Plesioneuron crassum subsp. chromeanum Takeuchi (Thelypteridaceae) is described as a new subspecies from one of Papuasia's most isolated karst districts. The subspecies is distinguished by bifacially glabrous pinnae with revolute lobes, conspicuously raised aerophores, and glandular-setiferous sporangia. Distributional records for Helicia acutifolia (Proteaceae) and Loranthus odoratus (Loranthaceae) are also reported with the new fern.