"Nepenthes fusca" subsp. "kostermansiana" was named from the herbarium material "Kostermans 21495", which was collected by André Joseph Guillaume Henri Kostermans on October 25, 1963, at 1000 m altitude along the Kelai River on Mount Nyapa (Njapa), Berau Regency, East Kalimantan. It is deposited at the National Herbarium of the Netherlands in Leiden. This taxon was initially thought to fall within the variability of "N. fusca", but in 2011 it was described as a distinct species, "N. epiphytica", with "Kostermans 21495" designated as its holotype.