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

Description

Overview and Authenticity

Offered here is a genuine Promicroceras calcite ammonite fossil from one of the most celebrated fossil localities in the world: Black Ven, Lyme Regis, Dorset, part of the UNESCO-listed Jurassic Coast of southern England. This specimen is a carefully selected, naturally preserved ammonite, with the photograph showing the exact fossil you will receive. As with all of our fossils, this piece is a 100% genuine specimen and is supplied with a Certificate of Authenticity, ensuring complete confidence for collectors, researchers, and gift buyers alike.

Full sizing details can be seen clearly in the accompanying photographs.

Geological Context

This ammonite originates from the Black Ven Marls, within the Lower Lias Group, dating to the Early Jurassic Period, approximately 199–191 million years ago. Black Ven is internationally renowned for its continuous marine sedimentary record and exceptional preservation of ammonites. During the Early Jurassic, this region lay beneath a warm, shallow epicontinental sea, where fine calcareous muds accumulated on the sea floor. These low-energy conditions were ideal for the burial and preservation of delicate shelled cephalopods such as Promicroceras.

Fossil Type and Species

Promicroceras is a small but highly diagnostic genus of ammonite belonging to the Order Ammonitida, Superfamily Eoderoceratoidea, and Family Echioceratidae. This genus is particularly significant in British Jurassic stratigraphy and is widely used as an index fossil. Specimens of Promicroceras are characteristic of the Sinemurian Stage of the Early Jurassic and are closely associated with the Promicroceras planicosta Biozone, making them important for precise geological dating.

Morphology and Notable Features

Promicroceras ammonites are noted for their evolute coiling, allowing earlier whorls to remain visible, and for their distinct ribbing, which typically bifurcates or curves gently across the flanks. The shell form is generally compressed, with a relatively wide umbilicus and a well-defined venter. This specimen exhibits attractive calcite mineralisation, enhancing both its visual appeal and structural integrity. The calcite infill highlights the original shell geometry while preserving fine morphological details valued by collectors and palaeontology enthusiasts.

Depositional Environment

The Black Ven Marls represent a marine shelf environment, deposited below wave base in relatively calm conditions. Periodic oxygen-poor episodes on the sea floor limited scavenging and bioturbation, allowing ammonite shells to settle intact and become rapidly buried. These conditions contributed to the exceptional abundance and quality of ammonite fossils found at Lyme Regis, a locality historically associated with early palaeontological discoveries.

Collecting and Display

This Promicroceras calcite ammonite is an excellent example of a classic British Jurassic fossil. It is well suited for private collections, educational displays, museums, or as a scientifically meaningful gift. Its clear provenance, identifiable stratigraphic position, and attractive preservation make it both a visually striking and academically relevant specimen.

Every fossil we offer is individually selected for quality and authenticity, ensuring you receive a genuine piece of Earth’s deep history from one of the most important fossil sites in the world.