Systems of classification are primarily of value to
malacologists (people who study mollusks) and other
biologists.
Biological classification schemes are not merely a convenience, they are an attempt to show the actual
phylogeny (the
evolutionary relatedness) within a group of
organisms. Thus, a taxonomy can be seen as an attempt to elucidate part of the
tree of life, a
phylogenetic tree.
Gastropods are a
taxonomic class of animals which consists of
snails and
slugs of every kind, from the land, from
freshwater, and from
saltwater.
Ponder & Lindberg, 1997 Towards a phylogeny of gastropod molluscs: an analysis using morphological characters. was published by
Winston Ponder and
David R. Lindberg in 1997. This taxonomy assigns the various Gastropods into ranked categories, such as
sub-orders and
families, but does not address the classification of
genera or individual
species. This classification scheme is based on the molluscs' internal and external shapes and forms, but did not take into account any analysis of their
DNA or
RNA. Ponder & Lindberg (1997) used only four families to analyze the
Euthyneura. Further work by Dayrat & Tillier (2002) provided a great deal of detail about the relationships between within the Euthyneura. Ponder & Lindberg (1997) did not use Linnean
taxonomical ranks in their work, but the results of their paper were widely adapted and used with Linnean taxonomical ranks by other authors.
Class Gastropoda Cuvier, 1797
Incertæ sedis • Order
Bellerophontinaka (
fossil) • Order
Mimospirina (
fossil)
Subclass Eogastropoda Ponder &
David R. Lindberg, 1996 (earlier:
Prosobranchia) • Order
Euomphalida de Koninck 1881 (
fossil) • Superfamily
Macluritoidea • Superfamily
Euomphaloidea • Superfamily
Platyceratoidea , England. • Order
Patellogastropoda Lindberg, 1986 (true limpets) • Suborder
Patellina Van Ihering, 1876 • Superfamily
Patelloidea Rafinesque, 1815 • Suborder
Nacellina David R. Lindberg, 1988 • Superfamily
Acmaeoidea Carpenter, 1857 • Superfamily
Nacelloidea Thiele, 1891 • Suborder
Lepetopsina McLean, 1990 • Superfamily
Lepetopsoidea McLean, 1990
Subclass Orthogastropoda Ponder &
David R. Lindberg, 1996 (earlier
Prosobranchia,
Opisthobranchia)
Incertæ sedis • Order
Murchisoniina Cox & Knight, 1960 (
fossil) • Superfamily
Murchisonioidea Koken, 1889 • Superfamily
Loxonematoidea Koken, 1889 • Superfamily
Lophospiroidea Wenz, 1938 • Superfamily
Straparollinoidea • Grade
Subulitoidea Lindström, 1884 Superorder
Cocculiniformia Haszprunar, 1987 • Superfamily
Cocculinoidea Dall, 1882 • Superfamily
Lepetelloidea Dall, 1882 (deep sea limpets) Superorder "Hot Vent Taxa"
Ponder &
David R. Lindberg, 1997 • Order
Neomphaloida Sitnikova & Starobogatov, 1983 • Superfamily
Neomphaloidea McLean, 1981 (hydrothermal vents limpets) • Superfamily
Peltospiroidea McLean, 1989 Superorder
Vetigastropoda Salvini-Plawen, 1989 (limpets) of
Cyprus. A
serpulid worm is attached. • Superfamily
Fissurelloidea Fleming, 1822 (keyhole limpets) • Superfamily
Haliotoidea Rafinesque, 1815 (abalones) • Superfamily
Lepetodriloidea McLean, 1988 (hydrothermal vent limpets) • Superfamily
Pleurotomarioidea Swainson, 1840 (slit shells) • Superfamily
Seguenzioidea Verrill, 1884 • Superfamily
Trochoidea Rafinesque, 1815 (top shells) Superorder
Neritaemorphi Koken, 1896 • Order
