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Taxonomy of the Gastropoda

 
Wikipedia: Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
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Currently the leading system of classifying the gastropods (snails and slugs of all kinds) is the taxonomy of the Gastropoda as revised by Bouchet & Rocroi. This system of taxonomy was set forth in a paper entitled "Classification and Nomenclator of Gastropod Families", which was published in the journal Malacologia in 2005[1] written in collaboration with J. Frýda, B. Hausdorf, W. Ponder, Á. Valdés and A. Warén.

This system has superseded the taxonomy which was set forth by Ponder and Lindberg in 1997.

This taxonomy is considered to be one step closer to representing the evolutionary history of the phylum Mollusca, despite the fact that malacologists are, for the time being, having to use a classification which is a hybrid of the pre-existing, more traditional Linnaean taxonomy, and the more recent far-reaching revisions which are based on molecular work.

In the past, the taxonomy of gastropods was largely based on the morphological characters of the taxa, but recent advances are based more on the molecular characteristics of the DNA and RNA. This has made the taxonomical ranks 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 above the rank of superfamily (replacing the ranks suborder, order, superorder and subclass), while using the traditional Linnaean approach for all taxa below the rank of superfamily. All in all, 611 valid families are recognized. Of these, 202 families are exclusively fossil; this is indicated with a dagger †.

Whenever monophyly has not yet been tested, or where a traditional taxon of gastropods has now been discovered to be paraphyletic or polyphyletic, the term "group" or "informal group" has been used.

The classification of families into subfamilies 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.

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.)

† 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







This diagram was based on the following information. The list format makes clear which taxa are groups and informal groups:

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

Two superfamilies belongs to clade Sigmurethra, but they are not in the limacoid clade.

Changes since 2005

Taxonomic changes

Proposals and research

Based on nucleotide sequences of mitochondrial genomes Grande et al. (2008)[5] proposed these changes:

  • Pulmonata is polyphyletic
  • Euthyneura is not monophyletic because Pyramidelloidea should be included within Euthyneura
  • Opisthobranchia is not monophyletic because Siphonaria pectinata should be recognized as a member of the Opisthobranchia

References

  1. ^ a b Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdés Á. & Warén A. 2005. Classification and nomenclator of gastropod families. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. ISBN 3-925919-72-4. Issn = 0076-2997. 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278
  2. ^ a b Kaim, A., Jenkins, R.G., and Warén, A. 2008. Provannid and provannid−like gastropods from Late Cretaceous cold seeps of Hokkaido (Japan) and the fossil record of the Provannidae (Gastropoda: Abyssochrysoidea). Zoological Journal of the Linnean Society 154: 421–436.
  3. ^ Kiel, S., Campbell, K.A., Elder, W.P., and Little, C.T.S. 2008. Jurassic and Cretaceous gastropods from hydrocarbon seeps in forearc basin and accretionary prism settings, California. Acta Palaeontologica Polonica 53 (4): 679–703.
  4. ^ Geiger D. L.(8 May 2009) "A new species of Depressizona and the family rank of Depressizonidae". Zootaxa 2059: 57-59. abstract, full article.
  5. ^ Grande C., Templado J. & Zardoya R. 2008. Evolution of gastropod mitochondrial genome arrangements. BMC Evolutionary Biology 2008, 8:61. doi:10.1186/1471-2148-8-61

Further reading


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Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)".  Read more