Spiriferid Brachiopod
cf. Mucrospirifer mucronatus • Body fossil, Invertebrate Brachiopod
Geological Period
Devonian or Carboniferous (Paleozoic Era)
Estimated Age
360 to 410 million years
Preservation Type
Recrystallization (likely calcitic) and replacement
Condition Assessment
Very Good; the specimen shows clear rib articulation and a stable structure, though some wingtip abrasion is noted.
Taxonomic Classification
Phylum Brachiopoda, Class Rhynchonellata, Order Spiriferida, Family Spiriferidae, Genus Mucrospirifer (likely)
Morphological Description
Strongly biconvex shell with a long, straight hinge line giving it a winged appearance. Features a prominent central fold and sulcus with sharp radiating costa (ribs) that are well-defined across the surface.
Rock Matrix
Specimen is largely free from matrix, but residual fine gray shale or limestone is visible in the deepening sulcus.
Formation & Location
Widder Formation (Ontario, Canada) or Hamilton Group (New York, USA); commonly found in the Great Lakes region and Northeastern United States.
Size & Dimensions
Approximately 3-5 cm in width; typical size for a mature Spiriferid.
Value & Rarity
Estimated Market Value
USD $5.00 - $20.00
Auction Estimate
USD $10.00 - $30.00 (usually as part of a larger lot)
Rarity Assessment
Common; high abundance in Paleozoic fossil-bearing strata.
Scientific Significance
Key index fossils for the Middle Devonian; provides evidence of shallow, warm epicontinental sea environments and Paleozoic filter-feeding community structures.
Preparation Recommendations
Mechanical cleaning with a soft brush; store in low-humidity environment to prevent pyrite disease if metallic traces are present.
Notable Features
Features the classic 'butterfly' shape and exceptionally distinct plications (ribbing) converging at the umbo.