Origin and Habitat: Ariocarpus retususSN|2079]]SN|2079]] is widely distributed from north of Saltillo, Coahuila southwards to San Luis Potosi. Also found occur in Tamaulipas and Zacatecas.
Altitude range: High Chihuahuan desert at altitudes of between 1300 and 2000 metres above sea level. This species grows at lower altitudes (around 200 - 800 metres) of the Sierra Madre Oriental it is replaced by Ariocarpus retususSN|2079]]SN|2079]] ssp. trigonus.
Habitat: The species tends to favour limestone and rocky slopes in semi-desert vegetation. The original range of this species extended from Coahuila and Nuevo León in the north to San Luis Potosí in the south. However, much of this range has been modified by agricultural development. A. retusus is a perennial and obligate gypsophile, occurring regularly in Muhlenbergia grassland and Bouteloua grassland in Central Mexico. Ariocarpus species are the only succulents present in the Muhlenbergia grassland. Although A. retusus has a relatively extensive area of distribution and a large population, it has a very low density. It is a slow growing species. This species is threatened by illegal collecting and agricultural development, however, they do not represent major threats. It is found in commercial cultivation.

• Ariocarpus retusus Scheidw.
• Anhalonium areolosum Lem.
• Anhalonium prismaticum Lem.
• Anhalonium pulvilligerum Lem.
• Anhalonium retusum Salm-Dyck
• Cactus prismaticus Kuntze
• Mammillaria areolosa Hemsl.
• Mammillaria prismatica Hemsl.

• Ariocarpus retusus Scheidw.
• Anhalonium areolosum Lem.
• Anhalonium prismaticum Lem.
• Anhalonium pulvilligerum Lem.
• Anhalonium retusum Salm-Dyck
• Cactus prismaticus Kuntze
• Mammillaria areolosa Hemsl.
• Mammillaria prismatica Hemsl.
• Ariocarpus confusus Halda & Horáček
• Ariocarpus retusus subs. confusus (Halda & Horáček) Lüthy
• Ariocarpus elongatus (Salm-Dyck) Wettst.
• Anhalonium elongatum Salm-Dyck
• Ariocarpus trigonus var. elongatus (Salm-Dyck) Backeb.
• Mammillaria elongata (Salm-Dyck) Hemsl.
• Ariocarpus furfuraceus C.H.Thomps.
• Anhalonium furfuraceum J.M.Coult.
• Ariocarpus retusus var. furfuraceus (S.Watson) G.Frank
• Mammillaria furfuracea S.Watson
• Ariocarpus furfuraceus f. cristata Frič
• Ariocarpus furfuraceus f. monstruosus hort.
• Ariocarpus furfuraceus var. rostratus A.Berger
• Ariocarpus prismaticus hort. ex Cobbold
• Ariocarpus pulvilligerus K.Schum.
• Ariocarpus retusus f. cristata hort.
• Ariocarpus retusus subs. jarmilae Halda, Horáček & Panar.
• Ariocarpus retusus subs. panarottoi Halda & Horáček
• Ariocarpus retusus subs. pectinatus Weisbarth
• Ariocarpus retusus subs. scapharostroides Halda & Horáček
• Ariocarpus retusus var. sladkovskyi Halda & Kupčák
• Ariocarpus retusus subs. sladkovskyi Halda & Kupčák
• Ariocarpus retusus var. elongatus (Salm-Dyck) Backeb.

• Ariocarpus retusus subs. trigonus (F.A.C.Weber) E.F.Anderson & W.A.Fitz Maur.
• Anhalonium trigonum F.A.C.Weber in Bois
• Ariocarpus trigonus (F.A.C.Weber) K.Schum.
• Ariocarpus retusus subs. horacekii Halda & Panar.
• Ariocarpus elongatus subs. horacekii (Halda) Halda
• Ariocarpus trigonus var. horacekii Halda
• Ariocarpus trigonus var. minor M.Voldan

• Ariocarpus retusus cv. Cauliflower
• Ariocarpus retusus cv. Cauliflower King
• Ariocarpus retusus cv. Frumdosus
• Ariocarpus retusus cv. Frumdosus brevituberosus
• Ariocarpus retusus cv. Frumdosus f. variegata
• Ariocarpus retusus cv. Maruibo
• Ariocarpus retusus cv. Maruibo Cauliflower
• Ariocarpus retusus cv. Maruibo Pectinatus
• Ariocarpus retusus cv. Mituibo
• Ariocarpus retusus cv. Three Finger
• Ariocarpus retusus cv. Trefinger
• Ariocarpus retusus cv. Royal Tama Botan
• Ariocarpus retusus cv. Tama Botan
• Ariocarpus furfuraceus cv. Tama Botan
• Ariocarpus retusus f. major

Description: Ariocarpus retususSN|2079]]SN|2079]]us commonly known as the "Star Rock" is one of the largest species that distinguishes for the fat triangular tubercles forming a starry rosette. It is a widespread and extremely variable plant. Tubercle size and shape vary widely, a terminal areole is sometimes present at the tip. The vast amount of phenotypic variation in the species has led to the erection of several variants and has received numerous unnecessary names of no botanical value.
Habit: Solitary, slow growing geophyte cactus with tubercles slightly projecting above ground level. The flat tuberous body is below the soil.
Stem: Grey, or blue-green, flattened, globose, rounded on top, 3-12 cm high, 10-25 cm in diameter.
Tubercles: Leaf-like, divergent, erect, basally compressed, usually becoming attenuate at the apices, convex or nearly flattened adaxially and often with shallow adaxial undulations or wrinkling, not fissured, 1,5-4 cm long, 1-3,5 cm wide, nearly as wide as long.
Areoles: At the tips of the tubercles, rounded, 1-5 mm in diameter often only on younger specimens.
Flowers: Diurnal 4-5cm in diameter, 2-4,2 cm long, white to pink (or magenta), occasionally with reddish midribs.
Roots: Tap root.
Flowering time: Autumn.
Fruits: White, green, or rarely pinkish, 10-25 mm long, 3-10 mm in diameter.
Remarks: All of the Ariocarpus seedlings are spiny and quite different from adult specimens, though the spines are feather-like.

Bibliography: Major references and further lectures
1) Edward F. Anderson “The Cactus Family” Timber Press, 2001
2) Curt Backeberg “Cactus Lexicon” Sterling Publishing Company, Incorporated, 1978
3) Hiroshi Hirao “Colour encyclopaedia of cacti” Japan 1979 (Japanese language and script)
4) Willy Cullmann, Erich Götz (Dozent Dr.), Gerhard Gröner “The encyclopedia of cacti” Portland, OR: Timber Press, 1986
5) David Hunt, Nigel Taylor “The New Cactus Lexicon” DH Books, 2006
6) James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11/Aug./2011
7) Fitz Maurice, B & Fitz Maurice, W.A. 2013. "Ariocarpus retusus." The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 12 December 2014.

Cultivation and Propagation: This species is slow growing but certainly not as slow as some other types of cacti, it is of easy culture in a well drained, non-organic, free-draining soil compost, with ample water during the growing season. Use of a weak low-nitrogen fertilizer during the growing season can encourage growth. The main threat to their development is root rot. Ariocarpus should be kept dry whenever there is a threat of cold. The appearance of Ariocarpus can benefit greatly by watering the plants from the bottom. This practice will help to keep the “wool” on the top of the plant from becoming matted or discoloured. Need light shade to full sun. Frost Tolerance: Hardy to -10° C.
Propagation: It is probably the easiest species of the genus to raise from seed, but will generally take about 6-10 years to reach flowering size, occasionally grafted.