''Lithogenes'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of South American

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

of the family

Loricariidae Loricariidae is the largest family (biology), family of catfish (order Siluriformes), with over 90 genus, genera and just over 680 species. Loricariids originate from freshwater habitats of Costa Rica, Panama, and tropical and subtropical South A ...

. It is the only genus within the

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 botanical subfamily names with "-oideae", and zo ...

Lithogeneinae.

Taxonomy

''Lithogenes'' is the only genus within the subfamily Lithogeneinae. This genus and subfamily, the most basal group in Loricariidae, is the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the rest of the family. Relative to an

undescribed species In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. U ...

of Lithogeneinae, ''L. valencia'' has sister group relationship to ''L. villosus''.

Species

The three recognized species in this genus are: * '' Lithogenes valencia'' Provenzano, Schaefer, Baskin & Royero-Leon, 2003 * '' Lithogenes villosus'' Eigenmann, 1909 * '' Lithogenes wahari'' Schaefer & Provenzano, 2008

Appearance and anatomy

As members of the family Loricariidae, all ''Lithogenes'' species have a

suckermouth In fish, a suckermouth is a ventrally-oriented (inferior) mouth adapted for grazing on algae and small organisms that grow on submerged objects. All Loricariidae possess a suckermouth as do the cypriniform algae eaters of the genus '' Gyrinocheilu ...

. However, unlike most loricariids, species of the genus ''Lithogenes'' possess armor plating only on the latter half of the body. Their eyes are small and their bodies flattened.

Distribution and habitat

''L. villosus'' originates from the

Essequibo River The Essequibo River (; originally called by Alonso de Ojeda; ) is the largest river in Guyana, and the largest river between the Orinoco and Amazon River, Amazon. Rising in the Acarai Mountains near the Brazil–Guyana border, the Essequibo flows ...

drainage of the

Guiana Shield The Guiana Shield (; ; ; ) is one of the three cratons of the South American Plate. It is a 1.7 billion-year-old Precambrian geological formation in northeast South America that forms a portion of the northern coast. The higher elevations on ...

. An undescribed species of ''Lithogenes'' is known from the

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

basin of the Guiana Shield. ''L. valencia'' has only been known from six specimens collected in the 1970s from tributaries of the Lake Valencia in northern

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

; however, this area has since been polluted and this species possibly is now extinct. ''L. villosus'' lives in habitats dominated by

rapids Rapids are sections of a river where the river bed has a relatively steep stream gradient, gradient, causing an increase in water velocity and turbulence. Flow, gradient, constriction, and obstacles are four factors that are needed for a rapid t ...

over

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

, and ''L. valencia'' likely does, as well.

References

{{Taxonbar, from1=Q11761947, from2=Q147404 Loricariidae Fish of South America Catfish genera Taxa named by Carl H. Eigenmann Freshwater fish genera