Thelocactus bicolor ssp. flavidispinus (Backeberg) N.P. Taylor, CCI 5: 14 (1998).

Basionym: Thelocactus bicolor var. flavidispinus Backeb., Beitr. Sukk.-Kunde Pflege 4: 6 (1941).
Lectotype: Beitr. Sukk.-Kunde Pflege 4: 6 (1941), E.F. Anderson, Bradleya 5: 62 (1987).
Synonyms: Thelocactus bicolor var. flavidispinus Backeb., Beitr. Sukk.-Kunde Pflege 4: 6 (1941). Thelocactus flavidispinus Backeb., Cact. Succ. J. (US) 23: 150 (1951). Echinocactus flavidispinus Weniger, Cacti S. W. 87 (1970) nom. nud. Ferocactus bicolor var. flavidispinus N.P. Taylor, Cact. Succ. J. Gr. Brit. 41: 30 (1979).

Description
Stem single, ovoidal, 1.5-4.5 cm tall, 2-7 cm wide. Ribs 13, distinct. Tubercles rounded. Areoles with glands. Central spines 3-4, 15-25 mm long, ochre to reddish, straight, acicular. Radial spines 12-20, 10-15 mm long, ochre to reddish, straight, acicular. Flowers 60-80 mm wide, magenta with a red throat. Seeds 1.7 x 1.4 mm, testa cells convex with a verrucose surface sculpture.

Distribution
USA, Texas, Brewster Co. near Marathon, restricted to Caballos Novaculite soil, at an elevation of about 1200 metres above sea level. Its range lies within the Northern Chihuahuan subregion of the Chihuahuan Desert ecoregion.

Comments
This subspecies is noted for its straw-coloured spination; stem and flowers are smaller than the type.