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30-416: The halfmoon ( Medialuna californiensis ), also known as the blue perch , is a species of marine ray-finned fish , a sea chub from the subfamily Scorpidinae , part of the family Kyphosidae . It is native to the coasts of the eastern Pacific Ocean off western North America. It is fished for using hook and line and it is a desirable food fish. The halfmoon has an elongate, compressed, oval body with

60-551: A distinct grade of organization—i.e. a 'level of complexity', measured in terms of how differentiated their organ systems are into distinct regions or sub-organs—with a distinct type of construction, which is to say a particular layout of organ systems. This said, the composition of each class is ultimately determined by the subjective judgment of taxonomists . In the first edition of his Systema Naturae (1735), Carl Linnaeus divided all three of his kingdoms of nature ( minerals , plants , and animals ) into classes. Only in

90-424: A distinct rank of biological classification having its own distinctive name – and not just called a top-level genus (genus summum) – was first introduced by French botanist Joseph Pitton de Tournefort in the classification of plants that appeared in his Eléments de botanique of 1694. Insofar as a general definition of a class is available, it has historically been conceived as embracing taxa that combine

120-519: A dozen or more on the outer edge of kelp beds and in sea grass beds. These fish reach sexual maturity when they attain a length of about 20 centimetres (7.9 in) which is when they are roughly two years old. The spawning season runs from June through to October and they are broadcast spawners. The fertilised eggs and newly hatched larvae are planktonic. The larvae are most numerous off northern Baja California The juveniles will school with juvenile opaleye beneath floating rafts of kelp. The halfmoon

150-459: 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

180-449: A small pointed head. It has a small, horizontal mouth in which the upper jaw is partially hidden by the orbital bone when the mouth has closed. Each jaw has a single row of pointed teeth. It has a continuous dorsal fin which has 9–11 spines in the anterior portion which fold down into a scaly furrow, the posterior portion has 22–27 soft rays and these are higher than the spines. The anal fin has 3 spines and 17–21 soft rays. The caudal fin

210-419: A taxonomy of the flowering plants up to the level of orders, many sources have preferred to treat ranks higher than orders as informal clades . Where formal ranks have been assigned, the ranks have been reduced to a very much lower level, e.g. class Equisitopsida for the land plants, with the major divisions within the class assigned to subclasses and superorders. The class was considered the highest level of

240-726: A trait still present in Holostei ( bowfins and gars ). In some fish like the arapaima , the swim bladder has been modified for breathing air again, and in other lineages it have been completely lost. The teleosts have urinary and reproductive tracts that are fully separated, while the Chondrostei have common urogenital ducts, and partially connected ducts are found in Cladistia and Holostei. Ray-finned fishes have many different types of scales ; but all teleosts have leptoid scales . The outer part of these scales fan out with bony ridges, while

270-463: Is a prized species for recreational anglers using rod and line, it is a bycatch in traps and bait nets. In California its season runs from August to April. The flesh is lightly flavoured and the fish can be eaten as fillets or whole and cooked in a variety of methods. The halfmoon was first formally described as Scorpis californiensis in 1876 by the Austrian ichthyologist Franz Steindachner with

300-486: Is an omnivorous species with kelp, red algae and green algae making up the bulk of its diet but it also feeds on a diversity of small invertebrates such as crustaceans , sponges and sea anemones . They are schooling fish. The juveniles are occasionally reported far offshore, although they are more frequent around shallow subtidal areas and kelp beds with the adults. In their first year they can still be as small as 2.54 centimetres (1.00 in) and can be found in schools of

330-540: Is divided into the infraclasses Holostei and Teleostei . During the Mesozoic ( Triassic , Jurassic , Cretaceous ) and Cenozoic the teleosts in particular diversified widely. As a result, 96% of living fish species are teleosts (40% of all fish species belong to the teleost subgroup Acanthomorpha ), while all other groups of actinopterygians represent depauperate lineages. The classification of ray-finned fishes can be summarized as follows: The cladogram below shows

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360-412: Is marginally concave. Most of the head and body is covered in small, thick and rough scales except foe the area forward of the eyes. The colour is dark bluish grey to grey dorsally, paler ventrally sometimes with faint, narrow, vertical bars along the flanks. It has a dark blotch on the upper corner of the gill cover. The margins of the dorsal, anal and caudal fins are dark and the outer edge of each lobe of

390-453: Is rare north of Point Conception in California. The halfmoon is frequently observed high in the water column over rocks and at middle depths over kelp . Their preferred habitats are rocky reefs, kelp forests, floating kelp pads, and oil rigs. They are occasionally recorded near the surface of the water, but they are commonly found at depths between 3 and 40 metres (9.8 and 130 ft). This

420-432: 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

450-500: The Cyprinidae (in goldfish and common carp as recently as 14 million years ago). 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

