Vitalianthus lamyii (Marchantiophyta: Lejeuneaceae), a new species from the lowland rainforests of Brunei Darussalam

Vitalianthus R.M.Schust. & Giancotti (Lejeuneaceae), previously known only from the Neotropics and Southwestern China, is a small genus with three species. A fourth species, Vitalianthus lamyii, is newly described based on collections made in lowland rainforests of Brunei Darussalam, Borneo. This is the first record of Vitalianthus from Sundaland. A key to species of Vitalianthus is provided.