Grande et al. (2004) already suggested that Opisthobranchs would appear as a paraphyletic group unless Siphonaria be included. Dinapoli & Klussmann-Kolb (2010) confirm this result with new data (their Figure 2) but do not draw a formal conclusion regarding classification. They only state that "neither the monophyly of the Basommatophora (Siphonarioidea, Hygrophila and Amphiboloidea) nor the monophyly of the Thalassophila (Amphiboloidea and Siphonarioidea) is supported". Pending further clarification, the superfamily Siphonarioidea is here listed together with other Heterobranchs of unsettled phylogenetic position.