Fossil Oyster
cf. Gryphaea sp. • Body fossil, invertebrate marine bivalve
Geological Period
Jurassic (Callovian to Oxfordian epochs) / Cretaceous
Estimated Age
150 to 165 million years
Preservation Type
Original calcitic shell material preserved with minor internal sediment infilling and surface weathering.
Condition Assessment
Good condition with high completeness, displaying minor surface cracking and some matrix adhesion but structurally intact.
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Ostreidae, Genus: Gryphaea or Nanogyra
Morphological Description
Exhibits a strongly inequivalve shell with prominent concentric growth lines, a dark greyish-black coloration, and a curved umbo characteristic of pycnodont or ostreid bivalves.
Rock Matrix
Dark argillaceous marl and clay matrix, typical of coastal cliff exposures in Normandy.
Formation & Location
Falaises des Vaches Noires, between Villers-sur-Mer and Houlgate, Normandy, France.
Size & Dimensions
Approximately 5 to 6 cm in maximum length, matching average adult sizes for oysters found in these Jurassic-Cretaceous transitional beds.
Value & Rarity
Estimated Market Value
10 to 30 USD
Auction Estimate
15 to 25 USD
Rarity Assessment
Common, frequently found along the eroding coastal cliffs of Normandy.
Scientific Significance
Provides insights into shallow marine benthic paleoenvironments, ancient coastal shelf ecology, and sea-level fluctuations during the Mesozoic in the Anglo-Paris Basin.
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water or a pin vise to remove adhering clay matrix. Store in a stable, low-humidity environment.
Notable Features
Striking dark coloration derived from the organic-rich dark clays and marls of the Vaches Noires cliffs, with exceptionally clear concentric growth lamellae.
Notes
falaises des Vaches Noires