Hooker, Fl. Bor.-Amer. 1: 21. 1829.
Stems nearly erect or decumbent, never rooting nodally, hispid, strigose, or glabrous, base not bulbous. Roots sometimes fleshy and ± tuberous. Basal leaf blades narrowly ovate to oblong or semicircular in outline, simple to 3-5-lobed or -foliolate, 2.8-12.5 × 2.5-14 cm, leaflets or segments undivided or 1-2×-lobed or -parted, ultimate segments circular to linear, margins dentate, crenate, or entire, apex rounded to narrowly acute. Flowers: receptacle hispid; sepals reflexed 1-2 mm above base, 5-11 × 2-4 mm, hispid, hirsute, or glabrous; petals 5-6, abaxially yellow or red, adaxially yellow, 8-18 × 4-11 mm. Heads of achenes hemispheric to ovoid, 5-13 × 6-10 mm; achenes 2.8-4.5 × 1.8-3.2 mm, glabrous, margin forming narrow rib 0.1-0.2 mm wide; beak persistent, narrowly lanceolate to subulate, straight, 1.8-3.8(-4.8) mm.
Varieties 3: w North America.
The first two varieties ( Ranunculus orthorhynchus var. orthorhynchus and R . orthorhynchus var. platyphyllus ) are rather weak, intergrading extensively in California and Oregon. By contrast, R . orthorhynchus var. bloomeri often grows with the others with little or no intergradation (although intermediate populations are found in some areas), and it has been treated as a distinct species, R . bloomeri , by many taxonomists.