Boston J. Nat. Hist. 5: 111, plate 13, figs. 7–11. 1845.
Annuals, 5–25 cm (± scapiform); taprooted. Stems 1–25+, erect or ascending, simple, glabrous or densely tomentose, sometimes glabrescent. Leaves basal or subbasal; petiolate (petioles winged); blades oblanceolate, margins pinnately lobed, denticulate (teeth callose-tipped). Heads borne singly. Peduncles not inflated distally, ebracteate. Calyculi 0. Involucres cylindric to campanulate, 4–20 mm diam. Phyllaries 15–25 in 4–5 series, (centers green to reddish purple) unequal, outer ovate to orbiculate, inner linear to oblong, flat, margins papery-transparent, apices rounded or obtuse to subacute. Receptacles flat to weakly convex, smooth, paleate (paleae slender, bristlelike). Florets ca. 40; corollas cream to bright yellow. Cypselae tan, cylindric, (bases tapered) beaks 0 (or ca. 0.5 mm), 10–15-nerved, finely appressed-puberulent; pappi readily falling, of 10, distinct, white, plumose bristles in 1 series (adaxial usually shorter than abaxial). x = 7.
sw United States, nw Mexico.
Molecular phylogenetic studies by J. Lee et al. (2003) indicated that Malacothrix is polyphyletic and that Anisocoma and Calycoseris are nested within the subclade of Malacothrix that contains M. californica, the type species of that genus. Anisocoma shares its base chromosome number (x = 7) with Calycoseris and the species of Malacothrix with which it is most closely grouped. Anisocoma differs from Malacothrix and Calycoseris in having paleate receptacles and pappi of plumose, rather than barbellulate bristles.