1. Gastropoda

Chapter by:

Jonathan R. Hendricks, Paleontological Research Institution, Ithaca, New York

This chapter was lasted updated by the author on March 4, 2019.

Chapter citation:

J. R. Hendricks. 2017. Gastropoda. In: The Digital Encyclopedia of Ancient Life. https://www.digitalatlasofancientlife.org/learn/gastropoda/

Chapter contents:

1. Gastropoda
–– 1.1 Shell morphology
–– 1.2 Caenogastropoda
–– 1.3 Heterobranchia
–– 1.4 Neritimorpha
–– 1.5 Vetigastropoda
–– 1.6 Patellogastropoda
–– 1.7 Cocculiniformia
–– 1.8 Neomphalina
–– 1.9 Paleozoic gastropods
–– 1.10 Gastropods in the news

Class Gastropoda

Phylum Mollusca, Class Gastropoda

Common names of representatives: snails, slugs, and limpets.

Habitat(s): marine (salt water), freshwater (lakes and streams), and terrestrial (on land).

Feeding type(s): herbivorous (algae or plant eaters), carnivorous predators (meat eaters/hunters), detritivores (feed on dead organic matter), scavengers (feed on dead animals), and parasitic (feed on living animals).

Geological range: Cambrian to today.

Clade defining feature(s): torsion (see below), head present, shell (if present) univalved.

In terms of total diversity (~70,000 living species; Brusca and Brusca, 2003) and range of habitats occupied, gastropods are one of the most evolutionarily successful groups of animals and include snails and slugs. They occupy the world’s oceans, freshwater lakes and streams, and terrestrial ecosystems, including many backyards. Some are algae-eating herbivores, while others are venomous hunters of fish. Their strong, univalved shells have left behind a rich Cambrian to Recent fossil record that has been the focus of many paleobiological studies.

The name “Gastropoda” comes from the Greek roots “Gastro” (= stomach) and “pod” (= foot). Snails were given this name because many have the appearance of crawling around on their stomachs.

A cowry snail crawling on glass, revealing the underside of its foot.Creative Commons License
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Hear pronunciation of “gastropod:”

While gastropods have many different shell shapes (or no shells at all) and lifestyles, they are united by undergoing a process called torsion during their development. Initially, the mantle cavity (which holds the gills and sensory and excretory structures) and anus are positioned at the posterior end of the animal. Later in development, these structures are rotated counterclockwise up to 180 degrees, placing the mantle cavity and the organs it houses–as well as the anus–right above the animal’s head! Further, torsion causes the gut to become U-shaped and important nerves to cross over one another. Why gastropods undergo torsion remains unclear, but they all do it. To complicate matters, some gastropods (e.g., opisthobranchs) undergo torsion early in development, but then the process reverses itself back to nearly the starting condition later in development. Importantly, torsion is not related to the coiling of the shell, and the foot of the animal is unaffected by the process.

Shell Morphology

Click here to learn more about gastropod shell morphology.

Left: specimen of the naticid gastropod Naticarius plicatella from the Tamiami Fm. (Pinecrest Beds) of Florida (PRI 70044). Right: simulated shell generated using “Shell Parameter Space” by Resman et al., (2011). http://demonstrations.wolfram.com/shellparameterspace/

Groups of Extant Gastropoda

Recent molecular phylogenetic investigations of gastropod relationships have upended the traditional taxonomic classification scheme for the Class Gastropoda. While we now know that the older classifications (which include groups like “Archaeogastropoda” and “Mesogastropoda”) are no longer tenable, creating a new, stable classification for the Gastropoda remains very much a work in progress. This is in part because molecular sequence data have not yet resulted in phylogenetic hypotheses that consistently show the same relationships among the major groups of gastropods (this is due in part to variations among analyses in both the genetic regions and organisms sampled).

What has dramatically improved, however, is our understanding of which groups of extant species constitute the major clades of Gastropoda. The following seven clades are now generally accepted (click on each for more information):


A phylogenetic hypothesis of relationships for the five major clades (excluding Neomphalina and Cocculiniformia) was published by Zapata et al. (2014, fig. 3) and is redrawn (and simplified) here:

Phylogenetic hypothesis for the five major clades of extant gastropods, excluding Neomphalina and Cocculiniformia. Redrawn (and simplified) from Zapata et al. (2014, fig. 3). Creative Commons License
This work by the Digital Atlas of Ancient Life is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

It is important to note that many generalized forms within the Gastropoda have independently evolved multiple times. That is, they are evolutionarily convergent. Notable examples include include “slugs” (gastropods lacking shells into which they can fully retract) and “limpets” (gastropods with cap-like shells). Thus, “slugs” and “limits” do not constitute monophyletic groupings; rather, they are polyphyletic in origin.

Gastropod Diversity Patterns

The graphs below illustrate broad patterns of gastropod diversity over the span of the Phanerozoic Eon, both at the genus and family levels. These data were downloaded from the Paleobiology Database Navigator. Note the broad overall trend of gastropod diversity increasing over time.

