Description
Shirbuirnia stephani Ammonite Fossil – Buckman Bed, Lower Jurassic, Dorset
This genuine Shirbuirnia stephani ammonite fossil is a collectable Lower Jurassic marine cephalopod specimen from the Buckman Bed at the top of the Lower Lias, Sandford Lane, Sherborne Dorset, UK. Dating from the Sinemurian Stage of the Early Jurassic, this fossil is from the Obtusum Subzone and represents an ammonite from the ancient Jurassic seas that once covered parts of Britain.
This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. It has been carefully chosen as an individual fossil specimen, with a photo that shows the actual piece you will receive. Full sizing please see photo.
Geology and Geological Age
Shirbuirnia stephani comes from the Lower Jurassic Period, specifically the Sinemurian Stage, approximately 199 to 191 million years old. The specimen is recorded from the Buckman Bed at the top of the Lower Lias, a historically important part of Britain’s Jurassic marine succession. The Lower Lias is well known for its ammonites, marine reptiles, bivalves, belemnites and other fossils preserved in mudstones, limestones and associated marine sediments.
During the Sinemurian, much of the UK lay beneath warm shallow seas. These marine conditions were part of a broad seaway system that covered large areas of north-west Europe. Fine sediment settled on the sea floor, preserving the remains of ammonites and other marine organisms over millions of years. Fossils from these beds are important for understanding the development of Early Jurassic marine ecosystems and for correlating rock layers across Britain and Europe.
Fossil Type and Species
This specimen belongs to the ammonite species Shirbuirnia stephani, a Lower Jurassic ammonite associated with the Sinemurian of Britain. Ammonites were extinct marine cephalopods related to modern squid, octopus and cuttlefish, but unlike their living relatives, they possessed a coiled external shell divided internally into chambers.
The living ammonite occupied the outer body chamber, while the older chambers helped regulate buoyancy. This allowed the animal to move through the water column in search of food and suitable habitat. Ammonites are especially important fossils because they evolved rapidly and are widely used by palaeontologists for dating and matching Jurassic marine rocks.
Biozone and Stratigraphic Interest
This fossil is from the Obtusum Subzone, placing it within a carefully recognised Lower Jurassic ammonite succession. Ammonite zones and subzones are extremely useful in Jurassic stratigraphy because different ammonite species appeared, flourished and disappeared over relatively short geological intervals.
The Buckman Bed is of particular interest to collectors because it is linked with classic British Jurassic ammonite studies. Specimens from named beds and subzones are especially desirable because they carry stronger geological context than fossils with only a broad age or country of origin.
Morphology and Collectable Features
Shirbuirnia stephani displays the classic appeal of an Early Jurassic ammonite, with its naturally coiled shell form and scientific significance. Depending on preservation and growth stage, specimens may show visible whorls, ribbing, shell curvature, chamber structure, natural matrix contact, mineral replacement or sutural detail.
Ammonite ribs and shell ornament were part of the animal’s natural shell structure. These features may have helped strengthen the shell and can also assist with identification. In well-preserved ammonites, suture lines may be visible as intricate patterns marking where the internal chamber walls met the outer shell. These details are highly valued by collectors and students of palaeontology.
Sandford Lane, Sherborne Dorset Locality
Sherborne in Dorset is a notable British fossil locality associated with Lower Jurassic marine deposits. Fossils from this region help record the diversity of ammonite life in the Early Jurassic seas of the UK. A specimen with locality detail from Sandford Lane, together with the Buckman Bed, Obtusum Subzone and Sinemurian age, makes this a strong addition to a British Jurassic fossil collection.
This ammonite is suitable for fossil collectors, geology enthusiasts, educational collections, natural history displays, display cabinets and anyone interested in classic UK Jurassic fossils.
Depositional Environment
This Shirbuirnia stephani ammonite was preserved in sediments laid down beneath an ancient Jurassic sea. After the ammonite died, its shell settled onto the sea floor and was gradually buried by fine marine mud and sediment. Over time, compaction, mineral-rich groundwater and geological pressure transformed the remains into a fossil.
The specimen is a natural record of marine life from Early Jurassic Britain, when ammonites were abundant and diverse across the seas of Europe.
Authenticity and Display
This is a genuine Shirbuirnia stephani ammonite fossil from the Buckman Bed, top of the Lower Lias, Obtusum Subzone, Lower Jurassic, Sinemurian of Sandford Lane, Sherborne Dorset, UK. It includes a Certificate of Authenticity lifetime guarantee generic card. The fossil has been carefully selected, and the photo shows the actual specimen you will receive. Full sizing please see photo.
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