Laminifera rhombostoma, from Böttger (1863).

Belongs within: Heterobranchia.
Contains: Triptychia, Albinaria, Clausiliinae, Alopiinae, Phaedusinae.

The Clausilioidea are high-spired land snails with well-developed plicae.

The clausilioids
Published 23 February 2009
Agathylla biloba, photographed by V. Wiese, via

The Clausilioidea are a superfamily of Stylommatophora (land snails). In the system of Bouchet et al. (2005), four families are assigned to this group—Palaeostoidae, Filholiidae, Anadromidae and Clausiliidae. The first three of these are all fossil families, so the Clausiliidae include all living clausilioids. The relationship of the fossil taxa with the Clausiliidae is up for debate—Schileyko (1979) pointed out that the Filholiidae weren’t definite clausilioids (while he also thought that Urocoptidae, since excluded from the superfamily, were), while Wade et al. (2006) noted that the “Anadromidae” might be a polyphyletic group, with some related to the Clausilioidea and others to the Acavoidea.

Another clausiliid, Cochlodina laminata, photographed by D. Tymanov.

Their fossil associates notwithstanding, the Clausiliidae themselves are a clade of undoubted integrity (Wade et al. 2006), containing nearly 1300 living species. Most clausiliids are fairly small snails, though the largest, Megalophaedusa martensi, is a little under five centimetres long. All Clausilioidea are high-spired, with long narrow shells, and the Clausiliidae possess a unique feature called the clausilium, a calcareous plate attached to the opening of the shell that functions like an operculum, closing over the opening when the snail retreats inside (hence their common name of “door snails”). The foot of clausiliids appears surprisingly short (at least to me, but then I’m no expert on snails) compared to the length of the shell. The distribution of clausiliids seems somewhat spotty—main centres are Europe, eastern Asia and South America, with the South American taxa having probably invaded from Laurasia during the Cretaceous (Wade et al. 2006).

Mating clausiliid snails, photographed by T. Asami.

In the earlier post linked to above, I referred briefly to the division in land snails (which are always hermaphrodites) between “face-to-face” and “shell-mounting” copulation. Face-to-face mating is the more familiar behaviour, where the two mating snails (or slugs) lie alongside each other facing in opposite directions, extrude their genitalia and often both fertilise each other simultaneously. Among shell-mounters, in contrast, one snail climbs on top of the other, both face in the same direction, and generally insemination is unilateral with one individual donating and the other receiving sperm (however, after the iniatial sperm-donator has finished inseminating its partner, they may repeat the process with reversed roles). The two mating behaviours are closely (though not exactly) correlated with different shell shapes—face-to-face copulators are generally low-spired and rounded (like the common garden snail), while shell-mounters are usually high-spired (Davison et al. 2005). Clausiliidae, to match their high-spired shells, are invariably shell-mounters, though at least one clausiliid genus, Albinaria, differs from the others in that both individuals fertilise each other simultaneously.

On another page where I discussed snail chirality (whether their shells were left-handed or right-handed), I mentioned that face-to-face copulators cannot generally mate if they have differing chiralities, because they can’t readily bring their genital openings alongside each other. For shell-mounters, on the other hand, inter-chiral matings are far simpler and much more likely to be successful. In light of this, one might expect to see far more cases of reversed chirality among shell-mounters than face-to-face copulators, because the disadvantages of reversed chirality would not be as significant. And according to Asami et al. (1998), this is exactly what does happen—of those snail genera they surveyed including species with reversed chirality, over 90% were high-spired forms and probably shell-mounters.

Re-opening the door
Published 14 December 2009
A fantastic shot of the clausiliid Cochlodina laminata by Dietrich Meyer. The shell of this individual was 17 mm long.

As mentioned above, one of the characteristic features of Clausiliidae (the family including all living clausilioids) is that they have very narrow, tall shells. Cain (1977) found that the distribution of shell shapes among terrestrial snails tended to be bimodal—shells were usually very long and thin or short and flatter, with very few being only slightly elongate. At least one factor in this difference in shell shapes appears to be choice of feeding territory*—elongate snails prefer grazing on very steep or vertical surfaces whereas shorter snails prefer more horizontal surfaces (Goodfriend 1986). Studies on the behaviour of the clausiliid Cristataria genezarethana by Heller & Dolev (1994) found that they spent most of their lives sheltering in crevices—an individual snail would only be active for about six to twelve days of the year. Growth was estimated to be correspondingly slow—it may take eleven years for a Cristataria to reach maturity.

*In discussing possible reasons for the bimodality of shell shapes, Cain (1977) provided a very pithy summary of the problem in studying snail behaviour—”It is of course true that most species of snail when active are nocturnal or at least crepuscular, while conchologists are largely diurnal“.

