Annual or perennial herbs or shrubs of rocky sites, without latex; leaves usually op- posite; heads radiate or discoid, small to medium-sized; involucre cylindric to hemispheric, bracts subequal in 1–2 series, usually navicular, without hyaline margins; receptacles usually naked, smooth; ray florets pistillate, corollas yellow or white, often 3-lobed; disc corollas yel- low with 4–5 lobes of equal size; anther apical append- age usually ovate, thecae pale, without spurs (ecalcarate) or tails (ecaudate); pollen echinate and spherical; styles slender, deeply divided, apices of branches tapered to rounded with short hairs, style glabrous below the bifur- cation, at maturity style branches recurving; achene walls smooth, with phytomelanin layer; pappus of (usually two) bristles and crown of scales or absent.

Diagnostic Features

Rupicolous herbs and shrubs; glandular foliage; subequal, usually navicular phyllaries; epaleate receptacles; usually 4-lobed disc co- rollas; pale, ecaudate anthers; smooth, blackened achenes; and pappus (if present) usually of (1–)2 bristles and ru- dimentary scales.

Geographic distribution

Mmainly deserts of south- western North America (also Andes and Desventuradas Islands of South America).