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. Flowering Apr-Oct. Canyon sides, rocky arroyo floors, chaparral thickets, scrubs, dry banks; Tex.; Mexico (Tamaulipas). Thelypodiopsis shinnersii is known from Cameron County.