Congregation of aestivating individuals of the clausiliid snail Albinaria caerulea. This is one of the more widespread species of Albinaria, found in coastal western Turkey and the Cyclades islands of Greece, while an isolated population in Attica in Greece may have resulted from human transportation. Photo by Aydin Örstan.

Perhaps the most extensively studied clausiliid group is the Mediterranean genus Albinaria, found in southern Greece and Turkey. Albinaria shows a high level of apparent diversity—over 200 species and subspecies have been described. Many of these taxa occupy highly restricted distributions, and sympatry within the genus is rare. However, narrow hybrid zones exist between many “species”, and they can often be interbred readily in the laboratory (Douris et al. 1998), leading to the suggestion that the number of true species involved may be much lower and that many supposed “species” may instead represent ecotypes. Comparable patterns of diversity are known from other land snail genera; one of the most notorious examples is the West Indian genus Cerion, the taxonomy of which was an early research topic of Stephen Jay Gould and a strong influence in the development of his opinions on developmental constraints and evolutionary contingencies. Molecular studies of Albinaria have supported the recognition of certain species, but failed to distinguish between others (Giokas 2000). In some cases, two morphologically distinct “species” might form a clade together but remain intermixed within the clade, suggesting that they are indeed ecological variants of a single species.

Systematics of Clausilioidea
<==Clausilioidea [Clausiliacea, Clausilioidei, Clausilioinei]
| i. s.: SerrulastraE99
| |--S. amphiodonE99
| |--S. brandtiE99
| |--S. michaudiE99
| `--S. polyodonE99
| Pseudidyla moersingensisE99
| |--P. m. moersingensisE99
| `--P. m. undorfensisE99
| RegiclausiliaE99
|--Palaeostoa Andreae 1884 [Palaeostoidae]BR05
| |--*P. crenata (Sandberger 1871) [=Clausilia crenata]BR17
| `--P. exarataTTE93
| |--TriptychiaBR05
| `--Filholia Bourguignat 1877BR05
| `--*F. laevolonga (Boubée 1831) [=Bulimus laevolongus]BR17
|--Anadromidae [Anadrominae]BR05
| |--Conobulimus fuggeriTTE93
| |--Juvavina juvaviensisTTE93
| |--Anadromus Sandberger 1870BR05
| | `--*A. proboscideus (Mathéron 1843) [=Ampullaria proboscidea]BR17
| `--LycnusTTE93
| |--L. ellipticus Matheron 1832TTE93
| `--L. sanchezi (Vidal 1874)TTE93
| i. s.: MacrogastraHM07
| |--M. densestriataE99
| |--M. loryiE99
| |--M. multistriataE99
| |--M. schlickumiE99
| |--M. sessenheimensisE99
| `--M. ventricosa (Draparnaud 1801)HM07
| Rhiostoma Benson 1860GS96, BC01
| |--R. housei (Haines 1855) [=Cyclostoma (Pterocyclos) housei; incl. *R. haughtoni Benson 1860]BC01
| `--R. simplicilabre Pfeiffer 1862GS96
| AlbinariaGS96
| Isabellaria Vest 1867GS96
| |--I. adriani Gittenberger 1987GS96
| |--I. campylauchen (Boettger 1883)GS96
| |--I. confusa (Boettger 1878)GS96
| |--I. edmundi Gittenberger 1987GS96
| |--I. idyllica Gittenberger 1987GS96
| |--I. lophaechenaSG96
| `--I. vallata (Mousson 1859)GS96
| Sericata Boettger 1878GS96
| Dextrospira minutula Hrubesch 1965TTE93
| *Austrobalea africana [=Balea africana]PB27
| BabaP92
| Siciliaria (Gibbularia) gibbula (Rossmässler 1836)NB19
| |--S. g. gibbulaNB19
| |--S. g. niethammeri (Rensch 1934)NB19
| `--S. g. sanctangeli (Wagner 1925)NB19
|--Constricta Boettger 1877 [Constrictinae]BR05
| |--*C. kochi (Boettger 1877) [=Clausilia kochi]BR17
| `--C. tenuisculptaE99
|--Nenia Adams & Adams 1855 [=Neniastrum Bourguignat 1876; Neniastrinae, Neniinae, Neniini]BR05
| |--*N. tridens (Schweigger 1820) [=Clausilia tridens, *Neniastrum tridens]BR17
| `--N. bartletti (Adams 1866) [=Clausilia (Nenia) bartletti]A66
| |--Garnieria Bourguignat 1877 [Garnieriini]BR05
| | `--*G. mouhoti (Pfeiffer 1862) [=Clausilia mouhoti]BR17
| `--Tropidauchenia Lindholm 1924 [Tropidaucheniini]BR05
| `--*T. bavayi (Lindholm 1924) [=Clausilia bavayi, C. dorri var. cristata Bavay & Dautzenberg 1899]BR17
| |--Eualopia Boettger 1877 [Eualopiini]BR05
| | `--*E. bulimoides (Thomä 1845) [=Clausilia bulimoides]BR17
| `--Rillya Munier-Chalmas 1883BR05, BR17 [Rillyini]
| `--*R. rillyensis (de Boissy 1848) [=Pupa rillyensis]BR17
|--Oospiroides Wenz 1920 [Oospiroidesini]BR17
| `--*O. sinuatus (Michaud 1838) [=Clausilia sinuata]BR17
|--Polloneria Sacco 1886 [Polloneriini]BR17
| `--*P. pliocenica (Sacco 1886) [=Clausilia pliocenica]BR17
`--Laminifera Boettger 1863 [Laminiferinae, Laminiferini]BR05
| i. s.: L. miraE99
|--*L. (Laminifera) rhombostoma (Boettger 1863) [=Clausilia rhombostoma]BR17
`--L. (Laminiplica)E99
|--L. (L.) cesseyensisE99
|--L. (L.) meiniE99
`--L. (L.) villafranchianaE99

