This carefully chosen fossil is a genuine Cererithyris cf. intermedia brachiopod from the Inferior Oolite Group of Dorset, UK. Dating from the Bajocian Stage of the Middle Jurassic, it represents a marine filter-feeding animal that inhabited the warm, shallow seas covering southern Britain approximately 170 million years ago.
The listing photograph shows the actual fossil specimen you will receive. This is not a stock image or an example selected from a larger group. Please examine the photograph carefully to view the fossil’s complete dimensions, proportions, colour, preservation, shell features and any surrounding limestone matrix. Full sizing is shown in the photo.
The specimen is identified as Cererithyris cf. intermedia. In palaeontological identification, the abbreviation “cf.” is derived from the Latin word confer, meaning “compare with”. It indicates that the fossil displays features comparable to the named species, Cererithyris intermedia, while retaining an appropriately cautious identification.
Cererithyris is an extinct genus of articulated brachiopod. Brachiopods are marine invertebrates protected by two mineralised valves and have an extensive fossil record extending back into the early Palaeozoic Era.
Although brachiopods may resemble bivalve molluscs such as clams, oysters and mussels, they belong to a completely separate animal phylum. A bivalve has left and right shell valves positioned on either side of its body. A brachiopod instead has dorsal and ventral valves situated above and below the animal. Each brachiopod valve is generally symmetrical along its central axis, while the two valves commonly differ in size and shape.
Cererithyris brachiopods typically possess a compact, rounded to oval shell with two convex valves. The exterior may appear relatively smooth or carry fine growth lines recording the gradual enlargement of the shell during the animal’s lifetime.
The larger ventral valve may preserve a curved or projecting beak near the hinge. An opening in this region accommodated the pedicle, a muscular stalk that helped anchor the living brachiopod to a shell fragment, stone or other stable surface on the Jurassic seabed.
The anterior margin, where the valves met, may show gentle folding or curvature. These features could influence how water moved through the shell while the animal was feeding. The hinge region kept the valves aligned, and specialised muscles controlled their limited opening and closing.
Inside the shell, the animal possessed a lophophore, a ciliated feeding organ bearing numerous small tentacles. The lophophore generated water currents and filtered microscopic organic particles from the surrounding seawater. This allowed the brachiopod to remain attached to the seabed while continuously collecting suspended food.
Any natural fractures, incomplete margins, mineral staining, weathered surfaces, adhering limestone or areas of shell loss visible in the photograph are authentic results of burial, fossilisation, geological exposure and preparation. These features form part of the specimen’s individual geological history.
The Inferior Oolite Group is a well-known succession of Middle Jurassic sedimentary rocks exposed across parts of southern and western England. In Dorset, it is composed mainly of fossiliferous limestone, including beds containing shell debris, carbonate grains, iron-rich material and evidence of extensive activity by seabed organisms.
The term “oolite” refers to limestone containing ooids, which are small, rounded grains formed when calcium carbonate accumulated in layers around tiny particles in warm, agitated seawater. The word “Inferior” does not refer to the quality of the rock. It indicates that the Inferior Oolite lies stratigraphically beneath the younger Great Oolite succession.
Sedimentation during this period was often slow and interrupted. Currents could erode or rework exposed seabed material, while burrowing organisms disturbed and mixed recently deposited sediment. Shells and skeletal fragments accumulated locally, creating fossil-rich limestone beds that preserve evidence of diverse Middle Jurassic marine communities.
The Bajocian is the second stage of the Middle Jurassic Epoch, following the Aalenian and preceding the Bathonian. During this interval, Britain was located at a lower latitude than it is today and experienced a warmer climate.
Large areas of southern England were covered by shallow epicontinental seas. These marine environments varied from relatively quiet, muddy seabeds to areas influenced by stronger currents and active carbonate production.
Cererithyris lived as part of a diverse benthic community on the sea floor. Brachiopods shared this environment with ammonites, belemnites, bivalves, gastropods, crinoids, echinoids, corals and other marine invertebrates. Fish and marine reptiles occupied higher levels of the Jurassic ecosystem.
The hard shells of brachiopods provided protection from physical disturbance and smaller predators. Their attached or semi-stationary lifestyle allowed them to occupy areas where water movement continually supplied oxygen and suspended food particles.
During the Bajocian, the region now known as Dorset formed part of a broad marine shelf. Warm seawater encouraged the formation of carbonate sediment, while changing currents, sea levels and sediment supply produced the varied limestone beds of the Inferior Oolite Group.
The seabed included firm surfaces, loose shell material, carbonate sand and areas of softer sediment. Brachiopods could attach to suitable objects using their pedicles, positioning themselves above the substrate so that seawater could circulate efficiently through their partly opened shells.
Periods of stronger water movement occasionally transported shells and concentrated them into fossil-rich layers. Other specimens were buried close to where they lived, retaining more of their original form and association with the surrounding sediment.
After the brachiopod died, its shell settled onto the Middle Jurassic seabed. The valves may have remained joined or become separated as the soft tissues decayed. Burial beneath carbonate mud, ooids and broken shell material helped protect the remains from complete destruction.
As additional sediment accumulated, pressure compacted the deposit. Calcium-carbonate cement gradually bound the loose particles together, transforming the sediment into limestone. Mineral-rich groundwater could enter the shell, fill internal spaces and alter or recrystallise portions of the original material.
The resulting fossil may preserve original calcitic shell, recrystallised mineral matter, an internal mould, an external impression or a combination of these preservation styles. Its present appearance records both the anatomy of the original animal and the geological processes that acted upon it after burial.
This Cererithyris cf. intermedia specimen combines a recognised brachiopod identification with the famous Inferior Oolite geology of Dorset. Its recorded fossil type, geological group, stage and British provenance make it suitable for a documented fossil collection, educational display or specialist Jurassic cabinet.
The specimen would complement collections focused on brachiopods, Middle Jurassic marine life, British palaeontology, Dorset geology or fossil invertebrates. It also offers a tangible connection to the ancient sea that covered southern England during the Bajocian.
You will receive the exact Cererithyris cf. intermedia brachiopod fossil shown in the listing photograph. The fossil has been individually and carefully selected for its natural form, recognisable characteristics, geological provenance and collectable appeal.
This genuine fossil includes a generic Certificate of Authenticity card supported by a lifetime authenticity guarantee. It is an authentic prehistoric specimen rather than a cast, replica or artificially manufactured reproduction.
This Middle Jurassic brachiopod makes an excellent addition to a British fossil collection, geology cabinet, museum-style display or educational reference set. It is also a distinctive natural history gift for a fossil collector, palaeontology student, geology enthusiast, teacher or anyone fascinated by prehistoric marine life.