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

Basionym: Thelocactus schwarzii Backeb., Cact. Succ. J. Gr. Brit. 12: 81 (1950).
Lectotype: Cact. Succ. J. Gr. Brit. 12: 84 (1950), E.F. Anderson, Bradleya 5: 61 (1987).
Synonyms: Ferocactus bicolor var. schwarzii N.P. Taylor, Cact. Succ. J. Gr. Brit. 41: 30 (1979). Thelocactus bicolor var. schwarzii E.F. Anderson, Bradleya 5: 61 (1987).

Description
Stem single, ovoidal, 9 cm tall, 5.5 cm wide. Ribs 13, distinct. Tubercles rounded. Areoles with glands. Central spines 0-(1), 20-30 mm long, ochre to reddish, straight, acicular. Radial spines 13-14, 15-30 mm long, ochre to reddish, straight, acicular. Flowers 65-85 mm wide, magenta with a red throat and a white zone above it. Seeds 1.6 x 1.3 mm, testa cells convex with a verrucose surface sculpture.

Distribution
Mexico, Tamaulipas, occurring in Tamaulipan Thorn Shrub on rocky outcrops, at elevations of about 100 to 200 metres above sea level. Its range lies within the Tamaulipan Matorral ecoregion.

Risk assessment
Thelocactus bicolor ssp. schwarzii is placed in the category Pr (subject to special protection) of the Norma Oficial Mexicana NOM-059-SEMARNAT-2010.

Comments
This is a small-sized species which occurs outside the Chihuahuan Desert in Tamaulipan thorn forest. It is characterised by the lack of central spines, though, rarely, plants with a single central spine can be found amid those normally lacking this feature.