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 webs of skin supported by radially extended bony spines, as opposed to the bulkier, fleshy lobed fins of the sister class Sarcopterygii. Resembling folding fans, the actinopterygian fins can change shape and wetted area easily, 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 the internal skeleton.
Osteoglossiformes is a relatively primitive order of ray-finned fish that contains two sub-orders, the Osteoglossoidei and the Notopteroidei. All of at least 245 living species inhabit freshwater. They are found in South America, Africa, Australia and southern Asia, having first evolved in Gondwana before that continent broke up. In 2008 several new species of marine osteoglossiforms was described from the Danish Eocene Fur Formation dramatically increases the diversity of this group. This implies that the Osteoglossomorpha is not a primary freshwater fish group with the osteoglossiforms having a typical Gondwana distribution.
Arowanas are freshwater bony fish of the subfamily Osteoglossinae, also known as bony tongues. In this family of fish, the head is bony and the elongated body is covered by large, heavy scales, with a mosaic pattern of canals. The dorsal and anal fins have soft rays and are long based, while the pectoral and ventral fins are small. The name "bonytongues" is derived from a toothed bone on the floor of the mouth, the "tongue", equipped with teeth that bite against teeth on the roof of the mouth. The arowana is a facultative air breather and can obtain oxygen from air by sucking it into its swim bladder, which is lined with capillaries like lung tissue.
Osteoglossomorpha is a group of bony fish in the Teleostei.
The silver arowana is a South American freshwater bony fish of the family Osteoglossidae. Silver arowanas are sometimes kept in aquariums, but they are predatory and require a very large tank.
The Asian arowana comprises several phenotypic varieties of freshwater fish distributed geographically across Southeast Asia. While most consider the different varieties to belong to a single species, work by Pouyaud et al. (2003) differentiates these varieties into multiple species. They have several other common names, including Asian bonytongue, dragonfish, and a number of names specific to the different color varieties.
The arapaima, pirarucu, or paiche is any large species of bonytongue in the genus Arapaima native to the Amazon and Essequibo basins of South America. Arapaima is the type genus of the subfamily Arapaiminae within the family Osteoglossidae. They are among the world's largest freshwater fish, reaching as much as 3 m (9.8 ft) in length. They are an important food fish. They have declined in the native range due to overfishing and habitat loss. In contrast, arapaima have been introduced to several tropical regions outside the native range, where they are sometimes considered invasive species. In Kerala, India, arapaima escaped from aquaculture ponds after floods in 2018. Its Portuguese name, pirarucu, derives from the Tupi language words pira and urucum, meaning "red fish".
Osteoglossidae is a family of large freshwater fish, which includes the arowanas and arapaima. The family contains two subfamilies Arapaiminae and Osteoglossinae, with a total of five living genera.
Arapaima gigas, also known as pirarucu or simply arapaima, is a species of arapaima native to the basin of the Amazon River. Once believed to be the sole species in the genus, it is among the largest freshwater fish. The species is an obligate air-breather, so needs to come to the surface regularly to gulp air.
The African arowana or Nile arowana is a species of bonytongue. Despite being called an "arowana", the African arowana is more closely related to arapaimas, the only other members in the subfamily Arapaiminae, than the South American, Asian, and Australian arowanas in the subfamily Osteoglossinae. Compared to these, the African arowana has a more terminal mouth and is the only one that feeds extensively on plankton.
Scleropages is a genus of fish in the family Osteoglossidae found in Asia and Australia. All of these species are carnivorous and have great jumping ability. These species are highly valued as aquarium fish, particularly by those from Asian cultures. In 2003, a study redescribed several naturally occurring color varieties of S. formosus into four separate species. The majority of researchers dispute these redescriptions, arguing that the published data are insufficient to justify recognizing more than one Southeast Asian species of Scleropages and that divergent haplotypes used to distinguish the color strains into isolated species were found within a single color strain, contradicting the findings. They are considered monotypic, consisting of closely related haplotypes based on color. The ancestor of the Australian arowanas: S. jardinii and S. leichardti, diverged from the ancestor of the Asian arowanas about 140 million years ago, during the Early Cretaceous period. The morphological similarity of all seven species shows that little evolutionary change has taken place recently for these ancient fish. The genus had a much wider distribution during the early Cenozoic, with fossil remains known from the Paleocene of Niger and Belgium, and from the Eocene of China.
The black arowana is a South American freshwater bony fish of the family Osteoglossidae. Black arowanas are sometimes kept in aquariums, but they are predatory and require a very large tank. It is generally common, but large numbers are caught as food and for the aquarium fish trade.
Notopteroidei is a suborder of the order Osteoglossiformes that contains the extant families Gymnarchidae (aba), Notopteridae and Mormyridae (elephantfishes), as well as several extinct taxa. The Mormyridae are weakly electric fishes, able to locate prey in turbid water.
Lycoptera is an extinct genus of fish that lived from Lower Cretaceous, Barremian to Aptian in present-day China, North Korea, Mongolia and Siberia. Although there is record from Jurassic Formation in Siberia, its age remains questionable. It is known from abundant fossils representing sixteen species, which serve as important index fossil used to date geologic formations in China. Along with the genus Peipiaosteus, Lycoptera has been considered a defining member of the Jehol Biota, a prehistoric ecosystem famous for its feathered dinosaurs, which flourished for 20 million years during the Early Cretaceous, where it occurs abundantly in often monospecific beds, where they are thought to have died in seasonal mass death events. Lycoptera is a crown group teleost belonging to an early diverging lineage of the Osteoglossomorpha, which contains living mooneyes, arapaima, arowana, elephantfish and knifefish/featherbacks.
Acanthomorpha is an extraordinarily diverse taxon of teleost fishes with spiny fin rays. The clade contains about one-third of the world's modern species of vertebrates: over 14,000 species.
Opsithrissops is an extinct genus of prehistoric bony fish that lived during the Thanetian stage of the Paleocene epoch. It is a 120 centimetres (3.9 ft) fish in the family Osteoglossiformes which includes other bony-tongues such as the extant species of Arowana and Arapaima.
Tenuisentidae is a family of parasitic spiny-headed worms. The family contains two genera, each with one species.
Petrocephalus is a genus of ray-finned fish in the family Mormyridae. All the fish species of this genus are endemic to Africa.
Arapaima leptosoma is a species of freshwater fish endemic to Brazil. It is a member of the arapaimas, a genus of air-breathing fish that contains some of the world's largest freshwater fish. Like other members of the genus Arapaima, this fish can breathe air. It is known only from the confluence of the Solimões and Purus Rivers in Amazonas, Brazil, although due to the lack of obvious geographic barriers, it likely has a larger range.
Arapaima mapae is a species of freshwater fish endemic to Brazil, where it is known only from Lago do Amapá in Amapá State.
