Revision of the genus Pionosyllis (Polychaeta: Syllidae: Eusyllinae), with a cladistic analysis, and the description of five new genera and two new species

Pionosyllis Malmgren, 1867 is revised based on a cladistic analysis of the 41 species considered herein as valid, two newly described species in this paper (Basidiosyllis victoriae and Opisthodonta russelli), 11 species from other genera actually belonging, or related to, Pionosyllis, and 13 syllid species from different subfamilies. The phylogenetic analysis is based on 55 characters; a strict consensus Of 1200 equally parsimonious trees (length = 314 steps) was obtained. The clades containing species usually included within Pionosyllis are newly named within the frame of a new Linnean classification of the group (except for one, belonging to another subfamily). The diagnosis of Pionosyllis is emended, and five new genera arc proposed: Synmerosyllis, Basidiosyllis, Westheidesyllis, Perkinsyllis and Brevicirrosyllis. Paraehlersia San Martin, 2003, proved to be closely related to Pionosyllis. Seven species are transferred to Opisthodonta Langerhans, 1879, here emended, and three transferred to Nudisyllis Knox & Cameron, 1970 (according to San Martin & Hutchings, 2006). Opisthodonta uraga (Imajima, 1966) comb. nov. and Perkinsyllis longisetosa comb. nov. are redescribed. Pionosyllis compacta Malmgren, 1867, P. stylifera Ehlers, 1913, P. gigantea Moore, 1908, P. enigmatica (Wesenberg-Lund, 1950), and Nudisyllis magnidens (Day, 1953) comb. nov., are redescribed. Pionosyllis marquesensis Monro, 1939 and P. procera Hartman, 1965 likely belong to the Syllinae, thus they are not treated in the taxonomic account.