Ctenostreon Fossil Bivalve Jurassic Kimmeridge Clay Dorset UK Specimen – Ctenostreon sp Oyster Fossil Osmington Mills Kimmeridgian Jurassic

Description

Ctenostreon Fossil Bivalve from the Jurassic Seas of Dorset

This genuine Ctenostreon sp. fossil bivalve originates from the famous Kimmeridge Clay Formation at Osmington Mills near Weymouth, Dorset, United Kingdom. The fossil dates to the Upper Jurassic Period, Kimmeridgian Stage, approximately 157–152 million years ago, when southern Britain lay beneath warm shallow seas rich in marine life

Ctenostreon is an extinct genus of marine oyster-like bivalves, belonging to the family Gryphaeidae within the order Ostreida, a group of molluscs commonly referred to as oysters. Fossils of this genus are recognised for their distinctive irregular shell structure and robust growth forms adapted to life on soft marine substrates. Specimens from the Kimmeridge Clay are particularly desirable due to their association with one of the most famous fossil-bearing formations in the United Kingdom.

This specimen represents a classic Jurassic marine fossil from the renowned Jurassic Coast, an area internationally recognised for its geological significance and rich fossil record.

Geological Formation and Stratigraphic Context

The fossil originates from the Kimmeridge Clay Formation, a thick sequence of organic-rich marine mudstones deposited across southern England during the Late Jurassic. The formation takes its name from the village of Kimmeridge in Dorset, where the sedimentary sequence is well exposed along the coastline.

These sediments accumulated in a relatively deep offshore marine basin, where fine clay and organic material settled slowly on the seabed. Periodic low oxygen conditions helped preserve marine organisms, resulting in a fossil record that includes ammonites, bivalves, marine reptiles, fish, and other invertebrates.

The Kimmeridgian Stage represents a time of high global sea levels, when much of Europe was submerged beneath shallow epicontinental seas connected to the ancient Tethys Ocean.

Fossil Classification and Biological Characteristics

Ctenostreon belongs to the phylum Mollusca, class Bivalvia, a group of marine organisms characterised by shells composed of two hinged valves. Bivalves include clams, mussels, scallops, and oysters, and they have been a major component of marine ecosystems since the early Paleozoic.

Within this group, Ctenostreon is classified within the superfamily Ostreoidea, a lineage known for irregular shell forms adapted to attachment on hard surfaces or stable substrates.

These organisms were sessile filter feeders, meaning they remained fixed to the seabed while filtering microscopic organic particles from the surrounding water. Their shells often developed strong ridges and irregular growth patterns that helped stabilise them in dynamic marine environments.

Shell Morphology and Distinctive Features

Fossils of Ctenostreon are recognised by several characteristic morphological traits:

• Thick, irregular oyster-like shell valves
• Distinct radial ornamentation and growth ridges
• Curved shell profile adapted for attachment to substrate
• Robust calcitic shell structure

The uneven shell growth is typical of oysters and reflects how the organism adapted to its environment while anchored to surfaces such as shells, rocks, or firm sediment. Over time, mineralisation preserved the shell structure, allowing these fossils to survive for millions of years.

Specimens from the Kimmeridge Clay often show excellent preservation of shell detail, highlighting the natural ornamentation and structural complexity of these Jurassic molluscs.

Jurassic Marine Environment of the Kimmeridge Clay

During the Late Jurassic, the Dorset region was submerged beneath a broad marine basin that supported a diverse ecosystem. The warm waters hosted a wide range of marine organisms including ammonites, belemnites, crustaceans, fish, and large marine reptiles such as plesiosaurs and ichthyosaurs.

Bivalves like Ctenostreon formed an important component of the seabed community, helping to stabilise sediments and contributing to complex benthic ecosystems. These organisms thrived in nutrient-rich marine environments where plankton and organic material were abundant.

The fine clay sediments that accumulated in this basin eventually formed the Kimmeridge Clay Formation, which today represents one of the most fossil-rich Jurassic deposits in Europe.

Authentic Fossil Specimen

This fossil is a genuine Ctenostreon bivalve from the Kimmeridge Clay Formation of Dorset, UK. The specimen has been carefully selected for quality and display appeal.

The photograph shows the actual fossil specimen you will receive, allowing collectors to see the natural preservation and shell structure of this Jurassic oyster fossil.

Full sizing please see photo.

Certificate of Authenticity

This fossil includes a Certificate of Authenticity lifetime guarantee generic card, confirming that the specimen is a genuine natural fossil.

Fossils from the Dorset Jurassic Coast are highly regarded by collectors and geologists alike. A Ctenostreon bivalve from the Kimmeridge Clay represents a fascinating relic from the ancient Jurassic seas and offers a striking addition to any fossil collection, geological display, or educational exhibit.