Editing Gastropoda (section)

== Geological history and evolution ==
{{See also|List of marine gastropod genera in the fossil record}}
[[File:Trochonema.jpg|thumb|''[[Trochonema]]'' sp., an early gastropod from the Middle Ordovician of the [[Galena Group]] of [[Minnesota]].]]
[[File:JurassicMarineIsrael.JPG|thumb|Fossil gastropod and attached mytilid [[bivalve]]s on a Jurassic limestone bedding plane of the [[Matmor Formation]] in southern [[Israel]].]]

The first gastropods were exclusively marine, with the earliest known representatives appearing in the [[Furongian|Late Cambrian]] (e.g., ''[[Chippewaella]]'', ''[[Strepsodiscus]]'').<ref>{{Cite journal|title=Strepsodiscus (Gastropoda) in the Late Cambrian of Missouri |journal=Journal of Paleontology|volume=59|issue=3|pages=733–740|jstor=1304993|last1=Yochelson|first1=Ellis L.|last2=Nuelle|first2=Laurence M.|year=1985}}</ref> However, their only definitive gastropod feature is a [[coiled shell]], which raises the possibility that they may belong to the stem lineage of gastropods, or might not be gastropods at all.<ref>Budd, G. E., and S. Jensen. 2000: A critical reappraisal of the fossil record of the bilaterian phyla. Biological Reviews 75:253–295.</ref> Early Cambrian species such as ''[[Helcionella]]'', ''[[Barskovia]]'', and ''[[Scenella]]'' are no longer considered gastropods, and the small coiled ''[[Aldanella]]'' from the same period is probably not even a mollusk.{{citation needed|date=December 2024}}

It is not until the [[Ordovician]] that true [[crown-group]] gastropods appear.<ref name=":0">{{Cite journal |author=Be'Norr, K., and J. FnÍon |title=Notes on the evolution and higher classification of the subclass Neritimorpha (Gastropoda) with the description of some new taxa |journal=Geol. Et Palaeont 33 |year=1999 |pages=219–235 |url=http://www.paleoliste.de/bandel/bandel_1999d.pdf |access-date=2017-12-13 |archive-url=https://web.archive.org/web/20171213201725/http://www.paleoliste.de/bandel/bandel_1999d.pdf |archive-date=2017-12-13 |url-status=live }}</ref> By this time, gastropods had diversified into a variety of forms and inhabited a range of [[aquatic environment]]s. Fossil gastropods from the early [[Paleozoic]] are often poorly preserved, making identification difficult. However, the [[Silurian]] genus ''[[Poleumita]]'' contains at least 15 identified species. Overall, gastropods were less common in the [[Paleozoic]] than [[bivalves]].<ref name=":0" />

Most Paleozoic gastropods belong to primitive groups, some of which still exist today. By the [[Carboniferous]] period, many gastropod shell shapes found in fossils resemble those of modern species, though most of these early forms are not directly related to living gastropods. It was during the [[Mesozoic]] era that the ancestors of many extant gastropods evolved.<ref name=":0" /> One of the earliest known terrestrial gastropods is ''[[Anthracopupa]]'' (or ''[[Maturipupa]]''), found in the [[Carboniferous]] [[Coal Measure]]s of Europe.<ref>{{Cite journal |last1=Jochum |first1=Adrienne |last2=Yu |first2=Tingting |last3=Neubauer |first3=Thomas A. |date=2020 |title=First record of the Paleozoic land snail family Anthracopupidae in the Lower Jurassic of China and the origin of Stylommatophora |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/first-record-of-the-paleozoic-land-snail-family-anthracopupidae-in-the-lower-jurassic-of-china-and-the-origin-of-stylommatophora/294B5CB18D294A34BF7D814D1FD68701 |journal=Journal of Paleontology |language=en |volume=94 |issue=2 |pages=266–272 |doi=10.1017/jpa.2019.68 |bibcode=2020JPal...94..266J |s2cid=204269735 |issn=0022-3360 |access-date=2022-07-29 |archive-date=2023-08-23 |archive-url=https://web.archive.org/web/20230823114010/https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/first-record-of-the-paleozoic-land-snail-family-anthracopupidae-in-the-lower-jurassic-of-china-and-the-origin-of-stylommatophora/294B5CB18D294A34BF7D814D1FD68701 |url-status=live }}</ref> However, land snails and their relatives were rare before the [[Cretaceous]] period.<ref name=":0" />

