Description
Rare Echioceras Ammonite Fossil with Serpulid Worm from the Jurassic Coast
This exceptional Echioceras fossil ammonite featuring attached serpulid worm tubes originates from the Black Ven Marls of the Lower Lias at Stonebarrow Cliff, Charmouth, near Lyme Regis, Dorset, UK. The Jurassic Coast of southern England is one of the most famous fossil localities in the world and is recognised as a UNESCO World Heritage Site for its outstanding geological and palaeontological significance.
This specimen is particularly notable due to the presence of serpulid worm tubes preserved on the ammonite shell, providing direct evidence of ancient marine life interactions. The fossil ammonite and worm tubes together illustrate a fascinating example of post-mortem colonisation or marine encrustation, where organisms attached themselves to the ammonite shell while it rested on the seabed.
The fossil has been carefully selected for its preservation and rarity, displaying both the distinctive ammonite morphology and the attached serpulid structures. The listing photographs show the exact fossil specimen you will receive, allowing collectors to examine the fossil’s structure and preservation before purchase. Full sizing can be seen clearly in the listing images.
This fossil is a genuine specimen and includes a fully hand-signed Premium Certificate of Authenticity, confirming its authenticity and geological origin.
Fossil Identification and Scientific Classification
The ammonite belongs to the genus Echioceras, a well-known group of Early Jurassic ammonites commonly found within Lower Lias deposits along the Dorset coast.
Scientific classification includes:
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Cephalopoda
- Subclass: Ammonoidea
- Order: Ammonitida
- Superfamily: Psiloceratoidea
- Family: Echioceratidae
- Genus: Echioceras
The genus Echioceras was described by the palaeontologist Alcide d’Orbigny, whose work helped establish the scientific classification of many ammonite species from the Jurassic period.
Ammonites were marine cephalopods related to modern squid, octopus, and nautilus. They possessed coiled external shells divided into internal chambers used for buoyancy control.
Geological Age and Stratigraphic Context
This specimen originates from the Lower Lias Formation of the Early Jurassic Period, approximately 201 to 190 million years ago. The Lower Lias represents marine sediment deposits laid down shortly after the end of the Triassic Period.
The fossil comes from the Black Ven Marls, a sequence of clay-rich marine sediments exposed along the cliffs between Charmouth and Lyme Regis. These deposits are part of the Sinemurian Stage of the Early Jurassic.
Ammonites such as Echioceras are commonly associated with the Echioceras raricostatum biozone, an important stratigraphic marker used by geologists to identify specific layers within the Lower Lias sequence.
Morphology of Echioceras Ammonites
Echioceras ammonites are recognised by their distinctive shell structure and rib patterns.
Key morphological characteristics include:
- Planispiral coiled shell structure
- Narrow whorl cross-sections
- Fine ribbing extending across the shell surface
- Moderately open umbilicus exposing inner whorls
The shell consisted of a series of internal chambers separated by septa. The living animal occupied the outermost chamber while the inner chambers were filled with gas and fluid to regulate buoyancy within the water column.
Serpulid Worm Encrustation
One of the most fascinating aspects of this specimen is the presence of serpulid worm tubes attached to the ammonite shell.
Serpulids are marine polychaete worms belonging to the family Serpulidae. These organisms construct calcareous tubes that attach permanently to hard surfaces on the seabed.
Scientific classification of serpulid worms includes:
- Phylum: Annelida
- Class: Polychaeta
- Order: Sabellida
- Family: Serpulidae
In ancient marine environments, empty ammonite shells often served as hard substrates on otherwise soft seabeds, providing an ideal surface for organisms such as serpulid worms, bryozoans, or oysters to colonise.
The presence of serpulid tubes on the ammonite provides evidence of ecological interaction and post-mortem colonisation within the Jurassic marine environment.
Depositional Environment of the Black Ven Marls
During the Early Jurassic, the region that is now southern England was covered by a warm shallow epicontinental sea. Fine mud and marl sediments accumulated slowly on the seabed, creating ideal conditions for fossil preservation.
The marine ecosystem included:
- Ammonites such as Echioceras
- Belemnites
- Bivalves
- Marine reptiles including ichthyosaurs and plesiosaurs
- Worms and other invertebrates
Low-energy conditions on the seabed allowed delicate fossils and encrusting organisms to be preserved within the sediment.
Fossilisation and Preservation
When the ammonite died, its shell settled onto the seabed where it could become colonised by other marine organisms such as serpulid worms. Over time, the shell and attached organisms were buried within soft marine sediment.
Mineralisation processes over millions of years preserved both the ammonite shell and the worm tubes, allowing the fossil to retain its original biological structure.
The constant erosion of the cliffs at Charmouth and Lyme Regis continues to expose fossils from the Lower Lias formations, making this coastline one of the most productive fossil hunting locations in the world.
Collecting and Scientific Significance
Specimens showing multiple fossil organisms preserved together are particularly valued by collectors and researchers because they provide insight into ancient marine ecosystems and ecological interactions.
Collectors appreciate Echioceras fossils with serpulid attachments for several reasons:
- Clear ammonite shell morphology
- Rare example of fossilised marine colonisation
- Historic fossil locality along the Jurassic Coast
- Scientific value demonstrating Jurassic marine ecology
Such specimens are frequently displayed in fossil collections, natural history exhibits, and geological teaching collections.
Authentic Fossil Specimen
This specimen is a genuine Echioceras ammonite fossil with attached serpulid worm tubes from the Black Ven Marls of the Lower Lias at Stonebarrow Cliff, Charmouth, near Lyme Regis, Dorset, UK.
Key details include:
- Authentic Echioceras ammonite fossil
- Encrusted with fossil serpulid worm tubes
- Formation: Black Ven Marls
- Stratigraphy: Lower Lias, Sinemurian Stage
- Geological Age: Early Jurassic Period
- Locality: Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, UK
- UNESCO Jurassic Coast fossil locality
- Exact fossil shown in listing photographs
- Full sizing visible in listing images
- Includes fully hand-signed Premium Certificate of Authenticity
This remarkable fossil preserves evidence of Early Jurassic marine life interactions within the ancient seas of southern England, making it an outstanding and highly collectible addition to fossil collections and natural history displays.
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