Description
Genuine Pseudosubplanites Ammonite Fossil
This carefully chosen fossil is a genuine Pseudosubplanites sp. ammonite from Le Boisset in the Gard department of southern France. Dating from the Lower Berriasian Stage of the Lower Cretaceous and attributed to the Grandis Zone, it represents an extinct marine cephalopod that inhabited the western Tethys marine realm around the beginning of the Cretaceous Period.
The abbreviation “sp.” indicates that the specimen has been confidently identified as belonging to the genus Pseudosubplanites, while no individual species has been assigned. This is standard palaeontological terminology and provides an accurate genus-level identification without overstating the diagnostic detail preserved in the fossil.
The photograph shows the actual specimen you will receive, allowing its individual coiling, ribbing, preservation, colour, matrix and natural geological characteristics to be examined before purchase. Full sizing and proportions can be seen in the accompanying photograph.
This authentic fossil includes a generic Certificate of Authenticity card with a lifetime guarantee.
Fossil Classification and Geological Details
Scientific name: Pseudosubplanites sp.
Fossil type: Ammonite
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Family: Neocomitidae
Subfamily: Berriasellinae
Geological period: Cretaceous
Epoch: Early Cretaceous
Stage: Lower Berriasian
Biozone: Grandis Zone
Locality: Le Boisset, Gard, France
The genus Pseudosubplanites was established by the French palaeontologist Gérard Le Hégarat for distinctive ammonites from the Lower Berriasian of south-eastern France. Its type species is Pseudosubplanites berriasensis, and members of the genus are important components of early Berriasian ammonite assemblages.
Ammonites are particularly valuable in biostratigraphy because their shell forms evolved relatively rapidly and many groups were distributed across broad marine regions. Their fossils allow palaeontologists to identify the relative ages of sedimentary rocks and compare geographically separated geological sections.
Pseudosubplanites Shell Morphology
Pseudosubplanites ammonites typically possess a planispirally coiled and comparatively evolute shell. In an evolute ammonite, successive whorls overlap only slightly, leaving a broad central umbilicus and exposing much of the earlier growth.
The flanks are commonly ornamented with numerous ribs that originate near the umbilical margin. These primary ribs may divide into two or more secondary branches as they extend towards the outer part of the whorl. Additional shorter ribs can sometimes occur between the longer primary ribs, producing a dense and intricate pattern across the shell.
The outer edge of the ammonite shell is called the venter. Its shape, together with the degree of whorl overlap, ribbing pattern, whorl height and shell compression, provides important information when distinguishing Pseudosubplanites from related berriaselline ammonites.
The exact prominence of these features varies according to the specimen’s growth stage and preservation. Natural fractures, matrix attachments, worn sections, mineral deposits and incomplete areas are authentic geological characteristics acquired during fossilisation and later exposure.
Lower Berriasian Grandis Zone
The Berriasian is the earliest stage of the Cretaceous Period, immediately following the Tithonian Stage of the Late Jurassic. It records a transitional interval during which many ammonite lineages continued to develop within the warm marine environments of the Tethyan realm.
The Grandis Zone, also treated in some regional schemes as the Grandis Subzone within a broader Jacobi Zone, takes its name from Pseudosubplanites grandis. This characteristic ammonite is used to recognise and correlate part of the Lower Berriasian succession.
A biozone is a body of sedimentary rock identified through the occurrence of a particular fossil or fossil assemblage. The Grandis Zone attribution therefore gives this specimen a more precise geological context than the broader description of Lower Cretaceous alone.
The fossil represents a particularly significant chapter in Earth history close to the traditional boundary between the Jurassic and Cretaceous periods. Ammonites from this interval are important for studying faunal change and correlating marine deposits across France and the wider Mediterranean region.
Early Cretaceous Geology of Gard
Le Boisset lies within the Gard department of southern France, a region containing extensive Mesozoic limestone and marl deposited within the western Tethys marine realm. During the Lower Berriasian, the modern landscape of southern France did not exist. The area was covered by a warm sea in which carbonate mud and fine sediment accumulated on the seabed.
These marine sediments eventually hardened into limestone and marl. Later uplift, faulting and erosion associated with the complex geological development of southern France exposed the ancient deposits at the surface.
The Lower Berriasian sea supported ammonites alongside belemnites, nautiloids, bivalves, brachiopods, gastropods, echinoids and microscopic planktonic organisms. Fish and marine reptiles formed part of the broader ecosystem, while bottom-dwelling invertebrates occupied the sediment-rich seabed.
Fine-grained marine sediment could bury shells before they were completely destroyed by currents, scavengers or dissolution. This provided favourable conditions for the preservation of ammonite coiling and ribbed ornamentation.
Life of a Pseudosubplanites Ammonite
Ammonites were marine molluscs related to living squid, cuttlefish, octopuses and nautiluses. The animal occupied the final and largest section of its shell, known as the body chamber.
The older portion of the shell was divided into a sequence of chambers by curved internal walls called septa. These chambers were connected by a narrow tube known as the siphuncle. By regulating the proportions of liquid and gas within them, the animal could control its buoyancy and maintain its position in the water column.
Movement was achieved through jet propulsion. Water was drawn into the mantle cavity and expelled through a muscular funnel, pushing the ammonite in the opposite direction. Tentacles surrounding the mouth were probably used to locate and capture small prey.
As the ammonite grew, it added new calcium carbonate material around the aperture. The animal periodically moved forwards into a larger living space and formed a new septum behind itself, producing the chambered spiral structure preserved in the fossil record.
Natural Fossilisation and Preservation
After death, the ammonite shell descended to the Berriasian seabed. Its soft tissues decayed while fine marine sediment entered and accumulated around the shell. Continued burial helped protect the remains from complete destruction.
Over millions of years, pressure compacted the surrounding deposits into rock. Mineral-rich groundwater could recrystallise, replace or dissolve the original aragonitic shell material. Sediment that entered the empty shell hardened into an internal mould, preserving the ammonite’s form even where the original shell had disappeared.
Natural weathering, fractures, matrix attachments, mineral staining and incomplete areas record the specimen’s geological history and ensure that every fossil is individually distinctive.
This Pseudosubplanites sp. ammonite is suitable for fossil collectors, ammonite enthusiasts, geology students and educational natural-history displays. The photograph shows the exact carefully selected fossil specimen you will receive. Full sizing is shown in the photo. A generic Certificate of Authenticity card with a lifetime guarantee is included.
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