Description
Rare British Lytoceras cf. fimbriatum Ammonite Fossil
This carefully chosen fossil is a rare Lytoceras cf. fimbriatum ammonite from the Toarcian Stage of the Lower Jurassic Period. It originates from the South Petherton and Ilminster area of Somerset, United Kingdom, a historically important region for British Jurassic fossils and finely preserved marine invertebrates.
The abbreviation “cf.” means that the specimen compares closely with Lytoceras fimbriatum, while allowing for the natural limitations of fossil preservation. This is an authentic geological specimen rather than a replica or reproduction.
The photograph shows the actual fossil you will receive, so its individual preservation, natural colour, remaining shell detail, matrix and overall character can be examined before purchase. Full sizing and scale information can be seen in the accompanying photograph.
Toarcian Lower Jurassic Geology
The Toarcian is the final stage of the Lower Jurassic, following the Pliensbachian and preceding the Aalenian Stage of the Middle Jurassic. It represents an interval approximately 184 to 174 million years ago, when much of southern Britain lay beneath an extensive marine seaway.
The region now forming Somerset was occupied by warm Jurassic seas inhabited by ammonites, belemnites, bivalves, brachiopods, marine reptiles and numerous other organisms. Sediment accumulated across the seafloor and gradually buried the hard shells of marine animals. Under suitable conditions, these remains were mineralised or preserved as internal moulds within the surrounding rock.
The Jurassic strata around Ilminster and South Petherton have long been recognised for their fossil-bearing marine deposits. Fossils collected from this area provide evidence of changing sea levels, sedimentation and marine ecosystems during the Early Jurassic.
Distinctive Lytoceras Shell Morphology
Lytoceras belongs to the family Lytoceratidae, within the superfamily Lytoceratoidea and order Ammonitida. Members of this group are recognised by their highly evolute coiling, in which successive whorls overlap only slightly and leave much of the earlier shell visible.
This open, loosely coiled appearance creates a broad central umbilicus and distinguishes Lytoceras from more tightly coiled ammonites. The whorls are generally rounded in cross-section, producing a graceful and relatively simple overall shell form.
Lytoceras fimbriatum is particularly associated with fine, closely spaced growth lines or rib-like folds. In well-preserved examples, these delicate lines may form a fringed or finely pleated pattern around the shell. The species name “fimbriatum” refers to this characteristically fringed appearance.
The strength and visibility of these features naturally vary according to the ammonite’s age, the portion of shell preserved and the geological processes affecting the fossil after burial. Areas of attached matrix, compressed shell, mineral replacement, natural fractures and weathered surfaces are all expected characteristics of genuine Jurassic fossils.
An Ancient Marine Cephalopod
Ammonites were extinct marine cephalopods related to living squid, octopuses, cuttlefish and nautiluses. The animal occupied the final and largest part of the shell, known as the body chamber, while the older portion was divided internally into a sequence of smaller chambers.
These chambers were separated by walls called septa and connected by a narrow tube known as the siphuncle. By regulating fluid and gas within the chambered shell, the ammonite could control its buoyancy and move through different levels of the water column.
As the ammonite grew, it added new shell material around the opening and moved forward into progressively larger chambers. The older chambers were sealed behind the living animal, creating the familiar spiral structure seen in fossil ammonites.
Scientific Importance of Lytoceratid Ammonites
Ammonites are extremely useful to palaeontologists because they evolved rapidly and were distributed across wide marine areas. Particular genera and species can therefore help identify the relative age of sedimentary rocks and allow separate geological sequences to be compared.
Lytoceratid ammonites had a wide geographical distribution and form an important part of Jurassic marine faunas. Their distinctive open coiling and relatively conservative shell design make them readily recognisable within ammonite collections.
Lytoceras fimbriatum was originally described by the British naturalist and palaeontological illustrator James Sowerby. Fossils attributed to this species have been recorded from European Lower Jurassic marine strata and are valued for their elegant coiling and delicate ornamentation.
Somerset Fossil for Collection and Display
This rare Somerset ammonite would make an excellent addition to a British fossil collection, Lower Jurassic display, ammonite cabinet or educational geological collection. Its Toarcian age, classic lytoceratid form and South Petherton–Ilminster provenance give it particular interest for collectors of British palaeontology.
It would also make a distinctive gift for a fossil enthusiast, geology student, natural-history collector or anyone fascinated by prehistoric marine life.
Genuine Fossil with Certificate of Authenticity
This specimen includes a generic Certificate of Authenticity card carrying our lifetime guarantee of authenticity. Every fossil is individually selected for its natural character, scientific interest and suitability for display.
Natural imperfections, incomplete areas, small fractures, mineralisation, matrix attachments and differences in surface texture form part of the specimen’s long geological history and help ensure that every fossil is unique.
Fossil: Lytoceras cf. fimbriatum
Fossil type: Ammonite
Family: Lytoceratidae
Superfamily: Lytoceratoidea
Order: Ammonitida
Geological stage: Toarcian
Geological period: Lower Jurassic
Locality: South Petherton, Ilminster, Somerset, United Kingdom
Authenticity: Genuine specimen with Certificate of Authenticity lifetime guarantee card
Sizing: Full sizing can be seen in the photograph
Specimen supplied: The photograph shows the actual fossil you will receive
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