Door Snails Part IClausiliidae J. E. Gray, 1855 |
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| Door Snails (Clausiliidae) Part I | Door Snails (Clausiliidae) Part II | Door Snails (Clausiliidae) Part III |
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 Ruthenica filograna: Alpes-Maritimes, Provence-Alpes-Côte d'Azur, France. Photo: Gaëtan Jouvenez (iNaturalist). |
 Micropontica caucasica: Harz, Saxony-Anhalt, Germany. Photo: Tuber (iNaturalist). |
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 Nenia tridens: Canóvanas, Puerto Rico. Photo: Scott Bolick (iNaturalist). |
 Tauphaedusa tau: Sakyo Ward, Kyoto, Japan. Photo: Thomas Hernandez (iNaturalist). |
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Hartmut Nordsieck (1940 - 2022) on hnords.de: Comprehensive homepage on the topic of Clausiliidae: General Information, Extant Clausiliidae, Fossil Clausiliidae and Publications. |
 Alopia lischkeana cybaea: Zărnești, Brașov, Romania. Photo: Phil Benstead (iNaturalist). |
However, most door snails are smaller than 20 mm, only the largest door snail species native to Central Europe, the Ventricose Door Snail (Macrogastra ventricosa) grows to 19 mm shell length. The Small Door Snail (Clausilia rugosa parvula) on the other hand, true to its name, only reaches 9.5 mm shell length at most.
The largest of all door snail species, however, is not European, but Japanese: Megalophaedusa martensi (Photo below, on the right) can be more than 40 mm high!
 Neniatlanta pauli (Clausiliidae, Laminiferinae): Pyrénées At- lantiques, France. Photo: Maëlan Adam (iNaturalist). |
 Megalophaedusa martensi from Shizuoka, Japan. Photo: Takahashi, Wikipedia. |
Suborder:
Helicina
Superfamily: Clausilioidea
Family: Clausiliidae J. E. Gray, 1855
Source:
MolluscaBase eds. (2025):
Clausiliidae J. E. Gray, 1855.
Door Snails (Clausiliidae): Systematic List (Concise Version).
 Dubious Door Snail (Clausilia dubia). Photo: Martina Eleveld. |
Schileyko,
A. A. (2000): "Treatise on recent terrestrial pulmonate molluscs". Part 5.
Clausiliidae. - Ruthenica Suppl. 2 (5): 565 - 729.
 Balea perversa: Chateu de Dave, Namur, Belgium. Photo: Gilles San Martin (iNaturalist). |
Wolfgang
Weitlaner: "Geheimnis
der fliegenden Schnecke geklärt" (Innovationsreport.de, 27.01.2006, in
German).
Apart from their characteristic shell shape, the European door snail species are also different from most other snail species in that their shell is in most cases sinistral, i.e. coiled to the left instead of to the right. There are, however, species in some Clausiliid groups which are dextral, for example in the Alopiinae subfamily. Among those are the genus Alopia native to the Carpathian Mountains, as well as the genus Albinaria native to the Balkan region, both of which contain dextral species. And finally, so is the genus Cochlodina native to Central Europe, with species, such as the Plaited Door Snail (Cochlodina laminata) and the Pale Door Snail (Cochlodina fimbriata).
Door snails usually feed on algae they scrape off the substrate using their radula. Like the other terrestrial pulmonate snails, they are hermaphrodites. However, there are some door snail species like the European Common Door Snail (Alinda biplicata), which are ovoviviparous. That means that oviposition is delayed until the juveniles have hatched inside the mother's body and are born alive. There is also the possibility of eggs with developed embryos to be laid.
Their characteristic shell shape means a decisive evolutionary advantage for door snails: During dry periods they can hide in the smalles crevices in rocks or bark. This is especially important in the region of Europe where most different species are found: While the family as such has a palearctic distribution, most species are found on the Balkan peninsula, especially in Greece, also in Asia Minor and in the Caucasus mountains.
 Common Door Snail (Alinda biplicata) grazing algae on a stone. Videos: Martina Eleveld: View videos in new window!
Video 1.
