Gnatholebias is a small genus of annual killifish native to the seasonal savanna wetlands of the Orinoco llanos, straddling Colombia and Venezuela. Like other annual cyprinodontiforms, its species live in shallow pools that form during the wet season and dry out completely for months afterward; the adult fish die with the pool, but their eggs survive buried in the damp substrate, arresting development until the rains return and a fresh generation hatches. At around 4.5 in, both species in the atlas run larger than many annual killifish, with the elongated body and upturned, predatory mouth typical of surface-hunting genera in this group.
Gnatholebias hoignei and Gnatholebias zonatus are known mainly within the specialist killifish-keeping hobby rather than the general aquarium trade, where they circulate as traded eggs and fry among enthusiasts rather than retail stock. Keeping either species means replicating their natural cycle: a peat-based spawning substrate, a dry incubation period for the eggs, and a wet hatch, the same husbandry routine used across the annual-killifish hobby. Both species currently carry a Least Concern IUCN status.