RARE: Calycoceras gentoni British Chalk Ammonite Fossil – Cenomanian Cretaceous Glynde East Sussex UK – Certified Authentic

Description

RARE CALYCOCERAS GENTONI FOSSIL AMMONITE

This listing features a rare and scientifically significant specimen of the fossil ammonite Calycoceras gentoni, originating from the British Chalk of Glynde, East Sussex, United Kingdom. This ammonite represents one of the more distinctive forms from the Cenomanian stage of the Late Cretaceous, and is part of the esteemed Alice Purnell Collection.

This is the actual fossil shown in the listing photos, and you will receive exactly what is pictured. A scale cube (1cm squares) is included for reference—please consult the photo for full sizing.

As with all our offerings, this fossil is 100% genuine and is accompanied by a Certificate of Authenticity.

Fossil Classification:

• Species: Calycoceras gentoni
• Genus: Calycoceras
• Family: Acanthoceratidae
• Superfamily: Acanthoceratoidea
• Order: Ammonitida
• Class: Cephalopoda
• Phylum: Mollusca
• Type: Fossil ammonite

Geological and Stratigraphic Context:

• Geological Period: Cretaceous
• Stage: Cenomanian (approx. 100.5 – 93.9 million years ago)
• Formation: Chalk Group (Lower Chalk, including the Grey Chalk Subgroup)
• Location: Glynde, East Sussex, United Kingdom
• Depositional Environment: Shallow marine carbonate shelf environment. The British Chalk was laid down in warm epicontinental seas that were nutrient-rich and biologically diverse. These conditions were ideal for cephalopods such as ammonites.

Morphological Features:

Calycoceras gentoni exhibits a robust, evolute shell structure, often adorned with pronounced tubercles and strong, straight ribs radiating from the umbilical region. These ornamentations not only aid in identification but reflect adaptations to a dynamic marine environment.

Its suture pattern is complex and finely divided, typical of the Acanthoceratidae, and it is a visually striking ammonite due to its bold ornamentation.

Palaeontological Significance and Biozone:

Calycoceras gentoni is typically associated with the Upper Cenomanian ammonite faunas of Europe and has been referenced in zonal schemes helping to refine stratigraphic boundaries within the British Chalk. It may appear alongside other ammonites like Acanthoceras jukesbrownei and Mantelliceras mantelli, depending on locality.

While not the zonal index species itself, its occurrence helps in regional correlation and offers a clearer understanding of ammonite dispersal during transgressive marine episodes.

Provenance:

This fossil was selected from the Alice Purnell Collection, a long-established British palaeontological collection known for quality, locality-verified fossils. It was chosen for its completeness and representative preservation.

Authenticity & Condition:

• 100% genuine ammonite fossil
• No replicas or casts
• Cleaned, stabilised, and suitable for display
• From a reputable and documented collection
• Comes with a Certificate of Authenticity

This rare Calycoceras gentoni fossil is an excellent acquisition for collectors, educators, and institutions interested in the diversity and evolution of mid-Cretaceous marine ecosystems. Its rarity, preservation, and provenance make it a standout specimen.