Revis. Gen. Pl. 1: 303. 1891. 1891
Plants 10–60 (–120+) cm. Stems ± procumbent. Leaf-blades deltate to ± rhombic or ovate, 13–37 × 7–32 mm, faces sparsely scabrellous to glabrate or glabrescent, glanddotted. Fruits plumply ellipsoid to fusiform, weakly compressed, 7–9+ mm, 5–7-ribbed, lacking terminal spines, prickles ± uncinate, mostly along ribs. 2n = 22.
Phenology: Flowering year round, mostly Jul–Aug.
Habitat: Disturbed, often sandy sites
Elevation: 0–300 m
Introduced; Ala., Ark., D.C., Fla., Ga., La., Mass., Miss., N.C., Oreg., Pa., S.C., Tex., Va., South America, also in Mexico, West Indies, Central America, Europe, Asia, Africa, Pacific Islands (Hawaii)
Reports of Acanthospermum xanthioides (Kunth) de Candolle from New York are evidently based on specimens of A. australe.