Spectrolebias is a genus of small annual killifish (family Rivulidae) native to seasonal wetlands of south-central South America - the atlas records Bolivia, Brazil, and Paraguay, the Pantanal and Gran Chaco region. The atlas species are tiny, 1–2 in. Like other annual killifish, they are adapted to temporary pools that dry up on a seasonal cycle: eggs are laid into the substrate and survive the dry season in a dormant, diapause state, hatching quickly once rains refill the pools, so the adult generation itself lives out only a single wet season.
Annual-killifish keepers value Spectrolebias for its compact size and, in several species, notably elongated fin filaments in males - the epithet of S. filamentosus points directly at that trait. As with most annual killies in the hobby, breeding relies on a peat or soil substrate that is dried and later re-wetted to trigger hatching, a specialist but well-established technique. One atlas species carries CARES-listed status, and the mix of Data Deficient and Near Threatened ratings among the rest reflects how tightly these fish are tied to fragile, easily drained seasonal wetland habitat.