Crinoid Calyx with Stem Fragment
Crinoidea indet. cf. cup • Body fossil, marine invertebrate echinoderm
Geological Period
Mississippian / Carboniferous
Estimated Age
335 to 350 million years old
Preservation Type
Calcitic replacement and impression within a fine-grained carbonate matrix
Condition Assessment
Good. The calyx is largely intact though compressed, and the stem segment is clearly articulated, though some surrounding matrix weathering is visible.
Taxonomic Classification
Phylum Echinodermata, Class Crinoidea, Order Cladida, Family undetermined
Morphological Description
The specimen features a roughly circular, compressed crinoid calyx showing distinct radial plate structures and symmetry, attached to a short proximal stem fragment composed of stacked columnals with visible longitudinal ridges or facets.
Rock Matrix
Fossiliferous gray limestone / packstone containing various micro-fragment skeletal debris
Formation & Location
Borden Group or equivalent North American crinoid-bearing carbonate formations, commonly found in the Midwestern United States (Indiana, Kentucky)
Size & Dimensions
Calyx diameter approximately 1.5 cm; overall specimen length around 3.5 cm, consistent with small to medium-sized Paleozoic crinoids
Value & Rarity
Estimated Market Value
$50 - $150
Auction Estimate
$40 - $100
Rarity Assessment
Common, though well-associated calyx and stem specimens of this clarity are always sought after by educational collectors.
Scientific Significance
Important for understanding Paleozoic marine benthic ecosystems, shallow tropical carbonate environments, and the rapid accumulation of crinoidal limestones.
Preparation Recommendations
Mechanical preparation using a fine pneumatic stylus or micro-sandblaster with bicarbonate of soda to further expose plate sutures without damaging the delicate calcitic structure.
Notable Features
The direct physical association between the crinoid dorsal cup (calyx) and the attached proximal columnals provides a clear anatomical context of the organism's living posture.