This name is a synonym of Turbinicarpus saueri subsp. knuthianus (Boed.) Lüthy.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50181440) with original publication details: Repert. Pl. Succ. 19(1): 22 1983.
This name was in version 1 of The Plant List, record tro-50181440, and has not been changed.