An account of Aizoanthemum (Aizoaceae) with a new species from Cape Cross, Namibia

• A new species of Aizoanthemum, A. hispidifolium Klak is described. • Aizoanthemum galenioides is a new synonym for Aizoon papulosum . • Aizoanthemum galeniflorum is a new name for plants usually known as Aizoanthemum galenioides . • Aizoanthemum is endemic to the northern and central Namib. • A key and updated distributions for the five species of Aizoanthemum are provided. Study of type material shows that Aizoanthemum galenioides , described as Aizoon galenioides, is a synonym of Aizoon papulosum. We provide the new name Aizoanthemum galeniflorum for the plants usually known as Aizoanthemum galenioides . We describe a new species, Aizoanthemum hispidifolium, from around Cape Cross in Namibia. Aizoanthemum hispidifolium shares with A. galeniflorum the small yellow flowers but differs from it by the white hair-like papillae and a prostrate habit. We map the distributions for all five species of Aizoanthemum: A. dinteri is the most widespread and occurs from the Mossamedes district in southern Angola to the Rostock district in Namibia, with most collections made at altitudes above 500 m; A. hispidifolium, A. galeniflorum and A. mossamedense are confined to the hyper-arid coastal strip between Mossamedes (Angola) and Walvis Bay (Namibia), at altitudes below 200 m. We revise the description of Aizoanthemum and provide an updated key to the species.