Funaria macrocarpa (Funariaceae) is shown to be an earlier name for Costesia spongiosa (Gigaspermaceae). The species is, however, retained in the genus Costesia and a new combination is hence proposed: Costesia macrocarpa. The species, endemic to central Chile, belongs to the Gigaspermaceae, a small family with six mainly monospecific genera with a widely scattered distribution in the Southern Hemisphere. Both basionyms are lectotypified. A morphological description and a discussion of the geographic distribution of the species are provided.