In Mesozoic rocks, gastropods become more common in the fossil record, with well-preserved shells. Fossils are found in ancient beds from both freshwater and marine environments. Notable examples include the [[Purbeck Marble]] of the [[Jurassic]] and the [[Sussex Marble]] of the early Cretaceous, both from [[southern England]]. These limestones contain abundant remains of the pond snail ''[[Viviparus]]''.<ref name=":0" /> [[Cenozoic]] rocks yield vast numbers of gastropod fossils, many of which are closely related to modern species. The diversity of gastropods increased significantly at the start of this era, alongside that of bivalves.<ref name=":0" />

Certain trail-like markings preserved in ancient sedimentary rocks are thought to have been made by gastropods crawling over the soft mud and sand. Although these [[trace fossil]]s are of debatable origin, some of them do resemble the trails made by living gastropods today.<ref name=":0" />

Gastropod fossils may sometimes be confused with [[ammonite]]s or other shelled [[cephalopod]]s. An example of this is ''[[Bellerophon (genus)|Bellerophon]]'' from the limestones of the [[Carboniferous]] period in Europe, the shell of which is planispirally coiled and can be mistaken for the shell of a cephalopod.{{Citation needed|date=December 2024}}

Gastropods also provide important evidence of faunal changes during the [[Pleistocene]] epoch, reflecting the impacts of advancing and retreating [[ice sheets]].{{Citation needed|date=December 2024}}

[[File:Cretaceous_Gastropod_Fossils_Lebanon.jpg|thumb|Cretaceous_Gastropod_Fossils_Lebanon]]

===Phylogeny===
A [[cladogram]] showing the phylogenic relationships of Gastropoda with example species:<ref>{{Cite journal| doi = 10.1186/s12879-016-1944-x| pmid = 27793108| pmc = 5084317| issn = 1471-2334| volume = 16| issue = 1| pages = 618| last1 = Kenny| first1 = Nathan J.| last2 = Truchado-García| first2 = Marta| last3 = Grande| first3 = Cristina| title = Deep, multi-stage transcriptome of the schistosomiasis vector ''Biomphalaria glabrata'' provides platform for understanding molluscan disease-related pathways| journal = BMC Infectious Diseases| date = 2016| doi-access = free}}</ref>
{{Clear}}
{{clade
|label1=Gastropoda
|1={{clade
   |1={{clade
      |1={{clade
         |1={{clade
            |1={{clade
               |1={{clade
                  |1=[[Panpulmonata]] [[Panpulmonata#Cladogram|►]] [[File:False Limpet Shell Macro Digon3.jpg|100x100px]][[File:Ancylus fluviatilis O.F.Müller, 1774 (4206383684).jpg||100x100px]][[File:Grapevinesnail 01a.jpg|100x100px]][[File:Biomphalaria glabrata.jpg|100x100px]]
                  |2=[[Euopisthobranchia]] [[Euopisthobranchia#Cladogram|►]] [[File:Aplysia californica NHGRI-79108.jpg|100x100px]]
                  }}
               |2=[[Nudipleura]] [[Nudipleura#2010 taxonomy|►]] [[File:Glaucus atlanticus 1 cropped.jpg|100x100px]]
               }}
            |2=[[Caenogastropoda]][[File:Ampullaria ampullacea (Linné) (2999358117).jpg|100x100px]][[File:Acicula lineata (Draparnaud, 1801) (4309322782).jpg|100x100px]][[File:Epitonium-scalare--Trp-6.png|100x100px]][[File:Charonia tritonis.png|100x100px]][[File:Acanthina brevidentata (Wood, 1828) (3063441884).jpg|100x100px]][[File:Neverita didyma.jpg|100x100px]][[File:Oncomelania hupensis.jpg|100x100px]]
            }}
         |2=[[Neritimorpha]][[File:Theodoxus anatolicus (Récluz, 1841) (3000195752).jpg|100x100px]]
         }}
      |2=[[Vetigastropoda]][[File:Angaria Delphinus Shell Macro.JPG|100x100px]][[File:Oxystele variegata - ZooKeys-365-337-g004A.jpg|100x100px]][[File:Lucapina suffusa (Reeve, 1850) (4947706383).jpg|100x100px]][[File:Fissurella nimbosa Linné, 1758 (4426866577).jpg|100x100px]]
      }}
   |2=[[Patellogastropoda]] [[Patellogastropoda#2007 taxonomy|►]][[File:Patelloida pustulata (Helbling, 1779) (4631972937).jpg||100x100px]]
   }}
}}

[[Neomphaliones]] and [[Lower Heterobranchia]] are not included in the above cladogram.