Asteroceras Promicroceras Calcite Ammonite Fossil Jurassic Lyme Regis Dorset UK

Description

Authentic Asteroceras and Promicroceras Calcite Ammonite from the Jurassic Coast

Offered here is a genuine Asteroceras and Promicroceras calcite ammonite fossil with a cut base, collected from the renowned Black Ven Marls at Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, along England’s world-famous Jurassic Coast. This carefully selected specimen preserves two classic Lower Jurassic ammonite genera together, creating a scientifically informative and visually striking display fossil. The photographs show the exact specimen you will receive, and full sizing details are shown in the photos.

This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card, providing lasting confidence in provenance and collectability.

Geological Formation and Age

This specimen 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 laid down in a shallow epicontinental sea that covered much of southern Britain. Stonebarrow Cliff is one of the most important Lower Jurassic fossil localities in Europe, internationally recognised for its abundance of ammonites critical to Jurassic stratigraphy and palaeoenvironmental studies.

Fossil Type, Species, and Scientific Context

The specimen contains ammonites of the genera Asteroceras and Promicroceras, both belonging to the Order Ammonitida.

Asteroceras, part of the Superfamily Eoderoceratoidea and Family Eoderoceratidae, is a robust and well-known Lower Jurassic ammonite frequently cited in biostratigraphic studies of the Sinemurian.

Promicroceras, within the Family Echioceratidae, is a classic index fossil closely associated with the Promicroceras biozone, making it especially important for correlating Lower Lias marine sediments. The presence of both genera together enhances the scientific value of this specimen.

Morphology and Calcite Preservation

The ammonites display characteristic planispiral coiling with clearly defined whorls and strong ribbing across the flanks. Asteroceras typically shows broader whorls and bold rib ornamentation, while Promicroceras is more compact with pronounced, regular ribs. Calcite mineralisation enhances surface detail and gives the shells a pale, crystalline finish that contrasts beautifully with the darker marl matrix.

The cut base allows the fossil to stand upright securely, making it ideal for cabinet, shelf, or desk display without the need for additional supports.

Depositional Environment

During the Early Jurassic, the Charmouth and Lyme Regis area lay beneath a warm, shallow marine environment rich in ammonites, belemnites, fish, and marine reptiles. Fine sediments settled slowly on the sea floor, allowing ammonite shells to be buried rapidly after death. Periodic low-oxygen conditions reduced scavenging and disturbance, contributing to the exceptional preservation seen in ammonites from the Black Ven Marls. These conditions underpin the global significance of the Jurassic Coast fossil record.

Collecting, Display, and Educational Value

This Asteroceras and Promicroceras calcite ammonite fossil with cut base is ideal for serious fossil collectors, educational collections, museum displays, or refined interior presentation. Its combination of two diagnostically important ammonite genera, classic British Jurassic provenance, and practical display preparation makes it both scientifically informative and visually compelling. Ammonites from Stonebarrow Cliff are increasingly sought after, particularly well-prepared examples suitable for display. 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.