Description
Exceptional Planammatoceras Ammonite from the Lower Bajocian, Dorset, UK
This exquisite Planammatoceras fossil ammonite originates from the Lower Bajocian Stage of the Middle Jurassic Period, approximately 170 million years old, and was discovered at West Bay, Dorset, United Kingdom. Specimens of Planammatoceras are highly sought after for their elegant shell form and detailed ribbing, representing a classic ammonite type from the early Bajocian seas that once covered what is now southern England. This fossil offers a perfect combination of scientific importance, natural beauty, and geological heritage from one of Britain’s most iconic Jurassic localities.
Geological and Depositional Context
The Bajocian Stage marks a crucial point in the Middle Jurassic, a time when warm, shallow seas spread across much of southern England, forming the limestone and marl successions of the Inferior Oolite Group. The West Bay area near Bridport lies at the western end of the Jurassic Coast UNESCO World Heritage Site, famous for its continuous record of Jurassic marine life. Sediments from this period were deposited in tranquil offshore environments, rich in calcium carbonate, which promoted exceptional fossil preservation.
Ammonites like Planammatoceras thrived in these environments, evolving rapidly and leaving behind distinct shell forms that make them valuable biostratigraphic markers. The fossil-bearing strata at West Bay belong to the Inferior Oolite Formation, where fine-grained limestones and mudstones preserve marine invertebrates in superb detail, often with original shell ornamentation intact.
Species Overview – Planammatoceras
The genus Planammatoceras belongs to the family Stephanoceratidae, superfamily Stephanoceratoidea, order Ammonitida. It is recognised by its relatively compressed, planispiral shell, fine ribbing, and gently rounded whorls. The ribs are typically simple and evenly spaced, giving the ammonite a smooth, graceful appearance compared to the more ornate forms of later Bajocian genera such as Stephanoceras and Garantiana.
Planammatoceras is associated with the Laeviuscula Biozone of the Lower Bajocian, serving as a biostratigraphic indicator species within the European Jurassic sequence. Its distinctive morphology suggests it was a strong, hydrodynamic swimmer adapted to mid-water hunting, likely preying on small crustaceans and planktonic organisms in the clear, warm seas of the Jurassic.
Scientific and Collector Significance
Fossils of Planammatoceras hold considerable scientific value for understanding the early evolution of the Stephanoceratid ammonites. The species bridges morphological traits between earlier smooth forms and the heavily ribbed or tuberculate ammonites that came to dominate later in the Middle Jurassic. Because of its restricted stratigraphic range, Planammatoceras also plays an important role in correlating Bajocian deposits across different regions of Europe.
From a collector’s perspective, this specimen’s fine preservation, clean shell definition, and provenance from West Bay, Dorset make it an exceptional display fossil. It embodies the paleontological richness of Britain’s Jurassic Coast, combining aesthetic appeal with genuine scientific authenticity.
Condition and Authenticity
This 100% genuine fossil specimen has been carefully selected and prepared to showcase its natural form and characteristic features. The shell displays distinct ribbing and well-defined coiling, typical of the genus. The fossil has been gently cleaned to reveal its structure without altering the natural mineral surface. The photograph shows the exact specimen you will receive, ensuring accuracy and transparency.
Every purchase includes a Certificate of Authenticity, confirming the fossil’s species, geological age, and discovery locality.
Details at a Glance
- Genus: Planammatoceras
- Family: Stephanoceratidae
- Superfamily: Stephanoceratoidea
- Order: Ammonitida
- Age: Lower Bajocian Stage, Middle Jurassic (~170 million years ago)
- Formation: Inferior Oolite Group
- Locality: West Bay, Dorset, United Kingdom
- Condition: Genuine, naturally preserved fossil; carefully cleaned and stabilised
- Scale: Cube = 1 cm (see photo for full sizing)
- Included: Certificate of Authenticity
A Distinctive Piece of Britain’s Jurassic Heritage
This Planammatoceras fossil ammonite is a captivating representation of Jurassic marine life, perfectly preserved from the world-famous strata of West Bay. Its elegant form and historical significance make it a beautiful and meaningful addition to any fossil collection, connecting you directly to the ancient seas that shaped the geology of Dorset over 170 million years ago.
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