Rhynchospora unguinux (Cyperaceae), a new species of Rhynchospora sect. Pauciflorae from the Serra dos Carajás, Pará, Brazil

Rhynchospora unguinux is described as a new species of Cyperaceae from the Serra dos Carajás (Pará, Brazil). Morphological description, taxonomic comments, distribution, habitat data, a preliminary conservation status, and illustrations are provided. Rhynchospora unguinux is characterised by the caespitose habit, ciliate involucral bracts, vinaceous proximal and medial glumes with navicular apex, proximally plumose perianth bristles, and nutlets with involute claw-like margins with lamellar lobes. The new species is similar to R. subplumosa and R. trichochaeta but differs from them by the colour pattern of the spikelets, and the apex shape of the proximal and medial glumes.