9. Thelesperma filifolium (Hooker) A. Gray, Hooker’s J. Bot. Kew Gard. Misc. 1: 252. 1849.
Coreopsis filifolia Hooker, Bot. Mag. 63: plate 3505. 1836; Thelesperma filifolium var. intermedium (Rydberg) Shinners; T. intermedium Rydberg
Annuals (sometimes persisting), 10–40(–70+) cm. Cauline leaves crowded to ± scattered over proximal 1/2–3/4 of plant heights, internodes mostly 10–35(–50+) mm; lobes mostly linear to filiform, sometimes oblanceolate, 5–30(–55+) × 0.5–1(–3+) mm. Calyculi of 7–8+ linear to narrowly triangular bractlets (2–)4–8+ mm. Ray florets 8; laminae yellow to golden yellow (sometimes proximally suffused with red-brown), 12–20+ mm. Disc corollas red-brown or yellow with red-brown nerves, throats shorter than lobes. Cypselae 3.5–4+ mm; pappi 0.5–1(–2+) mm. 2n = 16, 18.
Flowering Mar–Aug(–Oct). Disturbed sites on clays or sandy soils, rocky slopes, often on limestone; 10–2200 m; Ark., Colo., Kans., La., Miss., Mo., Nebr., N.Mex., Okla., S.Dak., Tex., Wyo.; Mexico (Nuevo León).
As here circumscribed, Thelesperma filifolium includes plants that others have treated as a distinct species or variety: T. intermedium or T. filifolium var. intermedium, characterized as plants mostly 10–40 cm (versus taller); internodes "relatively short" (versus longer); calyculus bractlets mostly 1/4–1/2 lengths of phyllaries (versus more than 1/2 as long); ray corollas yellow (versus "golden yellow"); disc corollas yellow (versus sometimes red-brown); distribution mostly north and west of the typical form (Colorado, Kansas, Nebraska, New Mexico, w Oklahoma, South Dakota, c and w Texas, Wyoming).
According to A. Cronquist (1980), Thelesperma trifidum (Poiret) Britton has been misapplied (e.g., M. L. Fernald 1950) to T. filifolium.