Glycymeris glycymeris (Linnaeus, 1758)Arcoidea : Glycymerididae
To size: To 65mm. Shell Structure: Thick, robust. Equivalve: Equivalve. Equilateral: Appears equilateral but beaks just behind the midline. Tumidity: Not tumid. Outline: Subcircular, some with a distinct angular posterior margin, umbos low; dorsal margin short, straight; posterior a little more acute than anterior but both broadly rounded. Lateral margins in juvenile more straight. Contour: Dorsal area narrow, cleft; Evenly rounded.
Sculpture: Indistinct but of very numerous fine incised radial grooves cut by equally numerous comarginal lines and growth stops. Smaller shells appear ribbed and cancellate. Margin: Crenulate. Ligament: Duplivincular, strong, set on both sides of the beak. Hinge: Very strong, taxodont; teeth in two series separated by a small edentulous space set on an arched hinge plate, up to 12 teeth in each series. Pallial Musculature: Anterior adductor scar slightly larger than posterior. Periostracum: Pilose, of brown, dense, short hairs arising from radial grooves, usually persists only at margins. Colour: Mostly maculated white and brown, some more densely shades of brown all over; interior white or brown – purplish brown inside pallial line.
Distribution & Ecology
A shallow burrower, often exposed, in gravels and mixed substrates especially in areas of high current. At sublittoral and shelf depths in all areas but apparently absent from the southern North Sea.
Continental Shelf (to 200m)
Juveniles & Similar Species
At 0.5 mm the shell and inner margins are smooth, only two teeth on either side; by 2mm radial sculpture and marginal crenulations appear and teeth number 4 on each side.
Key Features & Similar Species
Externally early juveniles appear veneroid but hinge distinctive.
Listed are literature citing Glycymeris glycymeris (Linnaeus, 1758). Reference containing the species Type Description is highlighted.
Linnaeus C 1758. Systema Naturae. Editio decima. 1. Regnum Animale Holmiae, Laurentii Salvii. 824pp.
Thomas R D K 1975. Functional morphology, ecology, and evolutionary conservatism in the Glycymerididae (Bivalvia). Palaeontology. 18: 217–258.
Thomas R D K 1978. Shell Form and the Ecological Range of Living and Extinct Arcoida. Paleobiology. 4(2): 181-194.
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