Description
Genuine Brasoeisphinctes curvatus Ammonite Fossil
This carefully chosen specimen is a genuine Brasoeisphinctes curvatus ammonite fossil from Calvados in Normandy, France. It originates from the Poitou Formation and dates to the Upper Bajocian interval of the Middle Jurassic, representing an extinct marine cephalopod that lived approximately 168–170 million years ago.
Its identified species, documented geological formation, Upper Bajocian age and recorded French locality give this fossil excellent scientific and collectable interest. It would make a distinctive addition to a specialist ammonite collection, Jurassic fossil display, educational collection or cabinet of natural-history specimens.
The photograph shows the exact fossil specimen you will receive. Full sizing and scale information can be seen in the accompanying photograph.
Upper Bajocian Middle Jurassic Geology
The Bajocian Stage forms part of the Middle Jurassic Period and takes its name from Bayeux in Normandy. During the Upper Bajocian, much of the area now forming north-western France was covered by warm marine waters connected to the extensive Jurassic seas of western Europe.
Carbonate-rich mud, fine mineral particles, shell fragments and other marine sediments accumulated across the ancient seabed. These deposits were gradually compacted and cemented into limestone, marl and related sedimentary rocks. The resulting fossil-bearing strata preserve evidence of an ecosystem inhabited by ammonites, belemnites, nautiloids, bivalves, brachiopods, gastropods, echinoids and numerous other marine organisms.
When an ammonite died, its shell could settle onto the sea floor and become covered by sediment. The original aragonitic shell might later be mineralised, replaced or dissolved, leaving an external impression or a stone-filled internal mould. Burial pressure, sediment chemistry, mineral-rich groundwater and later weathering all influenced the fossil’s final appearance.
Variations in colouring, texture, matrix, completeness, mineral deposits and surface condition are therefore natural features created during fossilisation. Every authentic ammonite preserves a unique combination of biological form and geological history.
Brasoeisphinctes curvatus Shell Morphology
Brasoeisphinctes curvatus is an ammonite distinguished through characteristics of its coiled shell, including whorl proportions, umbilical width, ribbing and changes in ornamentation during growth. As with many Jurassic ammonites, the shell is planispirally coiled, meaning that its whorls developed within a single plane around a central umbilical region.
The shell is typically evolute in form, with the inner whorls remaining relatively exposed rather than being heavily overlapped by later growth. This produces a clearly visible umbilicus and gives the fossil an open, strongly coiled appearance.
Ornamentation commonly consists of numerous radial ribs extending across the flanks. These ribs may remain simple or divide as they approach the outer part of the whorl. Rib spacing, curvature and branching patterns can vary through the animal’s development, helping specialists distinguish related ammonite taxa.
Depending on its individual preservation, this specimen may display sections of the inner and outer whorls, ribbed flanks, umbilical region, ventral edge, internal chambers or surrounding Jurassic matrix. Its preserved details record both the original growth of the ammonite and the physical and chemical processes that affected the shell after burial.
Extinct Jurassic Marine Cephalopod
Ammonites were marine molluscs related to living squid, cuttlefish, octopuses and nautiluses. Unlike most modern cephalopods, they possessed a hard external shell divided internally into a series of chambers.
The animal occupied the final and largest section, known as the body chamber. The older chambers formed the phragmocone, which functioned as part of the ammonite’s buoyancy system. A narrow tube called the siphuncle connected these chambers and allowed the animal to regulate the balance of liquid and gas within them.
As the ammonite grew, it constructed progressively larger chambers around the outer edge of the shell. The partitions between the chambers met the shell wall along complex suture lines. These sutures, together with the shell’s ribbing, coiling style, whorl section and umbilical proportions, are important features used in ammonite classification.
Ammonites evolved rapidly and became widely distributed through Jurassic marine environments. Their fossils are therefore particularly useful in biostratigraphy, helping geologists identify and correlate rock layers of similar age across different regions.
Poitou Formation Fossil from Normandy
The Poitou Formation preserves marine sedimentary rocks deposited during the Middle Jurassic. Fossils from these strata provide evidence of the changing sea levels, sedimentary conditions and marine communities present in France during the Bajocian.
Calvados has exceptional importance in the history of Jurassic palaeontology. The Bajocian Stage was named after Bayeux, and ammonites from Normandy have played a major role in the study and subdivision of Middle Jurassic rock sequences.
A specimen retaining its species name, formation, geological interval and locality offers significantly greater scientific and collectable value than an ammonite without accompanying provenance. This Brasoeisphinctes curvatus is suitable for collectors of French fossils, Jurassic ammonites, extinct cephalopods and historically important European geological specimens.
Actual Specimen with Certificate of Authenticity
This is a genuine fossil specimen and not a cast, replica or reproduction. It has been individually selected for its natural form, geological character and collectable appeal.
The photograph shows the actual Brasoeisphinctes curvatus ammonite fossil you will receive. Full sizing is shown in the photograph.
A generic Certificate of Authenticity card is included with a lifetime guarantee of authenticity, providing lasting confidence that this is a genuine Middle Jurassic fossil.
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