Crinoid Stem Ossicle and Associated Bryozoan or Stromatoporoid Patch
Crinoidea indet. (ossicle cross-section), cf. columnal fragment • Body fossil, invertebrate (echinoderm columnal and colonial encrusting organism)
Geological Period
Ordovician to Mississippian (likely Ordovician or Silurian based on typical matrix and crinoid/bryozoan associations)
Estimated Age
450 to 400 million years
Preservation Type
Calcitic replacement and permineralization within a hardened carbonate-rich matrix
Condition Assessment
Good. The fossil is partially exposed in cross-section within the natural rock matrix with moderate surface weathering and iron staining.
Taxonomic Classification
Phylum Echinodermata, Class Crinoidea, Order Articulata; associated with Phylum Bryozoa or Porifera
Morphological Description
The specimen features a circular crinoid stem ossicle (columnal) showing radial symmetry and a central lumen (axial canal) filled with lighter mineral matrix. Surrounding the ossicle is a rich hash of fossiliferous debris embedded in the rock, alongside a larger, irregular reddish-brown weathered patch of calcitic skeletal accumulation, likely representing an encrusting bryozoan colony or sponge structure.
Rock Matrix
Fossiliferous limestone (packstone/wackestone) containing numerous micro-fragments of shells, crinoid debris, and secondary iron oxide staining (reddish-brown areas)
Formation & Location
Commonly found in Paleozoic limestone formations worldwide, such as the Cincinnati Arch region (USA), Anticosti Island (Canada), or the Silurian formations of Gotland (Sweden)
Size & Dimensions
The central crinoid columnal is approximately 5 to 7 millimeters in diameter, set within a larger hand-sample sized limestone matrix measuring roughly 10 cm across
Value & Rarity
Estimated Market Value
$15 - $30
Auction Estimate
$10 - $25
Rarity Assessment
Common. Crinoid ossicles and fossiliferous limestone hashes are widespread components of Paleozoic marine sedimentary rocks.
Scientific Significance
Provides insight into Paleozoic shallow marine crinoid-bryozoan thicket ecosystems, demonstrating how pelmatozoan columnals disintegrated post-mortem and became incorporated into carbonate muds.
Preparation Recommendations
Mechanical cleaning using a pin vise or air scribe under a microscope if further exposure of the columnal is desired, though the specimen is stable as-is. Store in a dry environment.
Notable Features
The clear circular cross-section of the crinoid columnal with its distinct central lumen, paired with the prominent reddish-brown weathered colonial organism patch, provides an educational snapshot of a diverse Paleozoic seafloor assemblage.