Faunal collections from mud-volcano sites in the Gulf of Cadiz, at depths between 355 and 3061 m, have revealed a high diversity (and in some cases high density) of tanaidaceans. The present study reports on nine new tanaidomorph species from eight different genera from this material. These include representatives of genera known elsewhere from non-vent- associated deep-sea habitats, but notably only the second and third (respectively) representatives of two genera, Coalecerotanais and Cristatotanais, known previously from cold-seep-habitats in the Gulf of Mexico. The genus Spinitanaopsis is synonymized with Cristatotanais. The tanaidacean records to date from hydrothermal vents or cold seeps are collated as a context for the present material. The possibilities of habitat-endemism in tanaidacean taxa associated with reducing environments and their biogeography are discussed.
