Brachiopod (Lamp Shell)
cf. Athyris sp. or Composita sp. • Body fossil / Invertebrate marine animal
Geological Period
Devonian - Carboniferous
Estimated Age
300 - 410 million years
Preservation Type
Recrystallized shell material and internal mold/cast on a split rock surface
Condition Assessment
Fair; partial preservation with some shell material missing, showing the interface between the matrix and the fossil
Taxonomic Classification
Phylum: Brachiopoda; Class: Rhynchonellata (likely); Order: Spiriferida or Athyridida
Morphological Description
Specimen shows a smooth, biconvex rounded shell with visible concentric growth lines. The shell shape is sub-circular to oval with a distinct pedicle opening area. No strong radial ribbing is present on these specific individuals, suggesting a smooth-shelled taxon.
Rock Matrix
Grey calcareous shale or fine-grained argillaceous limestone
Formation & Location
Common in the Mahantango Formation (USA), Much Wenlock Limestone (UK), or similar Paleozoic marine sediments globally
Size & Dimensions
Approximately 1.5 - 2 cm in width, which is average for these genera
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $25 USD (as part of a multi-specimen lot)
Rarity Assessment
Common; Brachiopods are among the most frequently found fossils in Paleozoic marine strata
Scientific Significance
Provides evidence of Paleozoic benthic marine environments. Brachiopods are essential index fossils for stratigraphic correlation and studying ancient filter-feeding ecosystems.
Preparation Recommendations
Keep dry; no chemical cleaning needed. Gentle mechanical cleaning with a soft brush can remove dust from the matrix pores.
Notable Features
Features multiple individuals on a single small matrix piece, demonstrating a death assemblage (thanatocoenosis) typical of seabed deposits.