Dianema is a small 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 freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 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...

 in the Callichthyinae subfamily of the armored catfish

Callichthyidae

Callichthyidae is a family of catfishes , called armored catfishes due to the two rows of bony plates running down the length of the body. This family contains some of the most popular freshwater aquarium fish, such as the Corydoras.-Taxonomy:The family derives its name from the Greek words kallis...

 family, and consists of two species, D. longibarbis and D. urostriatum. The type species

Biological type

In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...

 for this genus is Dianema longibarbis. The name is derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 di, meaning "two", and nema, meaning "filament". The two species of Dianema share approximately the same distribution, and are found in the Amazon River

Amazon River

The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

and lower courses of its tributaries. Dianema species have the habit of swimming midwater, as opposed to the bottom as in most callichthyids.