Lower Heterobranchia
# Lower Heterobranchia

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 subclass Heterobranchia.

Although the great majority of Lower Heterobranchs are indeed marine, a few have succeeded in making the transition to freshwater.

## Description

The shell shapes in this group are typically those that are seen in the sundial, pyramid, rissoella and orbitestellid families of snails.

## Taxonomy

### 2005 taxonomy

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 Cimidae
   * † Family Dolomitellidae
   * † Family Heterosubulitidae
   * † Family Kuskokwimiidae
   * † Family Misurinellidae
   * Family Orbitestellidae
   * Family Tjaernoeiidae
   * Family Xylodisculidae
* superfamily Acteonoidea
* superfamily Architectonicoidea
* superfamily Glacidorboidea
* superfamily Mathildoidea
* † superfamily Nerineoidea
* superfamily Omalogyroidea
* superfamily Pyramidelloidea
* superfamily Ringiculoidea
* superfamily Rissoelloidea
* † superfamily Streptacidoidea
* superfamily Valvatoidea

(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)

### 2010 taxonomy

Jörger et al. (2010) have redefined major groups within the Heterobranchia: they moved Glacidorboidea and Pyramidelloidea to Panpulmonata.

### 2014 taxonomy

Wägele et al. (2014): moved Rissoelloidea and Acteonoidea from Lower Heterobranchia to Euthyneura.

### 2016 taxonomy

Kano et al. (2016): moved Ringiculoidea from Lower Heterobranchia to Euthyneura.

So the following taxa remain within the Lower Heterobranchia:

* Unassigned to a superfamily (orbitestellid-shells)
   * Family Cimidae
   * † Family Dolomitellidae
   * † Family Heterosubulitidae
   * † Family Kuskokwimiidae
   * † Family Misurinellidae
   * Family Orbitestellidae
   * Family Tjaernoeiidae
   * Family Xylodisculidae
* superfamily Architectonicoidea
* superfamily Mathildoidea
* † superfamily Nerineoidea
* superfamily Omalogyroidea
* † superfamily Streptacidoidea
* superfamily Valvatoidea
