Solitary Rugose Coral (Horn Coral)
Rugosa gen. et sp. indet. (cf. Zaphrentis or Heliophyllum) • Body fossil (Internal/External Mold and Recrystallized Stem); Invertebrate
Geological Period
Paleozoic (likely Devonian to Carboniferous)
Estimated Age
300 - 400 million years
Preservation Type
Recrystallization and mineral replacement (likely calcite or silica) within a mold.
Condition Assessment
Fair; the specimen is highly weathered, partially obscured by the matrix, and lacks the fine detail of individual septa or the external theca.
Taxonomic Classification
Phylum: Cnidaria; Class: Anthozoa; Subclass: Rugosa; Order: Stauriida
Morphological Description
The specimen shows a cross-sectional view of a solitary coral. Visible features include a circular to sub-circular calyx area with faint evidence of radial septa (internal vertical plates) which are partially obscured by recrystallization. The 'horn' shape is suggested by the way the organism is embedded within the matrix.
Rock Matrix
Fine-grained, grey bioclastic limestone or calcareous siltstone with possible iron-oxide (limonite) staining in the vugs.
Formation & Location
Common in the Onondaga Formation (USA/Canada) or Carboniferous Limestones of the UK and Europe.
Size & Dimensions
Approximately 3-4 cm in diameter; typical for solitary rugose corals which usually range from 1 cm to 10 cm.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $20.00 USD
Rarity Assessment
Common; solitary corals are ubiquitous in Paleozoic marine deposits globally.
Scientific Significance
Provides evidence of Paleozoic marine benthic environments. Rugose corals were major reef builders and are essential for dating Paleozoic strata and understanding ancient seawater chemistry.
Preparation Recommendations
Mechanical cleaning with a dental pick or air-scribe could reveal more septal detail. Avoid acid baths unless the fossil is silicified and the matrix is pure limestone.
Notable Features
The specimen exhibits a 'vug' or small cavity below the main fossil body containing reddish-pink mineral deposits (possibly calcite or iron-rich sediment).