Gastropod Internal Mold
Indeterminate gastropod species; cf. Tylostoma or aff. Natica depending on original whorl expansion • Internal mold (steinkern), invertebrate body fossil
Geological Period
Likely Cretaceous or Paleogene, though the morphology spans the Mesozoic/Cenozoic Eras
Estimated Age
Approx. 50 to 100 million years
Preservation Type
Internal mold formation through sediment infilling and subsequent lithification; shell material has dissolved away (recrystallization/leaching).
Condition Assessment
Fair to Good; the internal mold is mostly complete but lacks fine surface detail due to the coarse nature of the infilling sediment.
Taxonomic Classification
Phylum: Mollusca, Class: Gastropoda, Order: Likely Sorbeoconcha
Morphological Description
Conical to globose spiral structure showing a stepped spire and a large body whorl. The specimen lack shell material, displaying the sediment that filled the shell interior (steinkern). Deeply impressed sutures are visible.
Rock Matrix
Fine-grained calcareous sandstone or calcarenite; light tan/buff coloring suggests a shallow marine depositional environment.
Formation & Location
Common in the Glen Rose Formation (Texas, USA) or similar Cretaceous chalk/limestone deposits in Europe and North Africa.
Size & Dimensions
Approx. 4-6 cm in length; typical for medium-sized predatory or scavenging sea snails.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $25.00 USD (typically sold in bulk lots)
Rarity Assessment
Common; internal molds of gastropods are among the most frequently found invertebrate fossils in sedimentary basins.
Scientific Significance
Provides evidence of paleo-water depth and salinity in ancient near-shore marine environments; serves as an index for local stratigraphy.
Preparation Recommendations
No further mechanical preparation needed; keep dry and store in a padded specimen box to prevent abrasion of the sandy surface.
Notable Features
Distinctive 'steinkern' (stone heart) preservation where the lack of an outer shell reveals the exact volume of the living organism's cavity.