Brachiopod (Spiriferid)
Mucrospirifer cf. mucronatus • Body fossil; Invertebrate (Brachiopoda)
Geological Period
Devonian or Mississippian
Estimated Age
360 to 410 million years
Preservation Type
Recrystallization/Replacement; likely calcitic preservation of the original shell structure.
Condition Assessment
Good; the specimen shows clear ribbing and a complete central valve, though the mucronate tips appear slightly weathered or abbreviated.
Taxonomic Classification
Phylum: Brachiopoda, Class: Rhynchonellata, Order: Spiriferida, Family: Spiriferidae
Morphological Description
Wing-like (strophic) shell shape with a prominent fold and sulcus. The hinge line is long and straight, tapering to sharp points or mucronate extensions. The surface is covered in fine, radiating costae (ribs).
Rock Matrix
Minimal matrix present, but likely derived from a greyish limestone or calcareous shale.
Formation & Location
Likely from the Silica Shale (Ohio/Michigan) or the Hamilton Group (New York), USA.
Size & Dimensions
Approximately 3-5 cm in width; typical size for adult Mucrospirifer specimens.
Value & Rarity
Estimated Market Value
$10 - $25 USD
Auction Estimate
$15 - $40 USD (usually sold in lots)
Rarity Assessment
Common; these are among the most frequently found fossils in Devonian marine deposits.
Scientific Significance
Spiriferid brachiopods are excellent index fossils for dating Paleozoic strata and provide evidence of ancient shallow-marine environments and filter-feeding ecosystems.
Preparation Recommendations
Requires minimal preparation; periodic dusting and storage in a dry environment to prevent any potential pyrite decay if metallic inclusions are present.
Notable Features
Prominent 'butterfly' or wing-like shape and well-defined sulcus in the center of the valve.