Featherfin Pearl Killi Simpsonichthys constanciae is a species of killifish from the family Rivulidae, endemic to Brazil. This small fish, reaching up to 6 cm in length, is found in temporary freshwater habitats like ponds in the So Joo basin in Rio de Janeiro. Its critically endangered according to the IUCN Red List.

The species name honors Constance White, an American watercolor painter who collected the type specimen with her husband. Have you seen this fish in an aquarium or are you interested in learning more about its conservation?