Echinocactus horizonthalonius subsp. nicholii (L.D. Benson) U. Guzmán in Cactaceae Syst. Init. 16: 17. 2003 sec. Guzmán & al. 2003
- ≡Echinocactus horizonthalonius var. nicholii L.D. Benson, Cacti Ariz., ed. 3: 23. 1969 syn. sec. Guzmán & al. 2003
- =Meyerocactus horizonthalonius subsp. nicholii (L.D. Benson) Doweld in Sukkulenty 1: 27. 1999 syn. sec. Guzmán & al. 2003