Fossil Ammonite – Gregoryceras riazi – Upper Oxfordian, Jurassic – Nevers, France – Genuine with Certificate of Authenticity

Description

Fossil Ammonite – Gregoryceras riazi

Geological Period: Jurassic

Stage: Upper Oxfordian (~157–154 million years ago)

Locality: Nevers, Nièvre, Bourgogne-Franche-Comté, France

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.

This listing features a well-preserved fossil ammonite of the species Gregoryceras riazi, originating from the Upper Oxfordian deposits near Nevers, France. This region is known for its finely layered marine limestones and marls that were deposited in a warm epicontinental sea during the Late Jurassic. The ammonite is a classic European species and provides excellent insight into the marine faunal diversity of this time.

Scientific Classification:

• Genus: Gregoryceras
• Species: riazi
• Family: Perisphinctidae
• Superfamily: Perisphinctoidea
• Order: Ammonitida
• Formally Described by: Oppel, 1865

Geological and Palaeoenvironmental Context:

• Zone / Biozone: Perisphinctes bifurcatus to Gregoryceras transversarium Zones (Upper Oxfordian ammonite zonation)
• Depositional Environment: Open marine, subtidal environment with low to moderate energy, rich in carbonate sedimentation. The area was part of the western Tethyan margin during the Late Jurassic.
• Stratigraphy: The Oxfordian stage at Nevers includes well-stratified marl-limestone alternations containing abundant macrofossils, particularly ammonites and bivalves.

Morphological Features:

Gregoryceras riazi typically exhibits a compressed, evolute shell with sharp ribbing and strong bifurcation patterns. The ribs are regularly spaced and extend over the venter, which may appear rounded or slightly flattened. This species is notable for its use in regional biostratigraphy and is commonly found in fossil-rich Upper Jurassic strata across central and western Europe.

This specimen displays excellent shell detail, showcasing the species’ classic ribbing and whorl development. It is a superb reference piece for collectors and educators alike.

Specimen Notes:

• The photo in the listing shows the actual specimen you will receive.
• Scale Rule Squares / Cube = 1cm. Please refer to the images for full sizing and proportions.

Ideal For:

• Fossil ammonite collectors
• Palaeontology enthusiasts
• Students and educators studying Jurassic marine ecosystems
• Decorative scientific displays

This is a rare and scientifically valuable ammonite fossil from a classic Upper Jurassic locality in France, offering both aesthetic and scientific appeal.