gracilissimus, Hippocampus Temminck [C. J.] & Schlegel [H.] 1850:274, Pl. 120 (fig. 6) [Fauna Japonica Last part (15); ref. 4375] Japan. Lectotype: RMNH 3927a. Paralectotypes: RMNH 24703 [ex RMNH 3927] (5). Lectotype selected by Boeseman 1947:196 [ref. 12876]. Spelled gracillimus in index (p. 322) and on Plate 120; first reviser not researched. •Valid as Acentronura gracilissima (Temminck & Schlegel 1850) -- (Araga in Masuda et al. 1984:89 [ref. 6441], Dawson 1985:17 [ref. 6541], Senou et al. 1994:2 [ref. 24335], Myers 1999:89 [ref. 23965], Lourie et al. 1999:168 [ref. 23993], Paulus 1999:2270 [ref. 24794], Nakabo 2000:533 [ref. 25086], Randall & Lim in Randall & Lim 2000:603 [ref. 25122], Nakabo 2002:533 [ref. 26001], Kuiter 2009:143 [ref. 30404], Lourie 2016:155 [ref. 34505], Hamilton et al. 2016:Supplement 1 [ref. 35615], Sonoyama et al. 2020:36 [ref. 37637], Short & Trnski 2021:818 [ref. 38639]). Current status: Valid as Acentronura gracilissima (Temminck & Schlegel 1850). Syngnathidae: Syngnathinae. Distribution: Western Pacific: New Caledonia, Indochina, South China Sea to Japan. Habitat: marine.