Asia-Tropical:, Borneo ‒ present (Sabah ‒ present, Sarawak ‒ present); New Guinea ‒ present; Philippines (Philippines ‒ present) Mindoro: present
Malesia: Borneo (Sabah, Sarawak), Philippines (Mindanao, Mindoro), New Guinea.
The above description is based on the largest plants from G. Mulu, but much smaller plants with pinnae 10 cm long may be fertile, especially on limestone. One collection from Mt Kinabalu has narrower fertile pinnae, little different from those of H. aspidioides but with sori almost all on connected veins. The larger specimens are intermediate between H. aspidioides and H. giganteum. They need experimental treatment to arrive at a better understanding of this relationship. The presence of scaly buds on the upper surface of costae is notable.