Oistoceras Fossil Ammonite Jurassic Coast Charmouth Lyme Regis Dorset UK – Lower Lias Green Ammonite Beds Specimen with COA

Description

Oistoceras Fossil Ammonite from the Jurassic Coast of Dorset

This genuine Oistoceras fossil ammonite originates from the renowned Green Ammonite Beds of the Lower Lias Formation at Stonebarrow Cliff, Charmouth near Lyme Regis, Dorset, United Kingdom. The fossil dates to the Early Jurassic Period approximately 190 million years ago, a time when warm shallow seas covered much of southern Britain.

The Jurassic Coast of Dorset and East Devon, a UNESCO World Heritage Site, is one of the most famous fossil locations in the world. The cliffs around Charmouth and Lyme Regis have produced exceptional marine fossils for over two centuries and continue to reveal remarkable specimens through natural coastal erosion.

The ammonite shown in the photographs is the exact fossil you will receive, carefully chosen for its preservation and natural detail. This specimen includes a fully hand-signed Premium Certificate of Authenticity, confirming it is a genuine fossil from the Jurassic strata of Dorset.

Please refer to the photographs for full specimen sizing and scale.

About Oistoceras – Early Jurassic Ammonite Cephalopod

Oistoceras is a genus of ammonite belonging to the large and diverse group of extinct marine molluscs known as Ammonoidea. These animals were related to modern squid, octopus, and cuttlefish, although ammonites possessed an external coiled shell divided internally into gas-filled chambers.

Taxonomic classification:

• Phylum: Mollusca
• Class: Cephalopoda
• Subclass: Ammonoidea
• Order: Ammonitida
• Superfamily: Eoderoceratoidea
• Family: Eoderoceratidae
• Genus: Oistoceras

Ammonites were highly successful marine predators that inhabited oceans around the world for over 300 million years before becoming extinct at the end of the Cretaceous Period. Species evolved rapidly, making them extremely valuable index fossils used by geologists to identify and date sedimentary rock layers.

The genus Oistoceras was formally described by the British palaeontologist Sydney Savory Buckman, whose detailed research on Jurassic ammonites greatly advanced the understanding of ammonite classification and stratigraphy.

Geological Context – The Green Ammonite Beds of the Lower Lias

This fossil comes from the famous Green Ammonite Beds, part of the Lower Lias sequence exposed along the cliffs of the Dorset coast. These rocks were deposited during the Pliensbachian Stage of the Early Jurassic, approximately 190 million years ago.

The Green Ammonite Beds consist primarily of marly limestones and clay-rich sediments that accumulated on the seabed of a shallow marine environment. The sediments often contain abundant ammonites, giving the beds their name.

The marine ecosystem preserved in these rocks included a diverse range of organisms such as:

• Ammonites and belemnites
• Marine reptiles including ichthyosaurs and plesiosaurs
• Bivalves and gastropods
• Crinoids and other echinoderms
• Fossil fish

Fine sediment deposition and relatively calm marine conditions allowed the shells of marine animals to be buried rapidly, preserving detailed fossil specimens within the rock.

Shell Morphology and Features of Oistoceras

The shell of Oistoceras forms the classic planispiral ammonite coil, where successive whorls expand outward while remaining tightly wound around a central axis. Internally the shell is divided by curved walls known as septa, creating chambers that helped the living animal regulate buoyancy.

Typical morphological characteristics of Oistoceras ammonites include:

• Moderately evolute coiling with visible inner whorls
• Strong ribbing across the flanks of the shell
• Rounded whorl sections
• Distinct growth lines reflecting shell expansion during the animal’s life

The ribbed shell structure provided strength while maintaining a relatively lightweight shell. By adjusting gas and liquid within the internal chambers, the ammonite could move vertically in the water column and navigate the marine environment while hunting small prey.

These features make ammonites among the most recognisable fossils in the world.

A Genuine Jurassic Coast Fossil with Premium Certificate

This specimen represents a genuine fossil from one of the most celebrated fossil sites on Earth. Fossils from the Charmouth and Lyme Regis area are highly sought after due to their historical importance and connection to the early discoveries that shaped modern palaeontology.

Key features of this fossil include:

• Genuine Oistoceras ammonite fossil
• Geological formation: Green Ammonite Beds, Lower Lias
• Age: Early Jurassic Period, Pliensbachian Stage
• Locality: Stonebarrow Cliff, Charmouth near Lyme Regis, Dorset, UK
• From the Jurassic Coast UNESCO World Heritage Site
• Well-preserved spiral ammonite morphology
• The exact specimen shown in the photographs
• Includes a fully hand-signed Premium Certificate of Authenticity

This fossil preserves the elegant spiral shell of an ancient marine cephalopod that once lived in the warm Jurassic seas covering southern England nearly 190 million years ago, offering collectors a remarkable and authentic piece of prehistoric marine life from the world-famous Jurassic Coast.