Oyster or Gryphaea fossil
Gryphaea cf. arcuata or related ostreid bivalve • Body fossil, invertebrate bivalve
Geological Period
Jurassic / Cretaceous
Estimated Age
160 to 145 million years
Preservation Type
Original calcitic shell material preserved within a concretionary matrix (unaltered to slightly recrystallized)
Condition Assessment
Good condition; the shell is partially embedded within the original matrix, showing good surface detail on the exposed umbo and growth lines with minor weathering on exposed edges
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Gryphaeidae, Genus: Gryphaea (or similar ostreid)
Morphological Description
Asymmetrical bivalve shell with a prominent, curved umbo on the lower valve and concentric growth lines visible on the surface. The specimen is partially embedded in a calcareous nodule.
Rock Matrix
Calcareous clay/marl matrix typical of marine sedimentary deposits
Formation & Location
Falaises des Vaches Noires, Normandy, France (Callovian-Oxfordian to Cretaceous formations)
Size & Dimensions
Approximately 3 cm in maximum dimension, comparable to standard sizes for juvenile to medium specimens of this taxon
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 25 USD
Rarity Assessment
Common, frequently found in the Jurassic and Cretaceous clay formations of Western Europe
Scientific Significance
Provides insight into shallow marine benthic paleoenvironments of the Mesozoic Era along the European epicontinental seas
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and pin vice to remove excess matrix if desired; store in a dry, stable environment
Notable Features
Clearly visible concentric growth lines and a well-preserved umbo region protruding from the surrounding marl matrix
Notes
falaises des Vaches Noires