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Subfamily Cynodontinae

Eigenmann, 1907 

genus Cynodon 

Agassiz, 1829

 

 

 

 

 

FROM FRANK MAGALLANES

 

The subfamily Cynodontinae can be easily distinguished by other characiformes by their oblique mouths and a pair of highly formed dentary canines. The species placement is complex and under debate. Howes's (1976) concept of the Cynodontini included Roestes. But Toledo-Piza (2000) remarked herein that Cyondontinae includes only the genera Cynodon, Rhaphiodon, and Hydrolycus. Lucena and Mendez (1998) placed the Cynodontinae together with the Roesteinae (which included Roestes and Gilbertolus) in the family Cynodontidae. The genus Cynodon (Agassiz, 1829) includes the following species by key:

 

 

THREE (3) VALID SPECIES

C. gibbus

Amazon and Orinoco R. basins and rivers of Guyana: Bolivia, Brazil, Ecuador, Guyana, Peru and Venezuela.

C. meionactis

Coastal rivers in French Guiana and Suriname

C. septenarius

Amazon and upper Orinoco R. basins and rivers of Guyana: Brazil, Guyana and Venezuela.

KEYS

1. Branched pelvic-fin rays 8; band of dark pigmentation covering caudal-fin base....................2

-- Branched pelvic-fin rays 7; no band of dark pigmentation covering base of caudal fin, orbital diameter 30.1--34.4 of HL (Rio Amazonas and its tributaries between mouths of Rios Içá and Tapajós; Essequibo River drainage and Demerara River in Guyana; upper portions of Río Orinoco basin in Venezuela.......................C. septenarius, a new species

2. Orbital diameter 24.9--33.8 of HL (mean 29.2), branched anal-fin rays 68-80 (2 specimens with 65 rays) (Rio Amazonas and Río Orinoco basins, Rupununi River in Guyana, Rio Tocantins drainage and Rio Pindaré system, state of Maranhão, Brazil).........................C. gibbus

-- Orbital diameter 29.8--34.4 of HL (mean 31.8), branched anal-fin rays 63-67 (upper Maroni River, French Guiana)......................C. meionactis

The species is very similar appearing to the genus Hydrolycus. The anal fin of this species helps in identifying between the genera. The anal fin starts anterior of the dorsal fin. In Hydrolycus the anal fin starts posterior of the dorsal fin. The fish is strictly ichthyophagous like other members of the clade.

 

REFERENCES

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UPDATED: 12/26/2011