|Silver arowana, Osteoglossum bicirrhosum|
Arowanas are freshwater bony fish of the family Osteoglossidae, also known as bonytongues. In this family of fish, the head is bony and the elongate body is covered by large, heavy scales, with a mosaic pattern of canals. The dorsal and the 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 the swim bladder, which is lined with capillaries like lung tissue. 
Osteoglossids are basal (primitive) fish from the lower Tertiary and are placed in the actinopterygiid order Osteoglossiformes. There are ten described living species: three from South America, one from Africa, four from Asia, and the remaining two from Australia.
The Osteoglossidae are the only exclusively freshwater fish family found on both sides of the Wallace Line. This may be explained by the theory that Asian arowanas (S. formosus) diverged from the Australian Scleropages, S. jardinii and S. leichardti, about 140 million years ago, making it likely that Asian arowanas were carried to Asia on the Indian subcontinent.
Osteoglossids are carnivorous, often being specialized surface feeders. They are excellent jumpers; it has been reported that Osteoglossum species have been seen leaping more than 6 feet (almost 2 metres) from the water surface to pick off insects and birds from overhanging branches in South America, hence the nickname "water monkeys". Arowana species typically grow to around 2 to 3 feet in captivity.
Several species of osteoglossid exhibit parental care. They build nests and protect the young after they hatch. All species are mouthbrooders, the parents holding sometimes hundreds of eggs in their mouths. The young may make several tentative trips outside the parent's mouth to investigate the surroundings before leaving permanently.
In the aquarium 
Arowanas are solitary fish and only appreciate company while young; adults may show dominance and aggression. Some compatible species often partnered with this fish are clown knifefish, pacu, oscars, plecostomus, jaguar cichlids, green terrors, gar, tinfoil barb, siamese tigerfish, and any other semi-aggressive fish that cannot fit in the arowana's mouth.
These fishes are best kept with live or frozen feed and they easily outgrow the tank within a span of 8 to 10 months. A large type aquarium of at least 150 gallons is preferable.
|This section's factual accuracy is disputed. (November 2008)|
The family contains two subfamilies, Heterotidinae and Osteoglossinae, with all but two of the ten extant species being members of the latter. Species are given with one or more prominent common names.
- Subfamily Heterotidinae
- Subfamily Osteoglossinae
- Genus Osteoglossum (Cuvier, 1829)
- Genus Scleropages
- Red-tailed golden arowana Scleropages aureus (Pouyad, Sudarto & Teugels, 2003)
- Green arowana or gold crossback arowana, Scleropages formosus (Schlegel & Müller, 1844)
- Scleropages inscriptus Myanmar arowana (Roberts, T.R. 2012) (Ref. 90179)
- Gulf saratoga, red saratoga or northern spotted barramundi, Scleropages jardinii ‡ (Saville-Kent, 1892)
- Red arowana, super red arowana, or chili red arowana, Scleropages legendrei (Pouyad, Sudarto & Teugels, 2003)
- Saratoga, silver saratoga or spotted barramundi, Scleropages leichardti ‡ Günther, 1864
- Silver Asian arowana, Scleropages macrocephalus (Pouyad, Sudarto & Teugels, 2003)
‡This species is one of two sometimes called the Australian arowana or Australian bonytongue.
A genetic study shows that the lineage leading to the arapaima and African arowana diverged about 220 million years ago, during the Late Triassic; the lineage leading to the silver and blackish blue arowanas of South America diverged about 170 million years ago, during the Middle Jurassic. The lineage leading to the Australian arowanas diverged from that leading to the Asian arowanas about 140 million years ago, during the Early Cretaceous.
Fossil record 
At least five extinct genera, known only from fossils, are classified as Osteoglossids; these date back at least as far as the Late Cretaceous. Other fossils from as far back as the Late Jurassic or Early Cretaceous are widely considered to belong to the arowana superorder Osteoglossomorpha. Osteoglossomorph fossils have been found on all continents except Antarctica. These fossil genera include Brychaetus, Joffrichthys, and Phareodus.
The name comes from the Indonesian arwana or nirwana, meaning fish of paradise.
- Allen, G. R.; Midgley, S. H.; Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Perth: Western Australia Museum. pp. 56–58. ISBN 0-7307-5486-3.
- Berra, Tim M. (2001). Freshwater Fish Distribution. San Diego: Academic Press. ISBN 0-12-093156-7.
- Ismail, Mohd Zakaria (1989). Systematics, Zoogeography, and Conservation of the Freshwater Fishes of Peninsular Malaysia (doctoral dissertation). Colorado State University. p. 25.
- Kumazawa, Yoshinori; Nishida, Mutsumi (1 December 2000). "Molecular Phylogeny of Osteoglossoids: A New Model for Gondwanian Origin and Plate Tectonic Transportation of the Asian Arowana". Molecular Biology and Evolution 17 (12): 1869–78. PMID 11110903. Retrieved 2006-07-12.
- Kumazawa, Yoshinori (2003). "The reason the freshwater fish arowana live across the sea". Quarterly Journal Biohistory (Winter). Retrieved 2006-07-02.
- Greenwood, P.H. & Wilson, M.V. (1998). In Paxton, J.R. & Eschmeyer, W.N. Encyclopedia of Fishes. San Diego: Academic Press. pp. 81–82. ISBN 0-12-547665-5.
- "Saratoga". Native Fish Australia. Retrieved 18 March 2013.
- "Gulf Saratoga". Native Fish Australia. Retrieved 18 March 2013.
- Guo-Qing, Li; Wilson, Mark V. H. (1998). "Osteoglossomorpha" (article). Tree of Life. Retrieved 2006-04-14.
- Lim, Eugene (2006). "Arowana / Arawana". Aquarium Lore. Archived from the original on 26 May 2006. Retrieved April 20, 2006.
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