Synonym(s): Adenophorus sarmentosus (Brack.) K. A. Wilson; Amphoradenium pinnatifidum (Gaudich.) Copel.; Am. sarmentosum (Brack.) Copel.; Polypodium adenophorus Hook. & Am.; P. pendulum sensu Gaudich., non Sw.; P. sarmentosum Brack. [Oligadenus pinnatifidus (Gaudich.) W. H. Wagner in unpublished checklists]

Endemic

Latin pinnatus, winged, feathered, + -fid, divided into many parts, describing the pinnatifid cutting of the frond.

Plants small, epiphytic or epipetric. Rhizomes short, erect. Fronds erect, arching, or pendulous, (2-)5-12+ em long. Stipes round at base, soon becoming winged and blend-ing into blades. Blades deeply pinnatifid to pinnatisect, ovate to lanceolate-ovate incised nearly to midrib, tips often elongate, marginal hairs absent to sparse; lobes close or distant, narrowly elongate-triangular, oblique, oblong, or linear, tips acute to broadly rounded, margins mostly entire, sometimes crenate on larger fronds, distal margins of lobes forming acute angles with midrib. Veins pinnate in each segment except on small-est fronds. Sori usually found on distal 2/3 of blade, solitary on smaller segments but present in 2, often irregular, rows on larger segments; glandular paraphyses present, sparse.

Occasional to abundant epiphyte in mesic to wet forests and along shaded streambeds, 240-1,680 m, all major islands. This polymorphic species is the most common one in the subgenus and the only species that grows on rocks. Some specimens have uniform fronds with short, rounded segments; others have irregular fronds with long, narrow segments and narrow, tapering tips.

Adenophoros pinnatifidus, a common wet-forest fern, is distinguished by fronds that are wider in the middle and tapering at both ends, long triangular lobes with the upper margins forming acute angles with the midribs, and hairless blade margins.