Annuals, 10-35 cm. Stems 1(-9), erect, branched from bases and distally, relatively sparsely leafy, glabrous. Cauline leaves: proximal narrowly oblanceolate to obovate, usually pinnately lobed (lobes oblong to triangular), not fleshy, ultimate margins ± dentate, faces glabrous; distal greatly reduced (margins entire or basally dentate, apices acute). Calyculi of 5-8+, subulate to lanceolate bractlets, hyaline margins 0.05-0.2 mm. Involucres ± campanulate, 6-9 × 4-6.6 mm. Phyllaries 12-15+ in 2(-3) series, lance-oblong to lance-linear, hyaline margins 0.05-0.2 mm wide, faces glabrous. Receptacles not bristly. Florets 30-61; corollas white or pale yellow, 6-10+ mm; outer ligules exserted 1-4 mm. Cypselae ± cylindro-fusiform, 1.7-2 mm, ribs ending 0.2-0.3 mm short of apices, ± equal (distal 0.2-0.3 mm of cypselae slightly expanded, smooth); pappi persistent, of 16-18 needlelike teeth plus 2 bristles. Pollen 70-100% 3-porate. 2. = 14. Flowering Mar-May. Sandy, open areas among bushes, Larrea-Lycium-Cercidium-Baccharis associations, Quercus, Pinus, Juglans woodlands; 400-1500 m; Ariz., N.Mex.; Mexico (Sonora). Malacothrix sonorae is found mainly in the Sonoran Desert (Tucson, Kofa, Pinal, White Tank, Baboquivari, and Waterman mountains).

Notes: Fruits ribbedPhyllaries scarious margined References: Kearney & Peebles; Arizona Flora. ASU specimans