Lepthoplosternum 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 freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 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 Callichthyinae subfamily of the armored catfish

Callichthyidae

Callichthyidae is a family of catfishes , called armored catfishes due to the two rows of bony plates running down the length of the body. This family contains some of the most popular freshwater aquarium fish, such as the Corydoras.-Taxonomy:The family derives its name from the Greek words kallis...

 family, and consists of six species.

Taxonomy

The type species

Biological type

In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...

 for this genus is Callichthys pectoralis. The name is derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 leptos, meaning "thin", the Greek hoplon, meaning "weapon", and the Greek sternon, meaning "chest" or "sternum". Lepthoplosternum is relatively basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 among callichthyines, being sister to the clade comprising Megalechis

Megalechis

Megalechis is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of 2 species.-Taxonomy:The type species for this genus is Callichthys thoracatus...

+ Dianema

Dianema

Dianema is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of two species, D. longibarbis and D. urostriatum. The type species for this genus is Dianema longibarbis. The name is derived from the Greek di, meaning "two", and nema,...

+ Hoplosternum

Hoplosternum

Hoplosternum is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of 3 species from South America, H. littorale, H. magdalenae, and H...

. Callichthys

Callichthys

Callichthys is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family, and consists of 4 species from South America. The genus Callichthys is distributed in most freshwater drainages of South America....

is the most basal genus in the subfamily.

L. stellatum and L. ucamara are hypothesized to form a partially unresolved polytomy

Polytomy

A polytomy , meaning many temporal based branches, is a section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies. In a phylogenetic tree, a polytomy is represented as a node which has more than two immediate descending branches...

 with L. pectorale and L. beni, which are sister-species

Cladistics

Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

 to each other. L. tordilho is sister to these four species and L. altamazonicum is the most basal species.

Distribution and habitat

Lepthoplosternum is widely distributed in cis

Cis

Cis may have the following meanings:* "Cis-" as a prefix of Latin origin, meaning "on the same side [as]" or "on this side [of]", with several derived usages:** In chemistry, cis- refers to cis-trans isomerism...

-Andean

Andes

The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 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...

 south of the Orinoco River basin. L. pectorale is from the Paraguay River

Paraguay River

The Paraguay River is a major river in south central South America, running through Brazil, Bolivia, Paraguay, and Argentina...

, L. altamazonicum is known only from the upper Amazon River

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 in Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

 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...

, L. beni is from the upper Madeira River

Madeira River

The Madeira River is a major waterway in South America, approximately 3,250 km miles long The Madeira is the biggest tributary of the Amazon...

 basin in Bolivia

Bolivia

Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

 and Peru, and L. tordilho is from the lower Jacui River

Jacuí River

The Jacuí River is a river in Rio Grande do Sul state of southern Brazil. The Jacuí empties into the Guaíba River, an estuarine arm of the Lagoa dos Patos, a large coastal lagoon connected to the Atlantic Ocean....

 drainage in southern Brazil. L. stellatum is so far known from the type locality only, the Igarapé Repartimento, a tributary of the mouthbay lake, Tefé Lake, some 6 km south of the town of Tefé

Tefé

Tefé is a city and a municipality in the state of Amazonas in Brazil. Its population was 70,809 as of 2005 and its area is 23,704 km². It is located about 500 km to the west of Manaus on the south bank of the Rio Solimões....

, Amazonas, Brazil. L. ucamara is known from the Pacaya-Samiria National Reserve

Pacaya-Samiria National Reserve

Pacaya–Samiria National Reserve is one of the largest protected areas in Peru with an area of more than km², containing a rich eco diversity and being the largest reserve in the country and the second largest in the Amazon region. The reserve is triangular shaped by Marañon and Ucayali River in...

 in the lower Ucayali River in Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

 and from the area of
confluence of the Solimões River and Japurá River

Japurá River

The Japurá River or Caquetá River is a river about long rising as the Caquetá River in the Andes in the Southwest of Colombia. It flows southeast into Brazil, where it is called the Japurá. The Japurá enters the Amazon River through a network of channels...

 in Brazil.

Lepthoplosternum species usually inhabit lentic or slow flowing water bodies and are often associated with marginal or floating vegetation. L. ucamara has even been found in hypoxic

Hypoxia (environmental)

Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...

 conditions. However, the type locality of L. stellatum is a stream, permanently flowing and well oxygenated.

Description

Lepthoplosternum species are the smallest callichthyines (maximum 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:...

 60.3 mm) and are easily recognized by two synapomorphies

Synapomorphy

In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...

: the lower lip with deep medial notch and a small, additional lateral notch forming fleshy projections on each side; and a single unbranched ray preceding the branched ones on the anal fin.