Pseudancistrus 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...

 Loricariidae

Loricariidae

Loricariidae is the largest family of catfish , with almost 700 species and new species being described each year. Loricariids originate from fresh water habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and...

.

Taxonomy

Pseudancistrus is a genus in the tribe

Tribe (biology)

In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...

 Ancistrini

Ancistrini

Ancistrini is a tribe of catfishes of the family Loricariidae.-Taxonomy:Ancistrini has previously been considered a loricariid subfamily. However, it was realized that the subfamily Hypostominae would be paraphyletic if Ancistrinae continued to be recognized...

 of the subfamily Hypostominae

Hypostominae

Hypostominae is a subfamily of catfishes of the family Loricariidae.Studies conducted with representatives of some genera of Hypostominae showed that within thisgroup, the diploid number ranges from 2n = 52 to 2n = 80...

. It was described by Pieter Bleeker

Pieter Bleeker

Pieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....

 in 1862, and redescribed by Jonathan Armbruster in 2004. Currently, there are 18 recognized 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...

 distributed in northern South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, with the inclusion of the genera Lithoxancistrus, Guyanancistrus, the species formerly known as Hemiancistrus megacephalus, as well as the most recently described Pseudancistrus corantijniensis. There is no single morphological feature which distinguishes the group from related genera. Despite this, Pseudancistrus is generally recognized as a monophyletic

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...

 group.

Within the genus there is what is called the P. barbatus group. This group comprises Guyanese derived Pseudancistrus bearing hypertrophied odontodes along the snout and nonevertible cheek plates. It includes the four species P. barbatus, P. corantijniensis, P. depressus, and P. nigrescens.

Distribution and habitat

Pseudancistrus species are found around the Guiana Shield in the Guyanas

Guyanas

Guyana is a country in South America.Guyana, Guayana, or Guiana may also refer to:*Guayana Esequiba, the territory of Guyana claimed by Venezuela*Guayana Region, an administrative region of Venezuela...

, Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

, and Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

. They are also found in northeastern Brazil in the Rio Jaguaribe

Jaguaribe River

The Jaguaribe River is a highly seasonal river in Ceará state of northeastern Brazil. Two large dams were constructed across the Jaguaribe, the Orós Dam, completed in 1960, and the Castanhão Dam, completed in 2003. The Castanhão Dam flooded the city of Jaguaribara, which was rebuilt nearby as the...

 and Rio Grande do Norte

Rio Grande do Norte

Rio Grande do Norte is one of the states of Brazil, located in the northeastern region of the country, occupying the northeasternmost tip of the South American continent. Because of its geographic position, Rio Grande do Norte has a strategic importance. The capital and largest city is Natal...

. They are associated with swift flowing water over gravel, cobble, and boulders.

Description

There is a considerable variation in size within this genus, up to around 20 cm standard length

Fish measurement

Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...

. Most species are not able to evert their cheek plates. In some species, odontodes on the snout may sometimes be extremely hypertrophied. Most species are dark gray, with lighter colouration on the abdomen. In some species, there are light-colored spots or blotches on the sides. Usually, the fins are similarly colored, but in some species there are bands on the caudal fin or an orange or red edging to the dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

and caudal fin.