Perisphinctes Ammonite Fossil Value Guide

The Perisphinctes Ammonite is a prized Middle to Late Jurassic cephalopod fossil known for its intricate, evolute spiral shell and prominent ribbing. Originating from the rich sedimentary deposits of Madagascar, these specimens serve as vital index fossils that once fueled medieval legends of 'snakestones'.

What affects the value of Perisphinctes Ammonite Fossil?

• Specimen size and the completeness of the outer whorls significantly impact the $350-$385 price range.
• The quality of the preparation, specifically how cleanly the sedimentary rock has been removed to reveal the ribbing, affects market value.
• Natural preservation of the original shell material versus heavy restoration or polishing can dictate collector interest.
• The clarity and definition of the ribbing across the entire diameter of the fossil.

How to Identify Perisphinctes Ammonite Fossil?

• Look for the characteristic 'Perisphinctid' ribbing which typically bifurcates or branches as it crosses the outer edge of the shell.
• Verify the origin as Madagascar, where calcium carbonate preservation often results in high-contrast detail between the fossil and matrix.
• Examine the shell structure for a wide, open umbilicus where all previous whorls remain visible in the spiral.
• Check for the presence of authentic suture patterns, which are complex, leaf-like lines visible on the surface of the internal mold.

History of Perisphinctes Ammonite Fossil

Ammonites are extinct cephalopods that lived during the Jurassic and Cretaceous periods. In medieval Europe, they were often called 'snakestones' because they were believed to be petrified snakes coiled up. This specific genus, Perisphinctes, is an index fossil for the Middle to Late Jurassic, helping geologists date the rock layers in which they are found.