Lucania is a small genus of killifish in family Fundulidae, native to fresh and brackish waters of Mexico and the United States. The atlas's three species - the bluefin killifish (L. goodei), interior topminnow (L. interioris), and rainwater killifish (L. parva) - are compact fish, 2–3 in, typical of the genus's modest size. They favor still or slow-flowing, heavily vegetated water: L. goodei is a familiar sight in clear, spring-fed streams and marshes of the southeastern United States, while L. parva is unusually tolerant of salinity and turns up in brackish coastal marshes and estuaries as well as fresh water.
The bluefin killifish is the species most familiar to hobbyists, prized in the native and temperate killifish community for the male's vivid iridescent blue anal fin and easy-going, community-friendly temperament - a rare case of a North American native holding its own against tropical imports. The rainwater killifish is occasionally kept too, valued for its brackish tolerance, while the interior topminnow is essentially unknown in the trade. One atlas species is flagged under the CARES conservation priority list, a reminder that even a widespread genus like this one can include range-restricted populations under real habitat pressure, alongside two species rated Least Concern and one not yet evaluated.