Nemocardium plumsteadianum

Nemocardium plumsteadianum

(J. Sowerby, 1813)

Common name Cockle
Fossil group Molluscs
Order Cardiida
Family Cardiidae
Genus Nemocardium
Taxonomic status Accepted
Geological age Ypresian

Summary

Nemocardium plumsteadianum was a cockle-like bivalve and a shallow-burrowing suspension feeder. A muscular foot allowed cardiids to reposition themselves in soft sediment while the gills filtered suspended organic particles.

Its inflated valve, prominent umbo and radial ornament are typical cardiid features.

Quick Identification

Look for: an inflated rounded-triangular cockle valve with a prominent umbo and numerous narrow radial ribs crossed by growth lines.

Diagnostic Features

  • Valve inflated with a rounded to weakly triangular outline.
  • Umbone prominent and raised above the hinge line.
  • Exterior carries numerous narrow radial ribs.
  • Concentric growth lines cross the radial sculpture and may produce a textured surface.
  • Hinge is heterodont rather than a long comb-like row of equal taxodont teeth.

Fossil Details

Typical size
Small to medium cockle, generally centimetre-scale; a tighter adult range was not established in the sources used for this audit.
Fossil material
Shell, Internal Mould / Cast
Preservation
Radial ornament may remain visible on incomplete valves, but abrasion rounds the ribs and breaks the thin margins. Hinge damage can make separation from other cardiids difficult.

Similar Species

Recorded Fossil Sites

Synonyms & Previous Names

Cardium plumsteadianum; Protocardium plumsteadianum

References

  • 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