Description
This listing features a Graphoceras (Lioceras) concavum fossil ammonite from the Bajocian stage of the Middle Jurassic, collected in Somerset, United Kingdom. This is a scientifically and visually striking ammonite, recognised for its discoidal shell and fine ribbing—an iconic species from classic British Jurassic strata.
- Fossil Type: Ammonite (extinct marine cephalopod)
- Genus & Species: Graphoceras (Lioceras) concavum
- Size: See photo with 1cm scale cube for accurate measurements
- Geological Period: Jurassic
- Stage: Bajocian (~170–168 million years ago)
- Locality: Somerset, England, UK
- Family: Graphoceratidae
- Superfamily: Hildoceratoidea
- Order: Ammonitida
- Depositional Environment: Shallow marine sea with moderate-energy deposition; fine-grained mudstones and limestones typical of Bajocian successions
Geological & Scientific Significance:
Graphoceras (Lioceras) concavum is a key ammonite species from the Bajocian stage and is widely used as an index fossil. Its occurrence typically defines the Concavum Zone, an important biozone in Jurassic stratigraphy, especially in NW Europe.
These ammonites feature a compressed, discoidal shell with sharp ribbing and a moderately deep umbilicus. The fine suture patterns and involute coiling make this genus a favourite among both academic collectors and fossil enthusiasts.
Somerset is part of the Wessex Basin and has exposures of marine Middle Jurassic sediments that provide a window into a richly diverse palaeoenvironment filled with ammonites, bivalves, and early marine reptiles.
Notable Features:
- Strong, bifurcating ribbing with slight curvature on flanks
- Flattened venter with fine suture detail
- Stratigraphically significant ammonite used in global correlation
- A classic British Middle Jurassic fossil
Authenticity Guaranteed: All our fossils are 100% genuine specimens. This ammonite comes with a Certificate of Authenticity, confirming its scientific identity and locality.
Photo Disclosure: You will receive the exact specimen shown in the images. Scale cube is 1cm per square to provide accurate sizing.
This Graphoceras (Lioceras) concavum ammonite is a beautifully preserved piece of Jurassic history—perfect for collectors, educators, or anyone passionate about British geological heritage.
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