Bot. Gaz. 37: 262. 1904.
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, sometimes reflexed, faces sparsely stipitate-glandular 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.
Phenology: Flowering and fruiting early–late summer.
Habitat: Meadows, fellfields, talus slopes, rock crevices, dwarf coniferous forests in alpine and upper subalpine communities, on soils of usually granitic, sometimes limestone origin
Elevation: 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.