Heterobranchia
{{Taxobox
color = pink | name = Heterobranchia | image = sea angel.jpg | image_caption = Clione limacina | regnum = Animalia | phylum = Mollusca | classis = Gastropoda | subclassis = Orthogastropoda | superordo = Heterobranchia | subdivision_ranks = Orders | subdivision = Heterostropha
Opisthobranchia
Pulmonata
Heterobranchia (different-gilled snails) is a superorder of mollusks in the class of the gastropods.
The families included in this recently established superorder of mollusks (G. Haszprunar, 1985) have made a long evolutionary journey through the class of the gastropods. Earlier authors (as J.E. Gray, 1840) put the Heterobranchia as a borderline case between de Opisthobranchia and Pulmonata on the one hand, and the other gastropods on the other hand.
Only the similarity in the structure of the gills makes them eligible for membership, in spite of all differences.
The order Heterostropha is primarily characterized by a heterostrophic protoconch (apical whorls are coiled opposite to adult whorls).
The bodies of the Opisthobranchia have undergone detorsion (unwinding). They have essentially evolved back to the bilateral symmetry of their ancestors.
The mantle cavity of the Pulmonata has modified into an air-breathing organ. They are also characterized by detorsion and a symmetrical concentrated nervous system. They usually lack an operculum and are hermaphroditic. This order contains most land snails and slugs and many freshwater snails.Superorder Heterobranchia J.E. Gray, 1840
*Order Heterostropha P. Fischer, 1885 (sometimes Allogastropoda Haszprunar, 1985)
*Order Opisthobranchia Milne-Edwards, 1848
**Suborder Cephalaspidea P. Fischer, 1883 (headshield slugs)
**Suborder Sacoglossa Von Ihering, 1876 (sap-suckling slugs)
**Suborder Anaspidea P. Fischer, 1883 (sea hares)
**Suborder Notaspidea P. Fischer, 1883 (sidegill slugs)
**Suborder Thecosomata de Blainville, 1824 (sea butterflies)
***Infraorder Euthecosomata
***Infraorder Pseudothecosomata
**Suborder Gymnosomata de Blainville, 1824 (sea angels)
**Suborder Nudibranchia de Blainville, 1814 (nudibranchs, true sea slugs))
***Infraorder Anthobranchia Férussac, 1819
***Infraorder Cladobranchia Willan & Morton, 1984
*Order Pulmonata Cuvier in Blainville, 1814 (pulmonates)
**Suborder Systellommatophora Pilsbry, 1948
**Suborder Basommatophora Keferstein in Bronn, 1864 (freshwater pulmonates, pond snails)
**Suborder Eupulmonata Haszprunar & Huber, 1990
***Infraorder Acteophila (Dall, 1885 (formerly Archaeopulmonata)
***Infraorder Trimusculiformes Minichev & Starobogatov, 1975
***Infraorder Stylommatophora A. Schmidt, 1856 (land snails)
****Subinfraorder Orthurethra
****Subinfraorder Sigmurethra
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