The many published infrageneric names of the genus Frailea are a consequence of the high intraspecific diversity, but low diversity within local populations. This can be explained by the specific ecology and reproductive biology, in this combination unique within the family Cactaceae. Fraileas can be classified ecologically as stress-tolerant ruderals. The recently published Frailea mammifera subsp. angelesiae is presented here in detail, and a species from Paraguay, Frailea alexandri, is described here as new to science. Some Frailea names are typified here to stabilize use of the names.