Wallago is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of catfish

Catfish

Catfishes 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 heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

es (order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Siluriformes) of the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Siluridae, or "sheatfishes". They are found in rivers throughout southern Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

. Though the genus contains more than one species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, name "wallago" is also used as a common name for Wallago attu

Wallago attu

Wallago attu is a species of catfish in the family Siluridae, or "sheatfishes". The fish is commonly known by its genus name, wallago. Found in large rivers and lakes, it can reach 2.4 m total length...

.

Taxonomy

The monophyly

Monophyly

In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...

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

Synapomorphy

In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...

.

The genus has four species: W. attu

Wallago attu

Wallago attu is a species of catfish in the family Siluridae, or "sheatfishes". The fish is commonly known by its genus name, wallago. Found in large rivers and lakes, it can reach 2.4 m total length...

, W. leerii, W. maculatus, and W. micropogon

Wallago micropogon

Wallago micropogon is a species of the genus Wallago, which is a type of catfish. This species was recently discovered and is found only in the Mekong River drainage area, which includes southern Vietnam, northern Laos, and parts of Thailand . It is a freshwater fish....

. W. hexanema is considered a species of uncertain validity.

Description

Wallago species are large, predatory catfishes. The have five rays in their dorsal fin. The caudal fin is deeply forked and has pointed lobes; it is disconnected from the anal fin, which differs from some of the other silurid genera.