Structure and identification
The stem is usually solitary, obovoid or short-cylindrical, and dark green. The tuberous root has a distinctly narrowed transition zone. Tubercles are conical, with a complete groove and red glands surrounded by pale wool. In the young stage, a few lateral spines and one central spine dominate. Their number increases in adults. The main spines are thin and awl-shaped, partly flattened and curved. Flowers are pale yellow. [Dicht and Lüthy 2005, p. 51–52]
Habitat and variation
The monograph indicates southeastern San Luis Potosí and neighbouring Tamaulipas, primarily gravelly slopes and plains. The type locality was described on a stony ridge near shrubs and low woody vegetation. Root structure and changes in armature during development are particularly characteristic elements of the description. [Dicht and Lüthy 2005, p. 51–52]