Xipheroceras with Chambers Fossil Ammonite Black Ven Marls Lower Lias Jurassic Coast Lyme Regis Dorset UK

Description

Authentic Xipheroceras with Chambers Fossil Ammonite

This remarkable Xipheroceras with Chambers Fossil Ammonite is a genuine and beautifully preserved specimen from the Black Ven Marls, Lower Lias Formation, discovered along the Jurassic Coast at Black Ven, Lyme Regis, Dorset, UK. Dating back to the Lower Jurassic period (approximately 195–200 million years ago), this fossil showcases not only the classic ribbed shell of Xipheroceras but also its internal chamber structure, making it a scientifically significant and visually striking specimen.

Your fossil was discovered by our team members, Alister and Alison, on 09 October 2025, and has been professionally cleaned, prepped, and treated by Alison to reveal both the external and internal features in exquisite detail. The photo shows the exact specimen you will receive, ensuring full transparency and authenticity.

Geological Context and Origin

The fossil originates from the Black Ven Marls Member of the Charmouth Mudstone Formation, part of the Lower Lias Group that stretches along the UNESCO World Heritage Jurassic Coast. The Black Ven cliffs, between Charmouth and Lyme Regis, are among the most famous fossil-bearing localities in the world, known for their exceptional preservation of marine life and their deep connection to the history of palaeontology.

The Black Ven Marls were deposited in a quiet, offshore marine environment composed of fine muds and silts. Periods of low-oxygen (anoxic) seabed conditions inhibited decay, allowing for delicate preservation of shell material and even internal structures such as the ammonite’s chambers. These sediments represent the Sinemurian Stage of the Early Jurassic and correspond to the Xipheroceras dudressieri Biozone, a key stratigraphic marker in European Jurassic geology.

The combination of slow sedimentation, anoxia, and occasional storm-driven burial events resulted in the formation of fossil layers like this one — capturing ammonites in extraordinary detail, often with mineral replacement highlighting their natural structure.

Scientific Classification

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Subclass: Ammonoidea
• Order: Ammonitida
• Superfamily: Eoderoceratoidea
• Family: Eoderoceratidae
• Genus: Xipheroceras
• Age: Early Jurassic (Sinemurian Stage)
• Formation: Black Ven Marls, Lower Lias
• Locality: Black Ven, Lyme Regis, Dorset, UK

Xipheroceras is an important genus within the family Eoderoceratidae, and its characteristic morphology defines the Xipheroceras Zone, one of the major ammonite biozones used in early Jurassic stratigraphy.

Morphological Features and Preservation

This Xipheroceras specimen displays the distinctive evolute coiling, where all the whorls are visible from the side, and the strong, forward-curving ribs typical of the genus. These ribs extend across the flanks to a slightly keeled venter (outer rim) and are often accentuated by small tubercles near the umbilicus. The preservation is exceptional, revealing both the outer shell sculpture and the internal chambers (phragmocone) that once controlled buoyancy.

The visible chambers are particularly significant, as they reveal the intricate internal architecture that allowed the ammonite to regulate its position in the water column. The shell’s outer surface shows delicate ribbing and a subtle sheen due to calcite and pyrite mineralisation, characteristic of ammonites from the Black Ven Marls.

The fossil has been carefully prepared to highlight both surface and cross-sectional features. The scale cube (1 cm) provides accurate size reference, with full measurements listed in the accompanying images. This is a premium-quality display specimen ideal for collectors, educators, and enthusiasts of natural history.

Palaeobiological and Scientific Significance

Ammonites such as Xipheroceras were free-swimming marine predators, related to modern squids and cuttlefish. Their chambered shells — or phragmocones — were divided by intricate suture patterns that strengthened the shell while maintaining buoyancy control. These internal structures, visible in this specimen, offer valuable insight into how these ancient cephalopods lived and moved through early Jurassic seas.

The Xipheroceras genus represents an evolutionary transition from earlier forms like Echioceras, developing stronger ribbing and more elaborate shell ornamentation — adaptations possibly linked to hydrodynamics and shell strength. Fossils from the Black Ven Marls are prized both scientifically and aesthetically for their completeness and the geological story they tell about the early evolution of marine life after the Triassic extinction.

Authenticity and Provenance

All of our fossils are 100% genuine specimens and come with a Certificate of Authenticity. Each piece is responsibly collected, professionally prepared, and stabilised for long-term preservation. No replicas, casts, or artificial enhancements are ever used — the specimen shown is the actual fossil you will receive.

This Xipheroceras with Chambers Fossil Ammonite is an outstanding example of Britain’s Jurassic heritage — a specimen that combines natural beauty, scientific value, and historical importance from the world-famous Jurassic Coast at Black Ven, Lyme Regis, Dorset, where Earth’s ancient history is written in stone.