Description
Genuine Osperlioceras Ammonite Fossil from France
This carefully selected specimen is a genuine Osperlioceras sp. ammonite fossil from the Upper Toarcian Insigne Zone of Aveyron, Occitanie, southern France. It represents an extinct marine cephalopod that lived during the closing part of the Early Jurassic, when broad seas covered much of western Europe.
The fossil has been identified to the genus Osperlioceras. The abbreviation “sp.” is standard scientific terminology indicating that the specimen can be confidently assigned to this genus without attribution to a particular species. This careful level of identification preserves the fossil’s scientific accuracy while recognising the distinctive shell characteristics associated with the genus.
The listing photograph shows the exact fossil specimen you will receive, rather than a stock or representative image. Its individual preservation, colour, matrix, natural texture and visible shell detail can therefore be examined before purchase. Full sizing is shown in the accompanying photograph.
Fossil Classification and Geological Details
Scientific identification: Osperlioceras sp.
Fossil type: Ammonite
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Superfamily: Hildoceratoidea
Family: Hildoceratidae
Geological period: Jurassic
Epoch: Early Jurassic
Stage: Toarcian
Stratigraphic position: Upper Toarcian
Ammonite biozone: Insigne Zone
Locality: Aveyron, Occitanie, France
The genus is also encountered in palaeontological literature under the spelling Osperleioceras. It belongs to the Hildoceratidae, an important family of Early Jurassic ammonites that includes many characteristic forms used to identify and correlate Toarcian marine strata.
Characteristic Osperlioceras Shell Morphology
Osperlioceras ammonites generally possess compressed, streamlined shells coiled in a single plane. The shell consists of a succession of enlarging whorls arranged around a central depression known as the umbilicus. Each new whorl was added as the animal grew, creating the recognisable spiral form associated with ammonites.
The flanks may appear flattened or gently convex, narrowing towards the outer margin of the shell. A defined ventral region and keel are characteristic features of many hildoceratid ammonites, contributing to a hydrodynamic profile suited to movement through open water. Depending on preservation, the specimen may also display curved ribs, growth lines, whorl boundaries or sections of its original shell surface.
The ribbing of Osperlioceras may be fine, curved or falcate, meaning that the ribs sweep forwards in a sickle-like pattern towards the venter. Rib strength and spacing could change during growth, so juvenile and adult portions of the same shell may show different ornamentation. This natural variation gives every fossil its own distinct appearance.
During life, the ammonite occupied the final and largest section of the shell, called the body chamber. The earlier part was divided into sealed chambers by internal walls known as septa. These chambers were connected by a narrow tube called the siphuncle, which helped regulate the balance of gas and fluid and allowed the ammonite to control its buoyancy.
Upper Toarcian Insigne Zone
The Toarcian is the final stage of the Early Jurassic Epoch and occurred approximately 184 to 174 million years ago. The Upper Toarcian represents the younger part of this stage, shortly before the beginning of the Middle Jurassic.
This specimen is recorded from the Insigne Zone, an ammonite biozone recognised within the Upper Toarcian succession of France. Biozones are intervals of rock identified through characteristic fossil assemblages and the evolutionary appearance of particular ammonite groups.
Ammonites are especially valuable as index fossils because they evolved rapidly, were abundant and occupied extensive marine environments. Their changing shell forms allow geologists to compare rocks from different areas and place them within a detailed chronological sequence. A zoned fossil such as this therefore carries useful stratigraphic information in addition to its natural decorative appeal.
Jurassic Marine Environment of Aveyron
During the Toarcian, the region now forming Aveyron lay beneath a warm marine basin connected to the western Tethys Ocean. The limestone plateaux, valleys and rocky landscapes of modern southern France developed from sediments originally deposited across this ancient seabed.
Fine carbonate mud, clay and organic material settled through the water and accumulated in layers. These environments supported diverse communities of ammonites, belemnites, bivalves, brachiopods, gastropods, crinoids, fish and other marine organisms. Larger predators, including marine reptiles, occupied the surrounding waters.
After death, an ammonite shell could drift briefly or descend directly to the seafloor. Burial beneath soft sediment protected it from complete destruction. Continued sedimentation, pressure and mineral-rich groundwater gradually transformed the surrounding material into rock while preserving the shell as mineralised fossil material, an internal mould or a combination of both.
The Toarcian deposits of Aveyron are particularly noted for their varied ammonite faunas. Fossils from these strata document evolutionary changes within Early Jurassic cephalopods and provide evidence for the changing marine conditions of southern France.
Actual Fossil Specimen and Certificate of Authenticity
This is a genuine fossil specimen and not a replica, cast or reproduction. It has been individually chosen for its natural character, collectable appearance and geological interest. Differences in colour, matrix, texture, completeness, mineralisation and surface preservation are authentic results of burial, fossilisation and later natural weathering.
The photographs form an important part of the listing and show the exact Osperlioceras sp. ammonite that will be supplied. Full sizing is provided in the photograph so the specimen’s dimensions can be assessed before purchase.
The fossil includes a generic Certificate of Authenticity card carrying a lifetime guarantee of authenticity. It is an excellent addition to an ammonite collection, French Jurassic display, geological teaching collection or natural-history cabinet and would make a distinctive gift for a fossil collector, palaeontology enthusiast or admirer of prehistoric marine life.
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