The areoles bear 2 central spines, blackish-gray, rigid, erect, and 2 cm long, along with 16 to 19 radial spines, glassy-white, radial, strong, and 2 to 6 mm long.

R. subterraneus is hermaphroditic but requires winged insects and ants for cross-pollination.

The small, greenish-brown fruits contain seeds dispersed by animals, water, and wind.

[3] Endemic to Mexico, R. subterraneus has a restricted distribution, primarily near Saltillo in Coahuila, Aramberri in Nuevo León, San Luis Potosí, and Tamaulipas, at elevations of 1400-1700 meters.

It thrives in xerophytic shrublands on shallow slopes with calcareous and gypsum soils, often growing alongside Agave lechuguilla, Pelecyphora strobiliformis, Turbinicarpus pseudopectinatus, Thelocactus hexaedrophorus, Ferocactus pilosus, Ferocactus uncinatus, Coryphantha glanduligera, and Echinocereus pectinatus.