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The three closely related genera Willowsia Shoebotham 1917 with 22 species, Janetschekbrya Yosii 1971 with 2 species and Americabrya Mari-Mutt & Palacios-Vargas 1987 with 3 species (the “Willowsia complex”) are examined in the light of a phylogenetic analysis and a re-evaluation of their original differential characters. A hypothesis based on 56 morphological characters is proposed for 15 Willowsia species and Americabrya arida Christiansen & Bellinger 1980. With Drepanosira hussi Neuherz 1976 as outgroup, three major clades are recovered: the species Willowsia samarkandica, a clade with 4 species, and a large clade with 10 species and Americabrya arida in a terminal position. Conversely, if Americabrya is used as outgroup with the Willowsia species as ingroup, all Willowsia including W. samarkandica constitute a monophyletic clade. Biogeographically, we show that the Willowsia complex …