Madroño 57: 251, figs. 1D, 2B. 2010.
Plants biennial, candelabra-form. Stems solitary, erect, straight; branches distal, distal longest, antrorse, straight; hairy. Leaves: blade 43–94(–115) × (4.3–)7.5–36 mm, widest intersinus distance 1–2.4 mm; proximal oblanceolate to elliptic, margins pinnatisect, lobes 8–20, perpendicular to leaf axis, 3.2–12(–15.7) mm; distal oblanceolate to elliptic, base not clasping, margins pinnatisect, lobes 8–20, perpendicular to leaf axis, 5.6–17.1 mm; abaxial surface with simple grappling-hook, complex grappling-hook, and occasionally needlelike trichomes, adaxial surface with needlelike trichomes. Bracts: margins entire or pinnate. Flowers: petals golden yellow, 13–18.5 × 3.7–6.1 mm, apex acute, glabrous abaxially; stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 10.2–14.7(–18) × (1.3–)2.5–4.4 mm, without anthers, second whorl with anthers; anthers straight after dehiscence, epidermis smooth; styles 10–12.5(–14) mm. Capsules cylindric, 11–19 × 5–7.5 mm, base tapering, not or diminutively longitudinally ridged. Seeds: coat anticlinal cell walls sinuous, papillae 42–48 per cell. 2n = 20.
Phenology: Flowering Jul–Aug.
Habitat: Roadcuts, slopes, dark loam, rocky soils.
Elevation: 2100–2200 m.
Mentzelia filifolia is known from the Chuska Mountains of Apache County, Arizona, and McKinley and San Juan counties, New Mexico.