A new species of rivuline killifish has been described from Brazil.
Killifish authority Wilson Costa of the Federal University of Rio de Janeiro named the species Rivulus kayapo in a paper in the journal Zootaxa.
Rivulus kayapo is a member of the Rivulus punctatus species group and was discovered in the Rio Caiapo drainage in Brazil's upper Rio Araguaia basin.
Costa said that the new Rivulus was similar in appearance to R. pinima in that both sexes lack bars on the flanks and the tail fin, and in sharing the presence of longitudinal rows of red spots on the flanks.
Females of both species also have a longitudinally elongated white mark above the caudal spot.
Costa said: "Rivulus kayapo differs from R. pinima in having more caudal-fin rays, the dorsal-fin origin more posteriorly placed, and fewer scales in the longitudinal and transverse series; and differs from all congeners of the R. punctatus species group by possessing a unique reticulate color pattern on the flanks in males."
The paper includes a dichotomous identification key for the Rivulus species found in the Araguaia and Tocatins basins.
The Rivulus genus contains around 100 species, many of which have been described by Costa.
For more details on the new killi see the paper: Costa WJEM (2006) - Rivulus kayapo n. sp. (Teleostei: Cyprinodontiformes: Rivulidae): a new killifish from the serra dos Caiaps, upper rio Araguaia basin, Brazil. Zootaxa 1368: 49-56 (2006)