Orthoceras (Straight-shelled Cephalopod)
Orthoceras sp. (Specific species often requiring internal cross-sectioning for confirmation) • Body fossil of an invertebrate marine mollusk
Geological Period
Devonian (possibly Silurian to Carboniferous)
Estimated Age
360 - 410 million years
Preservation Type
Recrystallization and replacement (likely calcite or aragonite) within a polished matrix
Condition Assessment
Good (commercially prepared and polished); shows partial shell wall loss but excellent internal structure visibility
Taxonomic Classification
Phylum: Mollusca, Class: Cephalopoda, Subclass: Nautiloidea, Order: Orthocerida, Family: Orthoceratidae, Genus: Orthoceras
Morphological Description
Elongated, conical orthoconic shell featuring distinct transverse septa (internal chamber walls) and a visible central siphuncle tube. The specimen shows smooth external sutures where the septa meet the outer shell wall.
Rock Matrix
Black bituminous limestone, typical of the Erfoud region fossils
Formation & Location
Anti-Atlas Mountains, Morocco (Alnif or Erfoud regions)
Size & Dimensions
Approximately 5 to 8 centimeters in length; consistent with common commercial specimens of this taxon
Value & Rarity
Estimated Market Value
$10.00 - $25.00 USD
Auction Estimate
$15.00 - $30.00 USD
Rarity Assessment
Common; very high abundance in North African deposits and widely distributed in the fossil trade
Scientific Significance
Illustrates early cephalopod evolution and the development of chambered shells for buoyancy control in Paleozoic marine ecosystems
Preparation Recommendations
No further prep needed; keep away from acidic cleaners; display in a stable, low-humidity environment to prevent matrix weathering
Notable Features
Highly visible siphuncle running through the center of the camerae (chambers) and a classic high-contrast polished aesthetic