Trigonectes is a genus of killifish from the seasonal wetlands of central South America, recorded in the atlas from Brazil, Bolivia, Paraguay, and Argentina - broadly the Gran Chaco and Pantanal lowlands, where rivers spread into vast, shallow floodplains each wet season. Atlas species range 4–6.5 in, larger than many of their killifish relatives. As with other South American killifish of these seasonal floodplain habitats, life history tracks the flood pulse: fish spread into flooded grassland and marsh as water rises, then retreat as the dry season shrinks the water available to them.
None of the four species in the atlas carries an established common name, and Trigonectes is not a genus that shows up in the mainstream aquarium trade - it is known mainly from scientific collections and specialist killifish circles rather than pet-shop stock. Conservation data are correspondingly thin: of the four species, one is Vulnerable, one Endangered, and two Least Concern, a mixed picture that likely reflects how unevenly the Chaco-Pantanal wetlands have been surveyed as much as any real difference in rarity between species. Wetland drainage and conversion to agriculture and cattle ranching remain the standing pressures across this part of South America.