Cyrtoneritomorpha (
fossil) • Order
Neritopsina Cox & Knight, 1960 • Superfamily
Neritoidea Lamarck, 1809 Superorder
Caenogastropoda Cox, 1960 • Order
Architaenioglossa Haller, 1890 • Superfamily
Ampullarioidea J.E. Gray, 1824 • Superfamily
Cyclophoroidea J.E. Gray, 1847 (terrestrials) • Order
Sorbeoconcha Ponder &
David R. Lindberg, 1997 • Suborder
Discopoda P. Fischer, 1884 • Superfamily
Campaniloidea Douvillé, 1904 • Superfamily
Cerithioidea Férussac, 1822 • Suborder
Hypsogastropoda Ponder &
David R. Lindberg, 1997 • Infraorder
Littorinimorpha Golikov & Starobogatov, 1975 • Superfamily
Calyptraeoidea Lamarck, 1809 • Superfamily
Capuloidea J. Fleming, 1822 • Superfamily
Carinarioidea Blainville, 1818 (formerly called Heteropoda) • Superfamily
Cingulopsoidea Fretter & Patil, 1958 • Superfamily
Cypraeoidea Rafinesque, 1815 (cowries) • Superfamily
Ficoidea Meek, 1864 • Superfamily
Laubierinoidea Warén & Bouchet, 1990 • Superfamily
Littorinoidea (Children), 1834 (periwinkles) • Superfamily
Naticoidea Forbes, 1838 (moon shells) • Superfamily
Rissooidea J.E. Gray, 1847 (Risso shells) (includes genus
Oncomelania, schistosomiasis transmission vector) • Superfamily
Stromboidea Rafinesque, 1815 (true conchs) • Superfamily
Tonnoidea Suter, 1913 • Superfamily
Trivioidea Troschel, 1863 • Superfamily
Vanikoroidea J.E. Gray, 1840 • Superfamily
Velutinoidea J.E. Gray, 1840 • Superfamily
Vermetoidea Rafinesque, 1815 (worm shells) • Superfamily
Xenophoroidea Troschel, 1852 (carrier shells) • Infraorder
Ptenoglossa J.E. Gray, 1853 • Superfamily
Eulimoidea Philippi, 1853 • Superfamily
Janthinoidea Lamarck, 1812 • Superfamily
Triphoroidea J.E. Gray, 1847 • Infraorder
Neogastropoda Thiele, 1929 • Superfamily
Buccinoidea (whelks, false tritions) • Superfamily
Cancellarioidea Forbes & Hanley, 1851 • Superfamily
Conoidea Rafinesque, 1815 • Superfamily
Muricoidea Rafinesque, 1815 Superorder
Heterobranchia J.E. Gray, 1840 • Order
Heterostropha P. Fischer, 1885 • Superfamily
Architectonicoidea J.E. Gray, 1840 • Superfamily
Nerineoidea Zittel, 1873 (
fossil) • Superfamily
Omalogyroidea G.O. Sars, 1878 • Superfamily
Pyramidelloidea J.E. Gray, 1840 • Superfamily
Rissoelloidea J.E. Gray, 1850 • Superfamily
Valvatoidea J.E. Gray, 1840 • Order
Opisthobranchia Milne-Edwards, 1848 • Suborder
Cephalaspidea P. Fischer, 1883 • Superfamily
Acteonoidea D'Orbigny, 1835 • Superfamily
Bulloidea Lamarck, 1801 • Superfamily
Cylindrobulloidea Thiele, 1931 (has to be included in the Sacoglossa) • Superfamily
Diaphanoidea Odhner, 1914 • Superfamily
Haminoeoidea Pilsbry, 1895 • Superfamily
Philinoidea J.E. Gray, 1850 • Superfamily
Ringiculoidea Philippi, 1853 • Suborder
Sacoglossa Von Ihering, 1876 • Superfamily
Oxynooidea H. Adams &
A. Adams, 1854 • Suborder
Anaspidea P. Fischer, 1883 (sea hares) • Superfamily
Akeroidea Pilsbry, 1893 • Superfamily
Aplysioidea Lamarck, 1809 • Suborder
Notaspidea P. Fischer, 1883 • Superfamily
Tylodinoidea J.E. Gray, 1847 • Superfamily
Pleurobranchoidea Férussac, 1822 • Suborder
Thecosomata Blainville, 1824 (sea butterflies) • Infraorder
Euthecosomata • Superfamily
Limacinoidea • Superfamily
Cavolinioidea • Infraorder
Pseudothecosomata • Superfamily
Peraclidoidea • Superfamily
Cymbulioidea • Suborder
Gymnosomata Blainville, 1824 (sea angels) • Family
Clionidae Rafinesque, 1815 • Family
