Fucus thunbergii Mertens ex Roth, 1800 An annotated list of brown seaweeds (Phaeophyceae) from Nakadori Island (northern Goto Islands, Nagasaki, Japan) Belleza, Dominic Franco C. Tateishi, Hiroto Tanimae, Shin-Ichiro Kobayashi, Taishun Aota, Tomoyuki Urasawa, Toshiki Nishihara, Gregory N. Phytotaxa 2025 2025-03-18 694 1 1 24 (Mertens ex Roth) Kuntze, 1880 Kuntze 1880 Roth [136,762,697,724] Phaeophyceae Sargassaceae Sargassum Chromista Fucales 15 16 Ochrophyta species thunbergii  Basionym:  Fucus thunbergiiMertens ex Roth, 1800   Syntypelocality:— Chinaand Japanseas   Description and remarks:—The thalli of the specimens are bushy and can reach to about 45–50 cmhigh. The main axis is terete with a diameter of about 1–1.5 mm. The phylloids are slender and filiform, 3–5 mmlong and 0.5–1 mmwide with smooth or dentate margins. The vesicles are on stalks, ovate or fusiform with mucronate tips. Plants are dioecious and may form brancheswhich contain the terete receptacles that are 5–10 mmlong. Branches may arise from the main axis and branch lengths are usually longer near the base and shorter near the apex. This species forms a thick forests in Yokoura along the sheltered side of the small embayment on the rocky patches near the sandy areas in mid-late spring. In Naname, it was found along the periphery of the  S. horneriforests in early spring.   Materials examined:—18ECS1-4 (2, 3 and 10–14)