2n = 42

Slender suffruticose perennial with red brown or dark brown subterranean stems < 1.5 mm diam. Branches prostrate and < 30 cm long, or erect and < 10 cm long, c. 1 mm diam., light red brown, clad in simple, ascending to erecthairs, epidermis broken with age; internodes < 3 cm long on prostrate stems. Leaves imbricateon short erectshoots, imparipinnate, (1.5)-3.5-5 × (0.7)-1.7 cm; stipules 4-7 mm long, margins, tips, and abaxial face hairy, free portion acuminate, entire or bifid, ± = broad sheath; leaflets (1)-3-5 pairs, the distal leaflet and one or two upper pairs suborbicular in outline, truncate at apex, shallowly cuneate at base, 4-15 × 3-11 mm; upper surface dull, rich green, punctate with raised hair bases, and with distinct veins, lower surface glaucescent, moderately clad in ascending hairs; teeth 8-14, sharply incised, often red brown at least on margins, shortly penicillate, with white or pink hydathodes. Basal leaflet pairs < ½ the size of the penultimate pair, or linear and entire, smaller than stipule lobes. Hairs simple, unicellular, < 1.5 mm long, ascending from raised bases, on stipules, rachis, and leaflets. Scapes terminal on short shoots, (4)-7-15 cm long at flowering, hardly elongating as fruit matures, moderately hairy and roughened by raised hair bases, pale brown. (Frequently a second scape is produced from the axil of an upper leaf in the same season so that the shootappears forked). Scape bract 0, or foliose, occasionally subtending a single floret. Capitulum 6-8 mm diam. at flowering, 10-15 mm diam. (including spines) at fruiting. Bracteoles on receptacle linear, c. 3 mm long, with hairy margins. Florets c. 45-60, minutely stipitate. Hypanthium c. 1 mm long, enclosing perigynous ovary, clad in appressed hairs and bearing 4 barbed spines which reach above the hypanthium rim. Sepals 4, arising from hypanthium rim, joined at base to form a short tube, 1.2 mm long, ovate, thickened at tip, hairy on abaxial face. Petals 0. S tamens 2; filaments unequal, up to 2.5 mm long; anthers c. 0.4 × 0.5 mm, white. Style 1, 1.5 mm long, including white, fimbriate stigma 0.7 mm broad and protruding from aperture of hypanthium. Fruit indehiscent with a single achene enclosed in the hypanthium, obconic, c. 2.5 × 1.5 mm, red brown, moderately hairy, 4-ribbed; spines 1 per rib, slender, 4-6 mm long, pale brown, bearing a single rank of translucent, retrorse barbs at tip.

Suffrutex tenuis; caules c. 1 mm diam., ad 30 cm longi, proni et radicantes. Folia ad 5 cm longa, imparipinnata; foliola (3)—7—11, foliola distalia tria suborbiculata, supra viridia, punctata, subtus glaucescentia, pilis ascendentibus; dentibus penicillatis; stipuli integri vel bifidi. Scapus c. 7 cm longus. Stylus albus. Antherae albae. Fructus c. 2.5 × 1 mm, pilosus. Inter species sectionis Ancistrum bene evolutis glochideis fructus spinis carpelloque singulari. Differt a Acaena anserinifolia foliorum forma, stipulis integris, pilis ascendentibus, fructibus minoribus.