Taxonomy
In the taxonomy of Bouchet & Rocroi (2005), the superfamily Acteonoidea has been included into the informal group "Lower Heterobranchia" (Heterostropha sensu Ponder & Warén, 1988), also known as the Allogastropoda.
Only one of analyses by Jörger et al. (2010) indicates the Acteonoidea sister to Nudipleura. This clade that had resulted repeatedly in molecular studies with still limited "lower heterobranch" taxon sampling, either in a derived position or as a basal offshoot within Euthyneura. A recent molecular phylogeny on Acteonoidea suggest a common origin with lower heterobranch Rissoelloidea and a sister group relationship to Nudipleura. While the basal position of Acteonoidea was commonly accepted, some authors doubted the basal position of Nudipleura, which was originally considered as a highly derived taxon, and suspect rate heterogeneity and deviant base composition as causing this unnatural grouping. Based on potential synapomorphies in the reproductive system (presence of a ciliary stripe within the ampulla, androdiaulic or triaulic pallial gonoduct), Ghiselin already suggested a relationship between Acteonoidea and Nudipleura. However, Acteonoidea form a well-supported "lower heterobranch" clade with Rissoelloidea, confirming results by Aktipis et al. and Dinapoli and Klussmann-Kolb. The latter authors also recovered Nudipleura as the first offshoot of Euthyneura, which is confirmed by our study. Salvini-Plawen and Steiner grouped Umbraculoidea with Nudipleura, but none of the recent molecular or morphological studies support such a relationship.
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