Spiriferid Brachiopod
Spirifer cf. mucronatus or similar mucronate spiriferid • Body fossil, Invertebrate Brachiopod
Geological Period
Devonian to Carboniferous period
Estimated Age
320 to 415 million years
Preservation Type
Recrystallization/Replacement with calcitic mineralization; some surface weathering has smoothed the diagnostic ribbing.
Condition Assessment
Fair; the specimen is mostly complete but shows significant erosion and pitting on the shell surface, obscuring fine growth lines.
Taxonomic Classification
Phylum: Brachiopoda; Class: Rhynchonellata; Order: Spiriferida; Family: Spiriferidae
Morphological Description
Exhibits a characteristic 'wing-like' or semi-elliptical shape with a straight hinge line. Notched with a prominent medial fold and sulcus. The surface shows fine radiating ribbing known as costae, which are diagnostic of spiriferids.
Rock Matrix
Specimen is largely free from matrix, but residues suggest a grey limestone or calcareous siltstone environment.
Formation & Location
Widely found in the Hamilton Group of New York, USA, or the Eifel region of Germany; commonly associated with shallow marine paleoenvironments.
Size & Dimensions
Approximately 3.5 to 5 centimeters in width; within the standard range for common Paleozoic brachiopods.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $25.00 USD (typically sold in larger specimen lots)
Rarity Assessment
Common; spiriferid brachiopods are among the most frequently encountered invertebrate fossils in Devonian and Carboniferous marine deposits.
Scientific Significance
Brachiopods are vital index fossils for dating Paleozoic strata and provide evidence of past marine biodiversity and environmental conditions prior to the Permian mass extinction.
Preparation Recommendations
Low-impact mechanical cleaning with a soft brush; store in a dry, stable environment to prevent possible oxidation of trace sulfide minerals.
Notable Features
Features a classic 'butterfly' outline with well-defined lateral extremities and a deep sulcus, representing the peak of brachiopod morphological diversity.