Ranunculus arvensis var. tuberculatus de Candolle

Stems erect or ascending, sparsely pilose. Basal and lower cauline leaf blades obovate to rhombic in outline, 3-parted or 3(-5)-foliolate, 1.8-5.2 × 1.6-4.2 cm, leaflets oblanceolate or divided into oblanceolate or linear segments, leaflet base narrowly acuminate, margins entire or distally dentate, apex rounded or acuminate. Flowers pedicellate; receptacle sparsely hispid; sepals 5, spreading, 4-7 × 1-2 mm, strigose; petals 5, 5-8 × 2-4 mm. Heads of achenes discoid, 8-9 mm across; achenes 5-8 per head, 4-6.4 × 2.8-4.4 mm, faces and margin covered with long spines, glabrous; beak lance-subulate, straight, 1.6-3.8 mm.

Flowering spring (Mar-Jun). Grasslands, ephemeral pools, disturbed areas; 0-1200 m; introduced; Ark., Calif., D.C., Ga., Idaho, Ill., Kans., La., Miss., Mo., N.J., N.Y., N.C., Oreg., Pa., S.C., Tenn., Utah, Wash.; South America; native to Eurasia; Pacific Islands; Australia.