Opisthonema is a genus of herrings, the thread herrings, found in tropical waters of the Western Hemisphere. They get their name from a filamentous nature of the last ray of the dorsal fin. Currently, five species are in this genus. Species O. berlangai Berry & Barrett, 1963 (Galapagos thread herring) O. bulleri] (Regan, 1904) (slender thread herring) O. libertate (Günther, 1867) (Pacific thread herring) O. medirastre Berry & Barrett, 1963 (middling thread herring) O.oglinum (Lesueur, 1818) (Atlantic thread herring) References Clupeidae Marine fish genera Taxa named by Theodore Gill