Description
Genuine Rabenoides striolaris Ammonite Fossil
This carefully chosen specimen is a genuine Rabenoides striolaris ammonite fossil from Normandy, France. It dates to the Lower Kimmeridgian Stage of the Upper Jurassic and represents an extinct marine cephalopod that inhabited the seas of north-western Europe approximately 155 million years ago.
Ammonites were highly successful marine molluscs related to modern squid, cuttlefish, octopuses and nautiluses. They possessed externally chambered shells that combined protection with a sophisticated buoyancy system. Their long evolutionary history, rapid development of new forms and wide geographical distribution make ammonites some of the most important and recognisable fossils of the Mesozoic Era.
The species-level identification Rabenoides striolaris, together with its Lower Kimmeridgian age and Normandy provenance, gives this specimen excellent scientific, educational and collection interest. It is particularly suitable for collectors specialising in French ammonites, Upper Jurassic fossils and European marine palaeontology.
Rabenoides striolaris Shell Morphology
The shell of Rabenoides striolaris was planispirally coiled, meaning that its successive whorls developed within a single flat plane around a central umbilicus. As the animal grew, each new section of shell was added around the earlier whorls, gradually increasing the overall diameter.
The species name “striolaris” refers to a finely marked or striated character, reflecting the shell’s relatively delicate surface ornament. Depending on growth stage and preservation, the flanks may display fine radial ribs, striae or growth markings extending from the umbilical region towards the outer margin. These features record successive stages in the ammonite’s shell development.
Visible characteristics may include the central umbilicus, curved whorls, fine ribbing, growth lines, the outer venter and sections of the body chamber or chambered phragmocone. The exact appearance of an individual fossil is influenced by shell maturity, burial conditions, mineral replacement, weathering and the orientation in which it was preserved.
Natural fractures, incomplete margins, worn ornament, mineral-filled cracks and attached sedimentary matrix are normal characteristics of an authentic Jurassic ammonite. These features form part of the specimen’s individual geological history rather than indicating artificial manufacture.
Chambered Shell and Buoyancy System
Internally, the ammonite shell was divided by mineralised walls called septa. These created a succession of chambers collectively known as the phragmocone. The living animal occupied only the final and largest section of the shell, called the body chamber.
A narrow tube known as the siphuncle passed through the chambers. This structure helped regulate the proportions of liquid and gas within them, allowing the ammonite to adjust its buoyancy and maintain an appropriate position in the water column.
Where the septa met the outer shell, they formed intricate lines called sutures. Ammonitic sutures are highly folded and can be important for classification when exposed on a fossil’s surface. The complex chamber walls also helped reinforce the shell against pressure and physical stress.
The soft-bodied animal extended from the shell aperture and probably possessed arms surrounding a hard beak-like mouth. Movement was achieved through controlled jet propulsion, while the chambered shell provided support and buoyancy.
Life in the Lower Kimmeridgian Sea
During the Lower Kimmeridgian, Normandy lay beneath a broad marine environment connected to the seas covering much of western Europe. The present coastlines and landscapes did not yet exist, and the region formed part of an extensive Jurassic marine basin.
Rabenoides striolaris shared these waters with other ammonites, belemnites, bivalves, gastropods, brachiopods, echinoids, crustaceans, fish and marine reptiles. This varied community occupied habitats ranging from the sediment-covered seabed to open water within the marine basin.
The ammonite was probably an active but relatively controlled swimmer. It may have consumed small crustaceans, planktonic animals, juvenile molluscs and other suitably sized prey. Ammonites themselves were also an important food source for larger fish and marine reptiles.
After death, the soft tissues decomposed and the shell descended towards the seabed. Sediment could enter the open body chamber and any damaged internal chambers. The shell was then gradually buried beneath accumulating marine mud and carbonate material.
Over millions of years, compaction transformed the surrounding sediment into rock. Mineral-rich groundwater entered cavities and fractures, preserving or replacing the shell and producing the fossil’s present colour, texture and density.
Upper Jurassic Kimmeridgian Geology
The Kimmeridgian is a stage of the Upper Jurassic Period and is named after Kimmeridge in Dorset, southern England. Rocks of this age occur across several parts of Europe and preserve evidence of widespread Late Jurassic marine environments.
Kimmeridgian sediments can include limestone, marl, clay and mudstone, reflecting differences in water depth, sediment supply, oxygenation and biological productivity. Limestone developed largely from carbonate mud and skeletal debris, while marl formed from a mixture of calcium carbonate and fine clay.
Ammonite faunas changed repeatedly during the Kimmeridgian. Because many ammonite groups evolved comparatively quickly and were distributed through broad marine areas, their fossils are valuable for comparing rock successions and establishing detailed relative ages.
The preservation of this specimen records a sequence of natural events beginning with shell growth in the Jurassic sea, followed by death, seabed burial, mineralisation, lithification, uplift and eventual exposure through erosion.
Normandy Fossil Provenance
Normandy in northern France contains extensive sedimentary rocks deposited during the Jurassic Period. Its fossil-bearing strata preserve evidence of the marine ecosystems that occupied the region long before the formation of the modern English Channel.
During the Late Jurassic, northern France and southern Britain formed neighbouring parts of connected marine environments. Related ammonite communities therefore occur across both regions, allowing their sedimentary successions to be compared through palaeontological evidence.
A recorded Normandy provenance adds valuable geographical context to this specimen. It connects the ammonite to a recognised European fossil-producing region rather than identifying it only as a general Jurassic fossil.
The combination of species-level identification, Lower Kimmeridgian age and French locality makes this Rabenoides striolaris particularly suitable for an ammonite collection, geological cabinet, educational display or collection of genuine Upper Jurassic marine fossils.
Authentic Fossil with Certificate of Authenticity
This is a genuine natural fossil and not a replica, cast or manufactured reproduction. Its coiled form, surface ornament, colour and preservation result from the original ammonite shell and the geological processes it experienced over millions of years.
The photograph shows the actual carefully chosen specimen you will receive. Please examine the supplied images closely, as they provide the best record of its precise condition, preserved detail, attached matrix and individual appearance.
Full sizing please see photo.
The fossil includes a generic Certificate of Authenticity card supported by our lifetime guarantee of authenticity.
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