Stromatoporoid (Ancient Sea Sponge)
Labechia huronensis (aff.) • Body fossil; Invertebrate (Calcareous Sponge)
Geological Period
Late Ordovician (Richmondian Stage)
Estimated Age
445 to 450 million years
Preservation Type
Recrystallization safely preserved despite fluvial tumbling; the calcium carbonate skeleton has likely been replaced by more stable calcite or microcrystalline silica.
Condition Assessment
Fair to Good; while biologically complete as a fragment, the specimen is heavily water-worn and rounded by its time in a river bed, which has obscured fine microscopic details like pillars and astrorhizae.
Taxonomic Classification
Phylum: Porifera, Class: Stromatoporata, Order: Stromatoporida, Family: Uncertain, Genus: cf. Labechia
Morphological Description
Specimen exhibits a characteristic laminar or mamelon-stuctured growth pattern appearing as fine, parallel undulating lines (laminae). The surface shows a slightly fibrous or wood-grain texture which is typical of the weathered internal structure of these reef-building organisms.
Rock Matrix
Dense, fine-grained gray limestone/siltstone typical of the Cincinnatian Series; the specimen itself is the mineralized skeleton with little adhering matrix.
Formation & Location
Dillsboro Formation or Whitewater Formation of the Cincinnatian Series; found near Brookville, Indiana.
Size & Dimensions
Approximately 3-4 inches (75-100mm) in length; typical for fragmented or water-worn colonial masses of this period.
Value & Rarity
Estimated Market Value
$10.00 - $25.00 USD
Auction Estimate
$15.00 - $40.00 USD (as a bulk lot or decorative specimen)
Rarity Assessment
Common; Brookville and the surrounding Whitewater Valley are world-famous for Late Ordovician fossils, where these fragments are found in high concentrations.
Scientific Significance
Stromatoporoids were major reef-builders in the Paleozoic and are critical for understanding ancient sea level changes and the biodiversity of the shallow epicontinental seas that once covered Indiana.
Preparation Recommendations
No invasive preparation needed due to river-polishing. Clean with mild soap and water. Can be waxed or lightly oiled to bring out the contrast of the laminae.
Notable Features
The specimen has been naturally 'prepped' by the river, creating a smooth, tactile surface that showcases the internal growth layers, which are often mistaken for fossilized wood by amateur collectors.
Notes
brookville indiana in a river bed