Sagum posteli Delamare-Deboutteville & Nunes-Ruivo, 1954 (Copepoda: Siphonostomatoida: Lernanthropidae) parasitic on Epinephelus aeneus (Geoffroy Saint-Hilaire) in Turkish waters, with a key to the species of Sagum Wilson, 1913.

Sagum posteli Delamare-Deboutteville & Nunes-Ruivo, 1954 (Copepoda: Lernanthropidae) is reported from the white grouper Epinephelus aeneus Geoffroy Saint-Hilaire caught off the Turkish Mediterranean coast. This documents the first discovery of this species in the Mediterranean and is only the second record. The species is redescribed from adult females and the cephalothoracic limbs are described for the first time. The valid species of the genus Sagum Wilson, 1913 are reviewed, and the poorly described species S. poeyi Ortiz, Lalana & Suarez, 2003 is relegated as a junior synonym of S. texanum Pearse, 1952, described from the same host. A key is provided to females of the ten valid species of Sagum and the known hosts for all species are summarised.