Brachiopod (Spiriferid)
cf. Mucrospirifer sp. or Mediospirifer sp. • Body fossil; Invertebrate (Brachiopoda)
Geological Period
Devonian to Carboniferous (Mississippian)
Estimated Age
320 - 419 million years
Preservation Type
Replacement and recrystallization, likely by calcite or silica, preserving the exterior shell morphology in a petrified state.
Condition Assessment
Fair to Good; the exterior ornamentation is visible, but the margins (wings) appear somewhat worn/eroded, and the hinge detail is partially obscured by weathering.
Taxonomic Classification
Phylum Brachiopoda, Class Rhynchonellata, Order Spiriferida, Family Spiriferidae
Morphological Description
Displays a characteristic 'winged' or 'butterfly' shape with an elongated hinge line (mucronate). Surface features strong radial costae (ribbing) and a prominent fold and sulcus (a central depression and corresponding ridge). The specimen shows symmetric valve alignment typical of spiriferid brachiopods.
Rock Matrix
Finely grained limestone or calcareous shale; the specimen appears weathered out of its original matrix.
Formation & Location
Commonly found in the Hamilton Group (New York, USA), Widder Formation (Ontario, Canada), or similar Devonian marine deposits globally.
Size & Dimensions
Approximately 25-40 mm in width; this is a typical adult size for mid-sized Spiriferids.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $25.00 USD (as part of a larger lot)
Rarity Assessment
Common; Spiriferid brachiopods are among the most abundant and widely distributed Paleozoic fossils.
Scientific Significance
Spiriferids are vital index fossils for dating Paleozoic strata. They provide significant insights into ancient shallow-marine benthic ecosystems and water energy levels during the Devonian 'Age of Fishes'.
Preparation Recommendations
Gentle cleaning with a soft brush and water; no aggressive chemicals needed. Store in a dry environment with a protective label.
Notable Features
Features a distinctively wide hinge line which suggests it may have rested on soft substrate. The preservation shows the chevron-like ribbing patterns very clearly despite some surface weathering.