Titanolebias is a genus of large annual killifish from the seasonal marshes and temporary pools of South America's southern lowlands, recorded in the atlas from Uruguay, Argentina, Brazil, Bolivia, and Paraguay - broadly the Rio de la Plata basin and neighboring drainages. Atlas species span 3–8.5 in, making this one of the biggest-bodied genera in the entire killifish order; most annual killifish run just a few centimetres, but Titanolebias includes true giants among them. Like other annual killifish, these fish live in pools and marshes that dry out seasonally - the adults die off as the water disappears, and the next generation hatches from drought-resistant eggs buried in the mud once the rains return.
The hobby name for the group is pearlfish, and Titanolebias monstrosus - fittingly the Giant pearlfish - is the standout, an apex predator of its temporary-pool community that takes other fish as prey rather than subsisting on invertebrates alone, an unusual habit for a killifish. That predatory size and specialist annual-pool life cycle make these fish a demanding, minority interest even within the killifish hobby, needing large tanks and a true dry-incubation breeding regime rather than the simpler wet-spawning routine many aquarists are used to. Conservation status is a real concern: three of the atlas's four species are assessed Vulnerable and the fourth Endangered, reflecting how exposed ephemeral wetland habitat is to drainage and conversion for agriculture across the Pampas.