Fossil Sand Dollar Fragment
Clypeasteroida indet. (cf. Mellita or Encope) • Invertebrate body fossil (permineralized echinoid test fragment)
Geological Period
Neogene (Miocene to Pliocene)
Estimated Age
5 to 23 million years
Preservation Type
Permineralization and calcitic replacement with original echinoderm high-magnesium calcite structure preserved
Condition Assessment
Fair to Poor (incomplete fragment, missing margins and apical system, though internal micro-structure is well-exposed)
Taxonomic Classification
Phylum Echinodermata, Class Echinoidea, Order Clypeasteroida
Morphological Description
Fragmentary flat echinoid test displaying internal stereom microstructure, remnants of ambulacral grooves, and pore pairs. The internal lattice of calcium carbonate plates is clearly exposed due to breakage, showing the porous sponge-like structural network characteristic of echinoid internal ossicles.
Rock Matrix
Cleaned specimen with minimal to no remaining matrix, likely originating from a soft calcareous sandstone or sandy limestone formation
Formation & Location
Coastal Neogene marine deposits, commonly found in formations such as the Hawthorne Group (southeastern United States) or similar shallow marine sedimentary basins worldwide
Size & Dimensions
Approximately 5 to 8 centimeters across the preserved fragment, representing a portion of a medium-sized sand dollar typically 7 to 10 centimeters in full diameter
Value & Rarity
Estimated Market Value
5 to 15 USD
Auction Estimate
10 to 25 USD
Rarity Assessment
Common
Scientific Significance
Illustrates the internal skeletal architecture (stereom) of clypeasteroids, providing educational value regarding echinoderm taphonomy and micro-anatomy
Preparation Recommendations
Gentle brushing with soft bristles to remove residual dust. Store in a stable, dry environment away from excessive humidity to prevent degradation
Notable Features
Exposed internal porous stereom network providing a clear cross-sectional and textural view of echinoid skeletal construction
Notes
This is a piece of a sand dollar