Sargassum capillare Kützing, 1843b: 361–362 (type locality: "Im Indischen Ocean'' [Tranquebar, Tamil Nadu, India fide Grunow, 1915 [1915–1916]: 374]).—J. Agardh, 1848b: 346.— Kützing, 1849: 611.— Kützing, 1861: 5, pl. 16: figs. IIe,f.— G. Martens, 1868: 72–73.— De Toni, 1895b: 113.— Biswas & Sharma, 1950: 96.— S. Dixit, 1968: 18.
Sargassum tenue J. Agardh var.? capillare (Kützing) Grunow, 1915 [1915–1916]: 374 (`capillaris') (including Indian Ocean record).—K. Srinivasan, 1965: 244.— K. Srinivasan, 1967: 149, fig. 18.— V. Krishnamurthy & H. Joshi, 1970: 15.
Taxonomic synonyms:
* Sargassum tenue J. Agardh, 1848b: 303–304, nom. illeg. (type locality: "ad oras Hindostaniae'').—Kützing, 1849: 625–626.— J. Agardh, 1889: 84.— Reinbold, 1891b: 69.— De Toni, 1895b: 42.— Grunow, 1915 [1915–1916]: 372–375.— Biswas & Sharma, 1950: 87.— K. Srinivasan, 1965: 244.— K. Srinivasan, 1967: 149, fig. 44.— S. Dixit, 1968: 18.— V. Krishnamurthy & H. Joshi, 1970: 15.— Untawale, Dhargalkar, & Agadi, 1983: [23].
Carpacanthus tenuis G. Martens, 1868: 78–79.
* Sargassum gracile Greville, 1849 [1848–1849]: 504, pl. XI: upper figs. 1–3, nom. illeg. (type locality: India).—Greville, 1850: 229–230, pl. XV: upper figs. 1–3.
INDIAN OCEAN DISTRIBUTION: Gulf of Aden, India, Sri Lanka.
Note: The conspecificity of Sargassum gracile Greville and S. tenue J. Agardh was noted by J. Agardh (1889: 84). Both names are illegitimate, the former being a later homonym of S. gracile J. Agardh (1848b) and the latter a later homonym of S. tenue (Kützing) Endlicher (1843: 31) (Halochloa tenuis Kützing, 1843a: 56; type locality: Japan), which was referred by Kützing (1860: 35), Setchell (1933b: 198), and Yoshida (1983: 208, 216–217) to Sargassum siliquastrum (Mertens ex Turner) C. Agardh (1820: 21–22) (Fucus siliquastrum Mertens ex Turner, 1808–1809: 26–27, pl. 82; type locality: Nagasaki, Japan), a species not reported from the Indian Ocean. If the synonymy of Grunow (1915 [1915–1916]: 372–375) is followed, Sargassum capillare Kützing is the oldest name for the species.