Description
Clydoniceras discus Ammonite Fossil – Cornbrash Formation, Middle Jurassic, Dorset
This genuine Clydoniceras discus ammonite fossil is a collectable Middle Jurassic marine cephalopod specimen from the Cornbrash Formation at Sutton Poyntz, Dorset, UK. Dating from the Upper Bathonian Stage of the Middle Jurassic, approximately 167 to 166 million years old, this fossil represents an ammonite from the warm shallow seas that once covered southern Britain during the Jurassic Period.
This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. It has been carefully chosen as an individual fossil specimen, with a photo that shows the actual piece you will receive. Full sizing please see photo.
Geology and Geological Age
Clydoniceras discus comes from the Cornbrash Formation, a classic British Jurassic rock unit known for its fossiliferous limestone and shallow marine sediments. The Cornbrash Formation was deposited during the Bathonian Stage of the Middle Jurassic, at a time when much of southern England was covered by warm, shallow seas connected to a wider European marine system.
The term “Cornbrash” has long been used by geologists and collectors for a rubbly, shelly limestone that often contains abundant marine fossils. These sediments formed in relatively shallow, well-oxygenated marine conditions, where shell debris, carbonate mud and broken limestone material accumulated on the sea floor. Fossils from the Cornbrash can include ammonites, bivalves, brachiopods, gastropods, echinoids, belemnites and other marine invertebrates.
Fossil Type and Species
This specimen belongs to the ammonite species Clydoniceras discus, a distinctive Middle Jurassic ammonite associated with the Upper Bathonian of Britain. Clydoniceras is an ammonite genus within the order Ammonitida and is generally associated with the family Clydoniceratidae. Ammonites were extinct marine cephalopods related to modern squid, octopus and cuttlefish, but unlike their living relatives, they possessed an external coiled shell divided internally into chambers.
The living ammonite occupied the outer body chamber, while the earlier chambers helped regulate buoyancy. This allowed the animal to move through the water column in search of food and suitable habitat. Ammonites are especially important fossils because many species evolved rapidly and are widely used for dating and correlating Jurassic marine rock layers.
Morphology and Collectable Features
Clydoniceras discus is admired for its classic Middle Jurassic ammonite form. Depending on preservation and growth stage, specimens may show a compact, discoidal shell shape, visible whorls, smooth to gently ornamented flanks, shell curvature, chamber structure, natural matrix contact, mineral replacement or sutural detail. The species name discus reflects the disc-like appearance associated with this ammonite form.
Compared with more heavily ribbed Jurassic ammonites, Clydoniceras can have a more elegant and compressed shell profile, making it visually appealing as a labelled display fossil. In well-preserved examples, suture lines may be visible as intricate patterns marking where the internal chamber walls met the outer shell. These features are important in ammonite study and help show the biological complexity of these extinct cephalopods.
This specimen is especially desirable because it combines a named ammonite species, a clear Upper Bathonian age, the Cornbrash Formation and a named Dorset locality.
Cornbrash Formation and Sutton Poyntz Locality
Sutton Poyntz in Dorset is part of a region with a rich Jurassic geological record. Fossils from this area help document the shallow marine environments that existed across southern Britain during the Middle Jurassic. A Clydoniceras discus ammonite from the Cornbrash Formation is a strong addition to collections focused on British fossils, Dorset geology, Bathonian ammonites and classic Jurassic marine life.
The Cornbrash Formation is particularly valued by collectors because it represents a distinctive change in Jurassic marine conditions, with shelly limestones preserving evidence of active shallow sea floors. Specimens from named formations and localities carry stronger geological context than fossils labelled only as Jurassic or UK origin, making them especially useful for educational and display collections.
Depositional Environment
This Clydoniceras discus ammonite was preserved in sediments laid down beneath a warm Middle Jurassic sea. The environment would have included shallow marine water, carbonate sediment, shell banks and sea floors rich in invertebrate life. After the ammonite died, its shell settled onto the sea floor and became buried among shell debris, carbonate grains and fine marine sediment.
Over millions of years, burial, compaction and mineral-rich groundwater transformed the shell into a fossil. The resulting specimen is a natural record of marine life from Upper Bathonian Dorset, when ammonites were abundant and diverse across the Jurassic seas of Europe.
Authenticity and Display
This is a genuine Clydoniceras discus ammonite fossil from the Cornbrash Formation, Middle Jurassic, Upper Bathonian of Sutton Poyntz, Dorset, UK. It includes a Certificate of Authenticity lifetime guarantee generic card and is suitable for fossil collectors, geology enthusiasts, educational collections, natural history displays, cabinet display or as a distinctive gift for anyone interested in prehistoric marine life.
The fossil has been carefully selected, and the photo shows the actual specimen you will receive. Full sizing please see photo.
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