Figure 4.

Combined phylogeny of Mollusca and Annelida. The Mollusca tree is drawn from Smith et al. (2011), while the consensus phylogeny of Annelida and Sipuncula is based on Rouse and Pleijel (2001) and Struck et al. (2011). As in Figure 1, following the terminal name, in parentheses, is the estimated number of extant described and valid species for that group based on the World Register of Marine Species. Additional references for groups with nonmarine species are Bivalvia, which also includes many freshwater species (Graf 2013); Gastropoda, which includes numerous freshwater and terrestrial species (Cameron 2013); and Clitellata, which includes many freshwater and terrestrial species (Sket and Trontelj 2007; Wetzel and Reynolds 2011). The species count for the taxon Capitellida includes taxa such as Echiura and polychaetes formerly included in Scolecida, a taxon now shown to be polyphyletic (Struck et al. 2011). When available, common names are written above the branches.