Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)

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 of classifying gastropod mollusks. Gastropods are a taxonomic class of animals which consists of snails and slugs of every kind, and this system of classification is primarily of value to malacologists (people who study mollusks) and other biologists.

The Bouchet & Rocroi 2005 system of gastropod taxonomy was laid out in a book-length paper titled "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, but recent advances are based more on the molecular characteristics of the DNA and RNA. This has made the taxa and their hierarchy controversial, and the debate about these issues is not likely to end soon.

This proposed classification has tried to reconcile these recent advances by using unranked clades for taxa below the 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 have been 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 of gastropods, going from the subtribe to the superfamily. A full bibliographic reference is provided for each taxon; this includes the name of the author, the original publication, date of publication, type genus, nomenclatural status, and validity under the rules of the ICZN.

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

Contents

Main clades, groups and informal groups

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.)

† Paleozoic molluscs of uncertain systematic position


† Basal taxa that are certainly Gastropoda


Patellogastropoda


Vetigastropoda


Cocculiniformia

Neritimorpha

† Paleozoic Neritimorpha of uncertain systematic position


† Cyrtoneritimorpha


Cycloneritimorpha


 Caenogastropoda 

Caenogastropoda of uncertain systematic position


Architaenioglossa


Sorbeoconcha

 Hypsogastropoda 

Littorinimorpha


Ptenoglossa


Neogastropoda



Heterobranchia

Lower Heterobranchia

 Opisthobranchia 

Cephalaspidea


Thecosomata


Gymnosomata


Aplysiomorpha


Acochlidiacea


Sacoglossa


Cylindrobullida


Umbraculida

 Nudipleura 

Pleurobranchomorpha

 Nudibranchia 

Euctenidiacea

 Dexiarchia 

Pseudoeuctenidiacea

 Cladobranchia 

Euarminida


Dendronotida


Aeolidida






Pulmonata

Basommatophora

 Eupulmonata 

Systellommatophora

 Stylommatophora 

Elasmognatha


Orthurethra


Sigmurethra






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

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

(existing as fossils only)

Uncertain position (Gastropoda or Monoplacophora)

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

With anisostrophically coiled shells of uncertain position (Gastropoda?)

Basal taxa that are certainly Gastropoda

(existing as fossils only)

Clade Patellogastropoda

Clade Vetigastropoda

Clade Cocculiniformia

Clade Neritimorpha (= Neritopsina)

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

Clade Cyrtoneritimorpha

Clade Cycloneritimorpha

Clade Caenogastropoda

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

Informal group Architaenioglossa

Clade Sorbeoconcha

Clade Hypsogastropoda

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

Clade Littorinimorpha

Informal group Ptenoglossa

Clade Neogastropoda

Clade Heterobranchia

Contains the informal groups Heterobranchia, Opisthobranchia and Pulmonata

Informal group "Lower Heterobranchia" (= Allogastropoda)

Informal group Opisthobranchia

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

Clade Cephalaspidea

Clade Thecosomata

Clade Gymnosomata

Clade Aplysiomorpha (= Anaspidea)

Group Acochlidiacea

Clade Sacoglossa

Subclade Oxynoacea

Subclade Placobranchacea

Group Cylindrobullida

Clade Umbraculida

Clade Nudipleura

Subclade Pleurobranchomorpha

Subclade Nudibranchia

Contains the clades Euctinidiacea and Dexiarchia

Clade Euctenidiacea (= Holohepatica)

Contains the subclades Gnathodoridacea and Doridacea

Subclade Gnathodoridacea
Subclade Doridacea
Clade Dexiarchia (= Actenidiacea)

Contains the clades Pseudoeuctenidiacea and Cladobranchia

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

Contains the subclades Euarminida, Dendronotida and Aeolidida

Subclade Euarminida
Subclade Dendronotida
Subclade Aeolidida

Informal Group Pulmonata

Contains the informal group Basommatophora and the clade Eupulmonata

Informal Group Basommatophora

Contains the clade Hygrophila

Clade Hygrophila

Clade Eupulmonata

Contains the clades Systellommatophora and Stylommatophora

Clade Systellommatophora (= Gymnomorpha)
Clade Stylommatophora

Contains the subclades Elasmognatha, Orthurethra and the informal group Sigmurethra

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

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

See also

References

  1. ↑ 1.0 1.1 Bouchet P., Rocroi J.-P., Frýda J., Hausdorf B., Ponder W., Valdés Á. & Warén A. (2005). "Classification and nomenclator of gastropod families". Malacologia: International Journal of Malacology (Hackenheim, Germany: ConchBooks) 47 (1-2): 1–397. ISBN 3925919724. ISSN 0076-2997. http://www.archive.org/details/malacologia47122005inst. 

External links