Helicteresbinhthuanensis V.S.Dang (Malvaceae, Helicteroideae), a new species from southern Vietnam

Helicteresbinhthuanensis V.S.Dang, sp. nov. from Ham Thuan Bac District, Binh Thuan Province, Vietnam is described and illustrated. It is morphologically similar to H.angustifolia, which is a common species in mainland southeast Asia, and H.sphaerotheca, which is endemic to the Northern Territory, Australia, but differs from both by several salient characters such as leaf and calyx size, androgynophore length, petal color, and fruit shape. Photographs, a vernacular name, a preliminary conservation assessment, and a table of morphological characters comparing this new species to two closely related species also are provided.