Description
This listing features a beautifully preserved Arnioceras semicostatum ammonite fossil, embedded in a natural matrix filled with fossil bivalves, from the Lower Sinemurian stage of the Jurassic Period. Sourced from the fossil-rich beds of Yorkshire, United Kingdom, this unique block is a genuine snapshot of ancient marine life from around 196–190 million years ago.
The actual fossil block shown in the photos is the exact specimen you will receive. It has been carefully chosen for its detail and natural aesthetic, ideal for collectors, display, or educational use.
Geological & Palaeontological Details:
- Species: Arnioceras semicostatum
- Fossil Type: Ammonite in fossiliferous matrix with bivalves
- Family: Arietitidae
- Superfamily: Psiloceratoidea
- Order: Ammonitida
- Geological Period: Jurassic
- Stage: Lower Sinemurian
- Location: Yorkshire, UK
- Stratigraphy/Biozone: Semicostatum Zone – an important ammonite biozone within the Sinemurian, often used to identify the base of the Sinemurian in the UK.
- Depositional Environment: Shallow epicontinental sea with soft marine sediments, rich in ammonites, bivalves, and other benthic fauna, characteristic of the Cleveland Basin region during early Jurassic transgressive events.
Morphology & Features:
- Arnioceras semicostatum displays evolute coiling with broad whorls and strong, regularly spaced ribs extending to the ventrolateral shoulders
- Distinctive radial ribbing offers striking visual appeal and scientific diagnostic value
- The matrix also includes multiple fossilised bivalves, offering additional context for the palaeoenvironment
- These combined features make it an excellent reference specimen and decorative fossil block
Notability: Arnioceras semicostatum is a highly recognisable ammonite that serves as the index fossil for the Semicostatum Zone, making it extremely useful in biostratigraphic dating. Fossils from this zone are frequently used in geological research and education due to their abundance and clear stratigraphic significance.
Additional Details:
- All our fossils are 100% genuine specimens
- Comes with a Certificate of Authenticity
- Photo shows the exact item for sale
- Scale Rule / Cubes = 1cm – refer to the images for full sizing
Whether you’re a palaeontology enthusiast, academic, or fossil lover, this specimen captures a fascinating moment from Earth’s early Jurassic oceans. Add it to your collection and own a piece of prehistoric Yorkshire today!
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