Phreatobius dracunculus is a 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...

 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...

 in the 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...

 Phreatobius.

P. dracunculus was discovered from an artificial well in the village of Rio Pardo

Rio Pardo

For the Brazilian tribe, see Rio Pardo Rio Pardo is a municipality in the state of Rio Grande do Sul in Brazil. Its coordinates are . The population in 2004 was 37,395, the area is 2187.5 km² The elevation is 41 m....

, located in the drainage area of the Rio Branco

Branco River

The Rio Branco is the principal affluent of the Rio Negro from the north; it is enriched by many streams from the sierras which separate Venezuela and Guyana from Brazil. Its two upper main tributaries are the Urariquira and the Takutu...

 (Rio Madeira system, Amazon

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...

 basin).

This small fish reaches a maximum length of 3.8 centimetre

Centimetre

A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...

s (1.5 in

Inch

An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

) 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:...

. P. dracunculus differs from P. cisternarum

Phreatobius cisternarum

Phreatobius cisternarum is a species of catfish in the genus Phreatobius. This Brazilian fish is one of the few fish species that live underground in phreatic habitats. It has proved problematic in its classification, which remains uncertain....

in a number of ways, but the main differences are the absence of eyes (which are present in P. cisternarum) and the lack of dark pigmentation in the skin (while in P. cisternarum some faint dark pigment is always present). These fish are light pink.