Thetaxonomy of the Gastropoda as it was revised in 2005 byPhilippe Bouchet andJean-Pierre Rocroi is a system for the scientificclassification ofgastropodmollusks (Gastropods are ataxonomicclass of animals which consists ofsnails andslugs of every kind, from the land, fromfreshwater, and fromsaltwater). The paper setting out this taxonomy was published in the journalMalacologia. The system encompasses both living and extinct groups, as well as some fossils whose classification as gastropods is uncertain.
The Bouchet & Rocroi system was the first complete gastropod taxonomy that primarily employed the concept ofclades, and was derived from research onmolecular phylogenetics; in this context a clade is a "natural grouping" of organisms based upon a statisticalcluster analysis. In contrast, most of the previous overall taxonomic schemes for gastropods relied onmorphological features to classify these animals, and usedtaxon ranks such asorder, superorder and suborder, which are typical of classifications that are still inspired byLinnaean taxonomy.
In the Bouchet & Rocroi taxonomy, clades are used between the rank ofclass and the rank ofsuperfamily. The clades are unranked. Bouchet and Rocroi use six main clades:Patellogastropoda,Vetigastropoda,Cocculiniformia,Neritimorpha,Caenogastropoda, andHeterobranchia. 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 thenudibranch groups there are six separate clades above the level of superfamily, and in the case of most of theland 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. Since the publication of this taxonomic system in 2005, various proposals for changes have been published by other authors, for more information seechanges in the taxonomy of gastropods since 2005.
In 2017 this taxonomy was superseded by a revised taxonomy "Revised Classification, Nomenclator and Typification of Gastropod and Monoplacophoran Families" by Philippe Bouchet & Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong in Malacologia, 2017, 61(1–2): 1–526. The authors have reverted to adopting the traditional ranks above superfamily: order, subclass, as this was preferred by many users.[1]
Systems of classification such as this one are primarily of value tomalacologists (people who study mollusks) and otherbiologists. Biological classification schemes are not merely a convenience, they are an attempt to show the actualphylogeny (theevolutionary relatedness) within a group oforganisms. Thus, a taxonomy such as this one can be seen as an attempt to elucidate part of thetree of life, aphylogenetic tree.
The Bouchet & Rocroi 2005 system of gastropodtaxonomy was laid out in a book-length paper entitled "Classification and Nomenclator of Gastropod Families", which was published in the journalMalacologia[2] and which was written in collaboration with J. Frýda, B. Hausdorf,W. Ponder, Á. Valdés and A. Warén. This system supersedes the system ofPonder and Lindberg from 1997.Subsequent revisions by other authors have been made since the publication of this paper.
The taxonomy set out by Bouchet & Rocroi is an attempt to get one step closer to representing this part of theevolutionary history of the phylum Mollusca. Bouchet & Rocroi's classification system is a hybrid of the pre-existing, more traditionalLinnaean taxonomy along with some more recent far-reaching revisions which are based on molecular work and useclades astaxa, (seecladistics). In the past, the taxonomy of gastropods was largely based on themorphological characters of the taxa, such as theshell characteristics (including theprotoconch) in shelled species, and the internalanatomy, including the structure of theradula and details of thereproductive system. Recent advances are based more on themolecular characteristics of theDNA andRNA. 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 unrankedclades for taxa below the traditional rank of class (class Gastropoda) but above the rank ofsuperfamily (replacing the ranks subclass, superorder, order, and suborder), while still using the traditionalLinnaean 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. Whenevermonophyly (a single ancestry) has not yet been tested and confirmed, or where a traditional taxon of gastropods has already been discovered to beparaphyletic (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 arepolyphyletic, in other words if they consist of more than one lineage.
In this taxonomy 611 valid families are recognized. Of these, 202 families are exclusivelyfossil, 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 possiblehypothesis.
The publication Bouchet & Rocroi (2005)[2] also includes anomenclator of about 2400 suprageneric taxa (taxa above the level ofgenus) of gastropods, from the subtribe to the superfamily. A full bibliographic reference is provided for each taxon, giving the name of the authority, the original publication, the date of that publication, the type genus for the taxon, its nomenclatural status, and its validity under the rules of theICZN.
Since the publication of this taxonomic system in 2005, various changes have been published by other authors, for more information seechanges in the taxonomy of gastropods since 2005.
Here the information is displayed in the form of acladogram (an evolutionary tree of descent.) It is worth bearing in mind however that this taxonomy is provisional: many of the taxa are still only known as "groups" or "informal groups", and these are very likely to be changed as more information becomes available.
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This cladogram is based on the following information. The list format used below makes clear which taxa are informal groups rather than clades:
In the following, more detailed list, indentation is used only for the ranks of superfamily and family. The clade names are not indented, but their hierarchy is indicated by the size of the font used. A clearer sense of the hierarchy of the clades can be drawn from the list immediately above this one.
(Existing asfossils only)
(existing as fossils only)
Contains thePalaeozoic Neritomorpha of uncertain position and the cladesCyrtoneritimorpha andCycloneritimorpha
Contains the Caenogastropoda of uncertain systematic position, the informal groupArchitaenioglossa and the cladesSorbeoconcha andHypsogastropoda
Contains the cladesLittorinimorpha,Neogastropoda and the informal groupPtenoglossa.
Contains the informal groupsHeterobranchia,Opisthobranchia andPulmonata
Contains the cladesCephalaspidea,Thecosomata,Gymnosomata,Aplysiomorpha,Sacoglossa,Umbraculida,Nudipleura and the groupsAcochlidiacea andCylindrobullida.
Contains the cladesEuctinidiacea andDexiarchia
Contains the subcladesGnathodoridacea andDoridacea
Contains the cladesPseudoeuctenidiacea andCladobranchia
Contains the subcladesEuarminida,Dendronotida andAeolidida
Contains the informal groupBasommatophora and the cladeEupulmonata
Contains the cladeHygrophila
Contains the cladesSystellommatophora andStylommatophora
Contains the subcladesElasmognatha,Orthurethra and the informal groupSigmurethra
Two other superfamilies are part of the clade Sigmurethra, but they arenot in the limacoid clade:
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