Editing Gastropoda (section)

== Taxonomy ==
{{Further|Changes in the taxonomy of gastropods since 2005}}{{See also|Taxonomy of the Gastropoda (Ponder & Lindberg, 1997)}}

=== Current classification ===
The present backbone classification of gastropods relies on the results of phylogenomic analyses. Consensus has not been reached yet considering the relationships at the very base of the gastropod tree of life, but otherwise the major groups are known with confidence.<ref name=":1">{{Cite journal |last1=Cunha |first1=Tauana Junqueira |last2=Giribet |first2=Gonzalo |date=2019-03-13 |title=A congruent topology for deep gastropod relationships |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=286 |issue=1898 |pages=20182776 |doi=10.1098/rspb.2018.2776 |issn=0962-8452 |pmc=6458328 |pmid=30862305}}</ref><ref name=":2">{{Cite journal |last1=Uribe |first1=Juan E |last2=González |first2=Vanessa L |last3=Irisarri |first3=Iker |last4=Kano |first4=Yasunori |last5=Herbert |first5=David G |last6=Strong |first6=Ellen E |last7=Harasewych |first7=M G |date=2022-10-12 |editor-last=Oaks |editor-first=Jamie |title=A Phylogenomic Backbone for Gastropod Molluscs |url=https://academic.oup.com/sysbio/article/71/6/1271/6619577 |journal=Systematic Biology |language=en |volume=71 |issue=6 |pages=1271–1280 |doi=10.1093/sysbio/syac045 |pmid=35766870 |issn=1063-5157 |access-date=2023-08-10 |archive-date=2023-08-23 |archive-url=https://web.archive.org/web/20230823114119/https://academic.oup.com/sysbio/article-abstract/71/6/1271/6619577?redirectedFrom=fulltext |url-status=live |hdl=10261/279410 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Chen |first1=Zeyuan |last2=Schrödl |first2=Michael |date=2022-04-18 |title=How many single-copy orthologous genes from whole genomes reveal deep gastropod relationships? |journal=PeerJ |language=en |volume=10 |pages=e13285 |doi=10.7717/peerj.13285 |pmid=35497189 |issn=2167-8359|pmc=9048639 |doi-access=free }}</ref>

* Gastropoda
** Adenogonogastropoda<ref name=":2" /> (Angiogastropoda<ref name=":1" />)
*** [[Apogastropoda]]
**** [[Caenogastropoda]]
**** [[Heterobranchia]]
*** [[Neritimorpha]]
** [[Patellogastropoda]]
** [[Vetigastropoda]] (including [[Neomphaliones]])

[[File:Turritellatricarinata.jpg|thumb|A group of fossil shells of ''[[Turritella cingulifera]]'' from the [[Pliocene]] of [[Cyprus]]]]
[[File:Fulguropsis radula 01.JPG|thumb|right|220px|Five views of a shell of a ''[[Fulguropsis]]'' species]]
[[File:Gastropoda sp.JPG|thumb|220px|Microphoto (35x) of Gastropoda sp. from Holocene sediments of Amuq Plain SSE Turkey]]

=== History ===
Since [[Charles Darwin|Darwin]], biological taxonomy has attempted to reflect the [[phylogeny]] of organisms, i.e., the [[tree of life]]. The classifications used in taxonomy attempt to represent the precise interrelatedness of the various taxa. However, the taxonomy of the Gastropoda is constantly being revised and so the versions shown in various texts can differ in major ways.

In the older classification of the gastropods, there were four subclasses:<ref>Paul Jeffery.''Suprageneric classification of class Gastropoda''. The Natural History Museum, London, 2001.</ref>
* [[Opisthobranchia]] (gills to the right and behind the heart).
* [[Gymnomorpha]] (no shell)
* [[Prosobranchia]] (gills in front of the heart).
* [[Pulmonata]] (with a lung instead of gills)

The [[Taxonomy (biology)|taxonomy]] of the Gastropoda is still under revision, and more and more of the old taxonomy is being abandoned, as the results of [[DNA]] studies slowly become clearer. Nevertheless, a few of the older terms such as "opisthobranch" and "prosobranch" are still sometimes used in a descriptive way.

