Cynolebiasini .

This tribe is diagnosed by twelve synapomorphies (Costa, 1998): a broad posteroventral process of dentary; concave anterodorsal margin of opercle; anterior position of anal-fin origin in males; elongated filamentous rays on dorsal and anal fins of males; sexual dimorphism in number of dorsal- and anal fin rays; numerous anal-fin rays in males (19–32); elongated dorsal portion of cleithrum (Fig. 8c); absence of posteroventral flange of cleithrum (Fig. 8c); ventral tip of cleithrum ventrally directed (Fig. 8c); broad anteroventral tip of coracoids; numerous supraorbital neuromasts (12–25); and spawning within substrate (Costa, 1998). Its monophyly is supported also by molecular analyses (Costa et al., 2017a; Furness et al., 2015).

The tribe is composed of eight genera, with small to large adult body sizes (30 to 150 mm SL): Nematolebias Costa, with three medium-sized species (max. 80 mm SL) distributed in coastal basin of southeastern Brazil; Xenurolebias Costa, with four species with small sizes (max. 30 mm SL) endemic to the Atlantic Forest in southeastern Brazil; Ophthalmolebias Costa, with six species with small sizes (max. 65 mm SL) distributed in eastern Brazil (Costa, 2010); Simpsonichthys, with nine small-sized species (max. 55 mm SL) distributed in the central Brazil Plateau (Costa, 2010); Spectrolebias Costa & Nielsen, with nine small-sized species (max. 32 mm SL) distributed in the Paraguay, Guaporé, Xingu, Araguaia, and Tocantins river basins (Costa, 2010); Hypsolebias, with fortynine medium-sized species (max. 80 mm SL) distributed in Jequitinhonha, São Francisco, and Urucuia river basins (Costa, 2010); Cynolebias, with twenty two medium to large-sized species (50–120 mm SL) distributed in the São Francisco and Urucuia river basins (Costa, 2010); Austrolebias, with fortyeight small to large-sized species (35–150 mm SL) distributed in the La Plata, Patos-Merin, and southwestern Amazon basins (Loureiro, de Sá, 2016; Costa et al., 2017a; Volcan et al., 2017; Alonso et al., 2018).

According to a recent molecular phylogenetic analysis (Costa et al., 2017a), Nematolebias + Xenurolebias are the sister clade of the remaining genera, which relate to each other as follows: Spectrolebias, ((( Austrolebias, (( Simpsonichthys, Cynolebias), (Opthalmolebias, Hypsolebias))). However, Ponzetto et al. (2016), in a phylogenetic analysis based on one mitochondrial marker, had recently challenged the monophyly of Hypsolebias, with some species more closely related to Ophtlamolebias than to other Hypsolebias .