*Type species of generic name indicated


[A66] Adams, H. 1866. List of land and freshwater shells collected by Mr. E. Bartlett on the Upper Amazons, and on the River Ucayali, eastern Peru, with descriptions of new species. Proceedings of the Zoological Society of London 1866: 440–445.

Asami, T., R. H. Cowie & K. Ohbayashi. 1998. Evolution of mirror images by sexually asymmetric mating behavior in hermaphroditic snails. American Naturalist 152: 225–236.

[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.

[BC01] Boyko, C. B., & J. R. Cordeiro. 2001. Catalog of Recent type specimens in the Division of Invertebrate Zoology, American Museum of Natural History. V. Mollusca, part 2 (class Gastropoda [exclusive of Opisthobranchia and Pulmonata], with supplements to Gastropoda [Opisthobranchia], and Bivalvia). Bulletin of the American Museum of Natural History 262: 1–170.

Cain, A. J. 1977. Variation in the spire index of some coiled gastropod shells, and its evolutionary significance. Philosophical Transactions of the Royal Society of London Series B—Biological Sciences 277 (956): 377–428.

Davison, A., C. M. Wade, P. B. Mordan & S. Chiba. 2005. Sex and darts in slugs and snails (Mollusca: Gastropoda: Stylommatophora). Journal of Zoology 267 (4): 329–338.

Douris, V., R. A. D. Cameron, G. C. Rodakis & R. Lecanidou. 1998. Mitochondrial phylogeography of the land snail Albinaria in Crete: long-term geological and short-term vicariance effects. Evolution 52 (1): 116–125.

[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.

Giokas, S. 2000. Congruence and conflict in Albinaria (Gastropoda, Clausiliidae). A review of morphological and molecular phylogenetic approaches. Belg. J. Zool. 130 (Suppl. 1): 93–100.

[GS96] Gittenberger, E., & M. Schilthuizen. 1996. Parallelism in the origin of the G-type clausilial apparatus (Gastropoda, Pulmonata, Clausiliidae). In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 295–300. Oxford University Press: Oxford.

Goodfriend, G. A. 1986. Variation in land-snail shell form and size and its causes: a review. Systematic Zoology 35 (2): 204–223.

Heller, J., & A. Dolev. 1994. Biology and population dynamics of a crevice-dwelling landsnail, Cristataria genezarethana (Clausiliidae). Journal of Molluscan Studies 60 (1): 33–46.

[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.

[NB19] Nardi, G., A. Braccia, S. Cianfanelli & M. Bodon. 2019. Revision of the systematic position of Lindbergia garganoensis Gittenberger & Eikenboom, 2006, with reassignment to Vitrea Fitzinger, 1833 (Gastropoda, Eupulmonata, Pristilomatidae). Basteria 83 (1–3): 19–28.

[PB27] Pilsbry, H. A., & J. Bequaert. 1927. The aquatic mollusks of the Belgian Congo, with a geographical and ecological account of Congo malacology. Bulletin of the American Museum of Natural History 53 (2): 69–602, pls 10–77.

[P92] Poinar, G. O., Jr. 1992. Life in Amber. Stanford University Press: Stanford.

Schileyko, A. A. 1979. The sytem of the order Geophila (=Helicida) (Gastropoda Pulmonata). Transactions of the Zoological Institute, Academy of Sciences, USSR 80: 1–69.

[SG96] Schilthuizen, M., & E. Gittenberger. 1996. Allozyme variation in some Cretan Albinaria (Gastropoda): paraphyletic species as natural phenomena. In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 301–311. Oxford University Press: Oxford.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

Wade, C. M., P. B. Mordan & F. Naggs. 2006. Evolutionary relationships among the pulmonate land snails and slugs (Pulmonata, Stylommatophora). Biological Journal of the Linnean Society 87 (4): 593–610.

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