8b. Xanthisma spinulosum (Pursh) D. R. Morgan & R. L. Hartman var. chihuahuanum (B. L. Turner & R. L. Hartman) D. R. Morgan & R. L. Hartman, Sida. 20: 1408. 2003.
Machaeranthera pinnatifida (Hooker) Shinners var. chihuahuana B. L. Turner & R. L. Hartman, Wrightia 5: 311. 1976; Haplopappus spinulosus (Pursh) de Candolle var. chihuahuanus (B. L. Turner & R. L. Hartman) Gandhi
Perennials, 30–50 cm, often woody at base. Stems stiffly erect, usually much branched in proximal 1 / 2 – 2 / 3 ; mid internodes 2–5 mm. Leaves numerous, concentrated in proximal ± 1 / 2 , spreading to loosely ascending, often much reduced distally, margins of proximal pinnatifid to 2-pinnatifid, of distal coarsely dentate to ± entire, lobes linear to lanceolate, 3–5 mm, faces usually hairy, rarely glabrous, often densely stipitate-glandular. Heads 2–10+ in diffuse arrays. Peduncles relatively terminal and lateral, 0.5–2 cm. Involucres 12–15 mm wide. 2n = 8, 16.
Flowering spring–fall. Clayey to rocky washes, prairies, plains, roadsides; 1000–1800 m; Ariz., N.Mex., Tex.; Mexico (Chihuahua, Coahuila, Durango, Sonora).
Variety chihuahuanum is a Chihuahuan Desert taxon that extends into the southern United States.
