Oyster fossil
Exogyra cf. virgula or Gryphaea sp. • Body fossil, Invertebrate
Geological Period
Jurassic to Cretaceous
Estimated Age
160 to 150 million years
Preservation Type
Original calcitic shell material preserved with minor permineralization and clay matrix infill
Condition Assessment
Good, showing surface weathering and some matrix adhesion, but structurally complete for a single valve
Taxonomic Classification
Phylum Mollusca, Class Bivalvia, Order Ostreida, Family Ostreidae, Genus Gryphaea or Exogyra
Morphological Description
Irregular bivalve shell with a thick, robust structure, showing prominent concentric growth rings, a well-defined attachment scar, and an asymmetrical cupped valve morphology typical of cement-dwelling oysters.
Rock Matrix
Argillaceous limestone and dark calcareous marl/clay characteristic of the Vaches Noires coastal cliffs
Formation & Location
Callovian-Oxfordian formations of the Falaises des Vaches Noires, Normandy, France
Size & Dimensions
Approximately 4 to 5 centimeters in length, aligning well with typical medium-sized oyster specimens from the region
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 25 USD
Rarity Assessment
Common
Scientific Significance
Provides insights into shallow marine Jurassic shelf environments, benthic paleoecology, and substrate adaptation in epifaunal suspension feeders
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water to remove adhering clay matrix; store in a stable, dry environment
Notable Features
Clear attachment area indicating substrate preference and distinct concentric growth lamellae preserving ancient environmental fluctuations
Notes
falaises des Vaches Noires