Cliopsidae Costa, 1873 • Family
Hydromylidae Pruvot-Fol, 1942 • Family
Laginiopsidae Pruvot-Fol, 1922 • Family
Notobranchaeidae Pelseneer, 1886 • Family
Pneumodermatidae Latreille, 1825 • Family
Thliptodontidae Kwietniewski, 1910 • Suborder
Nudibranchia Blainville, 1814 (nudibranchs) • Infraorder
Anthobranchia Férussac, 1819 • Superfamily
Doridoidea Rafinesque, 1815 • Superfamily
Doridoxoidea Bergh, 1900 • Superfamily
Onchidoridoidea Alder & Hancock, 1845 • Superfamily
Polyceroidea Alder & Hancock, 1845 • Infraorder
Cladobranchia Willan & Morton, 1984 • Superfamily
Dendronotoidea Allman, 1845 • Superfamily
Arminoidea Rafinesque, 1814 • Superfamily
Metarminoidea Odhner in Franc, 1968 • Superfamily
Aeolidioidea J.E. Gray, 1827 '' or door snails, a small land
pulmonate which has a sinistral or left-handed shell, on the trunk of a tree, in
woodland,
England • Order
Pulmonata Cuvier in
Blainville, 1814 (pulmonates) • Suborder
Systellommatophora Pilsbry, 1948 • Superfamily
Onchidioidea Rafinesque, 1815 • Superfamily
Otinoidea H. Adams &
A. Adams, 1855 • Superfamily
Rathouisioidea Sarasin, 1889 • Suborder
Basommatophora Keferstein in Bronn, 1864 (freshwater pulmonates, pond snails) • Superfamily
Acroloxoidea Thiele, 1931 • Superfamily
Amphiboloidea J.E. Gray, 1840 • Superfamily
Chilinoidea H. Adams &
A. Adams, 1855 • Superfamily
Glacidorboidea Ponder, 1986 • Superfamily
Lymnaeoidea Rafinesque, 1815 • Superfamily
Planorboidea Rafinesque, 1815 • Superfamily
Siphonarioidea J.E. Gray, 1840 • Suborder
Eupulmonata Haszprunar & Huber, 1990 • Infraorder
Acteophila Dall, 1885 (= formerly Archaeopulmonata) • Superfamily
Melampoidea Stimpson, 1851 • Infraorder
Trimusculiformes Minichev & Starobogatov, 1975 • Superfamily
Trimusculoidea Zilch, 1959 • Infraorder
Stylommatophora A. Schmidt, 1856 (land snails) • Subinfraorder
Orthurethra • Superfamily
Achatinelloidea Gulick, 1873 • Superfamily
Cochlicopoidea Pilsbry, 1900 • Superfamily
Partuloidea Pilsbry, 1900 • Superfamily
Pupilloidea Turton, 1831 • Subinfraorder
Sigmurethra • Superfamily
Acavoidea Pilsbry, 1895 • Superfamily
Achatinoidea Swainson, 1840 • Superfamily
Aillyoidea Baker, 1960 • Superfamily
Arionoidea J.E. Gray in Turnton, 1840 • Superfamily
Buliminoidea Clessin, 1879 • Superfamily
Camaenoidea Pilsbry, 1895 • Superfamily
Clausilioidea Mörch, 1864 • Superfamily
Dyakioidea Gude & Woodward, 1921 • Superfamily
Gastrodontoidea Tryon, 1866 • Superfamily
Helicoidea Rafinesque, 1815 • Superfamily
Helixarionoidea Bourguignat, 1877 • Superfamily
Limacoidea Rafinesque, 1815 • Superfamily
Oleacinoidea H. Adams &
A. Adams, 1855 • Superfamily
Orthalicoidea Albers-Martens, 1860 • Superfamily
Plectopylidoidea Moellendorf, 1900 • Superfamily
Polygyroidea Pilsbry, 1894 • Superfamily
Punctoidea Morse, 1864 • Superfamily
Rhytidoidea Pilsbry, 1893 • Superfamily
Sagdidoidea Pilsbry, 1895 • Superfamily
Staffordioidea Thiele, 1931 • Superfamily
Streptaxoidea J.E. Gray, 1806 • Superfamily
Strophocheiloidea Thiele, 1926 • Superfamily
Trigonochlamydoidea Hese, 1882 • Superfamily
Zonitoidea Mörch, 1864 • ? Superfamily
Athoracophoroidea P. Fischer, 1883 (= Tracheopulmonata) • ? Superfamily
Succineoidea Beck, 1837 (= Heterurethra) Other extant classes of the Mollusca are
Bivalvia,
Scaphopoda,
Aplacophora,
Polyplacophora,
Monoplacophora and
Cephalopoda.
