Stems erect or decumbent, not rooting nodally, hirsute to nearly glabrous, base not bulbous. Roots fleshy and somewhat tuberous. Basal leaf blades ovate to deltate in outline, 3(-5)-foliolate, 2.5-14.9 × 2.3-19.9 cm, leaflets 1-2×-lobed or -parted, ultimate segments narrowly oblong to elliptic or lanceolate, margins toothed, apex narrowly acute to rounded-acute. Flowers: receptacle hispid; sepals reflexed 1-2 mm above base, 5-10 × 3-5 mm, hispid; petals 11-16, yellow, 8-21 × 2-5 mm. Heads of achenes globose to ovoid, 6-13 × 7-9 mm; achenes 2.4-3.4 × 2-2.4 mm, glabrous, margin forming rib or narrow wing 0.1-0.4 mm wide; beak filiform from deltate base, straight, 1.8-2.5 mm, filiform tip often deciduous, leaving 1-1.2 mm deltate beak.

Flowering late spring-summer (Jun-Aug). Stream banks, lakeshores, and marshes; 1000-2200 m; Ariz., Tex.; Mexico.

I am following G. L. Nesom (1993) in treating Ranunculus fasciculatus as a distinct species. This taxon was considered a variety of R . macranthus by L. D. Benson (1948) and a variety of R . petiolaris by T. Duncan (1980). These disparate opinions result from different interpretations of Mexican members of the R . petiolaris group.