Cynodontinae is a subfamily of tropical South American fish of the order Characiformes. They are characterized by an oblique mouth and very distinct canines. They are not prized as food fish, but are important in subsistence and commercial fisheries. Hydrolycus are game fish, having been recently added to the International Game Fish Association in the fly and rod class. Cynodontid fish are also sometimes housed in aquaria.


This monophyletic subfamily contains only a few species: three species of Cynodon, four speciecs of Hydrolycus, and one species in the monotypic Rhaphiodon genus, Rhaphiodon vulpinus. These fish have been previously classified within Characidae.

Rhaphiodon and Cynodon are sister groups to each other; these two genera together have a sister group relationship to the genus Hydrolycus.

Distribution and habitat

Cynodontinae species are found throughout the Orinoco and Amazon Rivers, as well as the rivers of the Atlantic slopes of the Guianas. Of the cynodontines, R. vulpinus has the greatest distribution, including the Paraná-Paraguay River and Uruguay River basins. Fossil teeth have been found in the Magdalena River basin and Argentina, where cynodontines are not currently found.

These fish live in mid- to surface-water levels in rivers, flooded forests, and lakes.

Appearance and anatomy

Cynodontines are distinguished by their oblique mouth and highly developed pair of dentary canine teeth. These fish can get relatively large; Hydrolycus species can reach 65 centimetres (26 in).


Hydrolycus species here are ordered based on their relationships from the most basal to the most apomorphic based on sister group relationships when possible. Descriptions and dates based on ITIS.

Rhaphiodon Agassiz in Spix and Agassiz, 1829

Cynodon Agassiz, 1829

Hydrolycus Müller and Troschel, 1844


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