Xenurolebias is only known by the description and represent a genus with 4 species (since 2014) of medium size. Costa has reviewed in details the genus Simpsonichthys, split it into several genera (upgraded from subgenus status), notably Xenurolebias which is discussed and not followed by Huber.

Xenurolebias is distinguished from all other Rivulidae by the presence of filamentous rays on the posterior margin of the Anal fin in female (vs. absence), by a caudal-fin lanceolate and asymmetric due to an expansion of the ventral portion of the fin in male (vs. caudal fin rounded or subtruncate, dorsal and ventral portion symmetric), and a unique color pattern consisting of a bar on the posterior portion of the caudal peduncle, posteriorly extending over the dorsal and ventral margins of the Caudal fin in male (vs. never a similar color pattern) (Costa, 2006).

Literature: Costa, W. J. E. M. 2010. Historical biogeography of cynolebiasine annual killifishes inferred from dispersal- vicariance analysis. Journal of Biogeography, 37: 1995-2004.

Ponzetto Josi M., Ricardo Britzke, Dalton T. B. Nielsen, Patricia P. Parise-Maltempi& Anderson L. Alves. 2016. Phylogenetic relationships of Simpsonichthys subgenera (Cyprinodontiformes, Rivulidae), including a proposal for a new genus. Zoologica Scripta, The Royal Swedish Acedemy of scienses.

Behaviour:

General behaviour is like that from most Simpsonichthys species as they like to dwell in small groups and are not very active in there environment. Not fast swimming but more peacefull standing in shaded places. They eat, as most other annuals do, mosquito larves and small flying insects or crusteans. See for more info the species page.