Spiriferid Brachiopod (Wing-shaped Brachiopod)
cf. Mucrospirifer mucronatus or Spirifer sp. • Body fossil; Invertebrate (Brachiopoda)
Geological Period
Devonian to Carboniferous (Mississippian)
Estimated Age
345 - 395 million years ago
Preservation Type
Recrystallization with replacement (likely calcitic or siliceous replacement of the original shell material)
Condition Assessment
Good. The specimen exhibits strong rib definition and a mostly intact hinge line, though some chipping is visible on the peripheral edges.
Taxonomic Classification
Phylum: Brachiopoda, Class: Rhynchonellata, Order: Spiriferida, Family: Spiriferidae
Morphological Description
Characterized by a wide, wing-like (strophic) hinge line and a prominent central fold and sulcus. The surface exhibits strong radial ribs (costae) branching from the umbo. The specimen shows a semi-circular to triangular outline typical of spiriferids.
Rock Matrix
Finely grained dark limestone or calcareous shale; the specimen appears to have been weathered out of its original matrix.
Formation & Location
Commonly found in the Hamilton Group (New York/Ontario) or the Silica Shale (Ohio/Michigan), USA. Also prevalent in Devonian deposits of Europe.
Size & Dimensions
Approximately 3-5 cm in width; this is a standard size for adult individuals of this genus.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $30.00 USD (typically sold in bulk lots)
Rarity Assessment
Common. These are among the most abundant Paleozoic fossils found in North American and European outcrops.
Scientific Significance
Spiriferid brachiopods are vital index fossils for dating Paleozoic strata. They provide significant data on ancient seafloor communities as sessile filter feeders and indicate healthy marine oxygen levels in historical shelf environments.
Preparation Recommendations
No further mechanical preparation is needed; clean with a soft brush and water if necessary. Store in a dry environment to prevent pyrite disease if metallic traces are present.
Notable Features
The 'butterfly' or wing-like extension of the hinge is particularly well-defined in this specimen, illustrating the morphological adaptation for stability on soft muddy substrates.