Promicroceras Calcite Ammonite Fossil Black Ven Marls Lower Lias Jurassic Coast Charmouth Lyme Regis Dorset UK Genuine Specimen with COA

Beautiful Promicroceras Calcite Ammonite Fossil from the Jurassic Coast, Charmouth, Dorset, UK

This exquisite Promicroceras Calcite Ammonite fossil was discovered by our own team members, Alister and Alison, on 2 October 2025, at Stonebarrow Cliff, Charmouth, near Lyme Regis, Dorset, United Kingdom. Carefully cleaned, prepared, and treated by Alison, this specimen represents one of the most iconic ammonites of Britain’s Lower Jurassic period, preserved in shimmering calcite within the famous Black Ven Marls Formation. The fossil’s fine ribbing and compact coiling, combined with its natural luster, make it a stunning example of early Jurassic marine life and a prized collector’s item from the UNESCO World Heritage Jurassic Coast.

Geological and Depositional Context

The Black Ven Marls Formation, part of the Lower Lias Group, dates to the Sinemurian Stage of the Early Jurassic (approximately 199–190 million years ago). These soft, blue-grey marls and clays were deposited in a shallow, subtropical marine environment, where fine sediments gently accumulated on the sea floor. Periodic anoxic conditions and rapid burial preserved marine organisms with exceptional detail — particularly ammonites, belemnites, and marine reptiles.
The Charmouth–Lyme Regis area, including Stonebarrow Cliff and Black Ven, is world-renowned for its fossil abundance and geological significance. The alternating marl and limestone beds record a continuous marine sequence spanning millions of years, providing critical insights into Jurassic paleoenvironments and faunal evolution. These deposits have yielded some of the most complete ammonite faunas in Europe and continue to serve as key reference sections for international stratigraphy.

Species Overview – Promicroceras

Promicroceras is a small, tightly coiled ammonite belonging to the family Eoderoceratidae, superfamily Eoderoceratoidea, order Ammonitida. It is one of the earliest representatives of the Eoderoceratid lineage and an important index fossil for the Obtusum Zone of the Lower Jurassic. The genus is characterised by its fine, sharp ribs, compressed whorl section, and smooth keel running along the venter. The intricate ribbing radiates outward in a regular, symmetrical pattern, reflecting both evolutionary elegance and hydrodynamic efficiency.
This specimen displays the distinctive calcite mineralisation typical of Promicroceras from the Black Ven Marls. Over millions of years, the original aragonite shell was replaced by transparent golden or honey-coloured calcite, giving the fossil a luminous, glassy appearance that captures and reflects light beautifully. Such preservation is highly prized among collectors and distinguishes Dorset Promicroceras from examples found elsewhere in the world.

Scientific and Historical Importance

Promicroceras has been a key genus in Jurassic biostratigraphy for more than a century. Its abundance, rapid evolutionary turnover, and global distribution make it an excellent indicator fossil for correlating early Jurassic marine rocks across Europe. Specimens from Charmouth have been extensively studied by palaeontologists since the 19th century, with the region’s fossils playing a major role in shaping early paleontological research.
The Lyme Regis–Charmouth coast is synonymous with fossil discovery, most famously associated with pioneering fossil collector Mary Anning, whose early 19th-century finds transformed scientific understanding of prehistoric life. Promicroceras fossils like this one are part of that same geological legacy, connecting collectors today with a history of discovery that stretches back over two hundred years.

Condition, Provenance, and Authenticity

This is a 100% genuine fossil specimen, professionally prepared by Alison to highlight its intricate detail and natural calcite beauty. The fossil retains its original shape and matrix context, displaying exceptional rib definition, coiling symmetry, and surface polish. The preservation of the calcite infill enhances both its aesthetic appeal and its scientific value.
The photograph shows the exact specimen you will receive — we never use stock images. Every fossil in our collection is hand-selected for its quality and authenticity. Your specimen comes complete with a Certificate of Authenticity, verifying its provenance, formation, and geological age.

Details at a Glance

• Genus: Promicroceras

• Family: Eoderoceratidae

• Superfamily: Eoderoceratoidea

• Order: Ammonitida

• Formation: Black Ven Marls

• Group: Lower Lias

• Age: Sinemurian Stage, Lower Jurassic (~199–190 million years ago)

• Biozone: Promicroceras / Asteroceras obtusum Zone

• Locality: Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, United Kingdom

• Depositional Environment: Shallow marine clay-marl sequence

• Discovered by: Alister and Alison on 02 October 2025

• Prepared by: Alison

• Condition: Genuine calcite ammonite; professionally cleaned and stabilised

• Scale: Cube = 1 cm (see photo for full sizing)

• Included: Certificate of Authenticity

A Dazzling Jurassic Calcite Ammonite from the Fossil-Rich Cliffs of Charmouth

This Promicroceras calcite ammonite from the Black Ven Marls of Charmouth is a breathtaking example of Dorset’s paleontological heritage. Its gleaming calcite preservation, fine ribbing, and perfect coiling make it both a scientifically important specimen and a stunning natural display piece — a timeless treasure from Britain’s world-famous Jurassic Coast.