Oyster or Gryphaea Shell Fragment
Gryphaea cf. dilatata or Exogyra sp. fragment • Body fossil, Invertebrate bivalve mollusc
Geological Period
Jurassic (Callovian to Oxfordian epochs)
Estimated Age
163 to 157 million years old
Preservation Type
Original calcitic shell material preserved with minor permineralization and sediment infilling
Condition Assessment
Fair condition; incomplete fragment representing a portion of a larger bivalve shell with noticeable edge wear and breakage
Taxonomic Classification
Phylum Mollusca, Class Bivalvia, Order Ostreida, Family Gryphaeidae, Genus Gryphaea or Exogyra
Morphological Description
The specimen exhibits prominent, radiating costae (ribs) along with concentric growth lines characteristic of an attachment area or shell ornamentation typically found in ostreid or gryphaeid bivalves. The fragment includes part of the umbonal or costate valve structure.
Rock Matrix
Argillaceous limestone and marly clay matrix typical of the coastal deposits of Normandy
Formation & Location
Falaises des Vaches Noires (Black Cow Cliffs) between Villers-sur-Mer and Houlgate in Normandy, France
Size & Dimensions
Approximately 20 mm to 25 mm in maximum dimension, roughly comparable in scale to the adjacent 2-euro coin (25.75 mm diameter)
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 25 USD
Rarity Assessment
Common, frequently found weathered out of the clay and limestone cliffs at Vaches Noires
Scientific Significance
Provides evidence of shallow marine benthic environments and warm shallow seas during the Jurassic period along the northern margin of the Paris Basin
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water to remove residual clay matrix. Store in a dry environment.
Notable Features
Distinctive radiating ribbed ornamentation pattern preserved on the exterior shell surface combined with a dark internal sediment infill at the base
Notes
falaises des Vaches Noires