Rare 5.75″ Fossil Ammonite Coroniceras (Metophioceras) janus | Jurassic Lower Pliensbachian Somerset UK | Genuine + COA

Description

This listing offers a rare and striking 5.75-inch fossil ammonite, Coroniceras (Metophioceras) janus, from the Lower Pliensbachian Stage of the Jurassic Period, collected from Radstock, Somerset, United Kingdom. The image displays the actual specimen you will receive. Each cube or square in the photo scale = 1cm — please refer to the image for full dimensions.

This is an exceptionally well-preserved and scientifically valuable fossil, ideal for discerning collectors, educators, or display purposes.

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.

Geological & Scientific Information:

• Fossil Type: Ammonite
• Species: Coroniceras (Metophioceras) janus
• Order: Ammonitida
• Superfamily: Eoderoceratoidea
• Family: Eoderoceratidae
• Geological Stage: Lower Pliensbachian (approx. 190.8 – 189.6 million years ago)
• Biozone: Jamesoni Zone, a key interval in ammonite biostratigraphy
• Formation: Charmouth Mudstone Formation (part of the Lower Lias Group)
• Locality: Radstock, Somerset, United Kingdom
• Depositional Environment: Offshore marine basin with fine-grained mudstones deposited in a low-energy, anoxic seabed environment ideal for fossil preservation

Morphology & Notable Features:

• Strongly evolute shell with all whorls visible
• Wide umbilicus and sharply defined ribbing
• Ribs are dense and bifurcate from the umbilical edge, running across the flanks to the venter
• The subgenus Metophioceras is distinguished by a slightly more compressed whorl profile and refined ribbing
• The preservation in this specimen clearly reveals ornamentation, suture patterns, and growth lines, making it an excellent reference fossil

Scientific Significance:

Coroniceras (Metophioceras) janus is a well-documented ammonite used to define the Jamesoni Zone, making it of high biostratigraphic importance in Lower Jurassic correlation. Specimens like this are used to date and correlate marine sediments across Europe and are part of the global ammonite zonation system developed over decades of palaeontological study.

This species has featured prominently in European Jurassic monographs and is a reference ammonite in British stratigraphy. Its subgenus Metophioceras represents a more specialised lineage within the classic Coroniceras group.

Ideal For:

• Advanced fossil and ammonite collectors
• Biostratigraphy or palaeontology reference collections
• Natural history or museum-quality displays
• Educational settings, geology departments, and historical enthusiasts

What You Will Receive:

• The exact 5.75″ specimen of Coroniceras (Metophioceras) janus shown in the photos
• Certificate of Authenticity
• Expert packaging to ensure safe and secure delivery