Simpsonichthys nielseni sp. n. (Teleostei: Cyprinodontiformes: Rivulidae): a new annual killifish from the São Francisco River basin, Brazil. Author Wilson J. E. M. Costa text Zootaxa 2005 1039 57 64 http://www.zoobank.org/urn:lsid:zoobank.org:pub:530BF492-C49E-44AE-98C6-414A6C3AA79D journal article z01039p057 [[ Simpsonichthys de Carvalho ]] Simpsonichthys de Carvalho is a speciose assemblage of Neotropical aplocheiloid annual killifishes, comprising 43 species from an area encompassing northeastern, central and eastern South America (Costa, in press). It includes several well-corroborated clades, often diagnosed by unique morphological characters (Costa, 1996, 2003, in press). The S. notatus species group, diagnosed by a derived frontal squamation, includes seven species: S. notatus (Costa, Lacerda & Brasil) and S. radiosus Costa & Brasil , from the Tocantins River basin and S. stellatus (Costa & Brasil) , S. rufus Costa, Nielsen & De Luca , S. trilineatus (Costa & Brasil) , S. auratus Costa & Nielsen , and S. similis Costa & Hellner , from the rio Sao Francisco River basin in Brazil and (Costa & Brasil, 2004; Costa, in press). A new species of this group is herein described.