As Kiesling and Metzing wrote (2006, 21: 17-18) "... a nice taxon was found by Angela Kiesling near Concordia (Entre Ríos, NW* Argentina). Comparisons with other species have shown that it is morphologically very similar to Frailea mammifera Buining & Brederoo, a species occurring near Don Pedrito, Rio Grande do Sul (Brazil)." To us, more than being similar it seems the same, since "The main difference is in the colour of the spination, which is reddish brown in the new taxon (versus yellow in Frailea mammifera)". The authors continue: "This Frailea has become common in cultivation and is often distributed with the provisional name 'Frailea angelesii'. In view of its disjunct distribution and distinctive characters, but also its overall similarity with Frailea mammifera, it should be classified as a subspecies rather than as species. To make the name available for the use in the New Cactus Lexicon [Hunt et al. 2006, text: 124], is described here at this rank". We find these arguments insufficient to justify the publication of a new taxon, for this reason we consider Frailea mammifera ssp. angelesiae R. Kiesling & Metzing an unnecessary synonym of F. mammifera. (Quoted from: Anceschi & Magli 2013b, 55-56)

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*Entre Ríos is located in the northeast of Argentina.