Shigeo Kurata
In his description of the Bornean species "N. campanulata", botanist Shigeo Kurata suggested that it may be closely related to "N. inermis". However, other taxonomists disagree with this hypothesis. While these two species are similar in general stature and pitcher morphology, they are not only separated by great geographical distance, but also occur in completely different habitats; "N. campanulata" is a lowland species endemic to limestone substrates, whereas "N. inermis" usually grows as an epiphyte at elevations of .