Abstract
In this study we assessed the phylogenetic relationships of the hydrothermal vent polychaete group Alvinellidae, based on parsimony analyses of combined morphological and molecular data. Morphological data were obtained from newly examined specimens and literature information of 16 terminal taxa belonging to Alvinellidae, Ampharetidae, Pectinariidae, Terebellidae, Trichobranchidae, and the outgroups Oweniidae and Sabellidae. Molecular data were based on 28S rRNA from 13 of the 16 morphological terminals (10 previously published sequences plus three new ones). The combined analysis indicated the clades ((Alvinellidae, Trichobranchidae) Pectinariidae) and (Ampharetidae, Terebellidae). Alvinellidae, Ampharetidae and Terebellidae, as currently delineated, are monophyletic. The positions of Trichobranchidae and Pectinariidae contradicted traditional views, and they also had low Bremer support and merit further studies. Well‐supported clades included Alvinellidae and Terebellinae. Previous statements that Alvinellidae are either nested within Ampharetidae or the sister to this taxon were not supported. The traditional but here contradicted view that Terebellidae and Trichobranchidae are closely related may be based on plesiomorphic similarities between these two taxa.