Rhynchonelliform brachiopod internal mold or pyritized fossil fragment
Brachiopoda indet. cf. Rhynchonella or small ostreid bivalve fragment • Body fossil (invertebrate marine shelly fossil, likely an internal cast or articulated small brachiopod/oyster fragment)
Geological Period
Jurassic (Callovian to Oxfordian)
Estimated Age
163 to 157 million years ago
Preservation Type
Calcification and partial replacement, presenting as a small steinkern or weathered fossil fragment
Condition Assessment
Fair to Good. Weathered fragment, missing complete bilateral symmetry or margins, but showing clear internal ribbing structures
Taxonomic Classification
Phylum Brachiopoda, Class Rhynchonellata, Order Rhynchonellida (or potentially Bivalvia, Ostreidae depending on exact symmetry)
Morphological Description
The specimen exhibits a small, irregularly shaped calcified or pyritized fragment with prominent radiating costae or ribbing converging toward a hinge-like apex. The surface shows distinct ridges and grooves typical of ribbed brachiopods or bivalves from the Jurassic formations of Normandy.
Rock Matrix
Marly limestone and argillaceous matrix typical of the coastal cliffs of Vaches Noires
Formation & Location
Falaises des Vaches Noires, Calvados department, Normandy, France (Oxfordian/Callovian marine formations)
Size & Dimensions
Approximately 15 mm in length, comparable to a standard small marine invertebrate fossil fragment from the region
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 20 USD
Rarity Assessment
Common, frequently found weathered out of the clay and limestone cliffs of the Vaches Noires
Scientific Significance
Provides local paleoecological data on the shallow marine benthic communities of the Jurassic Tethys/sub-Boreal seaway covering northern France
Preparation Recommendations
Gentle mechanical cleaning with a soft brush to remove loose clay matrix; store in a dry environment if any pyrite disease is suspected, though standard display is straightforward
Notable Features
Distinct radiating ribbed pattern contrasting sharply against the darker argillaceous rock matrix, recovered from one of France's most famous Jurassic fossil-hunting sites
Notes
falaises des Vaches Noires