Riddellia cooperi A. Gray, Proc. Amer. Acad. Arts 7: 358. 1868

Shrubs or subshrubs, (15–)25–30(–50+) cm. Stems pannose (white). Heads borne singly. Peduncles 35–60(–80+) mm. Involucres 6–8 mm. Rays 3–6; laminae (8–)12–20 mm, spreading to reflexed in fruit. Disc florets (6–)10–17(–25). Cypselae usually glabrous, sometimes gland-dotted; pappi of 4–6 oblong to ± lanceolate scales 2–2.5 mm. 2n = 32.

Flowering (Feb–)Apr–Jun(–Dec). Creosote-bush scrub, sandy washes; 100–2100 m; Ariz., Calif., Nev., Utah; Mexico (Baja California, Sonora).