Rare British Iridescent Rasenia uralensis Ammonite Fossil Oxfordian Jurassic England

Description

Rare British Iridescent Ammonite Fossil – Rasenia uralensis

This listing presents a rare British iridescent ammonite fossil, Rasenia uralensis, originating from the Ampthill Clay Formation, Oxfordian stage of the Jurassic period. Discovered near Wootton Bassett, Wiltshire, United Kingdom, this specimen dates to approximately 163 – 157 million years ago. Its striking natural iridescence, caused by the preservation of the original nacreous shell layers, makes it both a scientifically significant fossil and a visually captivating display piece.

The fossil photographed is the exact specimen you will receive, pictured alongside a 1 cm scale cube for accurate sizing. As with all our items, it comes with a Certificate of Authenticity, confirming that it is a genuine and carefully selected specimen of natural history.

Geological Context – Oxfordian, Jurassic Period

The Oxfordian stage marks the beginning of the Upper Jurassic, a period when much of southern England was covered by shallow epicontinental seas. The Ampthill Clay Formation, from which this ammonite originates, is a well-documented marine deposit rich in ammonites, bivalves, belemnites, and other marine fossils. These mudstone and clay layers were laid down in a calm, low-energy seabed environment, ideal for preserving fragile ammonite shells.

Wootton Bassett and the surrounding Wiltshire region are particularly well-known for producing beautifully preserved ammonites, some with remarkable iridescence, making them highly desirable for both collectors and researchers.

Scientific Classification

• Genus: Rasenia
• Species: Rasenia uralensis
• Order: Ammonitida
• Superfamily: Perisphinctoidea
• Family: Perisphinctidae
• Geological Stage: Oxfordian, Upper Jurassic (c. 163 – 157 million years ago)
• Formation: Ampthill Clay Formation
• Locality: Wootton Bassett, Wiltshire, United Kingdom

Morphological Features

The Rasenia uralensis ammonite displays a number of features that make it particularly distinctive:

• Iridescent shell surface, reflecting colours ranging from greens and purples to blues and silvers, caused by the microstructure of preserved nacre.
• Evolute coiling, with the earlier whorls clearly visible.
• Regular ribbing, running across the shell and enhancing its symmetry.
• Compressed whorl section, giving the ammonite a relatively flat, disc-like profile.
• Complex suture lines, marking the chamber divisions within the shell.

The combination of these traits highlights the intricate natural beauty of ammonites, while also reflecting their adaptability and evolutionary success during the Jurassic seas.

Paleoecological Importance

Ammonites such as Rasenia uralensis were free-swimming marine cephalopods, related to modern squids and cuttlefish. They lived in the open water column, using their chambered shells for buoyancy control while hunting small crustaceans, fish, and plankton.

Because of their rapid evolutionary rates and wide geographic distribution, ammonites like Rasenia are invaluable as index fossils. They allow geologists to precisely date and correlate marine rock layers across different regions. The presence of Rasenia uralensis in the Ampthill Clay Formation is an important marker for the Oxfordian stage.

Collector’s Value and Rarity

This British iridescent Rasenia uralensis ammonite represents a combination of rarity, beauty, and scientific value. Specimens with preserved iridescence are especially prized, as the delicate nacre is often lost during fossilisation. The shimmering play of colour across the shell makes it a striking natural display piece, while its geological context firmly anchors it in Britain’s rich Jurassic fossil heritage.

Collectors of ammonites and British fossils will appreciate the authenticity and provenance of this specimen, while educators and natural history enthusiasts will value its ability to illustrate both paleontological detail and the natural artistry of fossil preservation.

Key Details

• Species: Rasenia uralensis
• Age: Oxfordian, Upper Jurassic (c. 163 – 157 million years old)
• Formation: Ampthill Clay Formation
• Locality: Wootton Bassett, Wiltshire, United Kingdom
• Features: Iridescent shell, ribbed evolute form, complex suture lines
• Family: Perisphinctidae
• Order: Ammonitida
• Authentic specimen with Certificate of Authenticity
• Exact fossil photographed with 1 cm scale cube for reference

This is a rare opportunity to own an authentic British iridescent ammonite fossil from one of the most important Jurassic sites in the United Kingdom.