in Hooker & Baker,Syn. Fil. ed. 2 477. 1874.
Stems compact, ascending, stout, 5–10 mm diam.; scales bicolored, linear-subulate, 0.1–0.3 mm wide, centers dark-brown to black, thick, margins brown, thin, dentate. Leaves monomorphic, clustered on stem, 8–40 cm; croziers sparsely villous. Petiole dark-brown, lustrous, flattened or slightly grooved adaxially, without prominent articulation lines. Blade linear-oblong, 2-pinnate proximally, 1–4 cm wide; rachis brown throughout, straight, shallowly grooved adaxially, usually glabrous. Pinnae strongly ascending, not decurrent on rachis, usually with 5–11 ultimate segments; costae straight, 5–20 mm, usually shorter than ultimate segments. Ultimate segments linear, 5–20 mm, leathery, glabrous; margins on fertile segments strongly revolute, covering more than 1/2 abaxial surface, borders greenish, crenate; apex mucronate. Veins of ultimate segments obscure. Sporangia short-stalked, containing 64 spores, intermixed with abundant farina-producing glands.
Phenology: Sporulating summer–fall.
Habitat: Cliffs and rocky slopes, usually on igneous substrates, occasionally on serpentine
Elevation: 900–2700 m
Calif., Oreg., Wash.
The distinctive Pellaea brachyptera reportedly hybridizes with P. mucronata (A. F. Tryon 1957; D. B. Lellinger 1985); the hybrids are morphologically intermediate plants with malformed spores.
"thick" is not a number.