Micranthocereus is a genus of columnar cacti in the family Cactaceae, order Caryophyllales, endemic to Brazil. Described by the German cactologist Curt Backeberg in 1938, the genus encompasses approximately 10 accepted species, several of which were previously placed in separate genera. Notably, Austrocephalocereus and Siccobaccatus — once recognised as distinct genera — have since been subsumed into Micranthocereus as subgenera, reflecting advances in cactus systematics and phylogenetic understanding of the tribe Cereeae (subfamily Cactoideae). A third synonym, Viridicereus, was proposed in 2024 but is treated as a heterotypic synonym. The genus is placed in the subtribe Cereinae alongside other predominantly South American columnar cacti.
Members of the genus are slender, ribbed, erect or sometimes branching columnar cacti bearing dense areoles with fine spines. The name alludes to the small flowers ("micranth-") borne along a specialised lateral flowering zone known as a cephalium-like structure. Species are distributed across the dry interior uplands (campos rupestres and caatinga) of eastern Brazil, particularly in the states of Bahia and Minas Gerais, where they grow in rocky, well-drained soils under conditions of high light and low rainfall. Representative species include Micranthocereus estevesii, M. purpureus, M. flaviflorus, M. goebelianus, and M. streckeri.
Etymology
The name Micranthocereus derives from the Greek mikros (small) and anthos (flower), combined with cereus (the wax-taper cactus genus), referring to the small flowers characteristic of the genus. It was coined by Curt Backeberg in 1938.
Distribution
Micranthocereus is endemic to Brazil, with species concentrated in the dry rocky uplands of eastern Brazil — primarily the states of Bahia and Minas Gerais — where they inhabit campos rupestres and caatinga vegetation on well-drained, nutrient-poor soils.
Taxonomy Notes
The genus was described by Curt Backeberg in 1938 (Blätter für Kakteenforschung 1938(6): 18), with Micranthocereus polyanthus as the type species. Two formerly independent genera, Austrocephalocereus and Siccobaccatus, are now treated as subgenera within Micranthocereus, and a more recent proposal (Viridicereus Guiggi, 2024) is listed as a heterotypic synonym. The genus belongs to tribe Cereeae, subtribe Cereinae, in the subfamily Cactoideae of Cactaceae.
