Description
Genuine Lissoceras oolithicum Ammonite Fossil
This carefully chosen fossil is a genuine Lissoceras oolithicum ammonite from Maltot in Calvados, Normandy, France. It originates from the ferruginous oolite deposits of the Bajocian Stage of the Middle Jurassic and represents an extinct marine cephalopod that lived in the ancient European seas approximately 170 million years ago.
The photograph shows the actual fossil specimen you will receive rather than a stock image or representative example. Its individual shell form, natural colour, preservation, surface detail and surrounding matrix can therefore be examined before purchase. Full sizing and proportions are shown in the accompanying photographs.
Lissoceras oolithicum Shell Morphology
Lissoceras oolithicum is notable for the comparatively smooth and elegant shell form associated with the genus Lissoceras. The shell was planispirally coiled, with successive whorls wrapped around a central umbilicus in a single plane. Compared with many strongly ribbed Bajocian ammonites, Lissoceras commonly displays subdued ornamentation, giving specimens a distinctive streamlined appearance.
The whorls are generally compressed and relatively high, with gently convex flanks and a smoothly rounded outer margin known as the venter. Surface ornament may consist mainly of fine growth lines rather than the bold ribs and tubercles seen in more heavily ornamented Jurassic ammonites. These subtle features reflect the gradual enlargement of the shell as the animal matured.
The proportions of the whorls, degree of overlap, umbilical width and shape of the venter are important characteristics used when comparing smooth-shelled ammonites. Depending on preservation, these details may appear as original shell material, a mineralised surface, an external impression or relief preserved on a natural internal mould.
Life of a Middle Jurassic Ammonite
Ammonites were marine molluscs related to modern squid, cuttlefish, octopuses and nautiluses. Unlike most living cephalopods, they carried a prominent external shell that provided protection and assisted with buoyancy control.
The living animal occupied the final and largest section of the shell, known as the body chamber. Earlier portions were divided internally by curved walls called septa, creating a succession of chambers. These chambers were connected by a narrow tube called the siphuncle.
By regulating the proportions of liquid and gas within the chambered shell, the ammonite could adjust its buoyancy and maintain its position in the water column. Movement was probably achieved partly through jet propulsion, with water drawn into the mantle cavity and expelled through a muscular funnel.
Ammonites formed an important part of Jurassic marine ecosystems. They occupied a variety of open-water environments, feeding on small marine organisms while also serving as prey for fish, marine reptiles and larger cephalopods.
Bajocian Middle Jurassic Geology
The Bajocian is a stage of the Middle Jurassic Period, dating from approximately 170 to 168 million years ago. During this interval, large parts of western Europe were covered by warm, shallow seas divided by islands and low-lying land areas.
Marine sediments accumulated across the seabed as limestone, marl, clay and iron-rich deposits. These rocks preserve abundant evidence of Jurassic life, including ammonites, belemnites, bivalves, brachiopods, gastropods, echinoids and other marine organisms.
Ammonites are especially important to Jurassic geology because their shell forms evolved rapidly. Many species existed for comparatively limited periods, allowing palaeontologists to use them in biostratigraphy. This method compares fossil assemblages from different rock exposures to determine their relative ages and positions within the geological succession.
Ferruginous Oolite Formation
This specimen is recorded from the ferruginous oolite, known in French as the Oolithe ferrugineuse. Oolitic rocks consist of numerous small, rounded grains called ooids. These formed when mineral material accumulated in concentric layers around tiny particles while being moved by currents in shallow marine water.
Ferruginous ooids contain significant iron minerals, which often produce characteristic shades of brown, orange, rust-red or ochre within the rock and fossils. Such deposits typically formed where sediment accumulated slowly and seabed particles were repeatedly rolled or disturbed by waves and currents.
The iron-rich matrix can give ammonites from these beds a particularly attractive and recognisable appearance. Contrasting mineral colours may highlight the shell outline, whorls or remaining surface features, while attached matrix preserves part of the specimen’s original geological context.
Maltot, Calvados, Normandy Provenance
Maltot is situated in the Calvados department of Normandy in northern France. The surrounding region contains extensive Jurassic sedimentary rocks deposited within the ancient seas that once covered this part of Europe.
Normandy is well known for its fossiliferous Jurassic formations, including limestones, marls and oolitic beds containing ammonites and other marine fossils. Fossils from accurately recorded localities are particularly desirable because their provenance connects each specimen with a defined geographical and geological setting.
This ammonite retains its recorded Maltot locality, its identification as Lissoceras oolithicum and its origin from the Bajocian ferruginous oolite. These details enhance its scientific, educational and collectable interest.
Fossilisation and Natural Preservation
After the ammonite died, its shell settled onto the Jurassic seabed and was gradually buried by iron-rich marine sediment. Burial protected parts of the shell from complete destruction by currents, scavengers and biological activity.
Over millions of years, the sediment was compacted and cemented into rock. The original aragonitic shell could be partly preserved, replaced by minerals or dissolved to leave a mould. Sediment entering the empty chambers could harden into a natural internal cast that retained the shell’s overall shape.
Natural fractures, worn areas, small chips, mineral-filled cracks, matrix attachment and variations in surface texture are normal features of genuine fossils. They record the specimen’s burial, fossilisation and geological history and contribute to its individuality.
Collectable French Jurassic Fossil
This Lissoceras oolithicum ammonite would make an appealing addition to a collection of French fossils, Bajocian ammonites, Middle Jurassic cephalopods or ferruginous oolite specimens. Its smooth shell form and documented Normandy provenance make it suitable for a geological cabinet, educational collection, natural-history display or distinctive fossil gift.
The fossil has been individually selected, and the photographs show the exact specimen that will be supplied. Full sizing can be seen in the accompanying images.
This is a 100% genuine fossil specimen and includes a generic Certificate of Authenticity card with a lifetime guarantee.
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