Description
Genuine Asaphoceras Ammonite Fossil
This genuine ammonite fossil is identified as Asaphoceras sp. and originates from Aveyron in the Occitanie region of southern France. It dates from the Toarcian Stage of the Lower Jurassic and preserves the remains of an extinct marine cephalopod that inhabited the ancient European seas approximately 174 to 184 million years ago.
The abbreviation “sp.” indicates that the specimen has been identified confidently as belonging to the genus Asaphoceras, while a precise species-level determination has not been applied. This is standard scientific terminology for fossils that preserve the characteristic features of a genus but do not display every detail required for a secure species identification.
The specimen has been carefully chosen for its geological interest, recognisable ammonite form and documented French provenance. The listing photographs show the exact fossil you will receive, allowing its natural shape, preservation, matrix, mineral colouring and individual surface features to be examined before purchase. Full sizing and scale information are provided in the photographs.
Asaphoceras Identification and Ammonite Palaeontology
Asaphoceras belongs to the ammonites, an extinct and exceptionally diverse group of marine molluscs that flourished throughout much of the Mesozoic Era. Ammonites were members of the class Cephalopoda and were therefore related to living squid, cuttlefish, octopuses and nautiluses.
Its broad classification includes:
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Genus: Asaphoceras
Identification: Asaphoceras sp.
Ammonite identification is based on a combination of shell characteristics, including the degree of coiling, whorl proportions, width of the central umbilicus, rib shape, ventral structure and suture pattern. These features may change as the animal grows, meaning that the inner juvenile whorls can differ noticeably from the mature outer portion.
The preservation of individual fossils also affects identification. Some specimens retain sections of the original shell or mineral replacement, while others survive primarily as natural internal moulds created when sediment filled the shell chambers and later hardened.
Shell Form and Morphological Features
The shell of this Asaphoceras ammonite developed as a planispiral coil, with successive whorls growing around one another within approximately the same plane. The earlier whorls form the centre of the fossil, while the progressively larger outer whorls record the animal’s continued growth.
The visible central area is known as the umbilicus. Its width and the extent to which later whorls overlap earlier ones are important features used when comparing ammonites. More openly coiled shells are described as evolute, while tightly overlapping shells are described as involute.
Depending on preservation, the flanks may display ribs, folds or fine growth markings extending from the inner whorl towards the outer margin. Rib strength, curvature and spacing could change throughout development. Surface details may appear sharp where external shell ornament survives or more subdued where the fossil is preserved as an internal mould.
The outer edge of the ammonite shell is called the venter. Its original shape may have been rounded, flattened or more narrowly defined. Natural wear, compression or incomplete preservation can soften these features, giving each fossil its own distinctive appearance.
Chambered Shell and Buoyancy
Internally, the ammonite shell was divided by curved partitions called septa. These formed a succession of chambers connected by a narrow tube known as the siphuncle.
The living ammonite occupied only the final and largest body chamber. As the animal grew, it added new shell material around the aperture, moved forwards and sealed the older section behind itself with another septum.
The abandoned chambers contributed to buoyancy regulation. By controlling the balance of liquid and gas within them, the ammonite could maintain or adjust its position in the marine water column.
Where the septa met the outer shell wall, they produced intricate patterns called suture lines. These structures are important in ammonite classification and can provide evidence of evolutionary relationships between different groups.
The soft-bodied animal would have extended its head, eyes and muscular arms from the shell opening. It probably fed on small marine organisms, planktonic animals or organic material encountered within the surrounding sea.
Toarcian Lower Jurassic Age
This fossil dates from the Toarcian, the final stage of the Lower Jurassic. The Toarcian followed the Pliensbachian and preceded the Aalenian, which marks the beginning of the Middle Jurassic.
This interval was a period of significant environmental change and ammonite diversification. Marine communities underwent repeated episodes of migration, evolutionary development and extinction, producing a detailed succession of ammonite forms within the sedimentary record.
Ammonites are especially valuable index fossils because many species evolved quickly and existed for relatively restricted periods while becoming distributed across broad marine areas. Their fossils allow palaeontologists to divide sedimentary rocks into zones and subzones and compare similarly aged deposits from separate regions.
The recorded Toarcian age gives this specimen meaningful geological context and places it within a defined interval of Early Jurassic marine history.
Jurassic Marine Environment of Southern France
During the Toarcian, much of what is now southern France was covered by warm seas connected with the western Tethys Ocean. Shallow shelves, deeper basins and carbonate platforms extended across areas that are now inland landscapes.
These waters supported ammonites, belemnites, nautiloids, bivalves, gastropods, brachiopods, crustaceans, fish and marine reptiles. Microscopic plankton formed an important foundation of the food web and contributed organic and calcareous material to the seabed.
Fine mud, clay, carbonate particles and shell debris accumulated over long periods. Changes in sea level, water circulation, biological productivity, oxygen availability and sediment supply produced alternating deposits of limestone, marl and clay.
The ammonite represented by this fossil lived within the water column above that ancient seabed. Its chambered shell provided protection and buoyancy while it moved through a diverse Early Jurassic marine ecosystem.
Aveyron, Occitanie Fossil Provenance
Aveyron is internationally recognised for its fossil-rich Lower Jurassic rocks and its varied Toarcian ammonite faunas. The region contains extensive exposures of marine limestone and marl that preserve a detailed record of ancient seas and changing cephalopod communities.
Ammonites from Aveyron have contributed significantly to the study of Jurassic biostratigraphy and palaeontology. Their succession through the rock layers enables geologists to compare the region with equivalent marine deposits elsewhere in France, Britain, Germany and other parts of Europe.
A fossil retaining its genus identification, geological stage and regional locality provides substantially greater scientific and educational value than an ammonite offered without collection information. The documented Aveyron provenance connects this specimen directly with one of France’s classic Toarcian fossil regions.
Natural Fossilisation and Preservation
After the ammonite died, its shell descended to the seabed. Currents, scavenging organisms and sediment movement may have affected it before final burial.
Fine marine sediment entered the empty shell chambers and accumulated around the exterior. As further layers were deposited, pressure compacted the sediment and gradually transformed it into sedimentary rock.
The original shell was composed mainly of aragonite, a form of calcium carbonate that can dissolve, recrystallise or be replaced by other minerals during fossilisation. Sediment filling the chambers could harden into a natural internal mould that preserved the ammonite’s coiled form and portions of its original ornamentation.
Natural fractures, incomplete edges, worn shell areas, matrix deposits, mineral markings and variations in colour are authentic products of burial and geological alteration. These features form part of the fossil’s individual history and ensure that every specimen is unique.
Actual Specimen and Certificate of Authenticity
This is a genuine fossil specimen and not a cast, replica or artificial reproduction. The listing photographs show the exact Asaphoceras sp. ammonite that will be supplied, allowing its natural shell form, preservation, matrix, mineral colouring and individual surface characteristics to be viewed before purchase.
Full sizing is shown in the listing photographs.
The fossil includes a generic Certificate of Authenticity card carrying a lifetime guarantee. Its identifiable ammonite form, Toarcian age and documented Aveyron provenance make it an excellent addition to a Jurassic ammonite collection, French fossil display, natural-history cabinet or educational geological collection.
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