RARE 8.5″ Calycoceras Newboldiceras asiaticum Fossil Ammonite Middle Cenomanian Cretaceous Sussex UK – Genuine Collector Specimen

Description

Rare Calycoceras (Newboldiceras) asiaticum from the Middle Cenomanian

This exceptional 8.5-inch Calycoceras (Newboldiceras) asiaticum fossil ammonite is a stunning example of a mid-Cretaceous cephalopod from the world-renowned chalk deposits of Sussex, United Kingdom. Highly sought after by collectors for its size, rarity, and scientific importance, this specimen represents a snapshot of marine life from approximately 98–95 million years ago. The ammonite you see in the photographs is the exact piece you will receive, chosen for its completeness, strong ribbing, and aesthetic appeal.

Geological Age & Provenance

Originating from the Middle Cenomanian stage of the Late Cretaceous, this ammonite was preserved in the fine calcareous muds that would eventually form the iconic chalk landscapes of southern England. During this time, the region was submerged beneath warm, shallow epicontinental seas connected to the Tethys Ocean. These seas supported a rich diversity of marine life, with ammonites such as Calycoceras playing a dominant role in the mid-water ecosystems.

The Sussex chalk is globally recognised for producing well-preserved ammonites due to its stable depositional environment and high calcium carbonate content, which protected shells from dissolution and abrasion.

Species Profile & Scientific Classification

Calycoceras (Newboldiceras) asiaticum is a member of the family Acanthoceratidae, superfamily Acanthoceratoidea, order Ammonitida. This species is known for its robust, evolute shell, characterised by strong, widely spaced ribs that often bear prominent tubercles at the ventrolateral margins. The ribs sweep gracefully across the flanks, providing a distinctive ornamentation pattern that makes the species instantly recognisable.

As an important index fossil, C. asiaticum is valuable in refining Cenomanian biostratigraphy and is widely used to correlate marine deposits across Europe, Asia, and North Africa.

Morphological Features

This specimen displays all the key features that make Calycoceras (Newboldiceras) asiaticum a favourite among collectors and researchers:

• Large 8.5-inch diameter, offering an impressive display size.
• Strong radial ribbing running from the umbilicus to the venter.
• Well-developed tubercles positioned along the ventrolateral shoulder.
• Evolute coiling, allowing most of the earlier whorls to be visible.
• Excellent preservation, retaining original surface textures and details.

The combination of bold ribbing and pronounced tubercles not only makes this ammonite aesthetically striking but also scientifically valuable for morphological comparison.

Depositional Environment

The Middle Cenomanian seas of Sussex were calm, warm, and nutrient-rich, ideal conditions for ammonite proliferation. The fine-grained chalk sediments formed from the skeletal remains of microscopic plankton known as coccolithophores. After the ammonite’s death, its shell would have settled onto the seafloor, where it was gradually buried by these carbonate-rich deposits. Over millions of years, diagenesis transformed the sediment into chalk, preserving the ammonite in remarkable detail.

Collector Significance

This fossil holds special value for collectors due to:

• Its rarity in this size and quality from the Sussex deposits.
• Its scientific importance as an index fossil for Middle Cenomanian strata.
• Its excellent aesthetic qualities, making it a standout display piece.
• Its historical provenance, sourced from one of the UK’s most famous fossil-bearing formations.

Authenticity & Presentation

All of our fossils are 100% genuine specimens and come with a Certificate of Authenticity. This ammonite has been expertly selected and prepared to highlight its natural beauty and scientific interest, making it an ideal acquisition for both private collectors and educational displays.