Oistoceras Calcite Ammonite Fossil Jurassic Coast Stonebarrow Charmouth Dorset UK

Description

Specimen Overview

This offering presents a genuine Oistoceras calcite ammonite fossil recovered from the celebrated Green Ammonite Beds at Stonebarrow, near Charmouth and Lyme Regis, Dorset. The specimen has been carefully selected for its clear preservation, strong visual contrast, and natural presentation within the original matrix. Calcite replacement highlights the shell form against the characteristic green-grey sediment, allowing the ammonite’s morphology to be appreciated at a glance. The photographs show the exact fossil you will receive, with full sizing details provided in the images. As with all of our fossils, this specimen is 100% genuine and supplied with a Certificate of Authenticity.

Geological Formation & Provenance

The fossil originates from Stonebarrow, one of the most important exposures along the Jurassic Coast, a UNESCO World Heritage Site renowned for its continuous Lower Jurassic stratigraphy. The Green Ammonite Beds form part of the Lower Lias Group, deposited during the Early Jurassic, approximately 196–193 million years ago. These beds represent marine sediments laid down on a shallow continental shelf, where periodic changes in sediment supply and seawater chemistry resulted in the distinctive greenish matrix. Rapid burial within fine-grained sediments allowed ammonite shells to be preserved in excellent detail, often with calcite mineral replacement.

Fossil Type & Taxonomic Context

Oistoceras is an extinct genus of ammonite belonging to the Class Cephalopoda, Subclass Ammonoidea, and Order Ammonitida. Ammonites were free-swimming marine molluscs related to modern squid and cuttlefish and were among the most abundant and diverse predators in Jurassic seas. Oistoceras is particularly characteristic of certain Lower Lias intervals and is well known to both collectors and palaeontologists for its distinctive shell form and stratigraphic usefulness within Early Jurassic ammonite successions.

Morphology & Preservation

This Oistoceras specimen displays the characteristic coiled shell morphology of the genus, with clearly defined whorls and visible growth features that record the animal’s development through life. Calcite replacement has preserved the original shell geometry while enhancing surface detail, producing a subtle crystalline sheen when viewed under light. The surrounding Green Ammonite Bed matrix remains intact, preserving the fossil in its original geological context rather than as a removed or isolated shell. This in-situ preservation adds both scientific value and visual authenticity.

Scientific & Collecting Significance

Ammonites from Stonebarrow, Charmouth, and Lyme Regis have been collected and studied for over two centuries and were fundamental to the early development of geological and stratigraphic science. The Green Ammonite Beds are especially well known for producing classic Lower Lias ammonites with reliable provenance. Oistoceras is an important component of these assemblages and is frequently referenced in studies of Early Jurassic marine environments and ammonite evolution. Fossils from this locality are internationally recognised for their stratigraphic integrity and are highly sought after by collectors and educators alike.

Display, Care & Authenticity

This fossil is ideal for display in a private collection, educational environment, or natural history cabinet, offering both aesthetic appeal and geological context. The specimen has been carefully cleaned to reveal natural features, with no artificial restoration or reconstruction applied. It remains exactly as preserved by nature. You will receive the exact specimen shown, accompanied by a Certificate of Authenticity, confirming its origin and genuine status.

A classic and scientifically meaningful ammonite from one of the most famous fossil-bearing horizons on the Jurassic Coast, this Oistoceras calcite ammonite from the Green Ammonite Beds of Stonebarrow represents an authentic and visually striking piece of Early Jurassic marine history.