Fossil Shark Spine (Fin Spine fragment)
cf. Ctenacanthus sp. • Body fossil, Vertebrate (Chondrichthyes)
Geological Period
Carboniferous or Devonian
Estimated Age
300 to 360 million years
Preservation Type
Permineralization with probable carbonization and phosphatic replacement, resulting in a dark, lustrous finish.
Condition Assessment
Good (Incomplete); the specimen shows excellent surface detail and ornamentation but is a truncated segment of a much longer spine.
Taxonomic Classification
Phylum: Chordata, Class: Chondrichthyes, Order: Ctenacanthiformes (Likely), Family: Ctenacanthidae, Genus: cf. Ctenacanthus
Morphological Description
Elongated, slender, and slightly curved dorsal fin spine fragment. Features prominent longitudinal ridges and rows of small, bead-like tubercles/ornamentation. Dark brown to black coloration with a distinct central groove (vascular channel).
Rock Matrix
Cleaned specimen; typical matrix would be dark organic shale or fine-grained limestone.
Formation & Location
Possible sources include the Bear Gulch Limestone (USA), Glencartholm (Scotland), or the Cleveland Shale (USA).
Size & Dimensions
Approximately 4-6 cm in length; consistent with a partial spine from a medium-sized prehistoric shark.
Value & Rarity
Estimated Market Value
$40 - $85 USD
Auction Estimate
$50 - $100 USD
Rarity Assessment
Uncommon; while shark teeth are frequent finds, well-preserved ornamented fin spines are less common.
Scientific Significance
Shark fin spines are vital for understanding the evolution of Paleozoic Chondrichthyans, as their cartilaginous skeletons rarely fossilize. They provide data on defensive adaptations and species distribution.
Preparation Recommendations
No further preparation needed. Should be stored in a padded, acid-free container; avoid high humidity to prevent mineral oxidation.
Notable Features
Distinctive 'beaded' ornamentation along the longitudinal ridges, which is a diagnostic trait for Ctenacanthian sharks. The deep black color suggests a high organic content in the original burial environment.