Abstract
Two new species of Hyphessobrycon are described from the upper rio Tapajós basin, Mato Grosso, Brazil. Hyphessobrycon melanostichos is distinguished from its congeners by the combination of a conspicuous longitudinal broad black band beginning on the posterior margin of orbit and reaching the tip of middle caudal fin rays, a distinct vertically elongate humeral spot, and 16 to 18 branched anal-fin rays. Hyphessobrycon notidanos is distinguished from its congeners by the combination of an elongate dorsal fin in mature males, a vertically elongate humeral spot, 2-4 maxillary teeth, iii,8 dorsal-fin rays, and 16 to 21 branched anal-fin rays.
Highlights
Hyphessobrycon is the largest genus in the Characidae including more than one hundred valid species (Bertaco & Carvalho, 2005a), distributed from southern Mexico to the río de La Plata in Argentina
The largest diversity is found in the Amazon basin, where approximately half of the known species occur (Costa & Géry, 1994)
The genus was proposed by Durbin in Eigenmann (1908:100) as a subgenus of Hemigrammus Gill, differing from the latter by the absence of scales on the caudal-fin
Summary
Hyphessobrycon is the largest genus in the Characidae including more than one hundred valid species (Bertaco & Carvalho, 2005a), distributed from southern Mexico to the río de La Plata in Argentina. The great number and diversity of species included in Hyphessobrycon is the result of the lack of phylogenetic analyses of the species of the genus, which does not represent a single characiform clade. The current definition of the genus is noncladistic and results in the placement in Hyphessobrycon of all characid species with the combination of presumably simple characters, regardless their phylogenetic information content about relationships. Two new characid species were collected in July 2004 in an expedition that sampled fishes of a great number of right side bank tributaries of the Amazon, including the rio Tapajós, rio Madeira and rio Purus. Two new species of Hyphessobrycon from Chapada dos Parecis, Central Brazil mation, were found to be especially diverse in number of species. We conservatively describe the two new species in Hyphessobrycon according to the current definition of the genus as proposed by Eigenmann (1918)
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