Rugose Coral (Horn Coral)
Rugosa sp. (cf. Favosites or solitary rugose coral) • Body fossil, invertebrate marine organism
Geological Period
Ordovician to Permian (likely Silurian or Devonian)
Estimated Age
350 to 450 million years ago
Preservation Type
Silicification and complete calcitic replacement/permineralization
Condition Assessment
Good condition; partial, worn specimen retaining clear internal structural details but missing the apex and calyx margins
Taxonomic Classification
Phylum: Cnidaria, Class: Anthozoa, Subclass: Rugosa
Morphological Description
The specimen exhibits a distinctive grid-like or septal pattern with prominent parallel vertical ridges and perpendicular transverse structures (tabulae or dissepiments). The cross-section reveals internal coral skeleton septa radiating outward or arranged linearly.
Rock Matrix
Limestone and weathered calcareous shale
Formation & Location
Worldwide distribution in Paleozoic marine limestone formations, commonly found in the Midwestern United States (e.g., Ohio, Indiana, Kentucky)
Size & Dimensions
Approximately 2 to 3 cm in length, typical for small or fragmented solitary rugose corals
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $25 USD
Rarity Assessment
Common; rugose corals are widely distributed and abundant in Paleozoic fossil-bearing strata
Scientific Significance
Provides key evidence of ancient shallow tropical marine environments, reef ecosystems, and evolutionary developments in Paleozoic invertebrates
Preparation Recommendations
Gentle mechanical cleaning with a soft brush and water; no harsh acids due to potential damage to the calcitic matrix. Store in a stable, dry environment.
Notable Features
Well-preserved internal septal walls and rectangular grid pattern created by weathered growth lines and internal skeletal elements