A Revision of the Stylasteridae (Cnidaria, Hydrozoa, Filifera) from Alaska and Adjacent Waters

The stylasterid fauna of Alaska is revised, consisting of the description or redescription and illustration of 21 species, one additional subspecies, and a geographically adjacent species: Stylaster venustus. Six new species and one new subspecies are described: Errinopora fisheri, E. undulata, E. disticha, E. dichotoma, Stylaster crassiseptum, S. repandus, and Stylaster parageus columbiensis. Four subspecies are raised to species rank: Stylaster leptostylus, S. trachystomus, S. parageus, and Distichopora japonica, and five species and one subspecies were synonymized. A dichotomous key to the Errinopora species and tabular keys to the Errinopora and Alaskan Stylaster species are provided. The focus of the study was on the stylasterids from Alaska, primarily those from the rich Aleutian Islands, but also including records from British Columbia. This is the first revisionary work on this fauna since the seminal report by Fisher in 1938.