Helicinae

Belongs within: Helicoidei.
Contains: Helix.

The Helicinae is a group of snails native to the western Palaearctic, though several species have become distributed around the world through human transportation. Perhaps the best known such species is the garden snail Cornu aspersum, a large species with a globose brown shell patterned with lighter speckles and spiral bands. The white Italian snail Theba pisana is another widespread invasive species (particularly in hotter, drier habitats) with a white shell that may or may not be marked with spiral brown lines. The European banded snails of the genus Cepaea have historically received much attention as model species for studying population variation.

Cornu aspersum

Published 29 October 2009

The specimen illustrated above is a “scalariform” variant of the common garden snail, showing a developmental abnormality where the whorls of the shell, instead of coiling right up against each other, have grown spaced apart. In case by some incredible turn of events you don’t have five thousand of them crawling around in your back garden, a normal garden snail looks like this:

The special significance of that particular scalariform specimen is that it is the type specimen of Cornu copiae, type ‘species’ of the genus Cornu (the image is the illustration that appeared with the original description by Ignaz von Born in 1778). If the garden snail is regarded as distinct enough from Helix pomatia, the edible snail*, to be placed in a separate genus, Cornu is the oldest genus name that has been applied to a specimen of Cornu aspersum. However, there has been a lengthy debate about whether the name Cornu is properly available, which is why some authors have used the genus names Cantareus and Cryptomphalus (the following is based on info from websites here and here).

*So called because its the species most often used for eating. Cornu aspersum is apparently also quite edible, though I’ve never tried myself. If you do want to eat garden snails, I’m told that you should collect them live and feed them on flour for a couple of days before eating, so that any distasteful plant matter they may have eaten themselves has time to clear from their gut.

The ICZN states that names based on “teratological specimens as such” are not treated as valid names for species (Article 1.3.2). Some authors have therefore claimed that Cornu, whose type specimen is undoubtedly teratological, is invalid. Other authors, whom I would agree with, point out the use of the words “as such” and interpret the rule to mean that names based on teratological specimens are only invalid if they were published with the knowledge that the specimen was teratological (supporting this is Article 17.3 which states that the availability of a name is not affected by its being based on “a specimen which is an unusual example of the taxon”; also, normal vs. teratological is often a matter of degree rather than clear division). The use of Latin names as labels for unusual variants of known species was common practice in the eighteenth and nineteenth centuries (and even a little bit into the twentieth; botanists still follow this practice under certain circumstances). One example of such a label that remains in use today is the reference to the black form of the peppered moth Biston betularia as the “carbonaria form”. Such variant names were never intended by their original users to refer to any sort of evolutionarily or populationally distinct “species-level” taxon, which is why the ICZN excludes them. In his original description of Cornu copiae, Born gave no indication that he recognised the specimen as an unusual variant of Helix aspersa rather than a validly distinct species, so we can only assume that he genuinely believed it to be the latter (if he had specifically written something like “this unusual specimen of Helix aspersa to which I give the name Cornu copiae” it would have indicated otherwise).

Systematics of Helicinae

<==Helicinae [Belogona, Paurotaenia, Paurotaeniae, Siphonadenia]
    |  i. s.: Cornu Born 1788 [incl. Cantareus Risso 1826, Cryptomphalus de Charpentier 1837]SS10
    |           `--*C. aspersum (Müller 1774)SS10 (see below for synonymy)
    |         Eobania Hesse 1913C84, SS10
    |           `--*E. vermiculata (Müller 1774) [=Helix vermiculata]SS10
    |         Pseudotachea splendidaC84
    |         Alabastrina alabastritesC84
    |         LevantinaC84
    |           |--L. caesareanaC84
    |           `--L. hierosolymaH84
    |--Otala Schumacher 1817BR05 [OtaliniBR17]
    |    |--*O. lactea (Müller 1774) [=Helix lactea]BR17
    |    |--O. punctataC84
    |    `--O. vermiculataC63
    |--Allognathini [Allognathidae]BR17
    |    |--Allognathus Pilsbry 1888BR05
    |    |    `--*A. grateloupi (Graëlls 1846) [=Helix grateloupi]BR17
    |    `--Lampadia Albers 1854 [=Mitra Albers 1850 non Lamarck 1798; Lampadiini]BR17
    |         `--*L. webbiana (Lowe 1831) [=Helix webbiana, *Mitra webbiana]BR17
    |--ThebiniBR05
    |    |--‘Euparypha’ Hartmann 1843 (nom. rej.) [Euparyphinae, Euparyphini]BR05
    |    |    |--*E. rhodostoma (Draparnaud 1801) [=Helix rhodostoma]BR17
    |    |    `--E. areolata [=Helix (Euparypha) areolata]C64
    |    `--Theba Risso 1826SS10 (see below for synonymy)
    |         |--*T. pisana (Müller 1774)SS10 (see below for synonymy)
    |         `--‘Helix’ albella Linnaeus 1758BR05 [=*Jacosta albellaBR17, *Leucochroa albellaBR17]
    `--HeliciniBR05
         |--HelixBR05
         |--Creneatachea Zilch 1960 [incl. Crenea Albers 1850 non Risso 1826, Crena (l. c.); Crenae, Creneini]BR17
         |    `--*C. obtusecarinata (Sandberger 1858) [=Helix obtusecarinata]BR17
         |--Metachloraea Pfeffer 1930 [Metachloraeae, Metachloraeini]BR05
         |    `--*M. oxystoma (Thomä 1845) [=Helix oxystoma]BR17
         `--Cepaea Held 1837 [Cepaeae, Cepaeini]BR05
              |--*C. nemoralis (Linnaeus 1758)BR17 (see below for synonymy)
              |    |--C. n. nemoralisS84
              |    `--C. n. apenninaS84
              |--C. concudensisE99
              |--C. hortensis (Müller 1774)HM07 (see below for synonymy)
              |--C. moroguesiE99
              |--C. silvanaE99
              |--C. subsulcosaE99
              `--C. vindobonensis (Férussac 1821)HM07

