Parrya platycarpa Rydberg, Bull. Torrey Bot. Club 39: 326. 1912, not Hooker f. & Thomson 1861; Neuroloma rydbergii (Botschantzev) Botschantzev; P. nudicaulis (Linnaeus) Regel subsp. rydbergii (Botschantzev) Hultén; P. nudicaulis var. rydbergii (Botschantzev) N. H. Holmgren

Plants densely cespitose, caudex branched; densely glandular or, rarely, eglandular. Stems (0.3-)0.5-1.5 (-2.6) dm. Leaves: petiole (0.5-)1.5-5(-7) cm, to 5 mm wide at base; blade obovate to spatulate or broadly oblanceolate to lanceolate, (1-)2-5(-8) cm × (7-)13-26 mm, base cuneate or attenuate, margins incised to coarsely dentate, apex acute. Racemes 3-15-flowered. Fruiting pedicels (proximalmost) 4-15(-20) mm. Flowers: sepals oblong, 5.5-9 × 1.5-2.5 mm; petals lavender to purple, (15-)16-20(-23) × 7-9 mm, claw 8-12 mm, apex emarginate; median filaments 4-6 mm; anthers 1.5-2 mm. Fruits narrowly oblong to linear-lanceolate, (2-)3-5 cm × 5-7 mm; valves densely glandular; ovules 10-16 per ovary; style 0.5-1.5 mm. Seeds 4-5 × 3.5-4.5 mm; wing 1-2 mm wide.

Flowering late Jun-Jul. Barren rock slides, alpine tundra, finely divided limestone rubble, calcareous talus, shale slopes, alpine rocky slopes, crevices among boulders; 2900-3700 m; Utah, Wyo.

Parrya rydbergii, which is restricted to Uinta and Emmons mountains in Utah (Daggett, Duchesne, Summit, and Uintah counties) and Beartooth and Big Sheep mountains in Wyoming (Park and Sublette counties), was treated by E. Hultén (1971) as a subspecies of P. nudicaulis and reduced by R. C. Rollins (1993) to synonymy of that species. It is geographically disjunct from P. nudicaulis and can be easily distinguished from that nearest relative.