Wilson J. E. M. Costa & Gilberto C. Brasil, 2004, Simpsonichthys radiosus sp. n. (Teleostei: Cyprinodontiformes: Rivulidae): a new annual killifish from the upper Rio Tocantins basin, central Brazil., Zootaxa 737, pp. 1-7: 2

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[[ Genus Simpsonichthys  ZBK  ]]

Simpsonichthys Carvalho  ZBK  is the most diverse genus of Neotropical annual killifishes, comprising 40 valid species, all inhabiting seasonal pools in central and northeastern South America. Monophyly of Simpsonichthys  ZBK  and intrageneric species assemblages have been defined in recent phylogenetic studies (e. g., Costa, 2003). Among these assemblages, the clade herein termed Simpsonichthys notatus species group  comprises S. notatus (Costa & Brasil)  , from the upper Rio Tocantins basin, and S. stellatus (Costa & Brasil)  , S. rufus Costa & Nielsen  ZBK  , S. similis Costa & Hellner  ZBK  , S. trilineatus Costa & Brasil  , S. auratus Costa & Nielsen  ZBK  , from the middle Rio São Francisco basin, and S. ocellatus Costa, Nielsen & De Luca  ZBK  , from the Rio Jequitinhonha basin. It is diagnosed by a unique frontal squamation pattern, in which the A-scale has all margins free (Costa, 2003). A new species of this clade, collected in a temporary pool associated to the headwaters of the Rio Crixás, upper Rio Tocantins basin, central Brazil, is described.