Cochlostomatidae

Cochlostomas (Cochlostomatidae) are terrestrial snails with a shell lid (operculum) at their foot's end, more closely related to sea-living gastropods than to other terrestrial ones. In that they are similar to the round mouthed snails (Pomatiidae) and some other terrestrial operculate snail groups. But that is as close as the relationship goes, because they are no more closely related than being snails. Cochlostomas are most closely related to apple snails (Ampullarioidea) and thus to fresh-water living snails, such as the mud snails (Viviparidae). Round mouthed snails, on the other hand, are most closely related to the sea-living periwinkles (Littorinidae). That could mean that during the evolution of Cochlostomas their ancestors first occupied the fresh water from the sea, which led to the evolution of a group resembling the mud snails, of which then another group managed to occupy dry land. In the evolution of round mouthed snails, this development took place directly. And so it still does in the group of the coast snails (Ellobioidea), of which one recent terrestrial group are the thorn snails (Carychiidae).


Cochlostoma septemspirale from Switzerland.
Picture: Stefan Haller, (schneckenfoto.ch).
 
 
Cochlostoma henricae.
Picture: Helmut Nisters.

Cochlostomas have a turricular pointed shell with more or less rounded whorls and a circular aperture with a wide apertural lip. The shell surface shows a surface structure of more or less dense ribs, form and density of which are used for identification purposes like in the group of the door snails (Clausiliidae). Like round mouthed snails, Cochlostomas also have separate sexes.

Systematics

Class: Gastropoda
Subclass: Orthogastropoda
Superorder: Caenogastropoda
Order: Architaenioglossa
Superfamily: Cyclophoroidea
Family: Cochlostomatidae Kobelt 1902

Systematics of Gastropoda: Clade Caenogastropoda: Cyclophoridae resp. Cochlostomatidae.

Cochlostomas are among those snail groups that do not have a common or vernacular name, possibly because they are not well enough known to the general public. Cochlostoma, by the way, is Greek and means "circular mouth", referring to the rounded aperture of those snails.

 
Cochlostoma septemspirale, from the Salzkammergut, Austria.
Picture: Martina Eleveld.

Today, the genus Cochlostoma is divided into three subgenera, apart from Cochlostoma Jan 1830, those are Turritus Westerlund 1883 and Obscurella Clessin 1889.

Mollbase: Cochlostomatidae.

Small Cochlostoma - Cochlostoma (Cochlostoma) septemspirale (Razoumowsky 1789)

Description: The small Cochlostoma has a greyish-brown shell with three logitudinal rows of reddish brown spots. The shell surface is structured with six transversal ribs per millimetre. The shell mouth inside is white. The operculum is of a horn-like flexible consistence.

There is no considerable sexual dimorphism in Cochlostoma septemspirale. The snail's foot is undivided.

A picture of Cochlostoma septemspirale by Stefan Haller.


Cochlostoma septemspirale from Switzerland.
Picture: Stefan Haller, (schneckenfoto.ch).
 

Dimensions: H: 6.7 - 10.2 mm; W: 3.2 - 4.4 mm; N: 7 - 10. (Abbreviations).

Habitat and Distribution: The small Cochlostoma lives on calcareous ground, on rocks and trees, during dry periods also in the leaf litter and between rock rubble. The animal is rather slow-moving, very shy and only active during humid weather, closing the operculum during dryness. When the weather is wet enough, the small Cochlostoma can crawl up trees in a height of 2 metres. Cochlostoma septemspirale feeds on the remains of plants and grazes algae off stones and tree bark.

The distribution area of this species stretches from the Pyrenees over South Europe and southern Germany as far east as the Central Balkan Peninsula. There are no species of Cochlostoma on the British Isles (Anderson, R., 2008 - PDF).

In the mountains, the small Cochlostoma lives in altitudes of up to 2100 m MSL. In Germany, Cochlostoma septemspirale can be found in the Upper Rhine area, in south-eastern Bavaria, in the vicinity of Kelheim upon Danube and near the lowest part of the Altmühl river, a Danube tributary.

In Austria, two subspecies of Cochlostoma septemspirale are distinguished: C. s. septemspirale (Razoumowsky 1789) and C. s. heydenianum (Clessin 1879).

Francisco Welter-Schultes: Cochlostoma septemspirale species homepage.


With pictures by Stefan Haller:
http://www.schneckenfoto.ch.