Origin and Habitat: West and north of the Rio Apa in the Mato Grosso, Brazil.
Altitude range: Discocactus mamillosusSN|12041]]SN|12041]] is found at an altitude of 300 tot 700 metres above sea level.
Habitat and ecology: This species occurs in a narrow, rather hilly terrain on a sandy and gravely substrate of quartz and Pedra Canga (iron oxide), amongst grasses, low vegetation and sometimes shrubs.

• Discocactus mamillosus Buining & Bredero
• Discocactus hartmannii var. mamillosus (Buining & Bredero) P.J.Braun

• Discocactus heptacanthus (Barb.Rodr.) Britton & Rose
• Malacocarpus heptacanthus Barb.Rodr.
• Neodiscocactus heptacanthus (Barb.Rodr.) Y.Itô
• Discocactus boliviensis Backeb.
• Neodiscocactus boliviensis (Backeb.) Y.Itô
• Discocactus cangaensis Diers & Esteves
• Discocactus cephaliaciculosus Buining & Bredero ex P.J.Braun & Esteves
• Discocactus cephaliaciculosus subs. nudicephalus P.J.Braun & Esteves
• Discocactus crassispinus P.J.Braun & Esteves
• Discocactus crassispinus subs. araguaiensis P.J.Braun & Esteves
• Discocactus diersianus Esteves
• Discocactus estevesii Diers & Esteves
• Discocactus flavispinus Buining & Bredero
• Discocactus goianus Diers & Esteves
• Discocactus diersianus subs. goianus (Diers & Esteves) P.J.Braun & Esteves
• Discocactus diersianus var. goianus (Diers & Esteves) P.J.Braun & Esteves
• Discocactus griseus Buining & Bredero
• Discocactus catingicola var. griseus P.J.Braun & Esteves
• Discocactus hartmannii (K.Schum.) Britton & Rose
• Echinocactus hartmannii K.Schum.
• Neodiscocactus hartmannii (K.Schum.) Y.Itô
• Discocactus hartmannii subs. giganteus P.J.Braun & Esteves
• Discocactus hartmannii subs. setosiflorus P.J.Braun & Esteves
• Discocactus heptacanthus subs. melanochlorus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus melanochlorus Buining & Bredero
• Discocactus heptacanthus var. riomortensis P.J.Braun & Esteves
• Discocactus heptacanthus var. semicampaniflorus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus semicampaniflorus Buining & Bredero
• Discocactus lindaianus Diers & Esteves
• Discocactus magnimammus subs. bonitoensis Buining ex J.Theun.
• Discocactus hartmannii var. bonitoensis (Buining & Bredero) P.J.Braun
• Discocactus mamillosus Buining & Bredero
• Discocactus hartmannii var. mamillosus (Buining & Bredero) P.J.Braun
• Discocactus nigrisaetosus Buining & Bredero
• Discocactus catingicola var. nigrisaetosus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus pachythele Buining & Bredero
• Discocactus paranaensis Backeb.
• Discocactus patulifolius Buining & Bredero
• Discocactus hartmannii subs. patulifolius (Buining & Bredero) P.J.Braun & Esteves
• Discocactus hartmannii var. patulifolius (Buining & Bredero) P.J.Braun
• Discocactus piauiensis P.J.Braun & Esteves
• Discocactus prominentigibbus Diers & Esteves
• Discocactus rapirhizus Buining & Bredero
• Discocactus catingicola subs. rapirhizus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus silicicola Buining & Bredero
• Discocactus silvaticus Buining & Bredero
• Discocactus spinosior Buining & Bredero
• Discocactus squamibaccatus Buining & Bredero
• Discocactus squamibaccatus var. longiflorus P.J.Braun & Esteves
• Discocactus subterraneo-prolifer Diers & Esteves

• Discocactus heptacanthus subs. catingicola (Buining & Bredero) N.P.Taylor & Zappi
• Discocactus catingicola Buining & Bredero

• Discocactus heptacanthus subs. magnimammus (Buining & Bredero) N.P.Taylor & Zappi
• Discocactus hartmannii subs. magnimammus (Buining & Bredero) P.J.Braun & Esteves
• Discocactus hartmannii var. magnimammus (Buining & Bredero) P.J.Braun
• Discocactus magnimammus Buining & Bredero

Description: Discocactus mamillosusSN|12017]]SN|12041]] (= Discocactus hartmanniiSN|12017]]SN|33218]] var. mamillosus) is one of the geographical or morphological forms of Discocactus heptacanthusSN|12041]]SN|12017]]. It is a small globular cactus distinguished from the type species for its more numerous ribs (up to 22), small nipple-like tubercles on the edges, and fewer spines (5-7) in the areole. The name Discocactus mamillosusSN|12017]]SN|12041]] is not accepted by many botanists that treat it as synonym of Discocactus heptacanthusSN|33218]]SN|12017]] (Barb.Rodr.) Britton & Rose or of Discocactus heptacanthusSN|12041]]SN|12017]] subsp. magnimammus (Buining & Brederoo) Taylor & Zappi., but it still has a value for a collector because they identify plants with particular characters.
Stem: Green, about 15 cm in diameter and 8 cm tall.
Ribs: 16-22
Areoles: Oval. Areoles per rib 6 to 7 on plants with cephalium.
Radial spines: 5(-7), 5-11 mm long, yellow/white to brown, sligtly bent toward the plant's body.
Flowers: Night- blooming, sweet scented, white. The position of the stigma is at the the level of primary stamens.
Cephalium: Cream/white.
Fruit: Pale pink.

Bibliography: Major references and further lectures
1) Buining, A. F. H., Brederoo, A. (1974b) "Discocactus mamillosus Buining et Brederoo Spec. nov." Kakt. and. Sukk. 35 (10): 217-220
2) Discocactus Venlo 1980 page 188.

Cultivation and Propagation: Collectors consider this cactus genus from South America to be rarities as they are not the easiest plant to keep happy. it is rather difficult to grow and frost tender, should be kept at above 15° C if grown on its own roots (8°C if grafted) need full sun or afternoon shade. Young seedlings are generally grafted because they are slow growing and very rot prone when kept on their own roots and though they can’t endure long stretches of total dryness, too much water will rot them, as their weak root systems tend to be inefficient at sucking up water from wet soil. They generally resent being repotted and can take a long time to establish.
Propagation: Seed. Young seedlings are often grafted on a low stock to keep the plant in a good shape.