Gymnocalycium

Gymnocalycium, commonly called chin cactus, is a genus of about 70 South American species of cactus. The genus name Gymnocalycium (from Greek, "naked calyx") refers to the flower buds bearing no hair or spines. In a 2023 classification of the tribe Cereeae, it was placed as the only genus in the subtribe Gymnocalyciinae, having formerly been placed in the subtribe Rebutiinae.

==Description== The species of the genus Gymnocalycium are low-growing, usually solitary or sometimes small cushion-forming plants with globose, depressed-globular to short-cylindrical stems. The 4 to 15 (rarely more) ribs are usually broadly rounded, often sinuous, occasionally warty, and often have a "chin" just below the areoles. The thorns are very variable.