Structure and identification
The monograph describes usually solitary, sometimes offsetting plants with broad, rounded tubercles. Dark central spines are strong and point almost vertically near the apex. The dominant spine may have shorter companions. Orange or reddish glands occur in grooves and axils. Flowers are whitish yellow with a carmine stripe on the outer tepals. Juvenile armature is much sparser than adult armature. [Dicht and Lüthy 2005, pp. 65–66]
Habitat and variation
The monograph's authors recorded sites in San Luis Potosí, Guanajuato and Tamaulipas, on lava substrates on plains and slopes and in oak forests. Plants from exposed places more often had a spherical habit, while those growing in shade were elongated. A later morphological comparison also described this variation as associated with microhabitat. [Dicht and Lüthy 2005, p. 65–66; p. 41–42] [Vázquez-Benítez et al. 2016, p. 65–66; p. 41–42]
Related articles
Materials from the author's archive
The species also appears in Konrad Szychowski's private material archive. [Kaktologia 2009b, file p. 7] [Neciu b.d., file p. 1]