Description
Genuine Podagrosites podagrosum Ammonite Fossil
This carefully selected specimen is a genuine Podagrosites podagrosum ammonite fossil from the Upper Toarcian Insigne Zone of Aveyron, Occitanie, southern France. It represents an extinct marine cephalopod that inhabited the warm seas covering this region during the closing part of the Early Jurassic.
Its distinctive coiled shell, recorded species identification and precise stratigraphic information make this an appealing specimen for collectors of ammonites, French fossils and Jurassic marine life. Ammonites are also important index fossils because their rapid evolution and extensive geographical distribution allow palaeontologists to identify and correlate separate layers of marine sedimentary rock.
The listing photograph shows the actual fossil you will receive, rather than a stock photograph or representative example. Its individual shape, ornamentation, colour, matrix and natural preservation can therefore be examined before purchase. Full sizing is shown in the accompanying photograph.
Fossil Classification and Geological Details
Scientific name: Podagrosites podagrosum
Fossil type: Ammonite
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Superfamily: Hildoceratoidea
Family: Hildoceratidae
Subfamily: Grammoceratinae
Genus: Podagrosites
Geological period: Jurassic
Epoch: Early Jurassic
Stage: Toarcian
Stratigraphic position: Upper Toarcian
Ammonite biozone: Insigne Zone
Locality: Aveyron, Occitanie, France
The genus Podagrosites was established by the Swiss palaeontologist Jean Guex in 1973 and is classified within the Grammoceratinae, a subfamily of the Hildoceratidae. Members of this group form part of a significant Upper Toarcian ammonite succession that helps palaeontologists compare Jurassic marine deposits across Europe.
Characteristic Podagrosites Shell Morphology
The shell of Podagrosites podagrosum grew in a flat spiral known as planispiral coiling. Each successive whorl became larger as the animal matured, forming the familiar circular outline associated with ammonites. The central exposed area is called the umbilicus, the sides of the shell are the flanks, and the outermost margin is known as the venter.
Podagrosites is associated with a relatively compressed shell form and an open to moderately open umbilical region. The flanks may carry clearly defined ribs that begin near the umbilical margin and curve or incline across the shell. Depending on the specimen’s growth stage and preservation, these ribs may remain simple or develop variations in strength, spacing and direction towards the outer whorl.
The ornamentation can change as the ammonite grows, meaning that the inner juvenile whorls may differ noticeably from the mature outer portion. Fine growth lines, stronger primary ribs, whorl boundaries and sections of the ventral profile may all be visible according to the manner in which the fossil has been preserved and prepared.
These shell characteristics provide the specimen with its individual natural appearance while also offering features useful for palaeontological comparison. Any areas of attached matrix, mineral infill, incomplete shell or surface weathering are authentic parts of its geological history.
Chambered Shell and Ammonite Life
The living ammonite occupied the final and largest section of its shell, known as the body chamber. The older inner portion was divided into a succession of sealed chambers by curved internal walls called septa.
A narrow tube known as the siphuncle passed through these chambers close to the outer edge of the shell. It helped regulate the balance of liquid and gas inside them, allowing the ammonite to control buoyancy and maintain its position in the water column.
Where the septa met the shell wall, they formed complex suture lines. These may become visible if the original outer shell layer is removed through natural weathering or fossil preparation. Ammonitic sutures commonly display intricately divided lobes and saddles and are important features in the classification of extinct cephalopods.
The soft-bodied animal was related to other cephalopods and probably possessed well-developed eyes, grasping appendages and a muscular funnel used for jet-propelled movement. Its chambered external shell combined protection with an efficient buoyancy system.
Upper Toarcian Insigne Zone
The Toarcian is the final stage of the Early Jurassic Epoch, following the Pliensbachian and preceding the Aalenian Stage of the Middle Jurassic. It extended from approximately 184 to 174 million years ago, with the Upper Toarcian representing its younger portion.
This fossil is recorded from the Insigne Zone, a recognised interval within the Upper Toarcian ammonite succession. In detailed French schemes, the Insigne interval may be treated as a subzone within the broader Speciosum Zone. Published occurrences of Podagrosites podagrosum place the species within this Upper Toarcian Insigne succession.
Ammonite zones are identified through characteristic fossil assemblages and the changing occurrence of particular species. Because ammonites evolved relatively rapidly and occupied widespread marine environments, these zones allow geologists to compare rocks from separate localities with considerable precision.
The specimen therefore preserves more than the form of an individual prehistoric animal. It also represents a recognisable interval in the geological sequence of the Early Jurassic seas.
Jurassic Marine Environment of Aveyron
During the Toarcian, the region now forming Aveyron lay beneath a 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 these ancient seabeds.
Fine carbonate mud, clay and organic debris settled through the water and accumulated in layers. These environments supported ammonites, belemnites, bivalves, brachiopods, gastropods, crinoids, fish and numerous other marine organisms. Larger predators, including marine reptiles, inhabited the surrounding waters.
After death, the ammonite shell could drift briefly or descend directly to the seabed. Rapid burial beneath soft sediment helped protect it from scavenging, erosion and complete dissolution. Further layers gradually accumulated above the shell, compacting the sediment and transforming it into sedimentary rock.
Mineral-rich groundwater could enter the shell’s chambers, replace original shell material or create a solid internal mould. Later geological uplift and erosion exposed the fossil-bearing Toarcian rocks, allowing specimens such as this one to be discovered and prepared.
Actual Fossil and Certificate of Authenticity
This is a genuine fossil specimen and not a replica, cast or modern reproduction. It has been individually chosen for its natural character, geological interest and collectable appearance. Differences in colour, texture, matrix, mineralisation, completeness and surface preservation are authentic results of burial, fossilisation and natural weathering.
The listing photograph shows the exact Podagrosites podagrosum ammonite fossil that will be supplied. Full sizing is provided in the photograph so that 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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