Microderoceras Fossil Ammonite Lower Lias Black Ven Marls Jurassic Coast Lyme Regis Dorset UK

Description

Authentic Microderoceras Fossil Ammonite

This fine Microderoceras Fossil Ammonite is an authentic and beautifully preserved specimen from the Black Ven Marls, Lower Lias Formation, found along the world-renowned Jurassic Coast at Black Ven, Lyme Regis, Dorset, UK. Dating from the Lower Jurassic period (approximately 195–200 million years ago), this fossil represents one of the earliest known true ammonites, a marine cephalopod that once thrived in the warm, shallow seas of the Early Jurassic.

Your specimen was discovered by our team members, Alister and Alison, on 24 October 2025, and has been professionally cleaned, prepped, and treated by Alison to reveal its natural detail and form. The photograph shows the exact fossil you will receive, not a stock image, ensuring complete authenticity and provenance.

Geological Context and Origin

The fossil comes from the Black Ven Marls Member of the Charmouth Mudstone Formation, part of the Lower Lias Group that forms the base of the iconic Jurassic Coast World Heritage Site. The Black Ven cliffs are world-famous for their exceptional fossil deposits, first studied by Mary Anning in the early 19th century, and continue to yield remarkable examples of ammonites, belemnites, and marine reptile remains.

These marls were laid down in a low-energy, offshore marine environment, rich in fine clay sediments. The anoxic (oxygen-poor) seabed conditions allowed for excellent fossil preservation, often resulting in well-defined shell morphology and, in some cases, subtle pyrite mineralisation. The geological strata correspond to the Sinemurian Stage of the Early Jurassic, specifically within the Microderoceras birchi Zone, named for this very genus.

Scientific Classification

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Subclass: Ammonoidea
• Order: Ammonitida
• Superfamily: Eoderoceratoidea
• Family: Eoderoceratidae
• Genus: Microderoceras
• Age: Early Jurassic (Sinemurian Stage)
• Formation: Lower Lias, Black Ven Marls
• Locality: Black Ven, Lyme Regis, Dorset, UK

Microderoceras is a key index fossil for the Lower Jurassic, particularly the early Sinemurian biozones. Its presence allows geologists to precisely correlate rock layers across Europe. This genus represents one of the first true ammonites to develop complex, ribbed shells and a fully coiled, planispiral form after the Triassic extinction event.

Morphological Features and Preservation

This specimen displays the distinctive coiling and ribbing characteristic of Microderoceras. The shell is strongly ribbed with narrow, closely spaced ribs that extend radially across the whorls, and it typically shows a small, rounded keel along the venter. These ribs bifurcate from raised tubercles near the umbilical margin, a defining feature of this genus.

The fossil’s preservation within the Black Ven Marls highlights its delicate details and natural symmetry. The fine-grained matrix supports the ammonite securely, and subtle mineralisation gives the piece a soft sheen under light. The scale cube (1 cm) shown in the photo provides accurate sizing reference; full measurements are listed in the accompanying images. This is a collector-grade piece representing an important Lower Jurassic ammonite species.

Palaeobiological and Evolutionary Significance

Microderoceras is a member of the Eoderoceratidae family, which marks a key evolutionary step in ammonite diversification after the end-Triassic extinction. It represents one of the earliest forms to display the ornate ribbing and strong sutural complexity that would later define the Jurassic ammonites.

These creatures were fast-swimming marine predators, feeding on small crustaceans and plankton. Their planispiral shells and internal chambers (phragmocones) allowed them to regulate buoyancy and manoeuvre efficiently in open water. The abundance of Microderoceras fossils in the Sinemurian rocks of Lyme Regis demonstrates that this region was once a thriving marine ecosystem teeming with life.

Authenticity and Provenance

All of our fossils are 100% genuine specimens and come with a Certificate of Authenticity. Each piece is responsibly collected, professionally prepared, and carefully stabilised for long-term preservation. No artificial restoration or casting is used — the fossil shown is the actual specimen you will receive.

This Microderoceras Fossil Ammonite represents a true piece of British geological heritage from one of the most famous fossil sites in the world — the Jurassic Coast of Dorset. A perfect addition for collectors, educators, or enthusiasts of natural history, combining scientific value, aesthetic beauty, and historical significance in one outstanding specimen.