pitcher, T (1993). The Behavior of Teleost Fishes. London: Chapman & Hall.
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- ^ Clutton-Brock, T. H. (1991). The Evolution of Parental Care. Princeton, NJ: Princeton UP.
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- ^ Baylis, Jeffrey (1981). "The Evolution of Parental Care in Fishes, with reference to Darwin's rule of male sexual selection". Environmental Biology of Fishes. 6 (2): 223–251. doi:10.1007/BF00002788.
- ^ Wootton, Robert J.; Smith, Carl (2014). Reproductive Biology of Teleost Fishes. Wiley. ISBN 978-1-118-89139-1.
- ^ "Fossilworks: Andreolepis". Archived from the original on 12 February 2010. Retrieved 14 May 2008.
- ^ a b c Thomas J. Near; et al. (2012). "Resolution of ray-finned fish phylogeny and timing of diversification". PNAS. 109 (34): 13698–13703. Bibcode:2012PNAS..10913698N. doi:10.1073/pnas.1206625109. PMC 3427055. PMID 22869754. Archived from the original on 11 April 2015.
- ^ a b Betancur-R, Ricardo; et al. (2013). "The Tree of Life and a New Classification of Bony Fishes". PLOS Currents Tree of Life. 5 (Edition 1). doi:10.1371/currents.tol.53ba26640df0ccaee75bb165c8c26288. PMC 3644299. PMID 23653398. Archived from the original on 13 October 2013.
- ^ Laurin, M.; Reisz, R.R. (1995). "A reevaluation of early amniote phylogeny". Zoological Journal of the Linnean Society. 113 (2): 165–223. doi:10.1111/j.1096-3642.1995.tb00932.x.
- ^ a b "Chondrosteans: Sturgeon Relatives". paleos.com. Archived from the original on 25 December 2010.
- ^ Theodore Holmes Bullock; Carl D. Hopkins; Arthur N. Popper (2005). Electroreception. Springer Science+Business Media, Incorporated. p. 229. ISBN 978-0-387-28275-6.
- ^ Betancur-Rodriguez; et al. (2017). "Phylogenetic Classification of Bony Fishes Version 4". BMC Evolutionary Biology. 17 (1): 162. doi:10.1186/s12862-017-0958-3. PMC 5501477. PMID 28683774.
- ^ Nelson, Joseph, S. (2016). Fishes of the World. John Wiley & Sons, Inc. ISBN 978-1-118-34233-6.
- ^ "Actinopterygii". Integrated Taxonomic Information System. Retrieved 3 April 2006.
- ^ R. Froese and D. Pauly, editors (February 2006). "FishBase". Archived from the original on 5 July 2018. Retrieved 8 January 2020.
- ^ Van der Laan, Richard (2016). Family-group names of fossil fishes. doi:10.13140/RG.2.1.2130.1361.
- ^ Xu, Guang-Hui (9 January 2021). "A new stem-neopterygian fish from the Middle Triassic (Anisian) of Yunnan, China, with a reassessment of the relationships of early neopterygian clades". Zoological Journal of the Linnean Society. 191 (2): 375–394. doi:10.1093/zoolinnean/zlaa053. ISSN 0024-4082.
- ^ In Nelson, Polypteriformes is placed in its own subclass Cladistia.
- ^ In Nelson and ITIS, Syngnathiformes is placed as the suborder Syngnathoidei of the order Gasterosteiformes.