Rhizome erect, sometimes forming a trunk up to 60 cm tall. Stipe 90–410 mm long. Stipe and rachis densely clothed with scales of diverse form. Larger rachis scales usually ovate-lanceolate (those from the mid rachis 340–1620 mm at their mid length), becoming lanceolate-acicular in some plants from the Chatham Islands (those from the mid rachis 180–780 mm at their mid length); usually bicolorous, with an obvious dark brown centre surrounded on all sides by pale brown margins, but dark centre sometimes much reduced, particularly in some plants from the Chatham Islands, islands around Stewart Island, and the subantarctic islands, such that the rachis scales are uniformly pale brown; apex usually long and tapering; usually without marginal projections except for plants from the Chatham Islands, in which they may be very well developed; usually underlain by pale bristle-like scales. Lamina 230–1300 × 90–350 mm; narrowly elliptic to narrowly oblong; bipinnate; usually dark green above, paler below. Primary pinnae in 20–55 pairs, oblong. Secondary pinnae all stalked except those towards the apex of primary pinnae; with sharply pointed apex and prominent marginal teeth and/or crenulations. Sori round. Indusia peltate, ± flat, ± round; with entire although sometimes undulate and/or scalloped margins; central dark area usually insignificant (< 10% surface area, and usually < 5%). Annulus cells of sporangia 12–17, but most commonly 13–14. Spore exine 36–44 × 26–32 mm; length-width product 980–1400 mm2 (31 individuals, 16 populations).