Strombocactus

Strombocactus is a monotypic genus with a strong turnip-like root, a small, depressed, roughly spherical stem covered with spirally arranged overlapping tubercles, each with a spine-bearing areole at its tip. Strombocactus disciformis are low-growing, gray-green succulents with a broadly round, unbranched stem and root. In their natural habitats, they grow in a disk shape, half hidden in the ground, reaching around 8 cm in diameter and 2-3 cm in height. In cultivation, they become nearly spherical. Adult tubers can reach 15 cm in diameter, larger than the above-ground parts. The plant's spiral ribs are deeply notched, creating a wart-like appearance with a ratio close to the golden ratio (13:8). Areoles are located on the blunt ends of these warts, which are curved (straighter in cultivation) and have a square base. They rarely have more than four or five short, bristly thorns, which fall off after a few years. Flowers come from new growth at the crown, emerging from the youngest areoles. The flowers are white to cream or magenta and 2.5- to 3.5-cm long and open to about 4 cm in diameter. The 7-mm-long, thin-walled brown fruits contain 0.3-mm reddish-brown seeds. File:Strombocactus disciformis-IMG 3554.JPG|Growth habit File:Strombocactus disciformis.jpg|Flowers File:Strombocactus disciformis-IMG 3561.JPG|Spines File:Seedling of Strombocactus disciformis.jpg|Seedling File:Strombocactus disciformis - Pena Blanca.jpg|View of plant from the top ==Subspecies==

The species has two recognized subspecies: ==Distribution==

Strombocactus disciformis is found in the Mexican states of Querétaro, Hidalgo, and Guanajuato, growing on almost vertical, weathered limestone rocks at altitudes of 1000 to 1600 meters. File:Strombocactus disciformis (5780129599).jpg|Plant growing vertically in habitat in Pena Blanca, Queretaro File:Strombocactus disciformis (5780702818).jpg|Plants growing on rocks in Pena Blanca, Queretaro File:Strombocactus disciformis (5780683148).jpg|Plant growing with Mammillaria parkinsonii ==Taxonomy==

First described as Mammillaria disciformis by Augustin-Pyrame de Candolle in 1828, the specific epithet disciformis is derived from the Latin "discus" (disc) and "-formis" (shaped), referring to the plant's shape. Nathaniel Lord Britton and Joseph Nelson Rose reclassified it as Strombocactus in 1922. ==Conservation status==

Both subspecies are classified as Vulnerable on the IUCN Red List, which states that it has a limited range and "is experiencing a decline in mature individuals due to illegal overcollection". The species is listed in Appendix 1 of the Convention on International Trade in Endangered Species meaning commercial international trade is prohibited and non-commercial international trade is regulated. ==References==