Oyster or Gryphaea (Devil's Toenail)
Gryphaea cf. dilatata • Body fossil, invertebrate bivalve mollusk
Geological Period
Jurassic to Cretaceous (Callovian to Oxfordian)
Estimated Age
165 to 155 million years
Preservation Type
Original calcitic shell material preserved with minor sediment infill and matrix adherence
Condition Assessment
Fair, partial specimen embedded in matrix with visible weathering and fragmentation along the edges
Taxonomic Classification
Phylum Mollusca, Class Bivalvia, Order Ostreida, Family Gryphaeidae, Genus Gryphaea
Morphological Description
Thick, cupped shell fragment embedded in matrix, displaying prominent curved growth lines and radial ribbing typical of cement-dwelling bivalves.
Rock Matrix
Clay-rich marl and argillaceous limestone typical of coastal landslide deposits
Formation & Location
Falaises des Vaches Noires, Normandy, France (Callovian and Oxfordian formations)
Size & Dimensions
Approximately 3 cm across, consistent with medium-sized juvenile to adult oyster specimens
Value & Rarity
Estimated Market Value
5 - 15 USD
Auction Estimate
10 - 25 USD
Rarity Assessment
Common, frequently found weathering out of the clay cliffs of Normandy
Scientific Significance
Demonstrates shallow marine benthic paleoenvironments in the Jurassic Anglo-Paris Basin, providing data on soft-bottom epifaunal adaptations
Preparation Recommendations
Mechanical cleaning using soft brushes and pin vises to remove excess clay matrix; store in a dry environment to prevent matrix flaking
Notable Features
Collected from the famous fossil-rich Vaches Noires cliffs, showing characteristic deep-water or coastal clay-adhered fossilization common to the site
Notes
falaises des Vaches Noires