Cepaea hortensis (Müller 1774)^HM07 [=Helix (Acavus) hortensis^G40, H. nemoralis var. hortensis^A79, Tachea hortensis^C83; incl. Cochlea fasciata^G40]

*Cepaea nemoralis (Linnaeus 1758)^BR17 [=Helix nemoralis^BR17, H. (Acavus) nemoralis^G40, Tachea nemoralis^G40; incl. H. cincta^G40, H. qunquefasciata^G40, H. turturum^G40, Cochlea versicolor^G40]

*Cornu aspersum (Müller 1774)^SS10 [=Helix aspersa^C84, Cantareus aspersus^WFS04, Cryptomphalus aspersus^S84, Helix (Acavus) aspersa^G40; incl. Serpula cornucopia^G40, H. aspersa var. exalbida^H79, Cornucopia helicina^G40, Serpula helicina^G40, Cornucopia monstrosa^G40, Cochlea vulgaris^G40]

Theba Risso 1826^SS10 [=Xerophila Held 1837 (nom. rej.)^BR05; incl. Jacosta Gray 1821 (nom. rej.)^BR05, Leucochroa Beck 1837^BR05; Jacostidae, Leucochroea, Leucochroidae, Leucochroinae, Thebinae, Xerophilidae, Xerophilinae]

*Theba pisana (Müller 1774)^SS10 [=Helix pisana^SS10, H. (Heliomanes) pisana^G40, *Xerophila pisana^BR17; incl. H. multilineata var. albina^{W79, G40}, H. cingenda^G40, Teba cingenda^G40, H. petholata^G40]

*Type species of generic name indicated

References

[A79] Ashford, C. 1879. Land and freshwater shells observed in the neighborhood of Redcar. Journal of Conchology 2: 236–241.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[C83] Cain, A. J. 1983. Ecology and ecogenetics of terrestrial molluscan populations. In: W. D. Russell-Hunter (ed.) The Mollusca vol. 6. Ecology pp. 597–647. Academic Press.

[C84] Cain, A. J. 1984. Heterosematism in snails. Malacologia 25 (1): 161–172.

[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

[C63] Curtin, T. J. 1963. Snails from Turkey, Crete and Greece. Nautilus 76 (4): 132–135.

[E99] Esu, D. 1999. Contribution to the knowledge of Neogene climate changes in western and central Europe by means of non-marine molluscs. In: J. Agustí, L. Rook & P. Andrews (eds) The Evolution of Neogene Terrestrial Ecosystems in Europe pp. 328–354. Cambridge University Press.

[G40] Gray, J. E. 1840. A Manual of the Land and Fresh-water Shells of the British Islands, with figures of each of the kinds. By William Turton, M.D. A new edition, thoroughly revised and much enlarged. Longman, Orme, Brown, Green, and Longmans: London.

[H84] Heller, J. 1984. Shell colours of desert landsnails. Malacologia 25 (2): 355–359.

[H79] Hey, W. C. 1879. Contributions to a better knowledge of the land and freshwater shells of Yorkshire. Journal of Conchology 2: 310–314.

[HM07] Honek, A., & Z. Martinkova. 2007. A field method for quantifying the grazing activity of slugs, with particular reference to Arion lusitanicus (Mollusca). Malacologia 49 (2): 273–281.

[S84] Sacchi, C. F. 1984. Population ecology of Cepaea nemoralis and C. vindobonensis along the north Adriatic coasts of Italy. Malacologia 25 (2): 315–323.

[SS10] Stanisic, J., M. Shea, D. Potter & O. Griffiths. 2010. Australian Land Snails vol. 1. A. field guide to eastern Australian species. Bioculture Press: Mauritius.

[W79] Walker, B. 1879. Catalogue of the shell-bearing Mollusca of Michigan. Journal of Conchology 2: 325–337.

[WFS04] Winks, C. J., S. V. Fowler & L. A. Smith. 2004. Invertebrate fauna of boneseed, Chrysanthemoides monilifera ssp. monilifera (L.) T. Norl. (Asteraceae: Calenduleae), an invasive weed in New Zealand. New Zealand Entomologist 27: 61–72.