Discus Snails

Discidae Thiele, 1931 (1866)
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Eastern Wood Snail (Anguispira alternata): Leamington,
Ontario, Canada. Photo: Cameron Chevalier (iNaturalist).
Systematics

Stylommatophora
Unterordnung Helicina
Überfamilie Discoidea
Familie Discidae
Gattung Gonyodiscus
Gonyodiscus rotundatus (O.F. Müller, 1774)

Source: MolluscaBase eds. (2025): Gonyodiscus rotundatus (O. F. Müller, 1774).


Anguispira picta: Tennessee, USA.
Photo: Turner Brockman (iNaturalist).		  
The Discus Snails (Discidae) are a part of the superfamily of Discus Snails s.l. (Discoidea), and as such belong to the terrestrial pulmonate snails (Stylommatophora). As to the family's correct naming, there is some controversy:

The former scientific name Patulidae Tryon 1866 was derived from a younger synonym of Discus Fitzinger, 1833 - Patula Held 1837. However, it was deemed older and therefore more valid than the family name Discidae Thiele 1931 and thus CLECOM, as well as Mollbase, state this as the correct scientific name of the discus snail family.

In older publications, the genus Discus had been counted among the family Endodontidae Pilsbry 1895; however, the current scientific opinion does not support that: The current systematics by MolluscaBase based on Bouchet and Rocroi (2005) uses the family name Discidae (s.o.). This family contains the name-giving genus Discus (e.g. Discus ruderatus M. Hartmann, 1821), as well as the genus Gonyodiscus (e.g. Gonyodiscus rotundatus), apart from seven other genera (among them Anguispira, see pictures). The genus Patula on the other hand, today also is listed as Discus.

Bouchet, P.; Rocroi, J.-P. (2005): Classification and nomenclator of gastropod families. Malacologia. 47 (1-2): 1-397. (Link).
Salvador, R. B.; Brook, F. J.; Shepherd, L. D.; Kennedy, M. (2020). Molecular phylogenetic analysis of Punctoidea (Gastropoda, Stylommatophora). Zoosystematics and Evolution. 96(2): 397-410. (Link).

The Discus snails (Discidae), three species of which are native to Europe, are small. With a shell width of only 5 to 7 mm, they nevertheless are easily visible with an educated eye on fallen tree trunks and in the undergrowth. Their vernacular, as well as their scientific name is derived from the flat discus or lens shaped shell.

Spotted Discus Snail - Gonyodiscus rotundatus (O. F. Müller, 1774)


Spotted Discus Snail (Gonyodiscus rotundatus).
Photo: Robert Nordsieck.		  
   

Photo: Helmut Nisters.		  
Description: The Spotted Discus Snail (Gonyodiscus rotundatus) is most frequently encountered in Central Europe. It is different from its relative, the Brown Discus Snail (Discus ruderatus, see picture below), by a flatter shell with a more pronounced keel and a more strongly ribbed shell surface coloured in characteristic reddish-brown, equally spaced, transversal bands. The shell navel (umbilicus) in Gonyodiscus rotundatus is wider than one third of the shell's diameter.

  Discus rotundatus und Alinda biplicata
Spotted Discus Snail (Gonyodiscus rotundatus, below) and
Common Door Snail (Alinda biplicata, above).
Photo: Martina Eleveld.
   
 
Brown Discus Snail (Discus ruderatus) Sverdlovsk, Russia.
Photo: Alexey Yabs (iNaturalist).
Photo of Discus rotundatus by Stefan Haller.

Dimensions: W: 5,5 - 7 mm; N: 5½ - 6.

Habitat and Distribution: The Spotted Discus Snail lives in sheltered humid places of any kind: In forests, the snail is found in the undergrowth and under stones, between herbs, in the grass and on fallen tree trunks, often also under garden debris. In Grisons, Switzerland, Gonyodiscus rotundatus has been found in altitudes as high as 2700 m MSL.

The Spotted Discus Snail is almost ubiquitous in Central Europe, the species' distribution area even stretches as far north as southern Scandinavia: There it has been distributed by man (anthropogenically), in Finland it even lives in gardens and greenhouses. In Hungary, the species is only found in mountainous regions naturally, apart from that it lives in greenhouses in different locations.

A relative, the Brown Discus Snail (Discus ruderatus see picture left), on the other hand, has a one-colour brownish shell, lacking the characteristic transversal bands. Also, in Discus ruderatus the umbilicus is wide less than a third of the overall shell width.

Links

Wikipedia: Discidae.
Biolib.cz: Endodontidae (Systematic name obsolete).
Naturportal Südwest: Discidae (Schüsselschnecken).

Literature

Fechter, R.; Falkner, G.: "Weichtiere" (1990), Mosaik-Verlag München, p. 170 (In German).
Kerney, M.P.; Cameron, R.A.D.; Jungbluth, J.: "Die Landschnecken Nord- und Mitteleuropas" (1983), Parey-Verlag Hamburg und Berlin. pp. 135 cont. (In German).
Wiese, V. (2024): Die Landschnecken Deutschlands" (3. Ed.). Quelle und Meyer Verlag, Wiebelsheim, pp. 160 cont. (In German).
Geyer, D. (1927): "Unsere Land- und Süßwassermollusken" (3. Ed.). K. G. Lutz Verlag Stuttgart. pp. 68 cont. (In German).

Complete Species List for Austria

Source: MolluscaBase eds. (2025): Discidae Thiele, 1931 (1866).

 

Latest Change: 25.10.2026 (Robert Nordsieck).