Contr. Gray Herb. 206: 13. 1976.
Annuals; (often glaucous), glabrous throughout. Stems unbranched or branched distally, 3.5–8 dm. Basal leaves (soon withered); not rosulate; petiole (winged), 0.5–3.5 cm; blade pandurate to broadly obovate, 2–10 cm × 10–50 mm, margins entire or repand. Cauline leaves (proximalmost) petiolate or (distal) sessile; blade (proximalmost) pandurate to broadly obovate or (distal) obovate, base auriculate, margins entire or repand. Racemes lax. Fruiting pedicels often divaricate, sometimes ascending, straight, 4–13 mm. Flowers: sepals erect, purplish, 2.5–3.5 × 0.7–1 mm; petals white, narrowly oblanceolate, 3.5–4.5 × 1–1.2 mm, claw not developed; median filament pairs 1.5–2.5 mm; anthers ovate-oblong, 0.7–1 mm; gynophore 0.2–0.4 mm. Fruits divaricate to ascending, straight or curved, obscurely torulose, 3.2–7.5 cm × 0.9–1.2 mm; ovules 60–102 per ovary; style subclavate, 0.4–2.5 mm; stigma entire. Seeds 0.9–1.1 × 0.5–0.7 mm.
Phenology: Flowering Apr–Oct.
Habitat: Canyon sides, rocky arroyo floors, chaparral thickets, scrubs, dry banks
Tex., Mexico (Tamaulipas).
Thelypodiopsis shinnersii is known from Cameron County.