480-481: 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

510-651: 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. The earliest known fossil actinopterygian is Andreolepis hedei , dating back 420 million years ( Late Silurian ), remains of which have been found in Russia , Sweden , and Estonia . Crown group actinopterygians most likely originated near

540-611: The type locality given as San Diego , California. Ray-finned fish Actinopterygii ( / ˌ æ k t ɪ n ɒ p t ə ˈ r ɪ dʒ i aɪ / ; from actino-  'having rays' and Ancient Greek πτέρυξ (ptérux)  'wing, fins'), 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 skin supported by radially extended thin bony spines called lepidotrichia , as opposed to

570-926: The Devonian-Carboniferous boundary. The earliest fossil relatives of modern teleosts are from the Triassic period ( Prohalecites , Pholidophorus ), although it is suspected that teleosts originated already during the Paleozoic Era . The listing below is a summary of all extinct (indicated by a dagger , †) and living groups of Actinopterygii with their respective taxonomic rank . The taxonomy 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. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Class (biology) The class as

600-402: The adjacent diagram. The swim bladder is a more derived structure and used for buoyancy . Except from the bichirs , which just like the lungs of lobe-finned fish have retained the ancestral condition of ventral budding from the foregut , the swim bladder in ray-finned fishes derives from a dorsal bud above the foregut. In early forms the swim bladder could still be used for breathing,

630-457: The animal kingdom are Linnaeus's classes similar to the classes used today; his classes and orders of plants were never intended to represent natural groups, but rather to provide a convenient "artificial key" according to his Systema Sexuale , largely based on the arrangement of flowers. In botany, classes are now rarely discussed. Since the first publication of the APG system in 1998, which proposed

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660-463: The bichirs and holosteans (bowfin and gars) in having gone through a whole-genome duplication ( paleopolyploidy ). The WGD is estimated to have happened about 320 million years ago in the teleosts, which on average has retained about 17% of the gene duplicates, and around 180 (124–225) million years ago in the chondrosteans. It has since happened again in some teleost lineages, like Salmonidae (80–100 million years ago) and several times independently within

690-440: The bulkier, fleshy lobed fins of the sister class Sarcopterygii (lobe-finned fish). Resembling folding fans , the actinopterygian fins can easily change shape and wetted area , providing superior thrust-to-weight ratios per movement compared to sarcopterygian and chondrichthyian fins. The fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the articulation between these fins and

720-468: The caudal fin is white. Juvenile fish are blue above and silvery below. The maximum recorded total length of the halfmoon is 48 centimetres (19 in). The shape of the caudal fin is said to resemble a crescent moon, leading to the common name. The Halfmoon is native to the eastern Pacific Ocean along the western coast of North America from Vancouver Island in the north to the Gulf of California , although it

750-706: The different actinopterygian clades (in millions of years , mya) are from Near et al., 2012. Jaw-less fishes ( hagfish , lampreys ) [REDACTED] Cartilaginous fishes ( sharks , rays , ratfish ) [REDACTED] Coelacanths [REDACTED] Lungfish [REDACTED] Amphibians [REDACTED] Mammals [REDACTED] Sauropsids ( reptiles , birds ) [REDACTED] Polypteriformes ( bichirs , reedfishes ) [REDACTED] Acipenseriformes ( sturgeons , paddlefishes ) [REDACTED] Teleostei [REDACTED] Amiiformes ( bowfins ) [REDACTED] Lepisosteiformes ( gars ) [REDACTED] The polypterids (bichirs and reedfish) are

780-432: 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. Actinopterygii is divided into the subclasses Cladistia , Chondrostei and Neopterygii . The Neopterygii , in turn,

810-544: 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 to the giant oarfish , at 11 m (36 ft). The largest ever known ray-finned fish, the extinct Leedsichthys from the Jurassic , has been estimated to have grown to 16.5 m (54 ft). Ray-finned fishes occur in many variant forms. The main features of typical ray-finned fish are shown in

840-438: 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. Teleosts and chondrosteans (sturgeons and paddlefish) also differ from

870-425: The internal skeleton (e.g., pelvic and pectoral girdles). The vast majority of actinopterygians are teleosts . By species count, they dominate the subphylum Vertebrata , and constitute nearly 99% of the over 30,000 extant species of fish . They are the most abundant nektonic aquatic animals and are ubiquitous throughout freshwater and marine environments from the deep sea to subterranean waters to

900-461: The main clades of living actinopterygians and their evolutionary relationships to other extant groups of fishes and the four-limbed vertebrates ( tetrapods ). The latter include mostly terrestrial species but also groups that became secondarily aquatic (e.g. whales and dolphins ). Tetrapods evolved from a group of bony fish during the Devonian period . Approximate divergence dates for

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