Taxonomic revision of the seasonal South American killifish genus Simpsonichthys (Teleostei: Cyprinodontiformes: Aplocheiloidei: Rivulidae). Author Wilson J. E. M. Costa text Zootaxa 2007 1669 1 134 http://www.zoobank.org/urn:lsid:zoobank.org:pub:F23FABE8-719E-4F7E-B225-A9C5D45CCFCE journal article z01669p001 Subgenus Xenurolebias Costa, 2006 Xenurolebias Costa, 2006a: 16 (type species: Simpsonichthys myersi (de Carvalho); type by original designation). Diagnosis Distinguished from all other rivulids by the following unambiguous synapomorphies (Costa, 2006a): presence of filamentous rays on the posterior margin of anal fin in females (vs. absent in females), caudal fin lanceolate and asymmetrical due to expansion of ventral portion of fin in males (vs. caudal fin rounded or subtruncate; dorsal and ventral portion symmetrical), and a unique color pattern consisting of a bar on posterior portion of caudal peduncle, posteriorly extending over dorsal and ventral margins of caudal fin in males (vs. never a similar color pattern). Included species Only the type species, Simpsonichthys myersi (Carvalho). Distribution Rivers basins of eastern Brazilian coastal plains between rio Jucurucu , southern Estado da Bahia, and rio Doce, Estado do Espirito Santo (Fig. 1).