Oyster or Exogyra fossil
Gryphaea cf. or Exogyra sp. • Body fossil, invertebrate bivalve
Geological Period
Jurassic to Cretaceous
Estimated Age
160 to 145 million years
Preservation Type
Original calcitic shell material preserved with some surface weathering and minor encrustation
Condition Assessment
Good. The specimen is complete as an individual valve but shows surface wear, minor matrix adherence, and weathering consistent with beach or cliff-fall collection.
Taxonomic Classification
Phylum Mollusca, Class Bivalvia, Order Ostreida, Family Gryphaeidae or Ostreidae
Morphological Description
Thick, irregular calcitic shell showing pronounced concentric growth lines, a slightly curved or hooked umbo area typical of oysters, and a somewhat distorted, bulbous morphology adapted to a sessile benthic lifestyle.
Rock Matrix
Calcareous marl and clayey limestone typical of coastal fossiliferous deposits
Formation & Location
Falaises des Vaches Noires, Normandy, France (Callovian to Oxfordian and Cretaceous formations)
Size & Dimensions
Approximately 25mm to 30mm in length, comparable to standard small-to-medium specimens of Jurassic oysters found in the region
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 25 USD
Rarity Assessment
Common. Oysters and related bivalves are abundantly found in the Vaches Noires cliffs.
Scientific Significance
Provides insights into shallow marine Jurassic ecosystems, paleodepositional environments, and benthic community structures along the ancient European shelf.
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water, or a pin vise to remove minor matrix from crevices. Store in a dry, stable environment.
Notable Features
Distinctive rugged surface texture with well-defined growth lamellae characteristic of high-energy shallow marine environments in the Jurassic seas of Normandy.
Notes
falaises des Vaches Noires