Description
Genuine Sonninia sp. Ammonite Fossil
This listing is for a genuine Sonninia sp. ammonite fossil from the Inferior Oolite Group at West Bay, Dorset, UK. Dating from the Bajocian Stage of the Middle Jurassic, this specimen represents a classic British Jurassic ammonite from one of the most famous fossil-bearing coastlines in the world.
Sonninia ammonites are highly collectable marine cephalopods, known from Middle Jurassic rocks and valued for their scientific interest, attractive shell form, and connection to the rich ammonite faunas of southern England. This fossil is a carefully chosen piece, and the photograph shows the actual specimen you will receive. Full sizing can be seen in the photo.
Geology, Age and Location
This ammonite comes from the Inferior Oolite Group, a well-known Middle Jurassic rock unit exposed in parts of Dorset and surrounding regions of southern England. The name “Inferior Oolite” refers to a sequence of limestone, sandstone, marl, and oolitic sediments deposited in warm, shallow marine environments during the Middle Jurassic.
The fossil is Bajocian in age, approximately 170 to 168 million years old. The Bajocian was an important interval in ammonite evolution, with many distinctive genera appearing and diversifying in the shallow seas that covered parts of Europe. Ammonites from this stage are widely used by palaeontologists for dating and correlating Jurassic marine rocks because many species evolved rapidly and had broad geographical distributions.
West Bay, Dorset Jurassic Coast
West Bay, near Bridport in Dorset, forms part of the world-famous Jurassic Coast, a coastline internationally recognised for its outstanding geological record. The cliffs and foreshore around this area expose layers that preserve evidence of ancient seas, shifting shorelines, and the rich marine ecosystems that existed during the Jurassic Period.
The Inferior Oolite Group at West Bay was deposited in a shallow marine shelf setting. These warm Jurassic seas supported a wide variety of life, including ammonites, belemnites, bivalves, brachiopods, gastropods, echinoids, crustaceans, fish, and marine reptiles. Fossils from this region are especially desirable because they combine strong geological provenance with classic British fossil collecting appeal.
Fossil Type and Species Details
Sonninia was an ammonite, an extinct marine mollusc related to modern squid, cuttlefish, octopus, and nautilus. Like other ammonites, it had a coiled external shell divided internally into chambers. The living animal occupied the final body chamber, while the earlier chambers helped regulate buoyancy in the water.
Sonninia ammonites are often recognised by their planispiral coiled shells, ribbed ornament, and distinctive whorl shape. Depending on the species and preservation, they may show strong ribs, a compressed to moderately inflated shell profile, and an outer whorl that reflects their active marine lifestyle. The genus belongs within Phylum Mollusca, Class Cephalopoda, Subclass Ammonoidea, Order Ammonitida, Superfamily Hammatoceratoidea, and Family Sonniniidae.
The genus Sonninia was named by Bayle in 1879 and is an important group within Bajocian ammonite faunas. Sonninia species are particularly useful in Middle Jurassic biostratigraphy, helping geologists compare and date marine rock sequences across different regions.
Ancient Marine Environment
During the Bajocian, the area now known as Dorset was covered by warm, shallow seas on the edge of the European landmass. The sediments of the Inferior Oolite Group record these marine conditions, including periods of carbonate deposition, shelly seabeds, and shifting currents. Ammonites such as Sonninia would have lived in the open water, moving through the sea as predators or opportunistic feeders within the Jurassic food web.
The fossil-bearing rocks of this age preserve a snapshot of a dynamic Middle Jurassic ecosystem. The presence of ammonites is especially significant because their shells were often carried, buried, and preserved in marine sediments, leaving behind some of the most iconic fossils found along the Dorset coast.
Collectible British Jurassic Ammonite
This Sonninia sp. ammonite fossil is a desirable specimen for collectors interested in British fossils, Jurassic Coast material, Middle Jurassic ammonites, or classic Dorset geology. Its named genus, Bajocian age, Inferior Oolite Group origin, and West Bay locality make it suitable for fossil collections, educational displays, natural history cabinets, geology teaching, and display pieces.
This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. The photograph shows the actual fossil you will receive, making this a carefully selected and accurately represented piece from the Middle Jurassic marine rocks of West Bay, Dorset.
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