Rhynchospora seccoi, a new species of Rhynchospora sect. Tenues (Cyperaceae) from Brazilian Amazon (Serra dos Carajás, Pará State)

Rhynchospora seccoi, a new species of Rhynchospora sect. Tenues (Cyperaceae) is herein described and illustrated. This new species from Serra dos Carajas (Para State, Brazil) is morphologically similar to R. tenuis and R. riparia, but differs by being annual and having often cauline leaves, a synflorescence comprising 1 terminal and 2-3 axillary paniculodia, a nutlet with a rounded apex, a nutlet surface with 8-10(12) transverse ridges of vertically oriented linear cells, and a persistent style-base that is brown, shallowly triangular, and shortly bilobed at the base, with the lobes not extending along the shoulders of nutlet.