Description
Shirbuirnia reliati Ammonite Fossil – Inferior Oolite, Middle Jurassic, Somerset
This genuine Shirbuirnia reliati ammonite fossil is a collectable Middle Jurassic marine cephalopod specimen from the Inferior Oolite of Yeovil, Somerset, UK. Dating from the Bajocian Stage of the Middle Jurassic, approximately 170 to 168 million years old, this fossil represents an ammonite from the warm shallow seas that once covered large parts of southern 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 reliati comes from the Inferior Oolite, one of the classic Jurassic fossil-bearing rock units of southern England. The Inferior Oolite is especially well known for its marine limestones, oolitic sediments, shelly beds and rich fossil content. These rocks were formed during the Bajocian Stage of the Middle Jurassic, a time when Britain lay much closer to the equator and was covered by warm, shallow, tropical to subtropical seas.
The name “oolite” refers to the small rounded grains, known as ooids, that formed in agitated shallow marine water. These grains accumulated with shell debris, carbonate mud and marine sediment, later hardening into limestone. Fossils from the Inferior Oolite can include ammonites, bivalves, brachiopods, gastropods, echinoids, corals, belemnites and other marine organisms.
Fossil Type and Species
This specimen belongs to the ammonite species Shirbuirnia reliati, a Jurassic ammonite associated with the Bajocian of Britain. Ammonites were extinct marine cephalopods related to modern squid, octopus and cuttlefish, but unlike their living relatives, they possessed an external coiled shell divided internally into chambers.
The animal lived in the outer body chamber, while the older internal chambers helped control buoyancy. This allowed ammonites to move through the water column in search of food and suitable habitat. Ammonites are among the most important fossils for dating Jurassic rocks because many species evolved quickly and had distinctive shell forms, making them highly useful for identifying geological horizons.
Morphology and Collectable Features
Shirbuirnia reliati displays the classic appeal of a Jurassic ammonite, with its natural coiled shell form and important geological context. Depending on preservation and growth stage, the fossil may show visible whorls, ribbing, shell curvature, chamber structure, natural matrix contact, mineral replacement or sutural detail.
The ribs and shell ornament on ammonites were part of the original shell structure and may have helped strengthen the shell. In well-preserved examples, suture lines may be visible as intricate patterns marking where the internal chamber walls met the outer shell. These features are of particular interest to collectors because they show the biological complexity of ammonites and help distinguish different groups and species.
This specimen is especially desirable because it combines a named ammonite species, a clear Bajocian age, a classic British Jurassic formation and a well-known Somerset locality.
Inferior Oolite and Yeovil Fossil Locality
The Yeovil area of Somerset is part of a region long associated with important Jurassic fossil finds. The Inferior Oolite in this area preserves evidence of shallow marine environments that developed across southern England during the Middle Jurassic. These beds are particularly significant for ammonite collectors because they contain fossils from a time of active ammonite evolution and diversification.
Specimens from named British formations such as the Inferior Oolite are highly valued because they carry strong geological and locality information. A Shirbuirnia reliati ammonite from Yeovil is a suitable addition to collections focused on British fossils, Jurassic ammonites, Somerset geology, marine cephalopods and natural history display pieces.
Depositional Environment
This Shirbuirnia reliati ammonite was preserved in sediments laid down beneath a warm Jurassic sea. The environment would have included shallow carbonate waters, shifting sandbanks, oolitic shoals and shell-rich sea floors. After the ammonite died, its shell settled into the sediment and was gradually buried among carbonate grains and marine debris.
Over millions of years, the sediment compacted and cemented into limestone, while mineral-rich groundwater helped preserve the shell as a fossil. The resulting specimen is a natural record of marine life from the Bajocian seas of Somerset, when ammonites were abundant, diverse and important members of the Jurassic marine ecosystem.
Authenticity and Display
This is a genuine Shirbuirnia reliati ammonite fossil from the Inferior Oolite, Middle Jurassic, Bajocian of Yeovil, Somerset, UK. It includes a Certificate of Authenticity lifetime guarantee generic card and is suitable for fossil collectors, geology enthusiasts, educational collections, natural history displays, cabinet display or as a distinctive gift for anyone interested in prehistoric marine life.
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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