Brachiopod (Lamp Shell)
cf. Rhynchonella sp. • Body fossil, Invertebrate Molluscoid
Geological Period
Devonian to Carboniferous (Paleozoic Era)
Estimated Age
320 - 400 million years
Preservation Type
Recrystallization and replacement (likely calcitic or siliceous replacement of the original shell material)
Condition Assessment
Fair to Good. The specimen shows significant surface weathering and erosion, obscuring fine growth lines, though the primary ribbing remains visible.
Taxonomic Classification
Phylum: Brachiopoda, Class: Rhynchonellata, Order: Rhynchonellida, Family: Rhynchonellidae
Morphological Description
Small, biconvex valves with a triangular or sub-pentagonal outline. Visible strong radial costae (ribs) originating from the umbo (beak). Distinctive 'zigzag' commissure (the line where valves meet) and a well-defined sulcus and fold common to rhynchonellid brachiopods.
Rock Matrix
Specimen is weathered out of its original matrix; likely originated from a fine-grained limestone or calcareous siltstone.
Formation & Location
Commonly found in the Columbus Limestone (USA) or the Carboniferous Limestone Supergroup (UK/Europe).
Size & Dimensions
Approximately 1.5 cm - 2.5 cm in width; typical size for standard rhynchonellid specimens.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $30 USD (typically sold in bulk lots)
Rarity Assessment
Common. Brachiopods are among the most frequently discovered Paleozoic fossils worldwide.
Scientific Significance
Brachiopods are essential index fossils for dating Paleozoic strata. They provide data on ancient benthic marine environments and help reconstruct Paleozoic paleogeography.
Preparation Recommendations
Gentle cleaning with a soft brush and water. No heavy chemical cleaning is recommended due to the weathered surface. Store in a dry, padded container.
Notable Features
Features a classic rhynchonellid 'lamp shell' shape with prominent plications. The specimen appears to be a weathered whole-body fossil rather than a single valve.