Xenurolebias is a genus of killifish in the family Rivulidae, endemic to Brazil. The atlas's two species, X. izecksohni and X. myersi, are known only from Brazil, small fish in the 2–2.5 in range typical of the seasonal-pool killifish groups within Rivulidae. Like other genera adapted to temporary wetlands, Xenurolebias is presumed to inhabit shallow pools that fill during the rainy season and dry out completely for part of the year, a boom-and-bust habitat that has shaped the group's whole reproductive strategy.
Annual killifish of this kind lay eggs that bury into the mud substrate and enter diapause, a suspended state of development that lets the embryos survive the dry season buried in damp soil long after the adults that produced them have died; the eggs then hatch in a rush once the rains return and refill the pool, and the next generation races through its whole life cycle before the water disappears again. Xenurolebias is a genus of real conservation concern rather than a hobby mainstay: the atlas tally shows one species Vulnerable and the other Endangered, reflecting how exposed small, geographically restricted, seasonal-pool specialists in Brazil are to habitat loss and land drainage.