The Copionodontinae are a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

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, ...

es (order Siluriformes) of the family Trichomycteridae. It includes two

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

, '' Copionodon'' and ''

Glaphyropoma ''Glaphyropoma'' is a genus of small pencil catfishes native to Bahia in Brazil. Species There are currently two recognized species in this genus: * '' Glaphyropoma rodriguesi'' de Pinna, 1992 * '' Glaphyropoma spinosum'' Bichuette, de Pinna & ...

''.

Classification

Copionodontines are remarkably primitive in body form, and lack many of the

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 ...

previously used to diagnose the family Trichomycteridae. Little doubt exists that the Copionodontinae form a

monophyletic 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 gro ...

group, diagnosed by several unambiguous synapomorphies, including a unique

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...

composed of spatulate teeth not seen anywhere else in the Trichomycteridae. A few characters also support the genera ''Copionodon'' and ''Glaphyropoma'' as monophyletic subunits.

Distribution and ecology

Copionodontines occur exclusively in the

Chapada Diamantina Chapada Diamantina (; Portuguese for the "Diamond Plateau") is a region of Bahia state, in the Northeast of Brazil. This mountain range is known as “Serra do Espinhaço,” in Minas Gerais state, south of Bahia. Description The Chapada Dia ...

; though the plateau is drained by four river basins, so far, these fish are exclusively found in drainages associated with the

Paraguaçu River The Paraguaçu River () is a river in Bahia state of eastern Brazil. It runs from the Chapada Diamantina highlands of central Bahia to its mouth at the Baía de Todos os Santos. The Paraguaçu is the largest river entirely within Bahia. Its banks ...

. Copionodontines occupy the upper reaches of fast-flowing streams on rocky beds, often with tiny or no water flow in the dry season. Fish tend to concentrate on quiet, deep pools, though some individuals lodge in narrow rock crevices in fast-flowing sectors. Habitat preferences also vary according to species. Water in the upper reaches of the Chapada Diamantina is cool and usually black (organic matter-stained), but copionodontines are recorded in a few clear-water streams, as well. Usually, they share their environment with few or no other fish species.

References

Trichomycteridae Fish of Brazil Fish subfamilies Taxa named by Mário Cesar Cardoso de Pinna {{Trichomycteridae-stub