Stout biennial herbs; stems prickly. Leaves opposite, sessile, often fused basally, simple, entire, dentate or lobed, midrib prickly. Inflorescences globose, ovoid or cylindrical heads; involucral bracts in 1 or 2 rows, linear or narrow-lanceolate, erect or spreading, spine-tipped; receptacle bracts spine-tipped; epicalyx 4-angled, united with ovary below and cupular above. Calyx cupular, entire or obscurely 4-toothed or 4-lobed, ciliate, persistent in fruit, finally shedding; corolla with 4 subequal lobes; stamens 4, anthers exserted, versatile; stigma lateral. Fruit a cypsela, 4-angled, appressed-hairy.
About 15 species, from Eurasia and into tropical Africa; 2 species naturalised in Australia.