Perennials, ashy white, to 15 cm, tomentose. Stems spreading (mat-forming). Leaves opposite; blades (at least proximal) lobed (from near bases), 6-12 mm overall, lobes 3-7, stiff, filiform (distal blades often acerose). Peduncles 30-40 mm, glabrous or glabrate. Calyculi of 1-3 subulate bractlets, lengths less than ¹/2 phyllaries. Involucres obconic to campanulate, 3.5-4 mm. Phyllaries 9-15, margins of outer free less than ¹/3 their lengths, abaxially glabrous. Ray florets 7-10; corollas bright yellow, laminae 2-3 × 0.8-1.2 mm. Disc florets 20-40; corollas dull yellow, 2-2.5 mm. Cypselae 1.5-2.2 mm; pappi coroniform (of connate scales) 0.3-0.5 mm. Flowering summer. Rocky, calcareous outcrops and derived soils; 1200-1500+ m; N.Mex., Tex.; Mexico (Chihuahua, Coahuila, Nuevo León). Thymophylla greggii var. greggii resulted from publication of T. greggii var. radiata A. Gray. Dyssodia setifolia var. radiata (A. Gray) Strother is illegitimate.