Origin and Habitat: The main distribution is in the Mexican states of Querétaro and Hidalgo, south to the Valle de Mexico, north to Guanajuato and sporadically in San Luis Potosí.
Habitat: Limestone gravel on low hills and plain.

• Coryphantha radians (DC.) Britton & Rose
• Aulacothele radians (DC.) Monv.
• Cactus radians (DC.) Kuntze
• Mammillaria radians DC.

• Coryphantha cornifera (DC.) Lem.
• Aulacothele cornifera (DC.) Monv.
• Cactus cornifer Kuntze
• Mammillaria cornifera DC.
• Coryphantha bernalensis L.Bremer
• Coryphantha cornifera var. scolymoides (Scheidw.) Borg
• Cactus scolymodes (Scheidw.) Kuntze
• Coryphantha scolymoides (Scheidw.) A.Berger
• Mammillaria cornifera f. scolymoides (Scheidw.) Schelle
• Mammillaria radians var. scolymoides (Scheidw.) Schelle
• Mammillaria scolymoides Scheidw.
• Coryphantha cornuta (Hildm. ex K.Schum.) A.Berger
• Mammillaria cornuta Hildm. ex K.Schum.
• Coryphantha daimonoceras Lem.
• Mammillaria daimonoceras Lem.
• Mammillaria radians var. daimonoceras (Lem.) K.Schum.
• Mammillaria radians f. daimonoceras (Lem.) Schelle
• Coryphantha impexicoma Lem. ex Förster
• Coryphantha radians var. impexicoma (Lem.) Backeb. & F.M.Knuth
• Mammillaria cornifera var. impexicoma (Lem.) Salm-Dyck
• Mammillaria impexicoma Lem.
• Mammillaria radians var. impexicoma (Lem.) Salm-Dyck ex K.Schum.
• Mammillaria radians f. impexicoma (Lem.) Schelle
• Coryphantha maliterrarum L.Bremer
• Coryphantha radians (DC.) Britton & Rose
• Aulacothele radians (DC.) Monv.
• Cactus radians (DC.) Kuntze
• Mammillaria radians DC.
• Coryphantha radians f. cristata hort.
• Coryphantha radians var. pectinoides (J.M.Coult.) Bravo
• Cactus radians var. pectinoides J.M.Coult.

Description: C. cornifera/radians is a very variable species, normally solitary, rarely sprouting.
Stem: Flat globose to cylindrical, up to 8-15 cm in diameter, 6-12 cm tall, dull olive-green, apex depressed, with a blunt, depressed apex covered with e wool.
Tubercles: Tubercles are spirally arranged in series of 5 and 8. Conical, rhomboid at the base, obliquely cut, grooved above; on new growth the groove may show some felt. Basal diameter 12-16 mm, 8-14 mm tall. Axil at first woolly, then naked.
Areoles: Oval, 3mm long, 2,5 mm wide (when central spines absent), round 2 mm Ø (when central spine present)
Radial spines: 10 to 20 fairly stout, pale whitish, yellow or horn-coluoured, sometimes darker tipped, 0.9-1.6 cm long, horizontal, irregularly radiating, interwoven, needle-like, straight or slightly curved; in youth pectinate. Occasionally 3-4 thinner spines, more densely set.
Central spines: 0 or 1( to 3), dark brown, becoming grey from the base, subulate. The dominant central is straight, porrect, or curved downward, usually about 1 cm long, but it may be longer on older plants (up to 1,8 cm); the other two protruding laterally, and curved.
Roots: Fibrous root or semi-taproot.
Flowers: Very big, 5-7 cm wide, yellow (occasionally red), funnel shaped, 6-7 cm. The linear segments are lemon-yellow, sometimes red at the base. Filaments reddish to reddish-yellow. Anthers yellow, stigma pale yellow, stigma lobes whitish.
Fruits: Green, juicy with attached flower remnants, 20-25 mm long, 10 mm wide.
Seeds: Reniform (kidney-shaped), brown, 1,3 mm long.

Notes: Coryphantha corniferaSN|3908]]SN|3908]] is thought to be the taxon classified in 1828 by de Candolle as Mammillaria radiansSN|3916]]SN|3916]], but this is unclear, partly because of various name changes over the years. However the range of both Coryphantha radiansSN|3914]]SN|3914]] and Coryphantha corniferaSN|3908]]SN|3908]] is identical, and at most locations adult plants, either without central spines ("radians"), or with 1-4 central spines ("cornifera") can be found. The arrangement of the central spines is variable. With the exception of the absence or existence of centrals, all the other characteristics are absolutely identical, namely size and form of tubercles, number, size and arrangement of radial spines, flowers, fruits and seeds. Furthermore this species is one of those Coryphanthas which pass a purely radial-spined long youth stage in which they are already floriferous. Most of the plants after several years develop the central spines, giving the plant its sea urchin appearance.

Cultivation and Propagation: In culture C. cornifera/radians is without problems, and regularly shows its large yellow flowers. It does best in slight shade, but does well in full sun too. It is sensitive to overwatering (rot prone), and needs a very porous soil with good drainage. It flowers quite early, but needs about 8-12 years to reach the typical, definite outlook. It tolerates fairly low temperatures as long as it is kept dry (hardy to -5° C or less for short periods of time).
Propagation: Propagation is by seed.