Name and distribution
Epithelantha spinosior is an accepted species native to Coahuila and Nuevo León. The name at this rank was published in 1951. POWO recognises two subspecies, the nominate subsp. spinosior and subsp. huastecana. [2-WWW]
Site categories in the environmental study
In Aquino and colleagues' study, E. spinosior showed an association with luvic kastanozems and fold mountains. The environmental analysis used species-level identifications. It did not compare the two subspecies currently accepted in POWO separately. [Aquino et al. 2021, p. 4521–4525, ryc. 3]
In the tree based on four plastid DNA regions, E. spinosior belonged to a major lineage with E. bokei, E. cryptica, E. ilariae, E. micromeris and E. potosina. The coincidence of soil type with species distribution was one reason for considering the environment as a factor maintaining the distinctness of lineages. [Aquino et al. 2021, p. 4522–4527, ryc. 2–4]
A stem section underground
The 2019 revision recognised Epithelantha spinosior by its ordinary slender roots and the presence of an underground stem section. Plants had elliptical areoles with 19–25 spines. This description was based on material formerly identified as E. unguispina subsp. unguispina and subsp. huastecana. In total, 20 adult plants from four sites were compared. The underground stem was presented as a structural trait, without an experiment testing its burial or protection from temperature. [Aquino et al. 2019, p. 605–606, 610, 612, 615; ryc. 5L]
Both historically named groups had similar morphology in the selected set of traits and a shared lineage in the plastid tree. The authors used the older name E. spinosior in accordance with name priority at species level. In 2026, POWO retains two subspecies within E. spinosior, subsp. spinosior and subsp. huastecana. The revision's result describes the resolution of the traits and markers examined, while the current list reflects the accepted rank of both subspecies. [Aquino et al. 2019, pp. 606, 612, POWO subspecies records, as of 11 October 2026] [2-WWW]