Annual, often spiny herbs. Stem erect, branched. Leaves cauline, mostly alternate or sometimes whorled, petiolate, lamina lanceolate, linear, ovate, rounded–deltate or suborbiculate, often ± palmately or pinnately lobed, margins entire or ± toothed, hirtellous or ± strigose on either side, usually gland–dotted. Capitula discoid, solitary or in glomerules, unisexual, female and male capitula borne on the same plant. Female capitula sessile, axillary, borne at the base of male capitula, 2–flowered, involucre ± ellipsoid, enlarged at maturity. Phyllaries 2–seriate, outer free, inner mostly connate, enveloping the whole florets, except style branches, bearing spreading hooked spines, usually with 2 conic beaks at the apex, this prickly capitulum become hard on maturity (often called as bur); corolla absent. Male capitula: involucre ± saucer–shaped; phyllaries 6–16, in 1–2 series, distinct at bases. Receptacles conical to columnar; paleate, paleae spathulate to cuneiform or linear, membranous, distally ± villous or hirtellous; florets 5–30. Corolla whitish, ± funnel form, lobes 5, erect or reflexed. Cypselas black, ± fusiform, enclosed in obovoid to ellipsoid, hard, prickly phyllaries, 2–chambered burs. Pappus absent.
A small genus of 3 species, native of South America but now cosmopolitan in distribution as an invasive genus. Represented in Pakistan by two species.