Horn Coral (Rugose Coral)
Rugosa cf. Zaphrentis • Body fossil, invertebrate
Geological Period
Ordovician to Permian (likely Silurian or Devonian)
Estimated Age
350-450 million years old
Preservation Type
Permineralization and calcitic replacement within a fossiliferous matrix
Condition Assessment
Fair to Good; partial exposure of the coral exterior embedded in matrix with some surface weathering
Taxonomic Classification
Phylum Cnidaria, Class Anthozoa, Order Rugosa
Morphological Description
Solitary, conical corallite structure tapering to a pointed base, exhibiting prominent longitudinal septal ridges and a cup-like calice at the wider end showing radial symmetry.
Rock Matrix
Coarse, weathered argillaceous limestone / fossiliferous dolostone with visible fragmental debris
Formation & Location
Midwest United States (such as the Louisville Limestone or Silica Formation)
Size & Dimensions
Approximately 4 cm in length, consistent with small solitary rugose corals
Value & Rarity
Estimated Market Value
$15 - $40
Auction Estimate
$20 - $50
Rarity Assessment
Common
Scientific Significance
Provides insights into ancient shallow marine tropical ecosystems and paleoenvironments of the Paleozoic era
Preparation Recommendations
Mechanical matrix removal with an air scribe or pin vise under magnification, followed by optional stabilization with a dilute PVA or Paraloid B-72 solution
Notable Features
Clear display of radial septa within the calice opening and well-defined transverse growth wrinkles along the conical exterior wall