Redescription of schizodon dissimilis and appraisal of the dark barred species of the genus (Characiformes: Anostomidae)

Abstract

Schizodon dissimilis is redescribed on the basis of syntypes and non-type specimens from the Parnaíba, Jaguaribe and Mearim rivers, and lectotype and paralectotypes are designated. Schizodon dissimilis is distinct from the Amazonian and southeastern Brazil congeners by having four dark brown vertical bars without a midlateral dark brown stripe or a dark blotch on caudal peduncle. When compared with the northeastern Brazilian Schizodon and those from the São Francisco river, and with the remaining dark barred species S. australis, S. borellii, S. corti, S. fasciatus and S. intermedius, it is diagnosed by a combination of lateral line scale counts, color pattern and body proportions. The color pattern distinguishes S. dissimilis from S. fasciatus and the meristic and morphometric data are important in separating S. dissimilis from S. intermedius and S. borellii. Schizodon dissimilis and S. fasciatus have disjunct distributions, with the first occurring in northeastern basins, and the second widely distributed through the Amazon basin and rivers draining northward from the Guyana Shield. Schizodon intermedius and S. borellii are respectively native to the upper Paraná and Paraguay river basins while S. australis is known from the Paraná-Uruguay system and S. corti was described from Maracaibo, Venezuela.