Arnioceras Ammonite Fossil Multi Block Jurassic Lyme Regis Dorset UK Lower Lias

Description

Authentic Arnioceras and Cymbites Ammonite Multi Block from the Jurassic Coast

Offered here is a genuine Arnioceras ammonite fossil multi block with Cymbites, collected from the Black Ven Marls at Monmouth Beach, Lyme Regis, Dorset, part of England’s world-famous Jurassic Coast. This naturally formed fossil block preserves multiple ammonites together within their original Lower Jurassic matrix, providing an excellent snapshot of Early Jurassic marine life. The photographs show the exact specimen you will receive, carefully selected for clarity, balance, and scientific interest. Full sizing details are shown in the photos.

This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card, ensuring confidence in provenance and long-term collectability.

Provenance and Professional Preparation

This specimen was discovered by our own team members, Alister and Alison, on 09 January 2024 during fieldwork at Monmouth Beach. Following recovery, the fossil block was cleaned, prepared, and stabilised by Alison, ensuring the ammonites are clearly visible while retaining the integrity of the original matrix. Team-collected provenance provides a clear and traceable history, which is highly valued by collectors and educational institutions.

Geological Formation and Age

The fossil originates from the Lower Lias Group, deposited during the Early Jurassic Period, approximately 199–191 million years ago, within the Sinemurian Stage. The Black Ven Marls consist of fine-grained marine mudstones and marls formed in a shallow epicontinental sea that once covered southern Britain. Monmouth Beach is a classic Lyme Regis locality and is internationally recognised for producing diverse and well-preserved ammonite assemblages critical to Jurassic stratigraphy.

Fossil Species and Scientific Context

The ammonites preserved within this block belong to the genera Arnioceras and Cymbites, both members of the Order Ammonitida.

Arnioceras, within the Family Arietitidae, is a well-known Lower Jurassic ammonite characterised by its robust shell and strong ribbing, and it plays an important role in Early Jurassic biostratigraphic studies.

Cymbites is recognised for its more involute shell form and smoother whorls, providing an interesting morphological contrast within the same assemblage. The presence of multiple genera within a single block enhances the scientific and educational value of the specimen.

Morphology and Preservation

The ammonites display classic planispiral coiling, with differences in rib strength, whorl width, and shell involution clearly visible between Arnioceras and Cymbites. These variations illustrate ammonite diversity and evolutionary adaptation during the Early Jurassic. Natural mineralisation has preserved shell detail well, and retention within the original matrix maintains the spatial relationships between individuals, increasing both scientific integrity and visual appeal.

Depositional Environment

During the Early Jurassic, the Lyme Regis area lay beneath a warm, shallow marine environment rich in ammonites, belemnites, fish, and marine reptiles. Periodic storm events and sediment influx led to the accumulation of ammonite shells on the sea floor. Rapid burial by fine sediments, combined with episodes of low oxygen, reduced scavenging and disturbance, allowing multiple ammonites to be preserved together within the Black Ven Marls.

Collecting, Display, and Educational Value

This Arnioceras ammonite fossil multi block with Cymbites is ideal for serious fossil collectors, educational collections, museum displays, or refined interior presentation. Its combination of multiple ammonites, mixed genera, classic British Jurassic provenance, and team-documented discovery makes it both scientifically informative and visually striking. Multi-ammonite blocks from Monmouth Beach are increasingly sought after and comparatively scarce. Each specimen we offer is individually selected to ensure you receive an authentic and carefully curated piece of Early Jurassic marine history from one of the world’s most important fossil coastlines.