title: Lower Heterobranchia
text: # 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
  