Promicroceras Ammonite Bed Fossil Lower Lias Black Ven Marls Jurassic Coast Charmouth Dorset UK

Description

Authentic Promicroceras Ammonite Bed Fossil

This exceptional Promicroceras Ammonite Bed Fossil is a genuine and beautifully preserved specimen from the Black Ven Marls, Lower Lias Formation, found on the Jurassic Coast at Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, UK. Dating to the Lower Jurassic period (approximately 195–200 million years ago), this remarkable slab contains multiple Promicroceras ammonites preserved in natural association — a stunning display of ancient marine life captured in stone.

Your specimen was discovered by our team members, Alister and Alison, on 23 October 2025, and has been expertly cleaned, prepped, and treated by Alison to reveal the fine detail and natural beauty of each individual ammonite. The photograph shows the exact specimen you will receive, ensuring authenticity and provenance.

Geological Context and Origin

This fossil originates from the Black Ven Marls Member of the Charmouth Mudstone Formation, part of the Lower Lias Group on the UNESCO World Heritage-listed Jurassic Coast. The Stonebarrow and Black Ven cliffs near Charmouth are world-famous for their exceptional fossil preservation and historical importance, producing some of the finest ammonites ever discovered.

The fossil bed formed within a low-energy, offshore marine environment composed of fine-grained clays and muds that settled in a calm, oxygen-poor seabed. These conditions allowed for exceptional preservation, with minimal disturbance after death. Over millions of years, mineral-rich waters permeated the sediment, stabilising the ammonite shells and binding them into solid rock.

This specimen is part of the Sinemurian Stage of the Early Jurassic, specifically within the Promicroceras planicosta Zone, a key biozone named after this very genus. These deposits mark a significant chapter in the recovery and radiation of marine life following the end-Triassic mass extinction.

Scientific Classification

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Subclass: Ammonoidea
• Order: Ammonitida
• Superfamily: Psiloceratoidea
• Family: Promicroceratidae
• Genus: Promicroceras
• Age: Early Jurassic (Sinemurian Stage)
• Formation: Black Ven Marls, Lower Lias
• Locality: Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, UK

Promicroceras is one of the most recognisable ammonites from the Lower Jurassic and serves as an important index fossil used to define the Sinemurian biozone. Its abundance and distinctive morphology make it invaluable for correlating early Jurassic marine sediments across Europe.

Morphological Features and Preservation

The Promicroceras ammonite bed is a visually stunning piece, featuring multiple tightly coiled ammonites preserved in natural association. Each specimen exhibits the classic fine ribbing and small, planispiral shell typical of Promicroceras. The ribs are delicate, evenly spaced, and radiate elegantly from the centre of each whorl.

Some ammonites show subtle mineralisation, with occasional calcite or pyrite infill, adding natural contrast and highlighting their contours. The fossil bed matrix, composed of fine-grained marlstone, enhances the visibility of each ammonite and provides a striking display suitable for both collectors and decorative presentation.

The scale cube (1 cm) shown in the photo provides an accurate reference for size, and full measurements can be found in the accompanying images. The natural arrangement of the ammonites in this slab captures a true “snapshot” of early Jurassic marine life as it existed on the seafloor nearly 200 million years ago.

Palaeobiological and Scientific Significance

Ammonites such as Promicroceras were free-swimming cephalopods, related to modern squids and cuttlefish. Their chambered shells enabled precise buoyancy control, allowing them to hover or dart through the water column while hunting small planktonic organisms.

This multi-specimen bed offers valuable scientific insight into palaeoecology and sedimentation processes, demonstrating how clusters of ammonites accumulated under low-oxygen conditions on the Jurassic seabed. The Promicroceras planicosta Zone is a key marker horizon in Lower Jurassic stratigraphy, and specimens like this are used to understand environmental shifts and evolutionary recovery following major extinction events.

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 to preserve its natural state. No replicas, restorations, or artificial enhancements are ever used — what you see is the authentic geological specimen, exactly as discovered and expertly prepared.

This Promicroceras Ammonite Bed Fossil is an outstanding piece of British palaeontological heritage, combining scientific importance, natural artistry, and historical significance from the legendary Jurassic Coast of Charmouth, Dorset — a true collector’s specimen capturing the beauty and diversity of the ancient seas.