Abstract
A vittarioid fern from the Solomon Islands, which has long been treated as Antrophyum semicostatum, is described here as a new species, Antrophyum solomonense. A description, illustration, and distribution of the new species are presented. Boot-shaped paraphysal apical cells, rounded stipe in cross section, and thin rhizome scale cell walls are the diagnostic characteristics of A. solomonense. A molecular phylogeny inferred from four chloroplast markers further supports its systematic uniqueness.