Description
Genuine Eudmetoceras eudmetum Ammonite Fossil
This carefully chosen fossil is a genuine Eudmetoceras eudmetum ammonite from the Inferior Oolite Group at Bothenhampton Brickworks, Dorset, UK. It dates from the Middle Bajocian Stage of the Middle Jurassic and is recorded from the Humphriesianum Zone, an important ammonite biozone within the fossil-rich Jurassic succession of southern England.
This specimen represents an extinct marine cephalopod that inhabited the warm seas covering the Dorset region approximately 169 million years ago. The photograph shows the actual fossil specimen you will receive, allowing its natural preservation, shell form, ornamentation, colouration and attached matrix to be viewed before purchase.
Middle Bajocian Humphriesianum Zone
The Humphriesianum Zone is a recognised biostratigraphic division of the Middle Bajocian. It is named after characteristic ammonites used by geologists to identify and correlate marine rock layers of this age across Britain and continental Europe.
Ammonites are particularly valuable index fossils because many species evolved rapidly and were distributed across extensive marine environments. Their changing shell forms allow palaeontologists to divide the Jurassic rock record into detailed zones and subzones. A specimen recorded from the Humphriesianum Zone therefore carries important geological context beyond its visual appeal as a collectable fossil.
During the Middle Bajocian, southern Britain formed part of a broad marine shelf connected to the wider north-west European seas. These waters supported diverse communities of ammonites, belemnites, brachiopods, bivalves, gastropods, echinoids and other marine organisms.
Inferior Oolite Group Geology
The Inferior Oolite Group is a varied sequence of Middle Jurassic marine rocks found across southern England. It includes fossiliferous limestones, marls, sandy beds, iron-rich deposits and condensed horizons containing concentrations of prehistoric marine remains.
Oolitic limestone formed when tiny carbonate grains known as ooids developed around shell fragments or sediment particles. These grains were rolled by currents in warm, shallow seawater, gradually receiving repeated coatings of calcium carbonate before becoming incorporated into the seabed.
Sedimentation within the Inferior Oolite sea was not always continuous. Periods of erosion, strong current activity and reduced sediment supply could expose and rework the seabed. Fossils sometimes accumulated within condensed horizons where shells from successive marine communities became concentrated before final burial.
Bothenhampton Brickworks is associated with the historic fossil-bearing geology of west Dorset. Specimens from the locality provide an important connection to the area’s former extractive industries and its long-established tradition of Jurassic fossil collecting.
Eudmetoceras Shell Form and Ornamentation
Eudmetoceras was a planispirally coiled ammonite, meaning that its shell developed in a single flat spiral around a central umbilicus. The shell expanded as the animal grew, with each successive whorl forming a larger section around the earlier growth stages.
Members of the genus are generally recognised by their distinctive whorl proportions and developed shell sculpture. The flanks may carry pronounced ribs extending from the umbilical area towards the outer edge of the coil. Depending on growth stage, these ribs can vary in spacing, strength and curvature, creating a strongly textured appearance.
The outer margin of the shell, known as the venter, and the shape of the whorl section are important features used when comparing related ammonite genera and species. The appearance of these details on a fossil can be affected by natural compression, weathering, mineral replacement and the amount of surrounding matrix retained on the specimen.
The original shell was divided internally by curved walls called septa. These formed a series of chambers collectively known as the phragmocone. The living animal occupied the final body chamber, while the older chambers contained controlled amounts of gas and liquid that assisted with buoyancy.
Scientific Classification and Fossil Details
Fossil type: Ammonite
Scientific name: Eudmetoceras eudmetum
Order: Ammonitida
Geological period: Jurassic
Geological epoch: Middle Jurassic
Geological stage: Middle Bajocian
Biozone: Humphriesianum Zone
Geological unit: Inferior Oolite Group
Locality: Bothenhampton Brickworks, Dorset, United Kingdom
Ammonites belonged to an extinct and highly successful group of marine molluscs within the cephalopods. They were related to modern squid, cuttlefish, octopuses and nautiluses, although their shell forms and evolutionary history were distinct.
Fossilisation and Natural Preservation
After the ammonite died, its shell settled onto the Jurassic seabed or was transported by currents before burial. Sediment gradually covered the remains, protecting portions of the shell from complete destruction. Over millions of years, compaction and mineral-rich groundwater transformed the surrounding sediment into rock and preserved the ammonite as a fossil.
The original shell material may have been altered, replaced or dissolved during fossilisation. The resulting specimen may preserve sections of shell, a mineralised internal mould or a combination of both.
Any attached matrix, minor fractures, incomplete areas, worn ribbing, mineral deposits or natural colour variations are genuine geological characteristics. These features reflect the specimen’s burial, fossilisation, exposure and recovery from its host rock. Every naturally preserved ammonite is unique, with its own combination of shell detail and matrix.
Collectable Dorset Jurassic Ammonite
This Eudmetoceras eudmetum ammonite fossil would make an excellent addition to a collection of British fossils, Dorset ammonites, Bajocian fossils, Humphriesianum Zone specimens or Inferior Oolite fossils. Its recorded species, geological horizon and locality also make it suitable for educational displays, geological study collections, natural history cabinets or as a distinctive gift for a fossil enthusiast.
This is a 100% genuine fossil specimen and includes a Certificate of Authenticity generic card with a lifetime guarantee. The fossil has been individually selected for its collectable qualities, and the photograph shows the exact specimen that will be supplied.
Full sizing please see photo.
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