Meeting Abstract

64.2  Friday, Jan. 6  A new Sipuncula classification: reassessing and dating the sipunculan phylogeny using a six-gene dataset and fossil taxa KAWAUCHI, Gisele Y.*; SHARMA, Prashant P.; GIRIBET, Gonzalo; Harvard University, Cambridge; Harvard University, Cambridge; Harvard University, Cambridge

Sipuncula is a protostome phylum of contentious phylogenetic placement and an elusive internal phylogeny. Repeated attempts to infer sipunculan relationships have obtained discordant results. In this study we reassessed the internal phylogeny of Sipuncula using a six-gene dataset and larger target amplicons of nuclear ribosomal loci. We dated the molecular phylogeny, employing recently discovered fossil taxa to constrain node ages. Phylogenetic analyses using Bayesian inference, maximum likelihood, and parsimony approaches recover six major clades of Sipuncula across multiple analytical treatments. Some groups considered suspect in previous studies are vindicated, but most traditional sipunculan families were recovered as para- or polyphyletic groups. To redress the dissonance between the current classification and the phylogeny of Sipuncula, we provide a new and revised family-level classification of the group, which includes two new families that we erect herein: Siphonosomatidae and Antillesomatidae. Additional taxonomic action renders a total of six monophyletic families of Sipuncula. Barring the monotypic Antillesomatidae, we observe that the diversification of the revised families constitute ancient events that occurred in the Mesozoic or earlier.