Plants winter annuals, (often nearly acaulescent). Stems (often inflated into 2.3 cm thick crown), usually ascending, rarely decumbent, 0.8-2.2 dm (when formed). Basal leaves rosulate; petiole 0.5-3(-5) cm; blade margins usually 2-, rarely 3-pinnatisect, (2-)3-10(-15) cm; lobes 5-10(-15) on each side, (smaller than terminal); apical segment linear to oblong or ovate, 1-8(-12) × 0.5-1(-2.5) mm, margins entire. Cauline leaves (and bracts, when present) similar to basal, smaller distally. Fruiting pedicels usually from basal leaf axil, (20-)30-80(-100) mm. Flowers: sepals (caducous or tardily so), spreading, oblong, (6-)7-12(-14) × 2-3.5 mm, apex appendage well-developed, (1-)1.5-3 mm; petals broadly spatulate to obovate, (12-)15-20 × (5-) 6-9 mm, apex rounded; median filament pairs 6-10 mm, not dilated basally; anthers linear, 2-3 mm; gynophore (1-)1.5-3(-4) mm. Fruits oblong to elliptical, latiseptate, 1.4-3.5(-4) cm × (8-)10-17 mm, (slightly fleshy when green, thick, papery), base and apex acute; valves prominently reticulate-veined; replum strongly flattened; septum complete; ovules 28-40 per ovary; style (2-)3.5-6(-7) mm, strongly flattened basally. Seeds 5-7 mm diam.; wing 1-2 mm. 2n = 14.

Flowering Feb-Apr. Grassy banks, pastures, salt draws, gypseous llano, roadsides, sandy alluvium, limestone or sandy areas, creosote bush scrubland, open flats; 600-1900 m; N.Mex., Tex.; Mexico (Chihuahua, Coahuila, Nuevo León).

Selenia dissecta rarely produces racemes, and most flowers originate from the axils of basal leaves that cover an inflated stem reduced to a crown.