Fossil Sea Urchin (Echinoid)
Clypeus cf. or Cassidulus sp. • Invertebrate body fossil, calcitic test replacement
Geological Period
Cretaceous
Estimated Age
66 to 145 million years
Preservation Type
Silicification and complete permineralization/replacement of the original calcium carbonate test by fine-grained quartz or chalcedony, imparting a polished, glossy appearance.
Condition Assessment
Very Good. The test is intact and fully three-dimensional with clear ambulacral petals, though exhibiting minor surface iron-oxide staining and minor abrasions.
Taxonomic Classification
Phylum Echinodermata, Class Echinoidea, Order Cassiduloida, Family Cassidulidae
Morphological Description
The specimen exhibits a rounded to slightly sub-pentagonal, domed test (shell) with a distinct five-rayed petaloid ambulacral system radiating from the apical center. The surface is smooth with fine punctations and micro-tubercles visible upon closer inspection, characteristic of irregular echinoids.
Rock Matrix
Free of matrix (freed specimen), showing remnants of iron-stained yellowish-brown chalcedony or chert on surface patches.
Formation & Location
Chalk formations and marine limestone deposits, commonly found in Western Europe (e.g., the English Chalk or similar deposits in France) or North Africa.
Size & Dimensions
Approximately 4 to 5 cm in diameter, which is a standard adult size range for this taxonomic group.
Value & Rarity
Estimated Market Value
$25 - $60
Auction Estimate
$20 - $50
Rarity Assessment
Common
Scientific Significance
Provides valuable insight into Cretaceous shallow marine benthic ecosystems, evolutionary adaptations of irregular urchins for burrowing, and ancient Tethys Ocean paleobiogeography.
Preparation Recommendations
No further preparation required. Store in a stable, dry environment away from excessive humidity. Clean gently with a soft dry brush if needed.
Notable Features
The specimen features exceptionally clear, well-defined petaloid ambulacra and a pleasing natural yellowish-brown honey color derived from mineral replacement.