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

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

This stunning 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 — one of the most famous fossil localities along the Jurassic Coast World Heritage Site. Carefully cleaned, prepped, and treated by Alison, this genuine specimen displays exquisite calcite mineralisation, detailed ribbing, and the characteristic coiling of Promicroceras, one of the most recognisable ammonites from the early Jurassic. Each photograph shows the exact fossil you will receive, making this a truly unique and authentic piece of Britain’s geological history.

Geological Context – Black Ven Marls, Lower Lias

This ammonite originates from the Black Ven Marls, part of the Lower Lias Group, dating to the Sinemurian Stage of the Early Jurassic period, approximately 199–190 million years ago. The sediments were deposited in a calm, shallow marine environment, once part of a broad tropical sea that covered much of southern England. Fine layers of mud, marl, and limestone accumulated on the sea floor, gradually burying and preserving marine organisms such as ammonites, belemnites, and fish remains.
Over time, chemical changes within the sediment replaced the original aragonite shell material with crystalline calcite, giving the ammonite its distinctive golden to honey-coloured sparkle. The Charmouth–Lyme Regis area, including Stonebarrow Cliff and Black Ven, is world-renowned for this type of calcite preservation, which makes each fossil both scientifically significant and visually striking. These fossil-bearing strata are also historically important, having been studied for more than 200 years and continuing to yield exceptional specimens that contribute to global geological research.

Species Overview – Promicroceras

Promicroceras belongs to the family Eoderoceratidae, superfamily Eoderoceratoidea, and order Ammonitida. It is an important early ammonite genus from the Sinemurian, and one of the most abundant fossils within the Asteroceras obtusum Biozone. Its small, tightly coiled, and finely ribbed shell structure distinguishes it from other ammonites of the same age. The whorls are compressed, with ribs extending continuously from the umbilicus to the venter, creating a beautifully symmetrical pattern typical of early Jurassic ammonites.
This morphology reflects Promicroceras’ adaptation to life as an agile, free-swimming predator in the open ocean. The ribbing and hydrodynamic form of the shell improved buoyancy control and movement efficiency, allowing the animal to occupy the midwater column in pursuit of plankton and small crustaceans. The genus is also a key index fossil used to identify and correlate Lower Jurassic marine deposits across Europe, particularly in Britain and northern France.

Scientific and Historical Importance

Fossils from the Charmouth–Lyme Regis coastline have played an instrumental role in the history of paleontology. The region gained worldwide fame through the work of Mary Anning and early 19th-century collectors who unearthed some of the most important fossil discoveries in Britain. The Promicroceras ammonite continues to hold great value for scientific study, providing vital information about evolutionary development, paleoecology, and biostratigraphy during the early Jurassic period.
The Jurassic Coast itself, stretching from Exmouth in Devon to Studland Bay in Dorset, is a UNESCO World Heritage Site celebrated for its continuous geological record spanning 185 million years of Earth’s history. Each specimen from these cliffs is a direct piece of that ancient record — a tangible link to a world long vanished beneath warm Jurassic seas.

Condition, Preparation, and Authenticity

This Promicroceras calcite ammonite has been professionally cleaned and stabilised by Alison using specialist tools and techniques to preserve all natural detail. The fossil retains its delicate ribbing and shows excellent preservation within its original matrix. The calcite infill gives it a bright, glassy finish that catches the light beautifully, revealing both scientific and aesthetic value.
The photo shows the exact fossil you will receive; we never use stock images. Each specimen in our collection is hand-selected for its quality, authenticity, and scientific integrity. Your fossil will arrive securely packaged with a Certificate of Authenticity, verifying its identification, geological formation, and precise locality.

Details at a Glance

• Genus: Promicroceras

• Family: Eoderoceratidae

• Superfamily: Eoderoceratoidea

• Order: Ammonitida

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

• Biozone: Asteroceras obtusum Zone

• Formation: Black Ven Marls

• Group: Lower Lias

• Locality: Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, UK

• Depositional Environment: Shallow marine muds and marls

• Discovered by: Alister and Alison on 02 October 2025

• Prepared by: Alison

• Condition: Genuine calcite ammonite; professionally cleaned and preserved

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

• Included: Certificate of Authenticity

A Classic British Calcite Ammonite from the Fossil-Rich Cliffs of Charmouth

This Promicroceras calcite ammonite fossil captures the essence of Dorset’s Jurassic heritage — a timeless natural treasure combining science, beauty, and history. Its glowing calcite finish, intricate ribbing, and perfect coiling make it a remarkable addition to any fossil collection or an unforgettable gift from Britain’s world-famous Jurassic Coast.