Description
Genuine Emileia (Otoites) cf. contractus Ammonite Fossil
This carefully chosen fossil is a genuine Emileia (Otoites) cf. contractus 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 specifically from the lower part of the Sauzei Zone, giving the specimen valuable stratigraphic context.
The photograph shows the actual fossil specimen you will receive, allowing its natural coiling, ribbing, mineralisation, colouration, preservation and surrounding matrix to be examined before purchase. This is an individually selected fossil rather than a representative stock image.
The abbreviation “cf.” means “compare with” and indicates that the ammonite closely resembles contractus in its preserved morphology, while allowing for the limitations of identification when a fossil is incomplete, partly concealed by matrix or does not display every diagnostic feature required for an absolute species assignment.
Lower Bajocian Sauzei Zone
The Sauzei Zone is an important ammonite biozone within the Lower Bajocian. Ammonite zones are defined by characteristic fossil assemblages and enable geologists to identify the relative age of marine sedimentary rocks with considerable precision.
A specimen recorded from the lower part of the Sauzei Zone belongs to a more narrowly defined interval within the early Bajocian succession. This detailed provenance increases its geological interest and connects it to a particular stage in the changing ammonite communities of the Middle Jurassic seas.
Ammonites are especially effective index fossils because their shell forms evolved relatively rapidly and many groups were distributed across broad marine regions. Changes in coiling, whorl proportions, ribbing, tuberculation and ventral structure allow individual fossil-bearing beds to be compared across Britain and continental Europe.
Emileia and Otoites Ammonite Morphology
Otoites is traditionally associated with the smaller, strongly ornamented form of the larger ammonite genus Emileia. These contrasting shell forms are widely interpreted as examples of ammonite dimorphism, with Otoites representing the smaller microconch form.
The shell was planispirally coiled, meaning that successive whorls developed around a central umbilicus within a single plane. The inner whorls may appear relatively open and strongly ornamented, allowing earlier growth stages to remain visible.
Prominent primary ribs typically rise from the umbilical region and extend across the flanks. These ribs may strengthen into raised nodes or tubercles before dividing into finer secondary ribs towards the outer edge of the shell. The resulting combination of robust ribbing, tuberculation and compact coiling gives otoitid ammonites their distinctive sculptural appearance.
In forms compared with contractus, the shell may display relatively compact proportions and closely arranged ornamentation. The exact appearance depends on the ammonite’s growth stage, the portion of shell preserved and the effects of fossilisation.
Juvenile whorls can carry dense ribs and pronounced tubercles, while later growth may show changes in whorl width, rib spacing and shell expansion. Some microconch ammonites also developed specialised mature apertural structures, although these delicate features are not always preserved.
Inferior Oolite Group Geology
The Inferior Oolite Group is one of the most important fossil-bearing Middle Jurassic rock successions in southern England. It contains oolitic and sandy limestones, marls, iron-rich beds and condensed fossil horizons deposited under changing shallow-marine conditions.
Oolitic limestone is partly composed of small rounded carbonate grains known as ooids. These formed when calcium carbonate accumulated in repeated layers around tiny shell fragments or sediment particles moving in warm, agitated seawater. The grains eventually settled onto the seabed and became cemented into limestone.
Sedimentation was frequently interrupted by changes in sea level, current strength and sediment supply. During periods of slow deposition, shells could remain exposed on the sea floor, where they might be worn, broken, transported or concentrated before final burial.
These processes created the richly fossiliferous horizons for which the Inferior Oolite is renowned. The marine fauna included ammonites, belemnites, brachiopods, bivalves, gastropods, echinoids and numerous other invertebrates.
Sandford Lane Quarry, Sherborne
Sandford Lane Quarry near Sherborne is associated with fossil-bearing Jurassic strata in north-west Dorset. The inland quarries and former workings around Sherborne have produced scientifically important ammonites from several levels of the Inferior Oolite succession.
During the Bajocian, this region formed part of a warm marine shelf connected to extensive seas across western Europe. Changing water depths, currents and sedimentary conditions created a varied sequence of fossil-rich deposits.
A specimen with recorded provenance from Sandford Lane Quarry has particular collectable value because its locality and stratigraphic position are documented. It provides a direct connection to Dorset’s Middle Jurassic geology and the long history of fossil study within the Sherborne district.
Scientific Classification and Geological Details
Fossil type: Ammonite
Scientific identification: Emileia (Otoites) cf. contractus
Family: Otoitidae
Superfamily: Stephanoceratoidea
Order: Ammonitida
Geological period: Jurassic
Geological epoch: Middle Jurassic
Geological stage: Bajocian
Biozone: Sauzei Zone, lower part
Geological unit: Inferior Oolite Group
Locality: Sandford Lane Quarry, Sherborne, Dorset, United Kingdom
Otoitid ammonites are characteristic elements of Lower Bajocian marine faunas. Their strongly ribbed and tuberculate shells are useful for palaeontological comparison and make them visually distinctive additions to specialist Jurassic collections.
Chambered Shell and Marine Lifestyle
The living ammonite occupied the final and largest section of the shell, known as the body chamber. Earlier sections were divided internally by curved walls called septa, creating a series of chambers collectively known as the phragmocone.
A narrow tube called the siphuncle connected the chambers and helped regulate their liquid and gas content. This enabled the animal to control buoyancy and maintain its position within the Jurassic water column.
Ammonites belonged to the cephalopods, the wider group of marine molluscs that includes modern squid, cuttlefish, octopuses and nautiluses. They were highly successful throughout much of the Mesozoic Era and developed an exceptional variety of shell forms and ornamentation.
Natural Fossil Preservation
After the ammonite died, its shell settled onto the seabed or was moved by currents before burial. Sediment gradually entered and covered the shell, protecting portions of it from complete destruction.
Over millions of years, geological pressure and mineral-rich groundwater transformed the surrounding sediment into rock. The original shell material may have been preserved, altered, replaced by minerals or dissolved to leave a natural internal mould.
Any incomplete areas, worn ribbing, small fractures, mineral-filled sections, attached matrix or natural colour variations are authentic geological characteristics. These features reflect burial, fossilisation, exposure and eventual recovery, giving every genuine ammonite an individual appearance.
Collectable Dorset Jurassic Ammonite
This Emileia (Otoites) cf. contractus ammonite fossil would make an excellent addition to a collection of British fossils, Dorset ammonites, Lower Bajocian fossils, Sauzei Zone specimens or Inferior Oolite fossils. Its documented identification, quarry locality and precise stratigraphic information also make it suitable for geological study, an educational display, fossil cabinet 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 carefully 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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