Species Account

Pododesmus squama (Gmelin 1791)

Anomioidea : Anomiidae

Tebble name: Monia squama (Gmelin)
Smith & Heppell name: n/a

To size: To 25mm. Shell Structure: Upper valve thin to fragile, opaque to hyaline; lower valve very thin, hyaline. Equivalve: Inequivalve, upper (left) valve convex; lower (right valve) flat. Equilateral: Inequilateral, beaks close to the middle of the dorsal margin. Tumidity: Profile flat. Outline: Upper valve subcircular but irregular conforming to attachment surface; lower valve as upper but with a large oval byssus aperture.

Sculpture: Upper valve with densely packed radial riblets (c.200), these minutely imbricated, in very thin shells this sculpture is obscure with faint impressions of the radially arranged scales; lower valve with growth lines only. Margin: Irregular but smooth. Ligament: In a half moon shaped pit beneath the beaks. Hinge: Obscure, some with traces of a median crural ridge directly above the ligament, in very thin shells the crural tooth may be prominent. Pallial Musculature: Upper valve with two scars the dorsal (byssus retractor) much larger and joined with the smaller single adductor scar. Scars with or without faint radiating furrows. Lower valve with a single faint adductor scar. Periostracum: Obscure. Colour: Upper valve colourless to tan to brown, thin shells often with brown radial rays on a pale background; often obscured by attached epifauna, internally the central area may be tinged green to yellow green. Lower valve white, semitransparent. Additional Characters: Anatomy: Ctendium with reflected filaments.

Distribution & Ecology

We have recognised this striated form from offshore to shelf edge depths, ranging from the Irish Sea to the Shetlands and northern North Sea.

Depth Range
Continental Shelf (to 200m)

Additional Information & Related Species

Additional Comments

Smith & Heppell (1991) regard P. patelliformis and P. squama to be varieties of the same species and therefore include only P. patelliformis in their list. At this time we agree that the muscle scar character used to separate the nominal taxa does not hold but we have observed that offshore shells may have a different sculpture from sublittoral and intertidal shells. This striated form was described by Lovén as P. striata and this form is included in the synonymy of P. squama by CLEMAM. Under P. squama we describe this striated form only.

Related Species


Listed are literature citing Pododesmus squama (Gmelin 1791). Reference containing the species Type Description is highlighted.

Gmelin J F 1791. Carli Linnaei systema Naturae per regna tria naturae. Editio decimatertia, aucta, reformata, Vermes Testacea 1 (6). Lipsiae. 3021-3910.
Winckworth, R I922. Note on the British species of Anomia. Proceedings of the Malacological Society of London. 15: 32-34.


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Record last modified: 17/05/2016