Perhaps the roots are anchored in the deep soil surrounding the base of the Exocarpos tree? I will go back for further investigation and maybe collect a specimen for proper id. Are there distinguishing features between Pteridium esculentum and Hypolepis sp? We found Bracken relatively close to this site; Hypolepis would be the first sighting for Mt Majura...
Distinguishing features are the spores: circular sporangia along the pinnules in Hypoleis, under recurved edges on Pteridium. Also check the colour of the rachis and any hairs.