Merianthera is a genus of flowering plants with up to now seven species occurring in eastern Brazil, in the states of Bahia, Espírito Santo, and Minas Gerais. It belongs to the tribe Pyramieae (Melastomataceae), and can be recognized by its shrubby or treelet habit with caducous leaves, 5-merous flowers with a strongly zygomorphic androecium, the latter with dimorphic stamens bearing complex dorsal connective appendages, as well as an inferior ovary and capsular fruits. We describe here a new species of Merianthera from two collections and a photographic record, all from the same locality, an inselberg in the Municipality of Jacinto, in northeastern Minas Gerais. Its candelabriform habit, with a fistulose stem, and solitary, axillary or cauliflorous flowers are only shared with M. burlemarxii. However, M. calyptrata R.Goldenb., Bochorny & Fraga sp. nov. has at least three characters that are absent in M. burlemarxii and all other species in the genus: the total absence of both a peduncle and bracteoles, the calyptrate calyx and the fruits developing from inferior ovaries and dehiscing through longitudinal slits. The first character appears to be unknown in other species in the family.

Tibouchina triprovincialis is a new species collected in the Brazilian states of Amazonas, Mato Grosso, and Rondônia. All gatherings from Amazonas and Rondônia come from the “Parque Nacional dos Campos Amazônicos”, while the single gathering outside it comes from northwestern Mato Grosso. Dense and extensive populations of this small shrub occur in “hyperseasonal savannas”, i.e. savannic enclaves in the middle of the Amazonian rainforest, with a thick herbaceous layer and very few shrubs or trees, growing on poorly drained soils. Tibouchina triprovincialis differs from both T. aspera and T. spruceana by the smaller leaves, with shorter petioles, 0.6–1.5 mm long (vs. 3–10 mm in T. spruceana, 2–10 mm in T. aspera) and blades 5–11 mm long (vs. 20–50 mm in T. spruceana, 20–80 in T. aspera), the abaxial surface densely covered with broad scales that conceal the surfaces of veins and the actual surfaces between the veins (vs. moderately covered with slender scales or trichomes that do not conceal the surfaces beneath, on both the veins and the actual surfaces between the veins). As for extinction risk, we suggest that T. triprovincialis should be regarded as “Least Concern” (LC).