''Wallago'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Siluriformes of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Siluridae Siluridae is the nominate family of catfishes in the order Siluriformes. About 105 living species of silurids are placed in 12 or 14 genera. Although silurids occur across much of Europe and Asia, they are most diverse in Southeast Asia, beyond ...

, or sheatfish. They are found in rivers throughout southern and southeastern

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

. The only extant species of this genus is ''

Wallago attu ''Wallago attu'' is a freshwater catfish of the family Siluridae, native to South and Southeast Asia. It is commonly known as helicopter catfish or wallago catfish. It has known by various names in different regions and languages, such as Borali(� ...

''.

Taxonomy

The

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

of this genus is ambiguous and it is not diagnosed by any

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

. The name is derived from Wallagoo, a Telugu name in Vishakapatnam noted by Patrick Russell in his 1803 book.

Species

There are currently 2 recognized species in this genus, of which only one is recent: * ''

'' (

Bloch Bloch is a surname of German origin. Notable people with this surname include: A–F * (1859-1914), French rabbi *Adele Bloch-Bauer (1881-1925), Austrian entrepreneur *Albert Bloch (1882–1961), American painter * (born 1972), German motor journal ...

& J. G. Schneider, 1801) (Wallago) *† ''Wallago maemohensis'' ( Roberts, 2014) (extinct since the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

) For a long time, the Wallago genus was thought to include more species, namely ''

Wallagonia leerii ''Wallagonia leerii'', also known as the Great Tapah, helicopter catfish, and formerly the striped wallago catfish is a species of catfish native to Southeast Asia. Its habitat ranges from the river drainages of Thailand through the Malayan penin ...

'' (helicopter catfish), ''

Wallagonia maculatus ''Wallagonia maculatus'' is a species of catfish in the family Siluridae (the sheatfishes) endemic to Malaysia, where it is known only from Sabah in northern Borneo. This species grows up to a length of SL. Until osteological research validate ...

'' and ''

Wallagonia micropogon ''Wallagonia micropogon'' is a species of catfish in the genus ''Wallagonia''. This species was recently discovered and is found in the Mekong River drainage area between southern Vietnam and northern Laos as well as Chao Phraya River in Thail ...

''. However, a close investigation by

Tyson R. Roberts Tyson Royal Roberts is an American ichthyologist. He has been described as "the world's foremost authority on ''Regalecus''". Roberts attended Stanford University, where he earned his B.A. in 1961 and a Ph.D. in 1968. His doctoral thesis was tit ...

of their osteological features yielded that all these species actually belong to two entirely separate genera of catfishes, and subsequently all species other than ''Wallago attu'' and the extinct ''Wallago maemohensis'' were re-categorized into the genus ''

Wallagonia Wallagonia is a recently established genus of Silurid catfishes, containing 3 distinct species, all of whom are native to Southeast Asia: *''Wallagonia leerii'' *'' Wallagonia maculatus'' *'' Wallagonia micropogon'' For the longest time, these ...

''. Additionally, it was found that Wallago and Wallagonia are not particularly closely related within the family of Siluridae. ''

Wallago hexanema ''Wallago hexanema'' is a species of catfish in the family Siluridae (the sheatfishes), native to Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a sub ...

'' is currently considered a ''

species inquirenda In biological classification, a ''species inquirenda'' is a species of doubtful identity requiring further investigation. The use of the term in English-language biological literature dates back to at least the early nineteenth century. The term t ...

''.

Description

The ''wallago'' species are large,

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

y catfishes. They have five rays in their

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is deeply forked and has pointed lobes; it is disconnected from the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

, which differs from some of the other silurid genera.

References

{{Taxonbar, from=Q311322 Siluridae Fish of Asia Freshwater fish genera Catfish genera Taxa named by Pieter Bleeker Fish genera with one living species