Bouchet & Rocroi, 2005 Philippe Bouchet and
Jean-Pierre Rocroi published their revised taxonomy in 2005. The system encompasses both living and extinct groups, as well as some fossils whose classification as gastropods is uncertain. This taxnomy was laid out in a book-length paper entitled "Classification and Nomenclator of Gastropod Families", which was published in the journal
Malacologia and which was written in collaboration with J. Frýda, B. Hausdorf,
W. Ponder, Á. Valdés and A. Warén. The Bouchet & Rocroi system was the first complete gastropod taxonomy that primarily employed the concept of
clades, and was derived from research on
molecular phylogenetics; in this context a clade is a "natural grouping" of organisms based upon a statistical
cluster analysis. Higher taxa are expressed as unranked
clades where known, and termed "informal groups" or groups" where monophyly (a single lineage) has not yet been determined, and where
polyphyly (more than one lineage) is suspected. Clades are used between the rank of
class and the rank of
superfamily. The clades are unranked. The taxonomy thus is an attempt to get one step closer to representing this part of the
evolutionary history of the phylum Mollusca. Bouchet & Rocroi's classification system is a hybrid of the pre-existing, more traditional
Linnaean taxonomy along with some more recent far-reaching revisions which are based on molecular work and use
clades as
taxa, (see
cladistics). The 2005 taxonomy differs from the 1997 taxonomy and other previous taxonomic schemes primarily in that they relied on
morphological features to classify these animals, and used
taxon ranks such as
order, superorder and suborder, which are typical of classifications that are still inspired by
Linnaean taxonomy. Morphological characteristics include
shell characteristics (including the
protoconch) in shelled species, and the internal
anatomy, including the structure of the
radula and details of the
reproductive system. Recent advances are based more on the
molecular characteristics of the
DNA and
RNA. This shift in emphasis has meant that the newer taxa and their hierarchy are subject to debate, a debate that is not likely to be resolved soon. This proposed classification has tried to integrate the results of recent molecular work by using unranked
clades for taxa below the traditional rank of class (class Gastropoda) but above the rank of
superfamily (replacing the ranks subclass, superorder, order, and suborder), while still using the traditional
Linnaean ranks for superfamilies and all taxa below the rank of superfamily (i.e., family, subfamily, tribe, genus, subgenus, and species. The clades have been given names which are similar to, or in some cases the same as, traditional Linnaean names for taxa above the level of superfamily. Whenever
monophyly (a single ancestry) has not yet been tested and confirmed, or where a traditional taxon of gastropods has already been discovered to be
paraphyletic (that it excludes some of its descendants) the term "group" or "informal group" has been used. Both Linnaean taxa and clades are invalid if it turns out they are
polyphyletic, in other words if they consist of more than one lineage. Bouchet and Rocroi use six main clades:
Patellogastropoda,
Vetigastropoda,
Cocculiniformia,
Neritimorpha,
Caenogastropoda, and
Heterobranchia. The first three of these major clades have no nesting clades within them: the taxonomy goes immediately to the superfamily level. Within the Caenogastropoda there is one extra clade. In contrast, within the Heterobranchia, for some of the
nudibranch groups there are six separate clades above the level of superfamily, and in the case of most of the
land snails, there are four clades above the level of superfamily. In some parts of the taxonomy, instead of "clade", Bouchet and Rocroi labelled groupings of taxa as a "group" or an "informal group". A clade must by definition contain only one lineage, and it was considered to be the case that these "informal groups" may either contain more than one lineage, or only contain part of a lineage. Further research will eventually resolve these questions. In this taxonomy 611 valid families are recognized. Of these, 202 families are exclusively
fossil, and this is indicated here with a dagger †. Superfamily names are standardized so that they all end in the suffix "-oidea", also commonly used for superorders and subclasses, replacing the "-acea" ending found especially in the older literature. Classification of families into subfamilies however is often not well resolved, and should be regarded as the best possible
hypothesis. The publication Bouchet & Rocroi (2005) The same work also included the
taxonomy of monoplacophorans. The work addresses the revision of family-level classification of gastropods, the standardization of nomenclature, and the designation or clarification of type taxa in accordance with international zoological rules (
International Code of Zoological Nomenclature). In response to the increasing use of online taxonomic databases, as well as user feedback expressing a preference for traditional hierarchical ranks (such as suborder, order, and subclass), this work reintroduces the use of formal
taxonomic ranks above the level of superfamily, instead employing terms such as "clade" and "informal group" as was done in the 2005 work. Its main objectives include: • updating classification schemes based on new data (including morphological and molecular evidence), • resolving inconsistencies, redundancies, and ambiguities in scientific names, that includes evaluation of name validity (addressing synonymy and homonymy), • designating or revising type genera and type species for individual families, • establishment of new taxonomic combinations where necessary. Methods used in this work include: • critical review of historical and modern literature, • analysis of morphological characters (such as
shell structure,
radula, and anatomy), • incorporation of molecular phylogenetic data. The results provide a reference framework for future taxonomic and biological research. This publication functions more as a taxonomic standard and a
reference work, than a "hypothesis" that someone reviews in a single article. There are altogether 721 gastropod families, that includes 245 exclusively fossil families and 476 recent families (with or without a fossil record). and by 943 works according
Google Scholar. The following cladogram shows a summary of the new gastropod taxonomy, according to the work's Contents section: ==Current taxonomy==