Sponge Fossil (Echinopora or Porifera)
Indeterminate poriferan (cf. Ventriculites or Porosphaera sp.) • Body fossil; invertebrate; silicified or recrystallized calcisponge
Geological Period
Cretaceous or Paleogene
Estimated Age
Approx. 60 to 120 million years
Preservation Type
Recrystallization or partial replacement by silica/calcite; heavily water-worn and abraded into a pebble-like form.
Condition Assessment
Fair; the specimen is complete as a fossilized unit but shows significant taphonomic wear, having been rounded by post-fossilization erosion.
Taxonomic Classification
Phylum: Porifera; Class: Demospongiae or Calcarea; Order: Uncertain; Family: Uncertain
Morphological Description
Small, subspherical to pebble-shaped body with a distinct pitted surface texture. The pits represent ostia (pores) where water entered the sponge body. Lack of central osculum on this face suggests a globular colonial or solitary form.
Rock Matrix
Specimen is a standalone lithified body; likely derived from a chalk or limestone matrix before being tumbled in a fluvial or marine environment.
Formation & Location
Commonly found in the Chalk Group of Western Europe (UK, France) or similar marine limestone deposits in North America.
Size & Dimensions
Approximately 2-3 cm in diameter; typical for small globular Cretaceous sponges.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $25 USD
Rarity Assessment
Common; these globular sponge fossils are frequently found in gravel deposits and coastal chalk outcrops.
Scientific Significance
Provides evidence of local benthic marine ecosystems and high concentrations of suspended silica/carbonate that allowed for the permineralization of porous structures.
Preparation Recommendations
No invasive preparation needed due to water-worn status. Clean with mild soap and water; store in a dry, padded container to prevent further abrasion.
Notable Features
The distinctive 'golf ball' texture created by the preservation of the spicular network and pore system is the diagnostic highlight.