Perennials, loosely cespitose, 1-9 cm; with branched caudices surmounting well-developed taproots. Stems densely hairy, sometimes also stipitate-glandular. Leaves: basal blades linear to spatulate, 10-50(-95) × 1.5-6 mm; cauline blades oblong to broadly lanceolate, 15-34 × 3-7 mm, gradually reduced distally; 3-5-nerved, margins entire, ciliate, sometimes stipitate-glandular, faces eglandular or sparsely stipitate-glandular. Heads 1(-2). Peduncles 3-8 mm. Involucres broadly campanulate, 8-20 × 7-12 mm. Phyllaries 16-34, in 3-4 (-5) series, 1- or weakly 3-5-nerved, ± equal, margins ciliolate at least distally; outer and mid green, ovate to oblong, 4.5-10.5 × 1.5-5.5 mm, foliaceous, apices rounded to obtuse, faces sparsely stipitate-glandular distally; inner green or usually anthocyanic, linear to narrowly oblong, 5-9 × 0.9-4 mm, chartaceous proximally, margins scarious, often fimbriate, sometimes stipitate-glandular, apices acute to acuminate, s ometimes reflexed, faces sparsely stipitate-glandu lar distally. Ray florets 10-16(-35); laminae elliptic, 6.5-8.5 × 1.5-3.5 mm. Disc florets 43-66; corollas narrowly funnelform, 4.5-7.5 mm, lobes erect to spreading, 0.8-1.2 mm, lengths ca. ¹ / 7 corollas; anthers 2.2-2.8 mm; style-branch appendages lanceolate, 0.8-1.1 × 0.3 mm wide, stigmatic lines 0.6-1 mm. Cypselae cylindric, 2-5 mm, 8-9-nerved, faces villous; pappus bristles ± 34-51, flexible. 2n = 18.

Flowering and fruiting early-late summer. Meadows, fellfields, talus slopes, rock crevices, dwarf coniferous forests in alpine and upper subalpine communities, on soils of usually granitic, sometimes limestone origin; 3100-4100 m; Colo., Mont., N.Mex., Wyo.

Tonestus pygmaeus is uncommon in Wyoming, known only from the Snowy Range of the Medicine Bow Mountains. Attribution of this species to Montana is based on historic collections.