Description
Rare Phyllopachyceras infundibulum Ammonite Fossil
This rare and genuine ammonite fossil is identified as Phyllopachyceras infundibulum and originates from Drôme in the Auvergne-Rhône-Alpes region of south-eastern France. It dates from the Barremian Stage of the Lower Cretaceous, when this part of Europe was submerged beneath an extensive marine basin connected to the ancient Tethys Ocean.
Phyllopachyceras infundibulum is a distinctive phylloceratid ammonite recognised for its compact shell, rounded form and refined ornamentation. It differs noticeably from heavily ribbed or spiny ammonites, offering a smoother and more elegant appearance that reflects the characteristic morphology of the Phylloceratidae.
The fossil has been carefully selected for its rarity, identifiable form and documented French provenance. The photographs show the exact specimen you will receive, allowing its natural preservation, colour, matrix and individual geological features to be examined before purchase. Full sizing and scale information are provided in the listing photographs.
Species and Scientific Classification
The species was originally named Ammonites infundibulum by the French palaeontologist Alcide d’Orbigny in 1840 and was later reassigned to the genus Phyllopachyceras. The original combination explains why the species authority is written in parentheses as Phyllopachyceras infundibulum (d’Orbigny, 1840).
Its broad scientific classification includes:
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Phylloceratida
Superfamily: Phylloceratoidea
Family: Phylloceratidae
Genus: Phyllopachyceras
Species: Phyllopachyceras infundibulum
Species authority: d’Orbigny, 1840
Ammonites were extinct marine cephalopods related to living squid, cuttlefish, octopuses and nautiluses. They possessed chambered external shells and were widespread throughout the world’s Mesozoic oceans.
Distinctive Phylloceratid Morphology
Phyllopachyceras possessed a compact, planispirally coiled shell with successive whorls strongly overlapping the earlier growth stages. This produced a relatively narrow umbilicus at the centre of the shell and a thick, rounded whorl profile.
The shell ornament is generally more delicate than that seen in many strongly ribbed Cretaceous ammonites. Depending on growth stage and preservation, the surface may display alternating longer and shorter ribs, subdued folds or fine growth lines. The comparatively smooth flanks, rounded venter and inflated shell section give these ammonites their characteristic streamlined appearance.
The original shell was divided internally by curved partitions called septa. These formed a sequence of chambers connected by a narrow tube known as the siphuncle. The living ammonite occupied the final and largest body chamber, while the earlier chambers helped regulate buoyancy.
Where preserved, the junctions between the septa and the shell wall form highly intricate suture patterns. Phylloceratid ammonites are particularly noted for their elaborate, leaf-like sutures, with deeply divided lobes and saddles resembling branching foliage. These complex patterns are important features in the classification of the group.
Barremian Lower Cretaceous Age
This specimen is recorded from the Barremian Stage of the Lower Cretaceous. The Barremian followed the Hauterivian and preceded the Aptian, representing an interval of Early Cretaceous time approximately 129 to 125 million years ago.
Ammonites underwent substantial diversification throughout this period. Many lineages developed prominent ribs, spines or irregular heteromorph shells, while phylloceratids retained a more conservative and recognisable shell design.
Because ammonite species evolved through time and were widely distributed across marine environments, their fossils are extremely useful for dating and correlating sedimentary rocks. Specimens with a recorded geological stage and locality therefore offer considerably more scientific value than fossils supplied without provenance.
Phyllopachyceras infundibulum is recorded from Hauterivian and Barremian deposits and forms part of the diverse ammonite fauna associated with Lower Cretaceous Tethyan marine successions.
Ancient Tethyan Marine Environment
During the Barremian, the region now forming south-eastern France lay beneath a marine basin along the northern margin of the Tethys Ocean. These waters separated parts of the ancient northern and southern continents and supported highly diverse marine ecosystems.
The sea contained ammonites, belemnites, nautiloids, bivalves, gastropods, brachiopods, echinoids, crustaceans, fish and marine reptiles. Microscopic plankton flourished in the water column and contributed organic and calcareous material to the sediments accumulating on the seabed.
The French Subalpine Basin received fine mud and carbonate-rich sediment from surrounding marine environments and nearby landmasses. Periodic changes in water depth, oxygen levels, sediment supply and ocean circulation produced the layered limestone and marl successions now exposed throughout the region.
The relatively streamlined shell of Phyllopachyceras is commonly associated with an actively mobile marine lifestyle. Its broad geographical distribution indicates that members of the genus were successful inhabitants of open-water Cretaceous environments.
Fossilisation and Natural Preservation
After the ammonite died, its shell descended to the seabed and was gradually covered by sediment. Soft tissues decomposed, while mud or carbonate material entered the empty shell and surrounded its exterior.
As additional sediment accumulated, pressure compacted the deposits and transformed them into sedimentary rock. Mineral-rich groundwater could alter, dissolve or replace the original shell material. Sediment hardened inside the shell chambers, sometimes producing an internal mould that preserved the ammonite’s overall shape and surface ornamentation.
The finished fossil may retain original shell material, mineral replacement, an internal mould or a combination of these forms of preservation. Natural fractures, incomplete edges, matrix, mineral deposits, surface weathering and variations in colour are genuine features created during burial, fossilisation and later geological exposure.
These individual characteristics are an important part of the specimen’s authenticity and ensure that no two examples are precisely identical.
Drôme, Auvergne-Rhône-Alpes Provenance
Drôme is internationally recognised for its extensive Lower Cretaceous marine rocks and exceptionally varied ammonite faunas. The region forms part of the French Subalpine geological province, where valleys, mountains, road cuttings and natural exposures reveal thick successions of limestone and marl.
These rocks have played an important role in the study of Lower Cretaceous stratigraphy and palaeontology. Generations of researchers and collectors have documented ammonites from the region, helping establish detailed systems for comparing Hauterivian, Barremian and younger marine deposits.
Fossils from Drôme are particularly desirable because they combine classic European provenance with a precisely understood marine geological setting. The association of this specimen with the Barremian Stage adds useful scientific context to its attractive natural form.
Actual Specimen and Certificate of Authenticity
This is a genuine fossil specimen and not a cast, replica or artificial reproduction. The photographs show the exact Phyllopachyceras infundibulum ammonite that will be supplied, including its natural shell form, preservation, colour, matrix and individual surface characteristics.
Full sizing is provided in the listing photographs.
The fossil includes a generic Certificate of Authenticity card carrying a lifetime guarantee. Its rare phylloceratid identity, elegant morphology, Barremian age and documented Drôme provenance make it an excellent addition to a Lower Cretaceous collection, French ammonite display, natural-history cabinet or educational geological collection.
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