Roots not proliferous. Stems ascending to erect, rarely branched; scales dark brown to blackish throughout, narrowly deltate, 2--4 × 0.25--0.45 mm, margins entire. Leaves weakly subdimorphic, fertile leaves taller and more erect than sterile leaves. Petiole reddish or purplish brown throughout, lustrous, 1--10 cm, 1/5--1 times length of blade; indument of dark brown to black scales, narrowly deltate at very base, grading into hairs distally. Blade highly variable and typically irregularly shaped, narrowly deltate to lanceolate, pinnatifid or 1-pinnate in proximal 1/3, 2--20 × 1--6(--13) cm, medium thick, sparsely pubescent adaxially only; base ± truncate; apex acute to long-attenuate, apical buds borne occasionally but not known to root in nature. Rachis reddish or purplish brown abaxially, fading to green distally, lustrous, glabrous. Pinnae in 0--3 pairs, often irregular in size and shape, deltate to narrowly deltate; proximal pinnae 5--30(--80) × 3--10(--15) mm; base truncate to obtuse, auriculate on both sides; margins entire to finely serrate or crenulate; apex obtuse to acute or occasionally attenuate. Veins somewhat evident, mostly free, rarely anastomosing. Sori 1--10(--15+) pairs per pinna, on both acroscopic and basiscopic lobes. Spores malformed (sterile form) or 64 per sporangium (fertile form). 2 n = 72, 144.
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