Oönopsis monocephala A. Nelson, Bot. Gaz. 31: 399. 1901; Haplopappus fremontii A. Gray subsp. monocephalus (A. Nelson) H. M. Hall

Heads 1–5(–6). Ray florets 0. Disc florets 66–150. 2n = 20.

Flowering Jun–Aug. Sparsely vegetated clay flats, gullies, and eroding toeslopes of limestone hills, alkaline, clayey, and calcareous soils with moderate to high erosion potential, usually in shortgrass prairies, also with Artemisia, Yucca glauca, Krascheninnikovia, sometimes in Sarcobatus flats; of conservation concern; 1200–1800 m; Colo.

Variety monocephala is known only from Las Animas County. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.