Gymnocalycium denudatum (Link & Otto) Pfeiff. ex Mittler, Taschenb. Cactuslieb. 2: 124. 1844 sec. Charles 2009
- ≡Echinocactus denudatus Link & Otto, Icon. Pl. Rar.: 17. 1828 syn. sec. Charles 2009
- ≡Cereus denudatus (Link & Otto) Pfeiff., Enum. Diagn. Cact.: 73. 1837 syn. sec. Charles 2009
- Lectotype (designated by Hunt, D.R. & Taylor, N. P. 2006: 8): [icon] plate 9 in Link & Otto, Icon. Pl. Rar.: 17. 1828
- =Echinocactus denudatus var. intermedius Hildm. in Gart.-Zeitung (Berlin) 4: 479. 1885 syn. sec. Kew WCVP (2019)
- ≡Echinocactus intermedius (Hildm.) Schelle, Handb. Kakteenkult.: 186. 1907 syn. sec. Kew WCVP (2019)
- ≡Gymnocalycium ×intermedium (Hildm.) M.H.J.van der Meer in Cact. Phantast. 2019(3)-1: 2. 2019 syn. sec. ???
- =Echinocactus denudatus var. octogonus K.Schum., Fl. Bras. 4(2): 248. 1890 syn. sec. Kew WCVP (2019)
- ≡Echinocactus denudatus f. octogonus (K.Schum.) Schelle, Handb. Kakteenkult.: 190. 1907 syn. sec. Britton & Rose 1922
- =Echinocactus megalothelon Sencke ex K.Schum., Gesamtbeschr. Kakt.: 415. 1897–1899 syn. sec. Charles 2009
- ≡Gymnocalycium megalothelon (Sencke ex K.Schum.) Britton & Rose, Cactaceae 3: 162. 1922 syn. sec. Charles 2009
- =Echinocactus denudatus var. delaetianus F.Haage in Monatsschr. Kakteenk. 8: 36. 1898 syn. sec. Britton & Rose 1922
- ≡Echinocactus denudatus f. delaetianus (F.Haage) Schelle, Handb. Kakteenkult.: 189. 1907 syn. sec. Britton & Rose 1922
- =Echinocactus denudatus var. leheideliana F.Haage in Cact. J. (London) 1: 90. 1898 syn. sec. WFO 2019
- =Gymnocalycium denudatum subsp. necopinum Prestlé in Gymnocalycium 17: 575. 2004 syn. sec. Kew WCVP (2019)
- =Gymnocalycium megalothelon subsp. prestleanum H.Till in Gymnocalycium 18: 625. 2005 syn. sec. Kew WCVP (2019)
- –Echinocactus denudatus var. typica K.Schum., Fl. Bras. 4(2): 248. 1890, nom. inval., syn. sec. Kew WCVP (2019)