Description
Genuine Esericeras eseri Ammonite Fossil
This carefully chosen fossil is a genuine Esericeras eseri ammonite from Caen in Normandy, France. Dating from the Upper Toarcian Stage of the Lower Jurassic, it represents an extinct marine cephalopod that lived in the ancient seas of western Europe approximately 174 to 178 million years ago.
Its recognisable coiled form, Jurassic age and French provenance make this specimen an appealing addition to an ammonite collection, geological display or cabinet of European fossils. It offers a tangible record of a marine ecosystem that existed long before the familiar landscapes of modern Normandy developed.
The photograph shows the actual fossil specimen you will receive, allowing its individual coiling, ornamentation, preservation, colour, matrix and natural geological characteristics to be examined before purchase. Full sizing and proportions can be seen in the accompanying photograph.
This authentic fossil includes a generic Certificate of Authenticity card with a lifetime guarantee.
Fossil Classification and Geological Details
Scientific name: Esericeras eseri
Fossil type: Ammonite
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Geological period: Jurassic
Epoch: Early Jurassic
Stage: Upper Toarcian
Locality: Caen, Normandy, France
Esericeras eseri belongs to the diverse ammonite faunas that flourished during the later Toarcian. These rapidly evolving marine molluscs are scientifically valuable because different ammonite species appeared and disappeared through relatively narrow intervals of geological time.
Their widespread distribution across Jurassic seas allows palaeontologists to compare fossil-bearing rocks from separate regions. A diagnostic ammonite can therefore provide evidence not only about the animal itself but also about the relative age and marine setting of the rock in which it was preserved.
Esericeras Shell Form and Ornamentation
Like other ammonites, Esericeras eseri possessed a planispirally coiled shell, with successive whorls growing around a central umbilicus in a single plane. The degree to which each outer whorl overlaps the earlier growth contributes to the shell’s overall form and is one of the features used in ammonite identification.
The shell may display ribs extending from the inner region of the whorl towards the outer margin. Their spacing, curvature and strength can change as the animal grows, creating a surface pattern that records successive stages of shell development.
The outer edge of an ammonite shell is called the venter. Its width and profile, together with the shape of the flanks, umbilical area and ribbing, help distinguish related ammonite forms. Fine growth lines may also be present where the original shell surface or an accurate external impression has survived.
The exact visibility of these characteristics depends upon the preservation and growth stage of the individual fossil. Natural fractures, worn sections, mineral deposits, matrix attachments and incomplete areas are authentic geological features rather than manufactured imperfections.
Upper Toarcian Geological Age
The Toarcian is the final stage of the Lower Jurassic, following the Pliensbachian and preceding the Aalenian Stage of the Middle Jurassic. The Upper Toarcian represents its later interval, when ammonite groups underwent considerable evolutionary diversification and change.
During this period, much of western Europe consisted of islands, shallow platforms and marine basins. Connections between these basins allowed ammonites and other pelagic animals to spread over broad geographical areas.
Ammonites are especially important in Toarcian biostratigraphy. Their successive appearances enable geologists to divide the rock record into zones, subzones and narrower faunal horizons. These divisions provide a far more detailed geological timeline than the broad designation of Lower Jurassic alone.
Upper Toarcian rocks record changing marine conditions following earlier environmental disruption during the stage. Variations in sea level, oxygenation, sediment supply and basin circulation influenced which organisms lived in particular regions and how their remains were preserved.
Jurassic Geology of Caen and Normandy
Caen lies within Normandy, a region celebrated for its extensive Jurassic sedimentary rocks and historically significant fossil localities. Although parts of Normandy are particularly renowned for Middle Jurassic deposits, the broader regional succession also records changing marine environments across a substantial part of Jurassic time.
During the Toarcian, the area formed part of a marine realm connected to the seas covering north-western Europe. Clay, marl, limestone and carbonate-rich sediment accumulated across the seabed as conditions changed.
The surrounding ecosystem supported ammonites alongside belemnites, bivalves, brachiopods, gastropods, crinoids and other marine invertebrates. Fish and marine reptiles occupied higher levels within the food web, while burrowing organisms lived within the soft sediment.
Sediment type affected how fossils formed. Fine mud could bury shells gently and preserve detailed impressions, while stronger currents could move, abrade or fragment remains before burial. Mineral-rich groundwater later altered the shells and surrounding rock, creating the preservation visible today.
Life of a Lower Jurassic Ammonite
Ammonites were extinct marine molluscs 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 older coiled section was divided into smaller chambers by curved internal walls called septa. A narrow tube known as the siphuncle connected these chambers and helped regulate their liquid and gas content. This chambered construction provided buoyancy control and allowed the animal to maintain its position within the water column.
Movement was achieved through jet propulsion. Water was drawn into the mantle cavity and expelled through a muscular funnel, pushing the ammonite in the opposite direction. Tentacles surrounding the mouth were probably used to capture small prey, gather food and explore the surrounding environment.
As the ammonite grew, new calcium carbonate shell material was added around the aperture. The animal moved forwards into a larger living chamber and formed additional septa behind itself, producing the spiral structure preserved in the fossil record.
Natural Fossilisation and Preservation
After death, the ammonite shell settled onto the Toarcian seabed. Its soft tissues decayed while sediment entered and accumulated around the shell. Burial helped protect the remains from complete destruction by currents, scavengers and chemical dissolution.
Over millions of years, pressure compacted the surrounding deposits into sedimentary rock. Mineral-rich groundwater could recrystallise, replace or dissolve the original aragonitic shell material. Sediment filling the shell chambers hardened into an internal mould capable of preserving the ammonite’s coiled shape and impressions of its original ornamentation.
Natural weathering, fractures, mineral staining, attached matrix and incomplete areas record the specimen’s long geological history. Each genuine fossil has undergone an individual sequence of burial, mineral alteration, tectonic movement and exposure, ensuring that no two examples are exactly alike.
This Esericeras eseri ammonite is suitable for fossil collectors, ammonite enthusiasts, geology students and educational natural-history displays. 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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