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Template:Taxonavigation/Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)

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The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi in 2005 is currently (2010) the most up-to-date overall system for classifying gastropod mollusks. Gastropods are a taxonomic class of animals which consists of snails and slugs of every kind, from land, from freshwater, and from saltwater. Systems of classification such as this one 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 such as this one can be seen as an attempt to elucidate part of the tree of life, a phylogenetic tree.

The Bouchet & Rocroi 2005 system of gastropod taxonomy was laid out in a book-length paper entitled "Classification and Nomenclator of Gastropod Families", which was published in the journal Malacologia[1] and which was written in collaboration with J. Frýda, B. Hausdorf, W. Ponder, Á. Valdés and A. Warén. This system supersedes the system of Ponder 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 considered to be one step closer to representing the evolutionary history of the phylum Mollusca. This 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). In the past, the taxonomy of gastropods was largely based on the morphological characters of the taxa, such as shell characteristics and 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 has made the newer taxa and their hierarchy controversial, and the debate about these issues is not likely to end soon.

This proposed classification has tried to integrate these recent advances in understanding 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 approach 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. Whenever monophyly (a single lineage) has not yet been tested and confirmed, or where a traditional taxon of gastropods has now been discovered to be paraphyletic or polyphyletic (contains more than one lineage), the term "group" or "informal group" has been used.

In this taxonomy 611 valid families are recognized. Of these, 202 families are exclusively fossil, and this is indicated here with a dagger †. The superfamily names are standardized so that they all end in the suffix "-oidea"; there are no longer any that end "-acea". The 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)[1] also includes a nomenclator of about 2400 suprageneric taxa (taxa above the level of genus) 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 the ICZN.

Since the publication of this taxonomic system in 2005, various changes have been published by other authors, see Changes in the taxonomy of gastropods since 2005.

Main clades, groups and informal groups edit

This information is displayed in the form of a cladogram (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 therefore are likely to turn out to be polyphyletic (in other words, they are likely to contain more than one lineage, and if so, they will be split in the future.) Template:Gastropoda taxonomy

The diagram above was based on the following information. The list format used below makes clear which taxa are groups and informal groups rather than clades:

Taxonomy edit

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 in their names. A clearer sense of their actual hierarchy can be drawn from the list immediately above this one.

Paleozoic molluscs of uncertain systematic position edit

(existing as fossils only)

Uncertain position (Gastropoda or Monoplacophora) edit

With isostrophically coiled shells of uncertain position (Gastropoda or Monoplacophora) edit

With anisostrophically coiled shells of uncertain position (Gastropoda?) edit

Basal taxa that are certainly Gastropoda edit

(existing as fossils only)

Clade Patellogastropoda edit

Clade Vetigastropoda edit

Clade Cocculiniformia edit

Clade Neritimorpha (= Neritopsina) edit

Contains the Palaeozoic Neritomorpha of uncertain position and the clades Cyrtoneritimorpha and Cycloneritimorpha

Clade Cyrtoneritimorpha edit

Clade Cycloneritimorpha edit

Clade Caenogastropoda edit

Contains the Caenogastropoda of uncertain systematic position, the informal group Architaenioglossa and the clades Sorbeoconcha and Hypsogastropoda

Informal group Architaenioglossa edit

Clade Sorbeoconcha edit

Clade Hypsogastropoda edit

Contains the clades Littorinimorpha, Neogastropoda and the informal group Ptenoglossa.

Clade Littorinimorpha edit

Informal group Ptenoglossa edit

Clade Neogastropoda edit

Clade Heterobranchia edit

Contains the informal groups Heterobranchia, Opisthobranchia and Pulmonata

Informal group "Lower Heterobranchia" (= Allogastropoda) edit

Informal group Opisthobranchia edit

Contains the clades Cephalaspidea, Thecosomata, Gymnosomata, Aplysiomorpha, Sacoglossa, Umbraculida, Nudipleura and the groups Acochlidiacea and Cylindrobullida.

Clade Cephalaspidea edit

Clade Thecosomata edit

Clade Gymnosomata edit

Clade Aplysiomorpha (= Anaspidea) edit

Group Acochlidiacea edit

Clade Sacoglossa edit

Subclade Oxynoacea edit

Subclade Placobranchacea edit

Group Cylindrobullida edit

Clade Umbraculida edit

Clade Nudipleura edit

Subclade Pleurobranchomorpha edit

Subclade Nudibranchia edit

Contains the clades Euctinidiacea and Dexiarchia

Clade Euctenidiacea (= Holohepatica) edit

Contains the subclades Gnathodoridacea and Doridacea

Subclade Gnathodoridacea edit
Subclade Doridacea edit
Clade Dexiarchia (= Actenidiacea) edit

Contains the clades Pseudoeuctenidiacea and Cladobranchia

Clade Pseudoeuctenidiacea ( = Doridoxida) edit
Clade Cladobranchia ( = Cladohepatica) edit

Contains the subclades Euarminida, Dendronotida and Aeolidida

Subclade Euarminida edit
Subclade Dendronotida edit
Subclade Aeolidida edit

Informal Group Pulmonata edit

Contains the informal group Basommatophora and the clade Eupulmonata

Informal Group Basommatophora edit

Contains the clade Hygrophila

Clade Hygrophila edit

Clade Eupulmonata edit

Contains the clades Systellommatophora and Stylommatophora

Clade Systellommatophora (= Gymnomorpha) edit
Clade Stylommatophora edit

Contains the subclades Elasmognatha, Orthurethra and the informal group Sigmurethra

Subclade Elasmognatha edit
Subclade Orthurethra edit
Informal Group Sigmurethra edit
limacoid clade edit
Informal group Sigmurethra continued edit

Two other superfamilies are part of the clade Sigmurethra, but they are not in the limacoid clade:

External links edit

  1. ↑ a b Template:Bouchet 2005
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