| Acteonoidea, Valvatoidea, Heterobranchia, Glacidorbidae, Amphiboloidea|
Lower Heterobranchia, also known as the Allogastropoda, is a group of rather specialized, highly evolved sea slugs and sea snails, (marine gastropod mollusks) within the clade Heterobranchia. Although the great majority of Lower Heterobranchs are indeed marine, a few have succeeded in making the transition to freshwater.
Lower Heterobranchia Wikipedia
The shell shapes in this group are typically those that are seen in the sundial, pyramid, rissoella and orbitestellid families of snails.
In the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005, the Lower Heterobranchia is an Informal Group. Superfamilies within the Lower Heterobranchia include:Unassigned to a superfamily (orbitestellid-shells)
† Family Dolomitellidae
† Family Heterosubulitidae
† Family Kuskokwimiidae
† Family Misurinellidae
† superfamily Nerineoidea
† superfamily Streptacidoidea
(Taxa that are exclusively fossil are indicated with a dagger †)
For a more detailed taxonomy see: Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)#Informal group "Lower Heterobranchia" (= Allogastropoda)
Jörger et al. (2010) have redefined major groups within the Heterobranchia: they moved Glacidorboidea and Pyramidelloidea to Panpulmonata.