Parancistrus 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 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...

. It includes two 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...

, P. aurantiacus and P. nudiventris.

Taxonomy

The three species Hypostomus aurantiacus, H. nigricans, and H. vicinus were described by François Louis de la Porte, comte de Castelnau

François Louis de la Porte, comte de Castelnau

François Louis Nompar de Caumont LaPorte, comte de Castelnau was a French naturalist, known also as François Laporte or Francis de Castelnau.-Life:Born in London, he studied natural history in Paris...

 in 1855. Parancistrus 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 P. aurantiacus designated as type. Later, P. nigricans and P. vicinus were deemed to be synonyms

Synonym (taxonomy)

In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

 of P. aurantiacus, making P. aurantiacus the only species of Parancistrus until P. nudiventris was described in 2005.

Distribution

P. aurantiacus is found in the Ucayali, Tocantins

Tocantins River

The Tocantins is a river in Brazil, the central fluvial artery of the country. In the Tupi language, its name means "toucan's beak" . It runs from south to north for about 2,640 km. It is not really a branch of the Amazon River, although usually so considered, since its waters flow into the...

 and Xingu River

Xingu River

The Xingu River , also called Rio Xingu, is a 1,230-mile long, river in north Brazil; it is a southeast tributary of the Amazon River.-Description and history:...

s. P. nudiventris is found in the Xingu River in 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...

.

Appearance and anatomy

Parancistrus is unique among loricariids due to the presence of fleshy folds on the naked area around 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 at the pectoral fin points insertion in the breeding males. Breeding males also have elongated odontode

Odontode

Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings. They comprise a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel, a structure similar to that of teeth. They generally do not have the same...

s on their bodies and pectoral fin spines.

Parancistrus have stout bodies that are completely plated in adults. The dorsal fin membrane connects to the adipose fin spine. Their color is typically slate gray to black, occasionally with white streaks. They have large gill

Gill

A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

 openings, which makes the genus different from all other loricariids except some Pogonopoma

Pogonopoma

Pogonopoma is a genus of South American catfish of the family Loricariidae. It includes three species, P. obscurum, P. parahybae, and P. wertheimeri.-Taxonomy:...

and Rhinelepis

Rhinelepis

Rhinelepis is a genus of South American catfish of the family Loricariidae. It contains two species, R. aspera and R. strigosa. It is one of three genera in the tribe Rhinelepini.-Distribution:...

.

P. aurantiacus reaches a length of about 19 centimetres (7.5 in) SL

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:...

.