Note: Rhipidosiphon Montagne (1842a: 14), which was merged with Udotea Lamouroux (1812: 186) by A. Gepp & E. Gepp (1904), was resurrected by Farghaly (1980: 248, 250), who distinguished it from Udotea primarily by its lack of lateral branching. In addition to R. javensis, the type species, Farghaly assigned five other species that have monosiphonous or polysiphonous stipes and monostromatic or polystromatic blades. As circumscribed by D. Littler & M. Littler (1990), the genus is restricted to species with a monosiphonous, uncorticated, and partially calcified stipe and a monostromatic blade in which the siphons do not anastomose. In addition to the type species, those authors recognized a previously undescribed close relative from the tropical western Atlantic, R. floridensis.
Rhipidosiphon javensis Montagne, 1842a: 15 (type locality: Leiden Island [Nyamuk-besar], near Jakarta, Java, Indonesia).—Farghaly, 1980: 251.— Segonzac, 1984: 103, table 1.— D. Littler & M. Littler, 1990: 35–36, figs. 6–11.— Wynne, 1993: 23, 25, fig. 14.
Udotea javensis (Montagne) A. Gepp & E. Gepp, 1904: 363–364, pl. 467: figs. 1–4 (including Indian Ocean record).—A. Gepp & E. Gepp, 1911: 110–111, pl. V: fig. 36.— Weber-van Bosse, 1913a: 116.— Egerod, 1952: 379–380, fig. 10.— Børgesen, 1954a: 9.— Pocock, 1958: 24.— W.R. Taylor, 1966a: 353.— Umamaheswara Rao, 1969d: 40.— Umamaheswara Rao, 1970c: 407–409, figs. 1, 3, 4.— Umamaheswara Rao, 1972: 221.— Egerod, 1975: 58–59, figs. 28, 29.— Jaasund, 1976: 29, fig. 60.— Hackett, 1977: 27.— Jaasund, 1977d: 514.— Pichon, 1978: 149, 301, 422.— Sartoni, 1979: 292–293, fig. 8c.— S. Dixit, 1980: 62–63.— Lawson, 1980: 16.— Seagrief, 1980: 22, fig. on pl. 3.— Segonzac, 1983: table 1, pl. I: fig. 8.— Teo & Wee, 1983: 54–56, fig. 54.— Untawale, Dhargalkar, & Agadi, 1983: [14].— Payri, 1985: 640.— Phang, 1985: color photo on p. 20.— Phang, 1986: 24.— Phang & Wee, 1991: 58.— Kalugina-Gutnik, Perestenko, & Titlyanova, 1992: 24 (table 1).— Titlyanova, Perestenko, & Kalugina-Gutnik, 1992: 45.
INDIAN OCEAN DISTRIBUTION: Comoro Islands, India, Indonesia, Malaysia, Maldives, Mauritius, Mozambique, Réunion, Seychelles, Singapore, Somalia, South Africa, Sri Lanka, Tanzania, Thailand.