Syngonanthus weddellii var. gracilis Moldenke, (1973) was described very briefly based on a single collection. A careful analysis reveals that this variety has dimerous flowers, free petals of the pistillate flower and bifid stigmatic branches. It is therefore misplaced in Syngonanthus Ruhland (1900). We transfer it to Paepalanthus Mart. (1834) at the species level, as it is distinct from morphologically similar species: Paepalanthus flaccidus (Bong.) Koern. (1863), Paepalanthus trichophyllus (Bong.) Koern. (1863), and Paepalanthus strictus Koern. (1863). The epithet gracilis is no longer available, hence, we have coined the name Paepalanthus rectifolius. We also provide a full description, illustrations, a distribution map, and pertinent comments.
Keywords: Brazil; Goiás; Nomenclature; Syngonanthus; Taxonomy.