Sea Urchin (Regular Echinoid)
cf. Hemicidaris or Clypeus sp. • Body fossil (Internal cast/Steinkern); Invertebrate
Geological Period
Late Jurassic to Early Cretaceous
Estimated Age
Approx. 163 to 100 million years
Preservation Type
Recrystallized replacement, likely by calcite or chalcedony, forming a solid mineralized cast of the internal cavity.
Condition Assessment
Good; the specimen is complete and retains distinct radial symmetry, though the sharp surface features (tubercles) have been lost to erosion or the casting process.
Taxonomic Classification
Phylum: Echinodermata; Class: Echinoidea; Order: Hemicidaroida or Cidaroida
Morphological Description
Sub-spherical to disk-shaped fossil displaying pentamerous symmetry. Visible are five ambulacral fields radiating from the apical system. The surface is smooth, suggesting a weathered test or an internal cast (steinkern), with faint petaloid patterns visible.
Rock Matrix
The specimen is largely freed from its matrix, but the yellowish-brown iron staining suggests a limestone or marly sandstone origin.
Formation & Location
Commonly found in the Tethyan deposits of North Africa (e.g., Morocco), Southern Europe, or the Jurassic Coast of the UK.
Size & Dimensions
Approximately 3 to 5 cm in diameter; typical for small to medium-sized regular echinoids of this period.
Value & Rarity
Estimated Market Value
$15.00 - $45.00 USD
Auction Estimate
$20.00 - $60.00 USD
Rarity Assessment
Common; fossil echinoids are abundant in marine sedimentary layers globally.
Scientific Significance
Provides evidence of marine benthic ecosystems and the diversification of echinoids during the Mesozoic Marine Revolution.
Preparation Recommendations
Minimal preparation required. Clean with a soft brush and distilled water. Store in a dry environment away from direct sunlight to prevent oxidation of surface minerals.
Notable Features
Features a high degree of vitreous luster indicating significant silica or calcite replacement. The radial bands are well-defined, illustrating the water vascular system's structural layout.