Astrophytum is a genus of six species, native to the Chihuahuan desert and occurring in north and central Mexico and southern Texas in the USA. Of these six species five, namely Astrophytum asterias, Astrophytum capricorne, Astrophytum coahuilense, Astrophytum myriostigma and Astrophytum ornatum are globose to short cylindrical cacti while the fifth, Astrophytum caput-medusae is a sprawling octopus-like plant. The first five species mentioned were discovered between the years 1828 and 1845. Astrophytum asterias, Astrophytum coahuilense and Astrophytum myriostigma are spineless while Astrophytum capricorne and Astrophytum ornatum have prominent spines. All five feature a star-shaped appearance when viewed from above hence the genus name Astrophytum, which means star plant. 
Despite the noticeable differences, all 5 species including Astrophytum caput-madusae feature a sort of flocking of white trichomes (or bumps) on the epidermis. The four original Astrophytum members have been extremely popular in cultivation and numerous exotic hybrids have been created that emphasise various features such as amount of flocking, number of ribs, lack of spines, etc. These plants are adapted to the varying extremes of the desert, from high daytime temperatures to frosty nights, and they tolerate dry conditions very well, like other cacti. 
The evolutional oldest and most southern species is Astrophytum ornatum from the Mexican federal states Hidalgo, Queretaro, Guanajuato and the south of San Luis Potosi. The species name “ornatum” means adorned. Commonly known as bishop's cap it was the first species that was sent to Europe in the year 1828. When the botanist De Candolle unpacked the plant from the overseas box he thought that the unknown cactus was affected by fungus after the ship journey of some months, but to his astonishment he proved that the complete body was strewed with white spots of tuft hair. One knows today that these spots represent a characteristic of Astrophytum which only they have. 
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