Description
Rare Coroniceras rotiforme Fossil Ammonite
This is a rare and impressive Coroniceras rotiforme fossil ammonite from the Bucklandi Zone of the Lower Sinemurian stage, Early Jurassic, collected from Keynsham, near Bristol, Somerset, United Kingdom. Measuring approximately 7 inches, with full sizing shown in the photograph, this is a substantial British Jurassic ammonite with excellent collector appeal and strong display presence.
The photograph shows the actual fossil specimen you will receive, allowing you to view its preservation, form, surface texture, colour and natural character before purchase. This carefully chosen fossil is supplied with a fully hand-signed Premium Certificate of Authenticity, confirming it as a genuine fossil specimen.
Geology and Jurassic Age
This ammonite dates from the Lower Sinemurian stage of the Early Jurassic, approximately 199 to 194 million years old. The specimen is from the Bucklandi Zone, an important ammonite biozone used by geologists and palaeontologists to date Lower Jurassic marine rocks. The Bucklandi Zone is named after the ammonite Coroniceras bucklandi and is one of the classic early Sinemurian fossil zones recognised in British Jurassic stratigraphy.
During the Lower Sinemurian, the Keynsham and Bristol area was covered by warm shallow marine seas. Sediments accumulated across the seabed, preserving the remains of ammonites, bivalves, brachiopods, belemnites, crinoids and other marine organisms. These fossil-bearing deposits form part of Britain’s rich Jurassic geological heritage and provide evidence of a very different prehistoric landscape beneath ancient seas.
Fossil Type and Species
This fossil is an ammonite, an extinct marine cephalopod related to modern squid, cuttlefish and nautilus. Ammonites lived in coiled, chambered shells and were active marine animals. The living creature occupied the final body chamber, while the internal chambers helped regulate buoyancy as it moved through the water column.
Species: Coroniceras rotiforme
Genus: Coroniceras
Family: Arietitidae
Superfamily: Psiloceratoidea
Order: Ammonitida
Class: Cephalopoda
Phylum: Mollusca
Coroniceras rotiforme is a classic Early Jurassic ammonite species. The species was originally described as Ammonites rotiformis by James Sowerby in the early 19th century, and it remains a well-known form within Lower Sinemurian ammonite faunas. Ammonites such as Coroniceras are particularly important because their rapid evolution and widespread distribution make them valuable index fossils for correlating Jurassic rock layers.
Morphology and Display Features
Coroniceras rotiforme is known for its bold, strongly ribbed shell form and classic planispiral ammonite shape. The shell is typically evolute, meaning the earlier whorls remain visible rather than being tightly enclosed by later growth. This gives the fossil an attractive open-coiled appearance and allows the natural growth pattern of the ammonite to be clearly seen.
The robust ribbing and rounded whorl profile are key visual features of Coroniceras ammonites. These ribs strengthened the shell and also help palaeontologists distinguish species and related genera. At approximately 7 inches, this specimen is a striking size for display, offering both visual impact and scientific interest. The natural spiral geometry makes it ideal for a fossil cabinet, educational collection, geology display or decorative natural history setting.
Keynsham, Bristol and Somerset Fossil Locality
Keynsham, near Bristol in Somerset, is part of a region with a long-established reputation for Lower Jurassic fossils. The area’s marine sedimentary rocks preserve remains from ancient Early Jurassic seas that once covered southwest Britain. Fossils from this region are highly collectable because they combine British locality interest, geological importance and classic ammonite preservation.
The Bucklandi Zone connection gives this specimen additional scientific value, placing it within a recognised Lower Sinemurian biostratigraphic interval. Ammonites from this zone help demonstrate the succession of Early Jurassic marine life and the use of fossils as natural time markers in geology.
Authenticity and Premium Certificate
This Coroniceras rotiforme ammonite is a genuine fossil specimen and includes a fully hand-signed Premium Certificate of Authenticity. The fossil has been carefully chosen as a quality collector’s piece, and the photograph shows the exact specimen supplied.
As with all genuine fossils, natural cracks, mineralisation, matrix, preparation marks, surface wear, colour variation and age-related features may be present. These characteristics are part of the fossil’s natural history and add to its individuality. This rare 7 inch Coroniceras rotiforme from the Bucklandi Zone of Keynsham, Bristol, Somerset is an excellent specimen for collectors of British fossils, Jurassic ammonites, Lower Sinemurian fossils and authentic natural history display pieces.
