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. 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