Fossilized Oyster Shell
Exogyra cf. costata • Body fossil, invertebrate bivalve mollusk
Geological Period
Cretaceous
Estimated Age
66 to 145 million years ago
Preservation Type
Original calcitic shell material preserved with some recrystallization and minor sediment infilling
Condition Assessment
Good condition; partial specimen showing moderate weathering along edges but clear structural features
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Order: Ostreida, Family: Ostreidae
Morphological Description
Irregularly shaped, thick shell fragment with foliated calcite layers, undulating growth lines, and rough exterior texture characteristic of cemented epifaunal suspension feeders.
Rock Matrix
Marl and fossiliferous limestone matrix with fine-grained calcareous sediment
Formation & Location
Gulf Coast formations of North America, such as the Coffee Sand or Demopolis Chalk
Size & Dimensions
Approximately 7 cm in length, within the standard size range for adult Cretaceous ostreids
Value & Rarity
Estimated Market Value
$15 - $45
Auction Estimate
$20 - $50
Rarity Assessment
Common, widely distributed globally in marine deposits of the Mesozoic and Cenozoic
Scientific Significance
Provides data on Late Cretaceous shallow marine shelf environments, benthic ecosystems, and paleoclimatic conditions
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water; store in a dry environment at stable room temperature
Notable Features
Clearly visible layered shell microstructures and encrusting traces on the surface