Solitary Rugose Coral (Horn Coral)
Species indeterminate; likely Genus Zaphrentis (cf.) or Grewingkia (aff.) based on septal structure • Body fossil of a solitary invertebrate marine organism
Geological Period
Devonian to Carboniferous (Mississippian/Pennsylvanian)
Estimated Age
300 - 400 million years
Preservation Type
Recrystallization/Silicification; the original calcium carbonate skeletal structure has likely been replaced by silica or recrystallized calcite.
Condition Assessment
Good; the external skeleton is well-preserved with clear growth rings, though the calice (top opening) and apex (tip) appear worn by erosion.
Taxonomic Classification
Phylum: Cnidaria, Class: Anthozoa, Order: Rugosa, Family: Zaphrentidae (cf.)
Morphological Description
Conical 'horn' shape with distinct longitudinal costae (ribs) and visible transverse growth lines (rugae). The specimen shows a curved, tapering morphology characteristic of solitary rugose corals.
Rock Matrix
Matrix-free; likely weathered out of a limestone or calcareous shale matrix. Surface shows iron-staining and mineral oxidation.
Formation & Location
Commonly found in the Onondaga Formation (USA/Canada) or similar Paleozoic marine limestone deposits globally.
Size & Dimensions
Approximately 4-6 cm in length; fits within the standard size range for adult solitary rugose corals of this genus.
Value & Rarity
Estimated Market Value
$5 - $15 USD
Auction Estimate
$10 - $25 USD (as part of a bulk lot)
Rarity Assessment
Common; solitary rugose corals are among the most abundant invertebrate fossils in Paleozoic strata.
Scientific Significance
Rugose corals are vital paleoenvironmental indicators, reflecting shallow, warm marine seas and high-calcium carbonate environments of the Paleozoic era.
Preparation Recommendations
Minor cleaning with a soft brush and water; no consolidants needed due to sturdy mineralization. Best stored in a dry, stable environment.
Notable Features
Distinctive 'rugae' (wrinkles) along the outer wall which give the order its name, and clear evidence of calcification rates visible through growth bands.