Description
Genuine Hammatoceras simulatum Ammonite Fossil
This genuine Hammatoceras simulatum ammonite fossil comes from Les Rives in Aveyron, Occitanie, southern France. It dates from the Middle Toarcian Stage of the Lower Jurassic Period, when the region formed part of an extensive marine environment inhabited by ammonites and many other prehistoric sea creatures.
This specimen has been carefully selected for its natural appearance, geological interest and individual fossil detail. The accompanying photographs show the actual fossil you will receive, allowing you to examine its preservation, matrix, colour, shell form and visible ornamentation before purchase. Full sizing and scale information can be seen in the photographs.
Each fossil is naturally unique. Variations in surface texture, mineralisation, matrix, shell completeness and preservation are authentic features created through fossilisation and more than 175 million years of geological history.
Middle Toarcian Geological Age
The Toarcian is the final stage of the Lower Jurassic Epoch and represents an important interval in ammonite evolution. During this time, ammonites diversified into a wide range of forms that are now used by palaeontologists to date and correlate marine sedimentary rocks.
The Middle Toarcian deposits of southern France are especially well known for their varied ammonite faunas. Fossils such as Hammatoceras simulatum are therefore valuable not only as display specimens but also as records of ancient marine biodiversity.
Ammonites evolved relatively quickly and many species existed for limited spans of geological time. This makes them useful index fossils, allowing rock layers from separate localities to be compared according to the ammonite assemblages they contain.
Hammatoceras Shell Form and Ornamentation
Hammatoceras ammonites are recognised for their strongly ornamented, planispirally coiled shells. The shell was divided internally into a series of chambers, with the living animal occupying the final and largest body chamber. Earlier chambers were connected by a tube called the siphuncle, which helped the ammonite regulate buoyancy within the water column.
Members of the genus commonly display an evolute shell form in which the earlier whorls remain visible around a relatively open central umbilicus. The flanks may carry prominent ribs that arise near the umbilical margin and extend outward towards the ventral region.
Depending on preservation and growth stage, the ribbing may appear curved, flexuous or divided. Stronger ornamentation, including raised rib endings or small tubercle-like features, can occur around the outer flanks. These characteristics gave the shell added structural strength and are important features used in ammonite identification.
The shell’s outer edge, known as the venter, may be comparatively narrow and can show a raised keel or defined ventral structure. The combination of coiling, ribbing, whorl shape and ventral form gives Hammatoceras its distinctive appearance.
Scientific Classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Superfamily: Hammatoceratoidea
Family: Hammatoceratidae
Genus: Hammatoceras
Species: Hammatoceras simulatum
Ammonites were extinct marine molluscs related to modern cephalopods, including squid, cuttlefish, octopuses and nautiluses. Their chambered shells were highly successful adaptations, and ammonites became widespread throughout the world’s Jurassic seas.
Ancient Marine Environment of Aveyron
During the Middle Toarcian, the area now known as Aveyron was influenced by warm marine conditions connected with the western Tethys Ocean. Fine mud, carbonate sediment and the remains of marine organisms accumulated across the seabed.
The ammonite shell would have settled onto the sea floor after the animal died. Rapid or gradual burial protected parts of the shell from complete destruction. As additional sediment accumulated, pressure compacted the layers and transformed them into sedimentary rock.
Mineral-rich groundwater later moved through the buried deposits, replacing or infilling parts of the original shell. This long fossilisation process preserved the ammonite as the specimen seen today. Any attached matrix provides part of the original geological context and contributes to the fossil’s natural character.
Les Rives Fossil Locality
Les Rives lies within the Aveyron department of the Occitanie region of France, an area known for Jurassic sedimentary exposures and scientifically important ammonite assemblages. Fossils from this region are collected and studied for their value in reconstructing Lower Jurassic marine environments and understanding ammonite evolution.
A locality-specific specimen such as this is particularly desirable because its geological origin and stratigraphic age are recorded. This makes it suitable for organised fossil collections, educational displays and comparative palaeontological study.
Genuine Actual Specimen with Certificate of Authenticity
This is a 100% genuine fossil specimen, not a replica, cast or modern reproduction. It includes a generic Certificate of Authenticity card with a lifetime guarantee, providing lasting reassurance regarding its genuine fossil status.
The specimen is suitable for:
- Ammonite and Jurassic fossil collections
- Natural-history and palaeontology displays
- Geological teaching and educational collections
- Display cabinets, studies and offices
- Gifts for fossil collectors and geology enthusiasts
- Reference or comparative fossil collections
The photographs form an important part of the listing and show the exact Hammatoceras simulatum ammonite fossil that will be supplied. Please refer to the photographs for full sizing and for a detailed view of the specimen’s condition, preservation and individual geological features.
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