Video 2. |
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"The Common Door Snail still is quite frequent,
however, some species of the family in Europe are very rare and their
populations threatened. Since the species predominantly lives in crevices, those
creatures also live in some of the most threatened biotopes, such as old stone walls,
isolated rocks and deadwood. In our gardens we can, however, also offer living sites and protection to those interesting creatures, if only not all crevices in walls are mortared up and some old wood or rocks is left lying in the shadows. Apart from door snails, there are also various other animal groups that will begin to use those hiding places and improve the garden's ecological value." Source: Weichtier des Jahres 2010 (Mollusc of the Year): Die Gemeine Schließmundschnecke (Common Door Snail)- Alinda biplicata (Montagu 1803) (In German). |
 Common Door Snail (Alinda biplicata): Bergh, Gelderland, Netherlands. Photo: Walter Wimmer (iNaturalist). |
 Papillifera papillaris: Hérault, Languedoc-Roussillon, France. Photo: Philippe Geniez (iNaturalist). |
Apart from form and sculpture of the shell, there is also the form of the
shell mouth (aperture) to be taken into consideration. There are round, oval and
even pear-shaped shell mouth. To identify the door snail species most common in
Europe, the aptly named Common Door Snail (Alinda biplicata), the neck
of the apertural whorl can be used: It has a characteristic neck groove (
Show picture in new window!).
Generally, all snail shells are compared from a point of view looking at the aperture with the shell tip looking up. Only that way distinguishing characters can be determined and compared specifically:
 Closing Apparatus (Clausiliar) of a door snail (Alinda biplicata). Photo: Jiří Novák, biolib.cz.
Enlarge with description! |
According to their position in the aperture, three main types of folds can be distinguished: The palatal folds in the outer wall of the apertural whorl. Opposite of those, on the side of the shell spindle (columella) there is the lower or columellar fold. Above it, on the upper rim of the apertural whorl, there is the upper or parietal fold. Below the columellar fold, there can be a further one called the subcolumellar fold.
Those fold, also called lamellae on the parieto-columellar (upper right) side, are parts of the clausiliar apparatus, a closing apparatus unique among gastropods from which the door snails derive their unusual name. The exact composition of this closing apparatus, however, can only be seen if the shell is opened using a pair of tweezers and examined using a binocular.
 Apertural spire of Alinda biplicata, opened. Visible are the shell spire (Columella) and the Clausilium. Photo: Mathijs Zonneveld (iNaturalist).
Enlarge! |
Closing apparatus (Clausiliar) of door snails: Schematic drawings with
description. Shown in the following text as
.
Hartmut Nordsieck:
hnords.de:
Für die
Bestimmung notwendige Fachausdrücke des Schließapparats (In German).
In most clausiliid species then a spoon-shaped calcareous plate becomes visible whith an elastic stem connected to the shell spindle (columella). When the snail is extended and moving around, this so-called clausilium is pressed against the shell wall. As soon as the snail withdraws into its shell, because of its elastic stem, the clausilium swings around, closing the shell mouth (aperture) (see picture on the right).
In 1982, H. Nordsieck was able to prove that
the clausilium most likely developed from one of the columellar lamellae ()
in an ancestral group of today's door snails, since this lamella is still
present in certain fossil species, but missing in today's door snails. However,
the latter do possess a clausilium, while the fossil species do not.
Nordsieck,
H. (1982): Die Evolution des Verschlußapparats der Schließmundschnecken
(Gastropoda: Clausiliidae). Arch. Moll. I 112 (1981) I (1/6) I 27—43. (Link).
The importance of the closing apparatus or clausiliar for the evolution of door snails is not entirely clear. However, H. Nordsieck (1982) already was of the opinion that the clausiliar most likely is a further means of protection against dryness and consequent desiccation, especially taking into account that a distribution hotspot of contemporary door snail species in Europe are the Balkan Peninsula and Asia Minor.
Hartmut Nordsieck:
hnords.de:
Sammeln
und
Bearbeitung
von Schließmundschnecken (In German).
 An example of a habitat of the Stocky Door Snail in Czechia. Hillside forest with ash trees in Domaslavické Údolí National Park. Source. |
 One dark and one amelanistic specimen of Pseudofusulus varians. Photo: Tomàš Burian, Source. |
Hartmut Nordsieck:
hnords.de: Hybridization in European Clausiliidae.
In the face of the partly quite small distribution areas of singular species of door snails, human influence can have special importance, since similar to island populations, endemic snail species can be threatened by roadworks, agriculture and environmental decline and thus large and irreversible damage can be caused. An example can be Pseudofusulus varians, a species already extinct in parts of its distribution area (the species occurs in the Eastern Alps and in the Northwestern Carpathians) or at least strongly reduced in numbers.
Pseudofusulus varians only lives in decidual forests with a large amount of deadwood, left to nature and not influenced by humans. Because of deforestation and removal of deadwood, the species' habitats are destroyed and entire populations disappear.