Genus-Level Data

Genus-level diversity patterns in Gastropoda. Data are from the Paleobiology Database Navigator.

Family-Level Data

Family-level diversity patterns in Gastropoda. Data are from the Paleobiology Database Navigator.

Gastropod Fossils

Worthenia tabulata from the Pennsylvanian Vamoosa Fm. of Osage County, Oklahoma (PRI 70108). Learn more here Creative Commons License
This work by the Digital Atlas of Ancient Life is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Examples of different kinds of Paleozoic gastropods may be viewed here.

Also visit the following Digital Atlas of Ancient Life pages to find out more about gastropod fossils from particular regions of the United States:

Gastropods in the News

A list of recent news stories about snails (ancient and modern) may be found here.

References for this Chapter

Bouchet, P. 2011. Neomphalina. Accessed on March 3, 2017 through WoRMS at http://www.marinespecies.org/aphia.php?p=taxdetails&id=579262.

Bouchet, P. and S. Gofas. 2013. Caenogastropoda. Accessed on February 2, 2017 through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=224570.

Costa, F. H. A., R. H. Nehm, and C. S. Hickman. 2001. Neogene Paleontology of the Northern Dominican Republic 22: The family Neritidae (Mollusca: Gastropoda). Bulletins of American Paleontology 359.

Frýda, J., P. R. Racheboeuf, B. Frýdová, L. Ferrová, M. Mergl, and S. Berkyová. 2009. Platyceratid gastropods — stem group of patellogastropods, neritimorphs or something else? Bulletin of Geosciences 84: 107-120. DOI: 10.3140/bull.geosci.1125.

Gofas, S. 2009. Cocculiniformia. Accessed on March 3, 2017 through WoRMS at http://www.marinespecies.org/aphia.php?p=taxdetails&id=156482.

Gofas, S. 2009. Neritimorpha. Accessed on February 7, 2017 through: MolluscaBase at http://www.molluscabase.org/aphia.php?p=taxdetails&id=156484.

Gofas, S. 2016. Heterobranchia. Accessed on February 3, 2017 through: MolluscaBase at http://http://www.molluscabase.org/aphia.php?p=taxdetails&id=14712.

Hartmann, H., M. Heß, and G. Haszprunar. 2011. Interactive 3D anatomy and affinities of Bathysciadiidae (Gastropoda, Cocculinoidea): deep-sea limpets feeding on decaying cephalopod beaks. Journal of Morphology 272(3): 259-279. Link.

Jörger, K. M., I. Stöger, Y. Kano, H. Fukuda, T. Knebelsberger, and M. Schröl. 2010. On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia. BMC Evolutionary Biology, 10: 323. DOI: 10.1186/1471-2148-10-323. Link.

Kohn, A. J. 2016. Human injuries and fatalities due to venomous marine snails of the family Conidae. International Journal of Clinical Pharmacology and Therapeutics, 54(7): 524-538. DOI: 10.5414/CP202630. Link.

Nakamura, K. et al. 2012. Discovery of new hydrothermal activity and chemosynthetic fauna on the Central Indian Ridge at 18–20 S. PLOS ONE 7(3): e32965. Link.

Nakano, T. and T. Sasaki. 2011. Recent advances in molecular phylogeny, systematics and evolution of patellogastropod limpets. Journal of Molluscan Studies, 77: 203-213. DOI: doi:10.1093/mollus/eyr016. Link.

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Osca, D., J. Templado, and R. Zardoya. 2015. Caenogastropod mitogenomics. Molecular Phylogenetics and Evolution, 93: 118-128. DOI: http://dx.doi.org/10.1016/j.ympev.2015.07.011. Link.

Ponder, W. F. and D. R. Lindberg. 1997. Towards a phylogeny of gastropod molluscs: an analysis using morphological characters. Zoological Journal of the Linnean Society, 119: 83-265. DOI: 10.1111/j.1096-3642.1997.tb00137.x. Link.

Raup, D. M. 1966. Geometric analysis of shell coiling: general problems. Journal of Paleontology 40: 1178-1190. Link.

Resman, J., M. Winerip, E. Cowdery, and A. Reed-Harris. 2011. Shell Parameter Space. Wolfram Demonstrations Project:  http://demonstrations.wolfram.com/ShellParameterSpace/.

Uribe, J. E., D. Colgan, L. R. Castro, Y. Kano, and R. Zardoya. 2016. Phylogenetic relationships among superfamilies of Neritimorpha (Mollusca: Gastropoda). Molecular Phylogenetics and Evolution 104, 21-31. DOI: http://dx.doi.org/10.1016/j.ympev.2016.07.021.

Zapata, F., N. G. Wilson, M. Howison, S. C. S. Andrade, K. M. Jörger, M. Schrödl, F. E. Goetz, G. Giribet, and C. W. Dunn. 2014. Phylogenomic analyses of deep gastropod relationships reject Orthogastropoda. Proceeding of the Royal Society, B, 281: 20141739. DOI: http://dx.doi.org/10.1098/rspb.2014.1739. Link.