Echinocactus horizonthalonius var. nicholii Echinocactus horizonthalonius var. horizonthalonius
Echinocactus horizonthalonius var. equitans Meyerocactus horizonthalonius Echinocactus horizonthalonius subsp. horizonthalonius Echinocactus horizonthalonius subsp. jarmilae Echinocactus equitans Echinocactus horizontalis Echinocactus horizonthalonius var. centrispinus Echinocactus horizonthalonius f. centrispinus Echinocactus horizonthalonius var. curvispinus Echinocactus horizonthalonius f. curvispinus Echinocactus horizonthalonius var. obscurispinus Echinocactus horizonthalonius f. obscurispinus Echinocactus horizonthalonius var. subikii Echinocactus laticostatus Echinocactus pachycornis Echinocactus horizonthalonius var. laticostatus Echinocactus horizonthalonius subsp. diabolicus
World Flora Online, http://www.worldfloraonline.org/, accessed June 20, 2024