Melocactus curvispinus subsp. curvispinus sec. Hunt 2006
- =Melocactus obtusipetalus Lem., Cact. Aliq. Nov.: 11. 1838 syn. sec. Hunt 2006
- ≡Melocactus curvispinus subsp. obtusipetalus (Lem.) Xhonneux & Fern.Alonso in Revista Acad. Colomb. Ci. Exact. 26: 357. 2002 syn. sec. Kew WCVP (2019)
- =Cactus maxonii Rose in Smithsonian Misc. Collect. 50: 63. 1907 syn. sec. Hunt 2006
- ≡Melocactus maxonii (Gürke) Gürke in Monatsschr. Kakteenk. 18: 93. 1908 syn. sec. Hunt 2006
- ≡Melocactus ruestii subsp. maxonii (Rose) Elizondo in Cact. Suc. Mex. 31: 53. 1986 syn. sec. Hunt 2006
- =Cactus oaxacensis Britton & Rose, Cactaceae 4: 289. 1923 syn. sec. Hunt 2006
- ≡Melocactus oaxacensis (Britton & Rose) Backeb., Cactaceae 4: 2587. 1960 syn. sec. Hunt 2006
- ≡Melocactus ruestii subsp. oaxacensis (Britton & Rose) Elizondo in Cact. Suc. Mex. 31: 52. 1986 syn. sec. Hunt 2006
- =Melocactus loboguerreroi Cárdenas in Cact. Suc. Mex. 12: 58. 1967 syn. sec. Hunt 2006
- ≡Melocactus curvispinus subsp. loboguerreroi (Cárdenas) Fern.Alonso & Xhonneux in Revista Acad. Colomb. Ci. Exact. 26: 356. 2002 syn. sec. Kew WCVP (2019)
- =Melocactus maxonii var. sanctae-rosae L.D.Gómez in Brenesia 10-11: 128. 1977 syn. sec. Hunt 2006
- ≡Melocactus ruestii subsp. sanctae-rosae (L.D.Gómez) Elizondo in Cact. Suc. Mex. 31: 54. 1986 syn. sec. Hunt 2006
- =Melocactus ruestii subsp. cintalapensis Elizondo in Cact. Suc. Mex. 31: 54. 1986 syn. sec. Hunt 2006