Brachiopod (Lamp Shell)
cf. Mucrospirifer or Neospirifer species • Body fossil / Invertebrate / Articulated Brachiopod
Geological Period
Devonian to Carboniferous (Mississippian)
Estimated Age
360 to 400 million years
Preservation Type
Recrystallization with heavy calcification; the original shell material has likely been replaced by calcite or silica minerals.
Condition Assessment
Fair to Good. The primary diagnostic features such as growth lines are visible, but the specimen shows significant surface weathering and possible abrasion at the hinge and wing tips.
Taxonomic Classification
Phylum: Brachiopoda, Class: Rhynchonellata, Order: Spiriferida, Family: Spiriferidae
Morphological Description
Specimen exhibits a sub-triangular to biconvex shell shape with prominent concentric growth lines (rugae). Visible sulcus (depression) on the pedicle valve and a corresponding fold on the brachial valve. The wing-like lateral extensions characteristic of the Spiriferida order appear suggestively though eroded at the extremities.
Rock Matrix
The fossil is largely free of matrix but shows remnants of a fine-grained silty limestone or calcareous shale adherence in the crevices.
Formation & Location
Commonly found in the Ferron Point Formation (Michigan, USA), the Silica Shale (Ohio, USA), or similar Devonian marine deposits in Europe and North Africa.
Size & Dimensions
Approximately 2.5 - 3.5 cm in width; this is a typical adult size for mid-sized spiriferid brachiopods.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $25 USD (as part of a bulk lot of invertebrates)
Rarity Assessment
Common. Brachiopods of this type are among the most abundant Paleozoic fossils found globally.
Scientific Significance
Brachiopods are vital index fossils for dating Paleozoic strata. This specimen illustrates the suspension-feeding biology of the Devonian sea floor and the diversity of the Rhynchonellata class prior to the Great Permian Extinction.
Preparation Recommendations
Mechanical cleaning using a soft brush or dental pick under magnification to remove surface debris. Avoid acidic cleaners which will dissolve the calcareous shell. Store in a dry environment in a padded mineral box.
Notable Features
Features well-defined concentric growth bands that indicate seasonal or pulse-based growth rates in a Paleozoic marine environment. The central sulcus is notably deep, suggesting a mature specimen.