Sipunculan phylogeny based on six genes, with a new classification and the descriptions of two new families

Kawauchi, G. Y., Sharma, P. P. & Giribet, G. (2012). Sipunculan phylogeny based on six genes, with a new classification and the descriptions of two new families. — Zoologica Scripta , 41 , 186–210. The internal phylogeny of Sipuncula has proven elusive, with the monophyly of multiple traditional groups in question. Repeated attempts to infer sipunculan relationships have attained discordant results, possibly owing to fragmentary molecular sequence data sets. We reassessed the phylogeny of Sipuncula using a six‐gene data set and with larger target amplicons of certain loci. We additionally dated the molecular phylogeny employing recently discovered fossil taxa to constrain node ages. Our multilocus data set recovers six major clades of Sipuncula across multiple analytical treatments. Some groups considered suspect in previous studies are vindicated (e.g. Aspidosiphonidae), but most traditional sipunculan families were recovered as para‐ or polyphyletic groups, especially Sipunculidae, whose members appear in three distinct clades. To redress the dissonance between the current classification and the phylogeny of Sipuncula, we provide a new classification of the group, wherein (i) we erect two new families, Siphonosomatidae fam. nov. and Antillesomatidae fam. nov.; (ii) Phascolionidae and Themistidae are synonymized with Golfingiidae, new synonymies (iii) Phascolopsis is transferred to Golfingiidae, new familial assignment ; and (iv) Lithacrosiphon is synonymized with Aspidosiphon , new synonymy . We observe that the origins of all families recognized are ancient, dating at least to the Mesozoic.