This name is a synonym of Gymnocalycium horstii subsp. buenekeri (Swales) P.J.Braun & Hofacker.
The record derives from WCSP (in review)
(data supplied on 2012-03-23)
which reports it as a synonym with original publication details: Cact. Succ. J. Gr. Brit. 40: 97 1978.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:115365-2.
This name was in version 1 of The Plant List, record kew-2835562, and has not been changed.