Eriocaulonis an aquatic and cosmopolitan genus with 478 species. It is characterized by diplostemonous flowers and free petals with a black gland at the apex. There are few taxonomists studying Eriocaulon from Brazil. The species of this genus remain barely delimited, with inconsistent descriptions, and nomenclatural types not assigned or located. The analysis of nomenclatural types, specimens in scientific collections, and protologues enabled the recognition of 53 species of Eriocaulonfrom Brazil. Thirteen new synonyms and the elevation of five varietes to species level are proposed. Comments on taxonomy, geographic distribution, habitat, life form, and conservation category are provided.

Resumo Cyperaceae é uma família cosmopolita com mais de 5.000 espécies que ocorrem frequentemente em áreas úmidas. Foram encontradas 31 espécies desta família pertencentes a 10 gêneros (Ascolepis, Calyptrocarya, Cyperus, Eleocharis, Fimbristylis, Fuirena, Lipocarpha, Pycreus, Rhynchospora e Scleria) na bacia hidrográfica do Rio Araguaia, que está em sua maior parte inserida no Cerrado Brasileiro. São apresentadas breves descrições, distribuição geográfica, ilustrações, chaves de identificação e comentários.

Abstract Cyperaceae is a cosmopolitan family with over 5,000 species, which are often found in wet habitats. In this study we found 31 hydrophylic species of Cyperaceae, belonging to 10 genera (Ascolepis, Calyptrocarya, Cyperus, Eleocharis, Fimbristylis, Fuirena, Lipocarpha, Pycreus, Rhynchospora and Scleria), that occur in the Araguaia River Basin, located mainly within the Brazilian Cerrado (savanna). Short descriptions, geographic distribution, illustrations, identification keys and comments are presented.