Sargassum binderi Sonder var. ambiguum Grunow in Piccone, 1886: 48 (`ambigua') (type locality: Massawa, Eritrea).—Hauck, 1889 [1886–1889]: 188.— De Toni, 1895b: 47–48.— Reinbold, 1895a: 25.
Sargassum echinocarpum J. Agardh var. ambiguum (Grunow) Grunow, 1915 [1915–1916]: 383 (`ambigua') (including Indian Ocean record).
INDIAN OCEAN DISTRIBUTION: Kenya, Somalia.