Belemnite guard (rostrum)
Belemnitida indet. (likely belonging to a family such as Belemnitidae or Cylindroteuthididae common to the Vaches Noires) • Body fossil (internal shell/rostrum of an extinct cephalopod), invertebrate
Geological Period
Jurassic to Cretaceous (specifically Middle to Late Jurassic / Callovian to Oxfordian based on the Vaches Noires locality)
Estimated Age
165 to 155 million years old
Preservation Type
Permineralization and heavy recrystallization into fibrous calcite
Condition Assessment
Fair to Good. The specimen is an isolated, worn guard missing its phragmocone and alveolar cavity region (the upper portion where the chambered shell attached), showing moderate surface wear.
Taxonomic Classification
Phylum: Mollusca, Class: Cephalopoda, Subclass: Coleoidea, Order: Belemnitida
Morphological Description
Elongated, bullet-shaped or cylindrical calcite guard (rostrum) tapering slightly towards the apex. The surface appears somewhat eroded or weathered with a granular texture, lacking the pristine smooth glossy exterior often seen in well-preserved specimens. The cross-section visible at the base shows a dense, radial fibrous calcite structure typical of belemnite rostra.
Rock Matrix
None attached directly as a adhering matrix on the main shaft, though originating from the clayey-marl cliffs of the Vaches Noires formation
Formation & Location
Falaises des Vaches Noires (Black Cows Cliffs) between Villers-sur-Mer and Houlgate in Normandy, France
Size & Dimensions
Approximately 3.5 to 4 cm in length, which is within the standard size range for typical Jurassic belemnite guards found in the region
Value & Rarity
Estimated Market Value
5 USD to 15 USD
Auction Estimate
10 USD to 25 USD
Rarity Assessment
Common. Belemnite guards are among the most frequently encountered invertebrate fossils in Jurassic and Cretaceous marine deposits throughout Europe.
Scientific Significance
Belemnites are important index fossils for marine Mesozoic strata, helping geologists date and correlate marine sedimentary layers. They also provide paleoecological insights into ancient shelf seas, predator-prey dynamics, and marine temperatures via stable isotope analysis of the calcite.
Preparation Recommendations
Requires minimal preparation. Gentle washing with water and a soft brush to remove residual clay sediment. Store in a dry environment; no special consolidants needed unless active pyrite decay is present (unlikely for pure calcite guards).
Notable Features
Demonstrates the classic bullet-shaped silhouette of a belemnite rostrum with a weathered surface texture highlighting the internal radial crystalline structure at the broken proximal end.
Notes
falaises des Vaches Noires