Gyrodactylus corti Mizelle and Kritsky, 1967, originally described from captive wolf-eel (Anarrhichthys ocellatus) in California, was rediscovered during an outbreak of gyrodactylosis among captive A. ocellatus at a marine research facility in Vancouver, British Columbia, Canada. The new material is used for a supplemental description of the parasite, including scanning electron microscopy of haptoral hard parts and molecular characterization of the internal transcribed spacer and partial 18S rDNA. The parasite is a member of Malmberg's Gyrodactylus perlucidus group, members of which have a marginal hook sickle with a distinct proximal base and distinct toe and ledge, anchors with a stout root and slender shaft and point, a ventral bar with medium-sized anterolateral processes and a prominent posterior membrane, and a male copulatory organ (MCO) with multiple rows of small spines that, for G. corti, are made up of spines of 2 distinct sizes, the smaller of the 2 occupying the outer row. This study suggests that this form of MCO is not homologous to the multi-rowed MCOs present in basal members of Gyrodactylus sensu lato and thus is independently derived. Related species, all from the North Atlantic Ocean and Baltic Sea, include G. perlucidus Bychowsky and Poljansky, 1953, from eelpout Zoarces viviparus and Z. v. elongates; Gyrodactylus errabundus Malmberg, 1970, also from Z. viviparous; and Gyrodactylus anarhichatis Mo and Lile, 1998, from Atlantic wolffish (Anarhichas lupus Ayres, 1855) and spotted wolffish (Anarhichas minor). These parasites all appear to be members of a clade within Gyrodactylus whose common ancestor likely infected an ancestral Anarhichadidae host in the Pacific, having expanded into the Atlantic during the late Cenozoic and eventually colonized species of Zoarcidae. Although not adopted taxonomically, the presented molecular phylogeny provides strong support for Malmberg's subgenus Paranephrotus and its species groups.