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Basommatophora; Temporal range: Carboniferous–recent PreꞒ Ꞓ O S D C P T J K Pg N
	The larger of the two basommatophoran snails shown here is Lymnaea stagnalis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Informal group:	Pulmonata
Informal group:	Basommatophora; Keferstein in Bronn, 1864
Families
	See text
Diversity
	about 300 species

Basommatophora was a term that was previously used as a taxonomic informal group, a group of snails within the informal group Pulmonata, the air-breathing slugs and snails. According to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), whenever monophyly has not been tested, or where a traditional taxon of gastropods has now been discovered to be paraphyletic or polyphyletic, the term "group" or "informal group" was used.

Basommatophora are known from the Carboniferous to the Recent periods.^[2]

Most of the families in this suborder are air-breathing freshwater snails. The three most abundant families in terms of number of species are, the Lymnaeidae (pond snails), the Planorbidae (ramshorn snails) and the Physidae (pouch or bubble snails). These are found in ponds, creeks, ditches, and shallow lakes nearly worldwide.

The Siphonariidae on the other hand are unusual in that they have secondarily returned to the sea, and are now sea snails, limpet-like marine gastropods which live in the rocky intertidal zone but which still breathe air and become active at low tide. The single species in the family Amphibolidae is archaic and retains an operculum. It lives at such a high tidal level that it could perhaps be considered semi-terrestrial. Members of the family Chilinidae are confined to temperate parts of South America, and the Latiidae are limpet-like and confined to New Zealand.

Basommatophorans are characterized by having their eyes located at the base of their non-retractile tentacles, rather than at the tips, as in the true land snails Stylommatophora. The majority of basommatophorans have shells that are thin, translucent, and relatively colorless, and all except Amphibola lack an operculum.

Taxonomy

1997 taxonomy

In the older taxonomy of the Gastropoda (Ponder & Lindberg, 1997) the suborder Basommatophora consisted of the families :

Acroloxidae Thiele, 1931
Amphibolidae J. E. Gray, 1840 - only one species Amphibola crenata
Ancylidae
Carychiidae Jeffreys, 1830
Chilinidae
Lancidae
Latiidae
Lymnaeidae Rafinesque, 1815
Otinidae H. Adams & A. Adams, 1855
Physidae Fitzinger, 1833
Planorbidae Rafinesque, 1815
Siphonariidae J. E. Gray, 1840
Trimusculidae Zilch, 1959

2005 taxonomy

The informal group Basommatophora contains the following superfamilies and the clade Hygrophila (according to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)):

Superfamily Amphiboloidea Gray, 1840
- Family Amphibolidae Gray, 1840
Superfamily Siphonarioidea Gray, 1827
- Family Siphonariidae Gray, 1827
- † Family Acroreiidae Cossmann, 1893

Clade Hygrophila

Superfamily Chilinoidea Dall, 1870
- Family Chilinidae Dall, 1870
- Family Latiidae Hutton, 1882
Superfamily Acroloxoidea Thiele, 1931
- Family Acroloxidae Thiele, 1931
Superfamily Lymnaeoidea Rafinesque, 1815
- Family Lymnaeidae Rafinesque, 1815
Superfamily Planorboidea Rafinesque, 1815
- Family Planorbidae Rafinesque, 1815
- Family Physidae Fitzinger, 1833

The family Ancylidae has been reduced in the new taxonomy to the status of tribe Ancylini Rafinesque, 1815 of the subfamily Planorbinae Rafinesque, 1815 of the family Planorbidae Rafinesque, 1815.

The family Carychiidae has been reduced in this taxonomy to the status of subfamily Carychiinae Jeffreys, 1830 of the family Ellobiidae L. Pfeiffer, 1854 (1822).

The family Lancidae has been reduced in this taxonomy to the status of subfamily Lancinae Hannibal, 1814 of the family Lymnaeidae Rafinesque, 1815.

2010 taxonomy

More recently, the Basommatophora was found to be polyphyletic, and so Jörger et al. (2010)^[3] moved its three members, the (superfamily Siphonarioidea, superfamily Amphiboloidea, and clade Hygrophila) into a new taxon, Panpulmonata.^[3]

References

^ Correa C. A., Escobar J. S., Durand P., Renaud F., David P., Jarne P., Pointier J.-P. & Hurtrez-Boussès S. (2010). "Bridging gaps in the molecular phylogeny of the Lymnaeidae (Gastropoda: Pulmonata), vectors of Fascioliasis". BMC Evolutionary Biology 10: 381. doi:10.1186/1471-2148-10-381.
^ (in Czech) Pek I., Vašíček Z., Roček Z., Hajn. V. & Mikuláš R.: Základy zoopaleontologie. - Olomouc, 1996. 264 pp., ISBN 80-7067-599-3.
^ ^a ^b Jörger K. M., Stöger I., Kano Y., Fukuda H., Knebelsberger T. & Schrödl M. (2010). "On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia". BMC Evolutionary Biology 10: 323. doi:10.1186/1471-2148-10-323.