Caligus bifurcatus Pearse, 1952

Caligus bifurcatus is the only species in the genus described as possessing bifurcate tines on the sternal furca. A sternal furca with bifurcate tines can be found in some species of other caligid genera, including Lepeophtheirus, Tuxophorus Wilson, 1908, and Gloiopotes Steenstrup & Lütken, 1861, but not in any other Caligus. In the species level catalogue of Caligus produced by Margolis et al. (1975) there is no subsequent record of C. bifurcatus since its original description (Pearse, 1952). The type host of this species is the Live Sharksucker Echeneis naucrates Linnaeus, 1758, which is one of the two original hosts of another caligid, Tuxophorus caligodes Wilson, 1908 (Wilson, 1908).

Tuxophorus caligodes is characterised by the possession of bifurcate tines on the sternal furca, but it also has distinctive, paired dorso-lateral plates originating on the fourth pedigerous somite. Such lobes were not mentioned by Pearse in his description of C. bifurcatus but the outline of these plates can be discerned in his figure (Pearse, 1952: figure 18). In addition to the precise shape of the sternal furca, other characters are shared between these two taxa, such as the presence of posterolateral lobes on the genital complex of the adult female, the shape of the female abdomen, and the form and armature of leg 4, including the unusually robust protopodal segment. Caligus bifurcatus Pearse, 1952 is here recognised as a junior subjective synonym of Tuxophorus caligodes Wilson, 1908.