| | 1. Phyllaries generally > 2 mm wide; heads generally solitary, conspicuously peduncled; involucres 2–7 cm diam |
| C. nutans |
| | 1' Phyllaries generally < 2 mm wide; heads 1–several, often clustered at branch tips, short-peduncled or sessile; involucres 1–3 cm diam |
| |
| | 2. Involucres spheric or hemispheric |
| C. acanthoides |
| | 2' Involucres cylindric or narrowly elliptic |
| |
| | 3. Lower leaves 4–10-lobed; heads generally 2–5 per cluster; phyllaries not scarious-margined, ± persistently tomentose, tips scabrous |
| C. pycnocephalus |
| | 3' Lower leaves 12–20-lobed; heads 5–20 per cluster; phyllaries scarious-margined, glabrous to sparsely tomentose, tips not or barely scabrous, sometimes short-ciliate |
| C. tenuiflorus
|