Rugose Coral (Horn Coral)
Zaphrentis cf. or Heliophyllum cf. • Body fossil of a solitary invertebrate cnidarian
Geological Period
Devonian to Carboniferous (Mississippian)
Estimated Age
320 to 410 million years
Preservation Type
Recrystallization (calcite) and silicification; the original aragonite/calcite has been replaced by more stable minerals.
Condition Assessment
Fair to Good; the internal septal structure is somewhat eroded, and the proximal end (the tip) appears broken or worn.
Taxonomic Classification
Phylum: Cnidaria, Class: Anthozoa, Order: Rugosa, Family: Zaphrentidae (cf.)
Morphological Description
Conical 'horn-shaped' skeleton showing prominent longitudinal costae (ribs) on the exterior and radial septa visible on the calice (top opening) area. The specimen exhibits a curved, solitary growth form typical of rugose corals.
Rock Matrix
Partially attached light-colored limestone matrix; evidence of weathering and water-worn smoothing suggesting it was found in a gravel bed or stream.
Formation & Location
Commonly found in the Onondaga Limestone (USA), Jeffersonville Limestone (USA), or carboniferous limestone sequences in Europe.
Size & Dimensions
Approximately 3-4 cm in length; typical for small to medium solitary rugose species.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $25.00 USD (in a multi-specimen lot)
Rarity Assessment
Common; solitary rugose corals are among the most abundant Paleozoic fossils found globally.
Scientific Significance
Key index fossils for dating Paleozoic marine strata; they provide insights into ancient warm, shallow sea environments and coral reef evolution before their extinction at the end of the Permian.
Preparation Recommendations
Mechanical cleaning with a soft brush to remove surface debris; no chemical treatment required. Store in a dry environment to prevent further weathering.
Notable Features
Distinctive radial septal patterns on the distal end and clear growth lines (rugae) preserved on the outer shell.