Rhabdocidaris / Cidaris Echinoid Spine Fragment (or non-fossil animal claw/horn sheath)
cf. Rhabdocidaris sp. or Cidaris sp. spine fragment (or domestic animal claw sheath, e.g., Felis catus / Canis familiaris / Capra hircus) • Body fossil / Invertebrate structural component (Echinoid primary spine) or modern keratinous claw sheath
Geological Period
Late Jurassic to Cretaceous (if authentic fossil echinoid spine) or Holocene / Modern (if horn/claw sheath)
Estimated Age
Approximately 145 to 66 million years old (if fossilized echinoid radiole) or modern (<100 years)
Preservation Type
Silicification or calcification with calcitic luster (if echinoderm fossil) or unmineralized keratinous preservation (if modern bone/claw material)
Condition Assessment
Fair; complete conical sheath/spine structure present but shows wear around the open basal cavity edge and slight surface abrading
Taxonomic Classification
Phylum: Echinodermata, Class: Echinoidea, Order: Cidaroida, Family: Cidaridae / Rhabdocidaridae (cf. Cidaris sp. / Rhabdocidaris sp.)
Morphological Description
Conical, hollowed or deeply concave base with a tapering curved tip. Translucent yellowish to off-white coloration with visible fine longitudinal growth lines or fibrous structural grain. Outer surface shows smooth to faintly striated texture.
Rock Matrix
No rock matrix attached; clean isolated specimen
Formation & Location
Commonly Jurassic/Cretaceous limestone or chalk beds of Western Europe (e.g., Solnhofen Limestone, UK Chalk Group) if fossil; globally distributed if modern biological tissue
Size & Dimensions
Approximately 2.5 to 4.0 cm in length, within typical size range for cidaroid echinoid radioles or mammalian claw sheaths
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $25 USD
Rarity Assessment
Common (both as cidaroid urchin spine fragments in Cretaceous chalks and as modern animal claw/hoof sheath shedding)
Scientific Significance
Limited scientific significance as an isolated, out-of-context specimen lacking matrix or locality data; useful for educational identification exercises
Preparation Recommendations
Store in a dry, UV-protected container. If testing for fossilization, perform a hot-needle test (keratin will smell like burning hair, fossilized calcite/silica will not burn or produce smell).
Notable Features
Distinctive deep basal cup/hollow interior structure with thin sidewalls and translucent yellowish amber-like coloration.