Cymbites and Promicroceras Calcite Ammonite Fossil Split Nodule Jurassic Coast UK

Description

Genuine Cymbites and Promicroceras Calcite Ammonite Fossil

This is a rare and scientifically significant Cymbites and Promicroceras calcite ammonite fossil, preserved within a split Birchi nodule from the Black Ven Marls, Lower Lias, Jurassic Coast: Stonebarrow Cliff, Charmouth, Lyme Regis, Dorset, UK. This exceptional piece dates to the Early Jurassic Period (approximately 197–200 million years ago) and provides a stunning glimpse into the ancient marine life that once thrived in the Jurassic seas.

The specimen was discovered by Alister and Alison on 12 September 2025, with all professional cleaning, preparation, and treatment carried out by Alison. Each photograph provided is of the actual specimen you will receive, accompanied by a 1 cm scale cube for accurate sizing. As with all of our fossils, this piece comes with a Certificate of Authenticity.

Geological and Stratigraphic Context

This fossil comes from the renowned Black Ven Marls, part of the Lower Lias Group, exposed along the Jurassic Coast World Heritage Site. The Birchi nodules in this formation are world-famous for their remarkable preservation, often encasing ammonites in crystalline calcite that reveals both internal and external details.

The Lower Lias deposits formed in shallow marine environments where fine sediments rapidly buried marine organisms, resulting in exquisite preservation. The ammonites within these beds are key index fossils, helping palaeontologists establish detailed biostratigraphic frameworks for the Early Jurassic.

About Cymbites and Promicroceras

Cymbites belongs to the family Cymbitidae, superfamily Eoderoceratoidea, order Ammonitida. These ammonites are recognised by their rounded shells with fine ribbing and intricate suture lines, which are often beautifully highlighted in calcite preservation.

Promicroceras, from the family Eoderoceratidae, is one of the most iconic ammonites of the Lower Jurassic. It is a small but highly distinctive ammonite, known for its ribbed ornamentation and tightly coiled shell. Promicroceras is often found in large numbers along the Jurassic Coast and has become a favourite among collectors and palaeontologists for both its aesthetic appeal and stratigraphic importance.

Having both Cymbites and Promicroceras preserved together in one split nodule makes this piece especially desirable, as it showcases the diversity of ammonite life during the Lower Jurassic.

Morphological Features

This specimen displays calcite-filled chambers that sparkle under light, offering a beautiful natural polish. When split, Birchi nodules reveal both the external features of the ammonite shell and the internal cast, allowing collectors to study the complete morphology. The ribbing and whorl structures of both Cymbites and Promicroceras are clearly visible, providing a detailed view of Jurassic ammonite anatomy.

Scientific and Collector Importance

Ammonites like Cymbites and Promicroceras serve as important index fossils, allowing geologists to precisely date rock strata and understand the evolution of marine ecosystems. Their occurrence within the Black Ven Marls is key to defining certain biozones of the Sinemurian Stage of the Early Jurassic.

For collectors, this specimen offers a rare double ammonite association, preserved in calcite within a split nodule — an outstanding combination of natural beauty, educational value, and historical significance. It is also a tangible connection to the fossil-collecting history of the Jurassic Coast, an area made world-famous by pioneering fossil hunters such as Mary Anning.

A Unique Piece of Natural History

This Cymbites and Promicroceras calcite ammonite fossil split nodule is not just a collector’s item but a scientific treasure. It embodies the fascinating story of life and preservation during the Early Jurassic and provides a captivating addition to any fossil collection.

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.