Description
Very Rare Sonninia pseudotuberculata Ammonite Fossil – Inferior Oolite Group, Middle Jurassic, Dorset
This very rare genuine Sonninia pseudotuberculata ammonite fossil is a highly collectable Middle Jurassic marine cephalopod specimen from the Inferior Oolite Group at Oborne Wood, Dorset, UK. Dating from the Bajocian Stage of the Middle Jurassic, specifically the top of the Laeviuscula Zone, this fossil is approximately 170 million years old and represents an important ammonite from the warm shallow seas that once covered southern Britain.
This fossil is a genuine specimen and includes a fully hand-signed Premium Certificate of Authenticity. 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
Sonninia pseudotuberculata comes from the Inferior Oolite Group, one of the most famous fossil-bearing Middle Jurassic rock units of southern England. The Inferior Oolite is well known for its oolitic limestones, shell-rich beds, carbonate sediments and scientifically important ammonite faunas. These rocks were deposited during the Bajocian Stage, when Britain was positioned much farther south than today and lay beneath warm, shallow, tropical to subtropical seas.
The name “oolite” refers to small rounded carbonate grains called ooids, which formed in agitated shallow marine water. These grains accumulated alongside shell fragments, carbonate mud and the remains of marine organisms, later hardening into limestone. Fossils from the Inferior Oolite Group commonly include ammonites, belemnites, bivalves, brachiopods, gastropods, echinoids, corals and other marine invertebrates.
Fossil Type and Species
This specimen belongs to the ammonite species Sonninia pseudotuberculata, a rare Bajocian ammonite associated with the Inferior Oolite Group of Dorset. Sonninia is a recognised Middle Jurassic ammonite genus within the order Ammonitida and is generally placed within the family Sonniniidae. This group is known for distinctive Jurassic shell forms, often with strong ribbing, whorl variation and ornament that can be important for species-level identification.
Ammonites were extinct marine cephalopods related to modern squid, octopus and cuttlefish. Unlike their living relatives, ammonites possessed an external coiled shell divided internally into chambers. The living animal occupied the outer body chamber, while the earlier chambers helped regulate buoyancy and allowed the ammonite to move through the water column.
Laeviuscula Zone Stratigraphic Interest
This fossil is from the top of the Laeviuscula Zone, an important ammonite biozone within the Bajocian succession. Ammonite zones are extremely valuable in Jurassic geology because ammonites evolved rapidly and produced distinctive shell forms over relatively short intervals of geological time. This makes them excellent index fossils for dating and correlating marine rock layers.
A specimen identified to species level, with a recorded formation, locality and precise zonal position, carries strong geological and collecting value. The top of the Laeviuscula Zone gives this fossil a more refined stratigraphic context than a specimen labelled only as Middle Jurassic, making it especially desirable for collectors of British ammonites, Inferior Oolite fossils and well-documented Dorset material.
Morphology and Collectable Features
Sonninia pseudotuberculata is valued for its rare species attribution and classic Jurassic ammonite appearance. Depending on preservation and growth stage, specimens may show a naturally coiled shell, visible whorls, pronounced ribbing, tuberculate ornament, shell curvature, chamber structure, natural matrix contact, mineral replacement or sutural detail.
The species name pseudotuberculata reflects its connection with tuberculate or nodular shell ornament. These raised features, along with ribbing and whorl shape, formed part of the ammonite’s original shell structure and are important for identification. Such ornament may have helped strengthen the shell and gives the fossil a distinctive sculptural quality that appeals strongly to collectors.
In well-preserved ammonites, suture lines may be visible as intricate patterns marking where the internal chamber walls joined the outer shell. These sutures are one of the key features used by palaeontologists when studying ammonite classification, evolution and relationships between different Jurassic ammonite groups.
Oborne Wood, Dorset Fossil Locality
Oborne Wood in Dorset is associated with classic Middle Jurassic fossil-bearing strata and is a notable locality for collectors interested in the Inferior Oolite Group. Dorset is internationally recognised for its Jurassic geology, and specimens from named localities are especially valued because they provide clear provenance and stronger scientific context.
A very rare Sonninia pseudotuberculata ammonite from Oborne Wood is an excellent addition to a carefully labelled fossil collection. Its combination of named species, Bajocian age, Laeviuscula Zone position, Inferior Oolite Group origin and Dorset locality makes it suitable for advanced collectors, British fossil specialists, geology study collections and natural history display cabinets.
Depositional Environment
This ammonite was preserved in sediments laid down beneath a warm Middle Jurassic sea. The environment would have included shallow carbonate waters, oolitic shoals, shell banks and areas of marine sediment accumulation. After the ammonite died, its shell settled onto the sea floor and became buried among carbonate grains, shell debris and fine marine material.
Over millions of years, burial, compaction and mineral-rich groundwater transformed the shell into a fossil. The resulting specimen is a natural record of Bajocian marine life from Dorset, when ammonites were abundant, diverse and highly important members of Jurassic marine ecosystems.
Authenticity and Display
This is a genuine very rare Sonninia pseudotuberculata ammonite fossil from the Inferior Oolite Group, Middle Jurassic, Bajocian, top of the Laeviuscula Zone of Oborne Wood, Dorset, UK. It includes a fully hand-signed Premium Certificate of Authenticity and is suitable for fossil collectors, geology enthusiasts, educational collections, natural history displays, cabinet display or as a distinctive gift for anyone interested in rare British Jurassic fossils.
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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