Description
Genuine Cadomites Ammonite Fossil from Normandy
This carefully chosen fossil is a genuine Cadomites sp. ammonite from the Upper Bajocian Stage of the Middle Jurassic. It originates from Caen in Calvados, Normandy, France, a region internationally recognised for its historically important Jurassic rocks and richly fossiliferous marine deposits.
The photograph shows the actual fossil specimen you will receive, allowing you to examine its individual coiling, ribbing, preservation, colour, matrix and natural geological characteristics before purchasing. Full sizing and proportions can be seen in the accompanying photograph.
The abbreviation “sp.” indicates that the fossil has been confidently identified as belonging to the genus Cadomites, while no individual species name has been assigned. This is standard scientific terminology and provides an appropriately accurate identification for the specimen.
This authentic fossil includes a generic Certificate of Authenticity card with a lifetime guarantee.
Fossil Classification and Geological Age
Scientific name: Cadomites sp.
Fossil type: Ammonite
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Superfamily: Stephanoceratoidea
Family: Stephanoceratidae
Geological period: Jurassic
Epoch: Middle Jurassic
Stage: Upper Bajocian
Locality: Caen, Calvados, Normandy, France
The genus Cadomites was formally established by the French geologist and palaeontologist Ernest Munier-Chalmas in 1892. It is a recognised Middle Jurassic ammonite genus within the Stephanoceratoidea and is especially associated with Upper Bajocian and younger Jurassic marine deposits.
Ammonites such as Cadomites are important index fossils because their shell forms changed comparatively rapidly through geological time and many species were widely distributed through ancient seas. Their remains allow palaeontologists to compare rock layers from different locations and place them within detailed sequences of Jurassic time.
Cadomites Shell Form and Ornamentation
Cadomites ammonites are generally recognised by their evolute to moderately evolute coiling, broad central umbilicus and strongly developed ribbing. In an evolute shell, much of the earlier coiling remains visible rather than being completely concealed by the later outer whorls.
The shell is typically discoidal, with rounded whorl sections and a clearly defined central area. Primary ribs begin near the umbilical margin and extend across the flanks, often dividing into finer secondary ribs before continuing over the outer edge of the shell. Compared with some closely related stephanoceratid ammonites, Cadomites commonly displays relatively dense, fine and sharply defined ornamentation.
The aperture of a mature ammonite formed the opening through which the living animal’s head and tentacles projected. Adult members of this group could develop a specialised aperture with a thickened collar or lip, although the visibility of such features depends entirely upon the completeness and growth stage of the individual specimen.
The precise amount of visible ribbing, whorl detail, matrix and surface preservation differs naturally from fossil to fossil. Any worn areas, fractures, mineral deposits, incomplete sections or changes in colour are authentic results of fossilisation and geological exposure.
Upper Bajocian Geology of Caen and Calvados
The Upper Bajocian represents the later part of the Bajocian Stage within the Middle Jurassic. The Bajocian takes its name from Bajocae, the Latin name for Bayeux in Normandy, reflecting the major historical importance of Calvados in the study and classification of Jurassic rocks.
During the Upper Bajocian, the region now occupied by Normandy lay beneath a shallow sea connected to the broader marine basins covering much of western Europe. Layers of carbonate mud, limestone, clay, sand and locally iron-rich sediment accumulated on the seabed.
Changing sea levels, water depths, currents and sediment supply produced a variety of marine habitats. These environments supported ammonites alongside belemnites, brachiopods, bivalves, gastropods, echinoids and other invertebrates.
Some Cadomites species are known from finely divided Upper Bajocian ammonite biozones, including parts of the Niortense and Parkinsoni zones. Because this specimen is identified only to genus level, it is best understood more broadly as an Upper Bajocian ammonite without assigning it to a narrower biozone. Published research confirms that the genus forms an important component of Upper Bajocian ammonite assemblages.
Life in the Middle Jurassic Sea
Ammonites were extinct marine cephalopods related to living squid, cuttlefish, octopuses and nautiluses. The living animal occupied the final and largest portion of the shell, known as the body chamber.
The inner shell was divided into a sequence of smaller chambers by curved walls called septa. A narrow tube known as the siphuncle connected these chambers and enabled the ammonite to regulate the balance of liquid and gas within them. This chambered construction provided buoyancy control and allowed the animal to maintain its position in the water column.
Movement was achieved by jet propulsion. Water was drawn into the mantle cavity and expelled through a muscular funnel, pushing the ammonite through the sea. Tentacles surrounding the mouth were probably used to capture small prey, collect food and explore the surrounding environment.
The shell grew continuously throughout the ammonite’s life, with new calcium carbonate added around the aperture. Its changing whorl proportions and ribbing therefore preserve a record of growth from the juvenile shell towards adulthood.
Natural Fossilisation and Preservation
After the ammonite died, its shell settled onto the Jurassic seabed. The soft tissues decayed, while sediment gradually accumulated around and within the shell. Burial helped protect the remains from complete destruction by currents, scavengers and erosion.
Over millions of years, pressure compacted the surrounding sediment and mineral-rich groundwater altered the shell. The original aragonitic shell material could recrystallise, be replaced by other minerals or dissolve away completely. Sediment filling the shell could harden into an internal mould that retained the ammonite’s overall shape and ornamentation.
Natural cracks, matrix attachments, mineral staining, worn sections and incomplete areas are normal features of genuine fossils. Each records part of the specimen’s approximately 168-million-year geological history and makes the fossil individually distinctive.
Authentic Jurassic Collectable Specimen
This Cadomites sp. ammonite is suitable for fossil collectors, ammonite enthusiasts, geology students and educational natural-history collections. Its Upper Bajocian age, recognisable genus and classic Caen locality give it strong scientific, decorative and collectable appeal.
The specimen is ideal for display in a fossil cabinet, study, classroom, office or private collection. It also makes an unusual gift for anyone interested in palaeontology, Jurassic geology, extinct marine animals or fossils from France.
The photograph shows the exact carefully selected fossil specimen you will receive. Full sizing is shown in the photo. A generic Certificate of Authenticity card with a lifetime guarantee is included.
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