Basommatophora is a taxonomic informal group within the informal group Pulmonata. 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" has been used.
Basommatophora are known from the Carboniferous to the recent periods.
Most of the families in this suborder are air-breathing freshwater snails, but the Siphonariidae are unusual in that they have secondarily returned to the sea, and are now marine gastropods. 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 terrestrial.
In the older taxonomy the suborder Basommatophora consisted of the families :
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 .