Oxynoticeras Ammonite Fossil Cut and Polished Charmouth Jurassic Dorset UK Lower Jurassic Sinemurian Marine Cephalopod

Description

Genuine Oxynoticeras Ammonite Fossil Cut and Polished from the Jurassic Coast

This striking fossil ammonite identified as Oxynoticeras sp. originates from the famous Charmouth Mudstone Formation at Charmouth, Dorset, UK. Dating to the Lower Jurassic during the Sinemurian stage, approximately 199–190 million years ago, this specimen has been expertly cut and polished to reveal the beautiful internal structure of the shell chambers that once regulated the buoyancy of this ancient marine cephalopod.

The fossil shown in the photographs is the exact specimen you will receive. It has been carefully selected as an attractive example of this distinctive ammonite genus and displays the internal chambered structure that makes polished ammonites particularly fascinating to collectors and enthusiasts. Please refer to the photos for the full sizing and proportions of the fossil. The specimen includes a Certificate of Authenticity lifetime guarantee generic card confirming that it is a genuine fossil.

About Oxynoticeras – A Distinctive Early Jurassic Ammonite

Oxynoticeras belongs to the order Ammonitida, an extinct group of marine cephalopods closely related to modern squid, octopus, and cuttlefish. These animals thrived throughout the Mesozoic Era and were among the most abundant marine organisms of the Jurassic seas.

The genus Oxynoticeras is characteristic of the Lower Jurassic Sinemurian stage and belongs to the family Oxynoticeratidae within the superfamily Eoderoceratoidea. Ammonites of this genus are recognised for their compressed shells, sharp keel along the outer rim (venter), and strong ribbing that radiates across the whorls of the shell.

These features gave the shell a distinctive angular appearance and likely improved hydrodynamic stability as the animal moved through the water. Species of Oxynoticeras are frequently used by palaeontologists as biostratigraphic markers within Sinemurian strata because of their relatively short evolutionary time ranges and widespread distribution.

Internal Structure Revealed by Cutting and Polishing

This specimen has been professionally cut and polished to expose the internal architecture of the ammonite shell. Ammonites possessed a coiled shell divided into a series of chambers separated by curved walls known as septa. As the animal grew, it built new chambers while sealing off the older ones behind it.

These chambers were connected by a narrow tube called the siphuncle, which allowed the ammonite to regulate gas and liquid within the chambers to control buoyancy. The intricate suture patterns formed where the septa met the shell wall are a defining feature of ammonite anatomy and are often visible in polished specimens.

The polished cross-section allows collectors to observe the natural chamber arrangement and mineralisation that occurred during fossilisation, offering a unique window into the internal structure of this Jurassic marine organism.

Geological Context – Charmouth Mudstone Formation

The Charmouth Mudstone Formation is one of the most fossil-rich geological units in the United Kingdom and forms a significant part of the internationally renowned Jurassic Coast World Heritage Site. These sediments were deposited during the Early Jurassic in a shallow marine basin that covered much of southern Britain.

Composed mainly of grey mudstones and shales, the formation represents quiet offshore marine conditions where fine sediments slowly accumulated on the seabed. The calm depositional environment allowed delicate shells and skeletal material to become buried and preserved before decomposition.

Charmouth and Lyme Regis are globally famous fossil localities and have produced some of the most important Jurassic fossil discoveries in history, including marine reptiles, ammonites, belemnites, and fish. Fossils from this formation are often exceptionally well preserved due to rapid burial within fine sediment.

Jurassic Marine Life and Ecosystem

During the Sinemurian stage, the seas covering Dorset supported a thriving marine ecosystem. Ammonites like Oxynoticeras were abundant and played an important role in the marine food chain. They were active swimmers and likely preyed upon small fish, planktonic organisms, and crustaceans.

In turn, they served as prey for larger marine predators such as ichthyosaurs and early plesiosaurs. The widespread distribution and rapid evolution of ammonites make them among the most important fossils for understanding Jurassic marine environments and geological timescales.

Authenticity and Collectability

• Genuine Oxynoticeras ammonite fossil (cut and polished)

• Charmouth Mudstone Formation, Lower Jurassic

• Sinemurian stage, approximately 199–190 million years old

• Collected from Charmouth, Dorset, United Kingdom

• The exact fossil shown in the photographs is the specimen you will receive

• Includes a Certificate of Authenticity lifetime guarantee generic card

Cut and polished ammonites from the Jurassic Coast are highly desirable among collectors because they combine natural fossil preservation with a clear view of the internal shell structure. This Oxynoticeras specimen represents a beautiful and scientifically significant example of Early Jurassic marine life preserved within the historic fossil beds of Dorset.