Fossil Oyster Shell (Exogyra / Gryphaea / Ostrea species) with associated belemnite or bullet-like artifact/feature
Exogyra sp. or Pycnodonte sp. / Gryphaea sp. • Body fossil (Invertebrate - Bivalva) embedded with a second marine element (belemnite rostrum or mineralized fill)
Geological Period
Cretaceous (or Late Jurassic to Paleogene depending on locality)
Estimated Age
66 to 145 million years ago
Preservation Type
Original shell material retention with calcite recrystallization and heavy mineral staining/permineralization.
Condition Assessment
Fair to Good; robust calcitic shell structure preserved intact, showing weathering, edge abrasion, and minor matrix adhesion.
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Subclass: Pteriomorphia, Order: Ostreida, Family: Gryphaeidae or Ostreidae
Morphological Description
Thick, heavy, lamellar calcareous shell structure typical of oyster valves showing distinct growth squamose lines and layering; attached or embedded with a bullet-shaped dark, cylindrical structure (resembling a belemnite guard or iron/copper concretion/artifact).
Rock Matrix
Calcareous matrix / sandy limestone, cemented shell hash (coquina-like debris) holding the two structures together.
Formation & Location
Commonly found in Cretaceous coastal/shelf deposits such as the Atlantic Coastal Plain (e.g., Monmouth Group, New Jersey/Delaware) or Cretaceous beds in Texas, Western Interior Seaway, or the UK Chalk/Greensand.
Size & Dimensions
Approximately 8 cm to 12 cm (3 to 5 inches) in length; typical size range for adult Cretaceous bivalves.
Value & Rarity
Estimated Market Value
$15 - $40 USD
Auction Estimate
$20 - $50 USD
Rarity Assessment
Common (fossil oysters are abundant global marine fossils, though multi-taxa associations add mild interest).
Scientific Significance
Illustrates shallow-water marine shelf benthic ecosystems of the Mesozoic; useful indicator of paleotemperature, salinity, and high-energy depositional environments.
Preparation Recommendations
Keep in a dry environment to prevent flaking; clean gently with a soft dry brush; avoid acid cleaning or harsh chemical immersion.
Notable Features
Unusual visual juxtaposition of the thick, layered calcitic bivalve shell with an embedded elongated cylindrical feature, creating a distinctive composite specimen.