Description
Genuine Emileia (Otoites) cf. delicatus Ammonite Fossil
This carefully selected fossil is a genuine Emileia (Otoites) cf. delicatus ammonite from the Inferior Oolite Group at Sandford Lane Quarry, Sherborne, Dorset, UK. It dates from the Bajocian Stage of the Middle Jurassic and is recorded from the Sauzei Zone, an important ammonite biozone within the Lower Bajocian succession.
The specimen represents an extinct marine cephalopod that inhabited the warm seas covering southern Britain approximately 170 million years ago. The listing photograph shows the actual fossil specimen you will receive, allowing its natural shell form, ribbing, colouration, surrounding matrix and individual preservation to be viewed before purchase.
The abbreviation “cf.” means “compare with” and indicates that the specimen closely resembles Emileia (Otoites) delicatus. This careful identification recognises its characteristic features while allowing for the limitations that can arise when a naturally preserved fossil is incomplete, partly enclosed in matrix or lacks every feature required for an absolute species-level determination.
Lower Bajocian Sauzei Zone
The Sauzei Zone is a recognised ammonite biozone within the Lower Bajocian. Ammonite zones are defined using characteristic fossil assemblages and allow geologists to identify the relative age of individual marine rock layers with considerable precision.
Ammonites are particularly useful index fossils because their shell forms evolved rapidly and many genera were distributed across extensive Jurassic seas. Variations in coiling, whorl shape, ribbing, tuberculation and ventral structure enable palaeontologists to distinguish successive ammonite faunas and correlate sedimentary rocks between different regions.
A fossil recorded from the Sauzei Zone therefore has clear geological and stratigraphic significance. It represents a specific interval within the early Middle Jurassic and preserves evidence of the diverse ammonite communities that occupied the north-west European marine basin.
Emileia and Otoites Shell Characteristics
Emileia and the closely associated form Otoites belong to a group of strongly ornamented Bajocian ammonites. Their shells were planispirally coiled, meaning that each new whorl developed around the earlier growth stages within a single plane.
The inner whorls may be relatively open, leaving a visible central umbilicus. Strong primary ribs typically arise near the umbilical region and extend across the shell flanks. These ribs may strengthen into raised nodes or tubercles before dividing into secondary ribs towards the outer portion of the shell.
In more delicate forms associated with the name delicatus, the ribbing may appear comparatively fine, regular or closely spaced. The exact appearance varies according to the ammonite’s growth stage, preservation and the amount of shell exposed from the surrounding rock.
Juvenile whorls can differ significantly from mature growth stages. Early shell sections may display more prominent ribbing and tuberculation, while later whorls may become broader, smoother or differently proportioned. This change through growth is an important feature of many Bajocian ammonites and can make complete examples particularly informative.
Inferior Oolite Group Geology
The Inferior Oolite Group is one of the most important fossil-bearing Middle Jurassic rock successions in southern England. It includes oolitic limestones, sandy limestones, marls, iron-rich beds and condensed horizons formed under changing shallow-marine conditions.
Oolitic limestone contains numerous rounded carbonate grains known as ooids. These formed when calcium carbonate accumulated in repeated coatings around tiny sediment particles or shell fragments moved by currents in warm, agitated seawater. The grains eventually settled onto the seabed, where compaction and natural cementation transformed the sediment into limestone.
Deposition was not always continuous. Changes in sea level, current strength and sediment supply could interrupt accumulation and expose shells on the seabed. Fossils could then become worn, transported or concentrated before final burial. These processes helped create the rich ammonite assemblages for which the Inferior Oolite Group is renowned.
The associated marine ecosystem contained ammonites, belemnites, bivalves, brachiopods, gastropods, echinoids and other invertebrates. Their remains provide detailed evidence of the changing environments that existed across southern Britain during the Middle Jurassic.
Sandford Lane Quarry, Sherborne
Sandford Lane Quarry near Sherborne is associated with fossil-bearing Jurassic strata in north-west Dorset. Inland quarries and former workings around Sherborne have produced important ammonites and other marine fossils from the Inferior Oolite succession.
During the Bajocian, this area formed part of a shallow marine shelf connected to extensive seas across western Europe. The sediments deposited in these waters preserve a record of changing sea-floor conditions, biological communities and ammonite evolution.
A specimen with documented provenance from Sandford Lane Quarry has added scientific and collectable interest. It connects the fossil directly to a recognised British locality and to Dorset’s long-established history of geological research and fossil collecting.
Scientific Classification and Geological Details
Fossil type: Ammonite
Scientific identification: Emileia (Otoites) cf. delicatus
Family: Otoitidae
Superfamily: Stephanoceratoidea
Order: Ammonitida
Geological period: Jurassic
Geological epoch: Middle Jurassic
Geological stage: Bajocian
Biozone: Sauzei Zone
Geological unit: Inferior Oolite Group
Locality: Sandford Lane Quarry, Sherborne, Dorset, United Kingdom
Otoitid ammonites are important components of Lower Bajocian faunas. Their robust ribbing, tubercles and changing whorl proportions make them visually distinctive and useful for detailed biostratigraphic study.
Chambered Shell and Ammonite Biology
The living animal occupied the final and largest part of the shell, known as the body chamber. Earlier sections were divided by internal walls called septa, producing a sequence of chambers collectively known as the phragmocone.
A narrow tube called the siphuncle connected the chambers and enabled the ammonite to regulate their liquid and gas content. This helped the animal control its buoyancy and position within the Jurassic water column.
Where the septa met the inside of the shell, they formed intricate suture lines. These may become visible when the outer shell layer has been naturally weathered, removed during fossilisation or carefully exposed during preparation.
Ammonites belonged to the cephalopods and were related to the wider group containing modern squid, cuttlefish, octopuses and nautiluses. They developed an extraordinary variety of shell shapes and ornamentation before becoming extinct at the end of the Cretaceous Period.
Natural Fossilisation and Preservation
After the ammonite died, its shell settled onto the Jurassic seabed or was moved by currents before burial. Sediment gradually entered and covered the shell, protecting parts of it from complete destruction.
Over millions of years, pressure and mineral-rich groundwater transformed the surrounding sediment into rock. The original shell may have been preserved, mineralised, replaced or dissolved, leaving a natural internal mould. Many ammonites retain a combination of altered shell material, sediment-filled chambers and attached matrix.
Any incomplete areas, worn ribs, minor fractures, mineral-filled sections, colour variations or surrounding rock are authentic geological characteristics. These features record the specimen’s burial, fossilisation, exposure and recovery and make every genuine fossil unique.
Collectable Dorset Jurassic Ammonite
This Emileia (Otoites) cf. delicatus ammonite fossil would make an excellent addition to a collection of British fossils, Dorset ammonites, Sauzei Zone fossils, Bajocian specimens or Inferior Oolite fossils. Its recorded identification, biozone and quarry locality also make it suitable for a fossil cabinet, geological study collection, educational display or distinctive gift for a Jurassic 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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