Description
Genuine Hammatoceras simulator Ammonite Fossil
This genuine Hammatoceras simulator ammonite fossil originates from Aveyron in Occitanie, southern France. It dates from the Upper Toarcian Stage of the Lower Jurassic Period and is recorded from the Insigne Zone, an important ammonite biozone within the later part of the Toarcian.
This carefully selected fossil represents an extinct marine cephalopod that inhabited the warm prehistoric seas surrounding western Europe during the Jurassic. Its recognised species, documented geological age and French locality make it an appealing specimen for ammonite collectors, fossil enthusiasts and natural-history displays.
The photographs show the actual specimen you will receive, rather than a stock photograph or representative example. Please refer to the images for full sizing and for a detailed view of the fossil’s preservation, colour, matrix, ornamentation and individual geological characteristics.
Upper Toarcian Insigne Zone
The Toarcian is the final stage of the Lower Jurassic Epoch, following the Pliensbachian and preceding the Aalenian. The Upper Toarcian represents the later portion of this stage, when ammonite faunas continued to diversify across marine environments connected with the western Tethys Ocean.
This specimen is associated with the Insigne Zone, named after the characteristic ammonite Hammatoceras insigne. Ammonite zones are biostratigraphic divisions identified through particular species and fossil assemblages occurring within successive layers of sedimentary rock.
Because ammonites evolved rapidly, were widely distributed and often existed for relatively limited intervals, they are exceptionally useful index fossils. Palaeontologists use their changing assemblages to determine the relative ages of marine strata and to correlate rock sequences between geographically separated regions.
A fossil with recorded zone information therefore retains valuable geological context in addition to its appeal as a display specimen.
Hammatoceras Shell Morphology
Hammatoceras simulator possessed a planispirally coiled shell divided internally into numerous chambers. The animal occupied the final and largest body chamber, while the older sealed chambers formed the phragmocone. These chambers were connected by a narrow tube called the siphuncle, which helped regulate the balance of liquid and gas and allowed the ammonite to control its buoyancy.
Species of Hammatoceras typically display an evolute to moderately involute shell, depending on the animal’s age and growth stage. Juvenile whorls may be more openly coiled, leaving earlier portions of the shell visible around the central umbilicus. Later whorls can become more embracing as the shell increases in size.
The flanks commonly carry strong ribs beginning near the umbilical shoulder. These ribs may divide as they pass across the shell and can terminate close to the outer ventral region. Raised swellings or tubercle-like features may occur where the ribs originate or divide.
The outer margin, known as the venter, is commonly narrow and bears a defined keel. This combination of a keeled venter, prominent ribbing, shell proportions and changing ornamentation through growth helps distinguish Hammatoceras from related Toarcian ammonites.
Scientific Classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Superfamily: Hildoceratoidea
Family: Hammatoceratidae
Genus: Hammatoceras
Species: Hammatoceras simulator Monestier, 1921
The species was formally described by French palaeontologist Joachim Monestier in 1921. Ammonites were marine molluscs related to living cephalopods such as squid, cuttlefish, octopuses and nautiluses. They flourished throughout much of the Mesozoic Era and developed an extraordinary range of shell forms before becoming extinct at the end of the Cretaceous Period.
Jurassic Marine Environment of Aveyron
During the Upper Toarcian, the region now forming Aveyron was influenced by marine conditions associated with the western Tethyan realm. Fine mud, carbonate sediment and the remains of marine organisms accumulated across the seabed, creating the layers that would eventually preserve ammonites and other fossils.
After the ammonite died, its shell descended to the sea floor. Burial beneath sediment protected parts of it from scavengers, currents and complete dissolution. Continued deposition placed the shell under increasing pressure, compacting the surrounding sediment and gradually transforming it into rock.
Mineral-rich groundwater later passed through the buried deposits, filling internal spaces and preserving or replacing portions of the original shell. Any natural matrix, mineral deposits, surface weathering, fine fractures or incomplete areas visible on the specimen are products of this long geological history.
These natural features are expected in authentic fossils and give each specimen its own individual appearance. They are not manufacturing defects but evidence of burial, fossilisation and geological exposure over millions of years.
Actual Fossil with Certificate of Authenticity
This is a 100% genuine fossil specimen, not a cast, replica or modern reproduction. It includes a generic Certificate of Authenticity card with a lifetime guarantee, providing lasting reassurance regarding its genuine fossil status.
The exact Hammatoceras simulator ammonite fossil shown in the listing photographs will be supplied. Its natural preservation, shell detail, colour, matrix and surface condition will therefore match the specimen pictured.
This Upper Toarcian ammonite is suitable for Jurassic fossil collections, ammonite displays, geological reference cabinets, educational collections, natural-history interiors and gifts for fossil enthusiasts. Its identified species, Insigne Zone provenance and recorded Aveyron origin make it a distinctive addition to a collection of authentic French ammonites.
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