Rhizome not known. Fertile and sterile fronds similar, more or less erect, up to at least 2.5 m long, 50 cm wide. Stipes to at least 84 cm, shiny, rich red-brown, scales at the base broadly triangular, up to at least 0.7 by 0.2-0.3 cm at their bases, more or less entire, mid-brown, thin and concolorous, paler than the stipe surface and persistent, rigid, woody, blunt, spine-like outgrowths 0.1 cm diam. at their base and 0.1-0.35(-0.5) cm in length, protruding from the ridges and the inner face and from the deep groove on the adaxial surfaces. Lamina linear triangular, pinnate, with at least 40 pairs of pinnae. Rhachis and costae red-brown, becoming paler and stramineous towards the lamina apex in the dried specimen, glabrous, sometimes with spine-like outgrowths similar to those of the stipe on the basal ⅓ of the rhachis. Sterile pinnae linear-narrowly elliptic, up to 25 cm in length and 1.5 cm in width, sessile or subpetiolate, dried specimens coarsely papery, the margins serrate to dentate at their apices, basal pinnae slightly reduced, falcate. Fertile pinnae tending to be narrower in width, usually 0.8 cm but widening to over 1 cm towards the base and then narrowing suddenly to the costa at the junction with the rhachis, otherwise similar to the sterile pinnae but with up to ⅔ of the abaxial surface covered by the linear sori on either side of the pinna midrib. Spores 71.3 by 60 µm (from 3 herbarium specimens), perine costate, more markedly costate than spores of B. whelanii, costae rounded, surface scabrous to minutely rugulose.
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