Stocky Door
Snail
(Pseudofusulus varians).
Common Door
Snail -
Alinda biplicata (Montagu, 1803).
 Common Door Snail (Alinda biplicata). Photo: Sigrid Hof (Source). |
 Common Door Snail (Alinda biplicata) with a discus snail (Discus rotundatus). Photo: Martina Eleveld.
Enlarge! |
Description: The shell of the Common Door Snail is light
brown and relatively large. The shell surface shows distinctively visible ribs
accentuated in white. The density of those ribs on the last whorl of the shell
is about 6 - 7 ribs per millimetre. The slightly widened apertural lip does not
display any folds, and the aperture is slightly pointed at the bottom, with a
distinctive basal groove. The lower lamella is simple, an upper parietal lamella
is visible, looking into the aperture from a perpendicular view. .
Dimensions: H: 16 - 18 (- 22) mm; W: 3,8 - 4 mm.
Ecology and Distribution: The Common Door Snail predominantly lives in shadowy, rather humid places in the leaf litter of forests, on deadwood, ground vegetation (such as nettles), between rocks and on old stone walls. The snail is mainly ground dwelling but tends to climb up trees in humid weather. In man-made habitats, it is also often found and thus is among the door snail species most likely to be found in gardens, especially if there is also a stone wall. Dwarf forms of Alinda biplicata also are found in warm and dry (xerothermic) places. The species does prefer biotopes on calcareous ground.
Alinda biplicata generally is ovoviviparous, which means live juveniles are born, previously hatched in the mother's body. Favourable environmental conditions prevailing, it can also lay up to 11 eggs.
The Common Door Snail's distribution area spread over vast parts of Central Europe, from Northern France, Belgium and the Netherlands over Germany, Switzerland, Austria, Czechia and Slovakia as far as Hungary, Western and Southern Poland, in the Southwest as far as Bulgaria. In Southern England, the species is found in the Thames valley and in Eastern Cornwall; it has also successfully settled in gardens. Fossils from the Holocene epoch point towards the fact that the species apparently is domestic there. In isolated places, the species is also present in Denmark, Sothern Sweden and Southern Norway. This, however, might be due to introduction by humans.
In Switzerland, the Common Door Snail is found in altitudes of up to 800 m, in Austria and Bulgaria even up to 2300 m.
Bosnian Door Snail - Herilla bosniensis (Vest, 1867)
 Bosnian Door Snails (Herilla bosniensis) in their natural habi- tat in the Klausen gorge near Mödling, Lower Austria. Photo: © Alexander Mrkvicka, Vienna. |
 The view into the Klausen gorge near Mödling (Lower Aus- tria). Photo: Martina Eleveld.
Enlarge! |
Bosnian Door Snail
(Herilla bosniensis).
Italian Door Snail - Papillifera papillaris (O.F. Müller, 1774)
 Italian Door Snails (Papillifera bidens), two specimens ma- ting. Photo: Sigrid Hof (Source). |
A further presence of the species had already been known and identified since 1993 from the small Brownsea Island in Dorset on the English southern coast near Bournemouth. That population apparently had been introduced on rocks from Greece in the 1880s, but apparently belonged to the same species.
In the beginning, the door snails found in England had been identified as Papillifera bidens (Linnaeus, 1758). While a search went in England on for further populations of the species, which thankfully is rather distinctive, a rather heated discussion broke out among scholars, what the correct scientific name of the species was supposed to be.
The original name Papillifera papillaris first was abandoned for an older and therefore more valid name, Papillifera bidens (Linnaeus, 1758), which was also published in an IUCN Opinion in 2007. On the other hand, Kadolsky (2009) stated the opinion, that this name was not correct either since Linné originally had described another species, which today is called Cochlodina incisa. This species, however, is at best remotely similar to Papillifera bidens, since both are door snail. Therefore, H. Nordsieck, for example, expressed the opinion that Kadolsky's conclusions were untenable and the scientific name Papillifera bidens was absolutely correct.
In the end, the door snails found in Great Britain were included in the species Papilifera papillaris and the species name bidens, on the other hand, was used for a species of Cochlodina from Italy, which had formerly been called Clausilia (or Cochlodina) incisa and since is called Cochlodina bidens (Linnaeus, 1758) (see below).
Description,
ConchBooks).
 |
| The Homepage of Hartmut Nordsieck about Helicoidea, Cochlostoma and Clausiliidae at hnords.de |
Latest Change: 26.07.2026 (Robert Nordsieck).
