«Fruit of Aria», genus named so because of its analogy with the elongated fruits of Aria, the ancient Greek name for
the cork oak (not the mountain ash or rowan tree, as often reported In the literature).
A genus of compact, solitary plants, or growing In small clumps, geophytic, having a tap root and curious geometrical tubercles, without ribs and without spines, with strongly woolly areoles near the apex.
Flowers diurnal, self sterile, shortly funnel-shaped, variable in colours, white, yellow or pink to magenta, pollinated
by insects. Fruits naked, fleshy, white to pink, drying when ripe. Seeds tuberculate, pyriform (pear-shaped), black.
The genus Aríocarpus grows in a very scattered habitat, between northern Mexico and the southeastern United
States, in the Chihuahuan desert and eastward, along the Rio Grande, from 50 m up to 2200 m in altitude. It is adapted to arid areas with low vegetation cover ( , chaparral), often growing in full sun, or in the shade of shrubs, almost completely buried in the ground, mostly in cracks of rocks where it captures moisture, on hills, limestone miounds or terraces (pH7-8) or schistose (shale), sandy, muddy, gravelly or rocky alluvial plains predominantly with limestone, marl or clay-sand. A very mimetic genus, becoming almost invisible in its environment, which, in the absence of spines, has a corneal surface and alkaloids that allow an effective passive struggle against herbivorous.
Mexico (Chihuahua, Coahuila, Durango, Nuevo-León, Querétaro, San Luis Potosí, Tamaulipas, Zacatecas), USA

Currently 7 recognised species + one subspecies:
– Aríocarpus agavoides* (Castañeda) E.F.Anderson 1962
– Ariocarpus agavoides subsp. sanluisensis  Sotom., Arred., Sánchez Barra & Mart.Mend.
– Aríocarpus bravoanus* Hernández & E.F.Anderson 1992
– Aríocarpus bravoanus subsp. hintonii (Stuppy & Taylor) Anderson & Fitz Maurice 1997
– Aríocarpus fissuratus* (Engelm.) K.Schum. 1894
– Ariocarpus fissuratus subsp. lloydii  ( Rose ) U.Guzmán 2003
– Aríocarpus kotschoubeyanus* (Lem. ex K.Schum.) K.Schum. 1898
– Aríocarpus retusus* Scheidweiler 1838
– Aríocarpus scaphirostris* Boedeker 1930
– Aríocarpus trigonus* (F.A.C.Weber) K.Schum. 1898

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3723-9 (Vol. 1)