<p>Online Resource 3</p><p>Online Resource 3 Taxa included in the molecular analyses with NCBI GenBank accession numbers</p><p>Terminal taxa 18S 16S COI H3 Dorvillea erucaeformis (Malmgren, 1865) DQ779647 GQ478122 AY838868 --- Dorvillea rubrovittata (Grube, 1855) --- GQ415457 JQ310754 GQ415490 Eunice pennata (O.F. Müller, 1776) AY838849 AF321418 AY838870 DQ779731 Ophryotrocha lobifera Oug, 1978 --- GQ415464 GQ415481 GQ415500 Ophryotrocha orensanzi Taboada et al., 2013 --- KC123176 KC123178 KC123180 Parougia albomaculata (Åkesson & Rice, 1992) --- AF380115 EF464550 JQ310784 Parougia bermudensis (Åkesson & Rice, 1992) AF412802 JQ310753 JQ310767 JQ310785 Parougia eliasoni (Oug, 1978) --- GQ415470 GQ415489 GQ415507 Parougia oregonensis Hilbig & Fiege, 2001 --- JX536705 ------Parougia sp. Seep Clade CA (see Thornhill et al. 2012) --- JX536708 ------Parougia sp. Seep Clade OR (see Thornhill et al. 2012) --- JX536710 ------Protodorvillea kefersteini (McIntosh, 1869) DQ779670 AY838843 KF808171 DQ779759 Parougia diapason sp. nov. This study This study This study This study</p><p>References</p><p>Åkesson B, Rice SA (1992) Two new Dorvillea species (Polychaeta, Dorvilleidae) with obligate asexual reproduction. Zool Scr 21:351362 Grube AE (1855) Beschreibung neuer oder wenig bekannter Anneliden. Archiv für Naturgeschichte 21:81–136 Hilbig B, Fiege D (2001) A new species of Dorvilleidae (Annelida: Polychaeta) from a cold seep site in the northeast Pacific. P Biol Soc Wash 114:396–402 Malmgren AJ (1865) Nordiska Hafs-Annulater. Öfversigt af K. Vetenskapsakademiens förhandlingar 22:181–192 McIntosh WC (1869) On the structure of the British nemerteans, and some new British annelids. T Roy Soc Edin 25:305–433 Müller OF (1776) Zoologicae Danicae Prodromus, seu Animalium Daniae et Norvegiae indigenarum characteres, nomina et synonyma imprimis popularium. Hallageriis, Havniae [Copenhagen], 282 pp Oug E (1978) New and lesser known Dorvilleidae (Annelida, Polychaeta) from Scandinavian and northeast American waters. Sarsia 63:285–303 Taboada S, Wiklund H, Glover AG, Dahlgren TG, Cristobo J, Avila C (2013) Two new Antarctic Ophryotrocha (Annelida: Dorvilleidae) described from shallow-water whale bones. Polar Biol 36:1031–1045 Thornhill DJ, Struck TH, Ebbe B, Lee RW, Mendoza GF, Levin LA, Halanych KM (2012) Adaptive radiation in extremophilic Dorvilleidae (Annelida): diversification of a single colonizer or multiple independent lineages? Ecol Evol 2:1958–1970</p>