Named after botanist and plant ecologist Dr. Arthur Kruckeberg (1920- )
Rhizome: erect, short, sparsely scaly; scales light brown, gradually diminishing in size upwards.
Frond: 35 cm high by 3 cm wide, evergreen, monomorphic or weakly dimorphic, blade/stipe ratio: 4:1 to more usually 10:1.
Stipe: grooved, sparesly scaly, vascular bundles: 4 or more, in an arc.
Blade: 1-pinnate, lobed pinnae, sometimes pinnatifid, lanceolate, base narrowed, glossy, microscales lanceolate with few projections, confined to costa below.
Pinnae: 20 to 40 pair, rhombic-ovate, 0.5--1.5 cm, lower ones lobed at the base, the upper ear well-developed; margins toothed, spiny; veins free, forked.
Sori: round, undersides of the upper pinnae, indusium: peltate, central, sporangia: dark brown, maturity: midsummer.
Dimensionality: pinnae twisted somewhat out of plane of blade.
Habitat: rocks and cliffs in subalpine to alpine habitats, 2100–3200 m. in California, lower elevations north.
Distribution: western North America.
Hardy to -20°C, USDA Zone 6.