Oyster or Gryphaea fossil (Devil's Toenail)
Gryphaea cf. dilatata or Exogyra sp. • Body fossil, Invertebrate (bivalve mollusk)
Geological Period
Jurassic to Cretaceous (specifically Callovian to Oxfordian/Cretaceous based on the Vaches Noires locality)
Estimated Age
165 to 145 million years old
Preservation Type
Original calcitic shell material preserved through permineralization and minor recrystallization embedded in matrix
Condition Assessment
Good. The specimen is moderately complete with some surface weathering and matrix adhering to the margins, showing typical wear from wave action along the fossiliferous French coastline
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Gryphaeidae, Genus: Gryphaea or Exogyra
Morphological Description
Thick-shelled, highly inequivalve bivalve with a prominent, strongly curved or coiled umbo on the larger left valve. Smooth to undulating surface with faint growth lines and some surficial wear.
Rock Matrix
Marly limestone and calcareous clay typical of the Vaches Noires coastal cliffs in Normandy, France
Formation & Location
Callovian-Oxfordian and Cretaceous formations of the Vaches Noires cliffs (Falaises des Vaches Noires) between Villers-sur-Mer and Houlgate, Normandy, France
Size & Dimensions
Approximately 5 cm to 7 cm in maximum length, falling well within the typical size range for Jurassic oysters
Value & Rarity
Estimated Market Value
10 to 30 USD
Auction Estimate
15 to 40 USD
Rarity Assessment
Common. Gryphaea and related oyster fossils are abundant in the Vaches Noires and similar European Mesozoic deposits
Scientific Significance
Illustrates shallow marine benthic paleoenvironments of the Jurassic/Cretaceous epicontinental seas covering northern France, providing insights into substrate adaptation and evolutionary morphology of cementing bivalves
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water to remove excess clay matrix. Store in a stable, dry environment
Notable Features
Classic distinctly curved umbo characteristic of 'Devil's Toenail' oysters, directly traceable to a famous paleontological locality (Vaches Noires)
Notes
falaises des Vaches Noires