Internal Mold of a Gastropod or Chalk Sponge Fragment
Likely a partial steinkern of a gastropod such as Gyrodes sp. or a weathered Porosphaera sp. sponge fragment • Steinkern (internal mold) or body fossil; Invertebrate
Geological Period
Cretaceous
Estimated Age
70 to 100 million years
Preservation Type
Silicification or Calcification; primarily preserved as an internal mold (steinkern) where the shell has dissolved, leaving the sediment fill.
Condition Assessment
Fair; the specimen is heavily weathered by beach action (abrasion), lacking fine surface detail or the original outer shell.
Taxonomic Classification
Phylum: Mollusca (Gastropoda) or Phylum: Porifera (Spongia)
Morphological Description
A tapered, cylindrical specimen showing spiral-like groove patterns. The surface is porous and weathered, displaying evidence of internal whorls characteristic of a gastropod interior or the skeletal structure of a calcareous sponge. The base is narrower than the top, suggesting a coiled or branching growth habit.
Rock Matrix
Chalk or flint-related limestone commonly found as erratic pebbles on the Suffolk coast.
Formation & Location
Upper Cretaceous Chalk Group; derived from offshore deposits or local glacial till, found at Southwold, Suffolk, UK.
Size & Dimensions
Approximately 4-6 cm in length and 2-3 cm in width; typical size for a medium-sized Cretaceous invertebrate fragment.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $20 USD (likely as part of a bulk lot of beach-found fossils)
Rarity Assessment
Common; such eroded chalk fossils are frequently found along the Suffolk and Norfolk coastlines.
Scientific Significance
Provides evidence of the rich marine life inhabiting the Late Cretaceous seas of Europe; demonstrates the transport of fossils via glacial and coastal processes in the East Anglia region.
Preparation Recommendations
No invasive preparation needed; wash with distilled water to remove salts and store in a dry environment to prevent further erosion of the chalky surface.
Notable Features
The distinct spiral grooves suggest the internal anatomy of a coiled organism, and the beach-worn patina indicates a long period of hydraulic transport.
Notes
Southwold beach UK