Glycymeris plumstediensis

Glycymeris plumstediensis

(J. Sowerby, 1813)

Common name Ark Shell
Fossil group Molluscs
Order Arcida
Family Glycymerididae
Genus Glycymeris
Taxonomic status Accepted
Geological age Ypresian

Summary

Glycymeris plumstediensis was a thick-shelled glycymerid bivalve. Glycymerids are marine suspension feeders that live at or just beneath the sediment surface, using a muscular foot for limited movement and the gills to filter food.

The rounded shell and long row of numerous small hinge teeth are characteristic of the group.

Quick Identification

Look for: a thick, rounded ark-shell valve with a prominent central umbo, many small hinge teeth in a long row and fine radial sculpture crossed by growth lines.

Diagnostic Features

  • Valve rounded to subcircular and relatively thick.
  • Umbone prominent near the middle of the dorsal margin.
  • Hinge carries a long series of numerous small taxodont teeth.
  • Exterior bears fine radial sculpture crossed by concentric growth lines.
  • Inner ventral margin is commonly crenulated rather than completely smooth.

Fossil Details

Typical size
A centimetre-scale bivalve; adult valves are typically several centimetres across.
Fossil material
Shell, Internal Mould / Cast
Preservation
Thick valves can remain recognisable after abrasion, but the taxodont hinge and crenulated inner margin are easily damaged. Worn shell surfaces may lose much of the fine radial sculpture.

Similar Species

Recorded Fossil Sites

References

  • Glibert, M.; Van de Poel, L. (1965). Les Bivalvia fossiles du Cénozoique étranger des collections de l’Institut royal des Sciences naturelles de Belgique. I. Palaeotaxodontia et Eutaxodontida. Mémoires de l'Institut royal des Sciences naturelles de Belgique, 77, 112 pp.. Institut royal des Sciences naturelles de Belgique, Bruxelles View reference
  • Wrigley, A. (1931). The Lower Eocene Mollusca of Abbey Wood and of High Halstow, Kent. The Vertebrate Faunas of the English Eocene, 1, 110–112. British Museum (Natural History), London View reference
Last Reviewed
22 August 2026 Reviewed by Sam Harris