Perennials or subshrubs, 10-30(-50) cm. Cauline leaves crowded to ± scattered over proximal ¹/3-¹/2 of plant heights, internodes mostly 5-50(-80+) mm; lobes mostly linear to filiform, sometimes oblanceolate, (5-)15-75 × 0.5-1(-2) mm. Calyculi of 3-5+ ovate to oblong bractlets 1-3 mm. Ray florets usually 8, rarely 0; laminae yellow, 4-8(-12+) mm. Disc corollas red-brown, throats shorter than lobes. Cypselae 4-5+ mm; pappi usually 1.5-2+ mm, rarely 0. 2n = 44.

Flowering Mar-Jun. Disturbed sites on sands or clays; 10-200 m; N.Mex., Tex.; Mexico (Nuevo León, Tamaulipas).

Thelesperma ambiguum is similar to T. megapotamicum; it may be better treated as a variety of the latter.