The siphonostomatoid parasitic copepod Caligus macrurus Heller, 1865 is redescribed based on new material collected from the gill filaments and pharynx of tripletail Lobotes surinamensis Bloch (Lobotidae) caught in Iskenderun Bay, Turkey. Key diagnostic characters and newly observed taxonomic features are reported, supported by light and scanning electron microscopy observations. This is the first report of C. macrurus from Mediterranean waters. Caligus macrurus is also recognised as conspecific with the better known Caligus bennetti Causey, 1953, found on the same host, which becomes a junior subjective synonym of C. macrurus. Caligus O.F. Muller, 1785 and Sciaenophilus van Beneden, 1852 have both been treated as valid genera within the family Caligidae although numerous doubts have been expressed over the validity of the latter. The morphological evidence does not support generic level distinction and we recommend the transfer of all species currently placed in Sciaenophilus into Caligus as C. tenuis (van Beneden, 1852), C. pharaonis von Nordmann, 1832, C. nibeae Shen, 1957 and C. macrurus.