''Hydrolycus'' 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 freshwater

ray-finned fishes Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class (biology), class of Osteichthyes, bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built ...

belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Cynodontidae Cynodontidae, from Ancient Greek κύων (''kúōn''), meaning "dog", and ὀδούς (''odoús''), meaning "tooth", also known as dogtooth characins or vampire tetras, are a family of predatory, characiform freshwater fishes from South America ...

, the dogtooth characins. These fishes are found in

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

South America, where found in the

Amazon Amazon most often refers to: * Amazon River, in South America * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon (company), an American multinational technology company * Amazons, a tribe of female warriors in Greek myth ...

and

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 ...

basins, as well as rivers of the

Guianas The Guianas, also spelled Guyanas or Guayanas, are a geographical region in north-eastern South America. Strictly, the term refers to the three Guianas: Guyana, Suriname, and French Guiana, formerly British Guiana, British, Surinam (Dutch colo ...

. The genus includes the largest dogtooth characins, reaching up to in length. They have long, pointed teeth (shorter and less extreme in ''H. wallacei'') used for spearing their prey, generally smaller fish. In a study of the stomachs of 45 individuals, most were empty, but among the remaining the prey fish were 15–50% of the length ''Hydrolycus'' itself. In 1999 two new species were described, the first in this genus in 158 years.

Species

There are currently four described

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. * '' Hydrolycus armatus'' (

Jardine Jardine is a surname. Notable people with the surname include: * Al Jardine (born 1942), member of the Beach Boys * Alexander Jardine (British Army officer) (died 1799), Scottish army officer and author * Alexander Jardine (Medal of Honor) (1874– ...

, 1841) (Payara) * '' Hydrolycus scomberoides'' ( G. Cuvier, 1819) (Payara) * '' Hydrolycus tatauaia'' Toledo-Piza, Menezes & dos Santos, 1999 * '' Hydrolycus wallacei'' Toledo-Piza, Menezes & dos Santos, 1999

References

Cynodontidae Taxa named by Johannes Peter Müller Taxa named by Franz Hermann Troschel Freshwater fish of South America {{Characiformes-stub