New insights based on DNA sequencing of gastropods have produced some revolutionary new taxonomic insights. In the case of the Gastropoda, the taxonomy is now gradually being rewritten to embody strictly [[monophyletic]] groups (only one lineage of gastropods in each group). Integrating new findings into a working [[Taxonomy (biology)|taxonomy]] remain challenging. Consistent ranks within the taxonomy at the level of subclass, superorder, order, and suborder have already been abandoned as unworkable. Ongoing revisions of the higher taxonomic levels are expected in the near future.{{when|date=September 2024}}

[[Convergent evolution]], which appears to exist at especially high frequency in gastropods, may account for the observed differences between the older phylogenies, which were based on morphological data, and more recent gene-sequencing studies.

In 2004, Brian Simison and [[David R. Lindberg]] showed possible [[Paraphyly|diphyletic]] origins of the Gastropoda based on [[mitochondrial]] gene order and [[amino acid sequence]] analyses of complete genes.<ref>{{Cite web |title=Unitas malacologica, Newsletter number 21 december 2004 - a .pdf file |url=http://www.ucd.ie/cobid/unitas/newsletter/UMNewsletter_21.pdf |url-status=live |archive-url=https://web.archive.org/web/20110615172727/http://www.ucd.ie/cobid/unitas/newsletter/UMNewsletter_21.pdf |archive-date=15 June 2011 |access-date=9 March 2009}}</ref>

In 2005, [[Philippe Bouchet]] and [[Jean-Pierre Rocroi]] made sweeping changes in the [[systematics]], resulting in the [[Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)|Bouchet & Rocroi taxonomy]], which is a step closer to the evolutionary history of the [[phylum]].<ref name="Bouchet">Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & 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}}. 397 pp. [http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278 vliz.be] {{Webarchive|url=https://web.archive.org/web/20200714234835/http://www.vliz.be/en/imis?module=ref&refid=78278 |date=2020-07-14 }}</ref><ref>Poppe G.T. & Tagaro S.P. 2006. The new classification of Gastropods according to Bouchet & Rocroi, 2005. Visaya, février 2006: 10 pp. [http://www.journal-malaco.fr/bouchet&rocroi_2005_Visaya.pdf journal-malaco.fr] {{webarchive|url=https://web.archive.org/web/20070927101354/http://www.journal-malaco.fr/bouchet%26rocroi_2005_Visaya.pdf |date=2007-09-27 }}</ref> The Bouchet & Rocroi classification system is based partly on the older systems of classification, and partly on new [[cladistic]] research. In the past, the taxonomy of gastropods was largely based on [[phenetic]] morphological characters of the taxa. The recent advances are more based on molecular characters from [[DNA]]<ref>{{cite journal| author1=Elpidio A. Remigio| author2=Paul D.N. Hebert| name-list-style=amp| title=Testing the utility of partial COI sequences for phylogenetic (full text on line)| journal=Molecular Phylogenetics and Evolution| year=2003| volume=29| url=http://www.bolinfonet.org/pdf/MPEVsnailpaper.pdf| pages=641–647| doi=10.1016/S1055-7903(03)00140-4| pmid=14615199| issue=3| url-status=dead| archive-url=https://web.archive.org/web/20070927101355/http://www.bolinfonet.org/pdf/MPEVsnailpaper.pdf| archive-date=2007-09-27}}</ref> and [[RNA]] research. This has made the taxonomical ranks and their hierarchy controversial.

In 2017, Bouchet, Rocroi, and other collaborators published a significantly updated version of the 2005 taxonomy.<ref name="Bouchet2">Philippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. ''[http://www.bioone.org/doi/abs/10.4002/040.061.0201?journalCode=mala Revised Classification, Nomenclator and Typification of Gastropod and Monoplacophoran Families] {{Webarchive|url=https://web.archive.org/web/20230823114015/https://bioone.org/journals/malacologia/volume-61/issue-1-2/040.061.0201/Revised-Classification-Nomenclator-and-Typification-of-Gastropod-and-Monoplacophoran-Families/10.4002/040.061.0201.short|date=2023-08-23}}''. [[Malacologia]], 61(1-2): 1-526.</ref> In the [[Taxonomy of the Gastropoda (Bouchet et al., 2017)|Bouchet et al. taxonomy]], the authors used unranked [[clade]]s for taxa above the rank of superfamily (replacing the ranks suborder, order, superorder and subclass), while using the traditional [[Linnaean taxonomy|Linnaean approach]] for all taxa below the rank of superfamily. Whenever [[monophyly]] has not been tested, or is known 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.{{Citation needed|date=September 2023}}

Fixed ranks like family, genus, and species however remain useful for practical classification and remain used in the [[World Register of Marine Species]] (WoRMS). Also many researchers continue to use traditional ranks because they are entrenched in the literature and familiar to specialists and non-specialists alike.