Description
Genuine Dissoceras tabulatum Ammonite Fossil
This carefully selected specimen is a genuine Dissoceras tabulatum ammonite fossil from France, dating from the Middle Jurassic Period. Its recognised species identification, European provenance and distinctive chambered shell make it an appealing addition to a collection of French fossils, Jurassic ammonites or prehistoric marine life.
The Middle Jurassic was an important interval in ammonite evolution, during which numerous shell forms developed and diversified throughout the warm seas covering much of Europe. This fossil preserves evidence of one of those extinct marine cephalopods and offers a direct connection with an ancient ecosystem that existed more than 160 million years ago.
Dissoceras Shell Form and Ornamentation
Dissoceras tabulatum possessed a planispirally coiled shell, meaning that its successive whorls developed within a single plane. The ammonite’s morphology would have been defined by features such as the degree of whorl overlap, the width of the central umbilicus, the shape of the flanks and the form of the outer shell margin, known as the venter.
The specific name tabulatum refers to a flattened or tabulate characteristic, commonly associated in ammonite terminology with a relatively broad or flattened outer shell region. Depending upon the growth stage and preservation of the specimen, the fossil may display curved whorls, ribbing, changes in shell width, a visible umbilical region and portions of the ventral surface.
Ammonite identification is based on careful comparison of shell proportions and ornamentation. Palaeontologists consider the spacing and direction of ribs, the presence or absence of tubercles, the shape of the whorl section and changes that occurred as the animal matured. These details help separate related genera and species within the diverse Middle Jurassic ammonite fauna.
The exact characteristics visible on this individual specimen depend upon its natural preservation and the area exposed from the surrounding rock. It may retain mineralised shell material, impressions of the original surface or a natural internal mould formed when sediment hardened inside the empty shell.
Chambered Shell and Ammonite Biology
The ammonite shell was divided internally into a series of chambers by curved walls called septa. The living animal occupied the final and largest section, known as the body chamber, while the older chambered portion formed the phragmocone.
A narrow tube called the siphuncle passed through the chambers close to the outer edge of the shell. By regulating the balance of gas and liquid within these spaces, the ammonite could control its buoyancy and maintain an appropriate position in the water.
As the animal grew, it added new shell material around the open end and periodically formed another septum behind its body. This continuous growth produced the familiar spiral shape and recorded changes in shell ornamentation throughout the ammonite’s life.
Ammonites belonged to the extinct cephalopod group Ammonoidea and were related to modern squid, cuttlefish, octopuses and nautiluses. Their shells provided protection and buoyancy while their soft bodies probably included well-developed eyes, a beak-like mouth and arms used for capturing food.
Middle Jurassic Marine Environment
During the Middle Jurassic, large areas of present-day France were submerged beneath warm marine waters. France occupied an important geographical position between the shallow shelf seas of north-western Europe and the wider Tethyan marine realm farther south.
The environment varied from shallow carbonate platforms to deeper offshore basins. Limestone, marl, clay and other marine sediments accumulated as carbonate mud, mineral grains and the remains of marine organisms settled onto the seabed.
These seas supported diverse communities of ammonites, belemnites, bivalves, brachiopods, gastropods, echinoids and other invertebrates. Ammonites lived within the water column, while numerous shellfish and burrowing animals occupied the seabed below.
Changes in sea level, water depth, sediment supply and current strength created a varied geological succession. Some layers formed relatively quickly, while others accumulated slowly enough for shells and skeletal fragments to become concentrated on the sea floor.
Ammonites and Jurassic Biostratigraphy
Ammonites are among the most important fossils used to date Jurassic marine rocks. They evolved rapidly, produced numerous recognisable species and were distributed across wide geographical areas.
Successive ammonite groups appeared and disappeared through time, allowing palaeontologists to divide sedimentary sequences into detailed biozones. Fossil assemblages found in France can therefore be compared with equivalent Middle Jurassic rocks elsewhere in Europe.
Even when a precise bed or ammonite zone is not attached to an individual specimen, a securely identified species can provide useful information about the broader geological interval and the marine fauna present at that time.
The rich ammonite record of France has played an important role in the development of Jurassic palaeontology. Many French geological regions contain extensive marine sedimentary sequences that have been studied for their ammonites and other fossil organisms.
Natural Fossilisation Process
After this Dissoceras died, its shell descended to the Jurassic seabed. The soft tissues decayed, while sediment entered the body chamber and any internal chambers exposed through natural damage.
Further sediment gradually buried the shell. Over millions of years, pressure, compaction and mineral-rich groundwater transformed the surrounding material into solid rock. The original shell was composed principally of aragonite, a form of calcium carbonate that can dissolve or recrystallise during fossilisation.
Sediment filling the shell could harden into a durable internal mould, preserving the overall coiling and ornamentation after the original shell material had disappeared. In other cases, parts of the shell were replaced or coated by minerals circulating through the rock.
Natural matrix, mineral deposits, colour variation, worn ornamentation, incomplete whorls, small fractures and irregular edges are authentic results of fossilisation and prolonged geological exposure. These characteristics are part of the specimen’s history and make every fossil naturally unique.
Authentic French Fossil for Collection and Display
This genuine Dissoceras tabulatum ammonite is ideal for a collection of French fossils, Middle Jurassic ammonites, extinct cephalopods or European natural-history specimens. Its recognised species identification and distinctive fossil form give it strong geological, educational and display interest.
This is a carefully chosen individual specimen, and the photograph shows the actual fossil you will receive, rather than a representative example. Natural variations in shape, colour, matrix, mineralisation and preservation are genuine characteristics of the fossil.
Full sizing is shown in the photographs.
This fossil is a 100% genuine specimen and includes a generic Certificate of Authenticity card with a lifetime guarantee.
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