Androgynoceras Ammonite Fossil Lower Lias Jurassic Coast Charmouth Lyme Regis Dorset UK

Description

Androgynoceras Ammonite Fossil from the Jurassic Coast

This genuine Androgynoceras Fossil Ammonite was discovered at Stonebarrow Cliff, Charmouth, near Lyme Regis, Dorset, UK, a world-famous locality along the UNESCO-listed Jurassic Coast. Unearthed by our field collectors Alister and Alison on 06 November 2025, the specimen has been expertly cleaned, prepped, and treated by Alison to bring out its natural detail and ensure long-term stability. The photographs show the exact fossil you will receive, with a 1cm scale cube for accurate size reference. Every fossil we sell is a 100% genuine specimen, complete with a Certificate of Authenticity.

Species Overview: Androgynoceras – A Distinctive Early Jurassic Ammonite

Androgynoceras is a well-recognised genus of ammonite belonging to the order Ammonitida, superfamily Eoderoceratoidea, and family Liparoceratidae. These ammonites flourished during the Lower Jurassic (Pliensbachian Stage) and are an iconic feature of the Stonebarrow–Charmouth fossil beds.

Key identifying traits of Androgynoceras include:

• Thick, robust whorls with a rounded cross-section
• Strong radial ribbing, often bifurcating or branching toward the outer whorl
• Deeply incised suture lines, typical of early Jurassic ammonites
• Well-defined keel or ventral region, depending on the species variant

These features make Androgynoceras both scientifically important and highly attractive as display fossils.

Geological Setting: Black Ven Marls & Stonebarrow Cliff

This ammonite comes from the Black Ven Marls, part of the Lower Lias Group, forming some of the most fossil-rich Jurassic exposures in Europe. The marls and mudstones deposited here date to the Early Jurassic (approximately 190–183 million years ago).

Stonebarrow Cliff and the adjacent Charmouth area represent an ancient marine environment characterised by:

• Fine mud and silt deposition, perfect for fossil preservation
• Low oxygen seabed conditions, slowing decay
• Steady sediment accumulation, preventing shell disturbance
• High faunal diversity, including ammonites, belemnites, fish, and marine reptiles

These conditions helped preserve ammonites like Androgynoceras in exceptional detail.

Morphological Features and Notable Characteristics

This Androgynoceras specimen displays several classic morphological features:

• Bold, evenly spaced ribs radiating across each whorl
• Clear growth stages, visible in the whorl expansion
• Strong shell geometry, providing excellent structural definition
• Preserved ventral region, showing typical genus-specific shaping

The ammonite’s shell structure provides insight into buoyancy control, hydrodynamic movement, and evolutionary trends among early Jurassic cephalopods.

Biozone and Stratigraphic Significance

Androgynoceras is an important index fossil for parts of the Pliensbachian Stage, with species widely used in biostratigraphy across Europe. Its presence helps geologists and palaeontologists identify specific horizons within the Lower Jurassic sequence. Although this listing focuses on the specimen itself, the genus is strongly associated with beds found at Stonebarrow and Black Ven, reinforcing its geological importance.

Palaeoenvironment and Ecological Role

During the Early Jurassic, the seas covering what is now Dorset were warm, shallow, and rich in marine life. Ammonites like Androgynoceras occupied mid-water environments, swimming freely and feeding on planktonic animals, small crustaceans, and other invertebrates. Their shells protected them from predators such as juvenile ichthyosaurs and larger cephalopods.

The presence of this ammonite in the Black Ven Marls reflects:

• A thriving Early Jurassic marine ecosystem
• Rapid burial events, often related to storms or underwater mudflows
• Chemical conditions supportive of long-term preservation

This combination of biology and geology makes Androgynoceras one of the most iconic ammonite fossils from the Jurassic Coast.

Collector Appeal and Display Value

This Androgynoceras Fossil Ammonite is perfect for collectors, educators, and enthusiasts of natural history. Its robust morphology, clear ribbing, and excellent preservation make it a standout piece, while the provenance from Stonebarrow Cliff—one of the most famous fossil sites in the world—adds exceptional value.

Professionally prepared by Alison, the fossil retains its authentic structure and natural charm. Whether displayed in a cabinet, used in educational settings, or added to a focused ammonite collection, it offers both scientific relevance and visual impact.

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