Description
Rare Prodactylioceras Ammonite Fossil from Charmouth, Dorset
This rare ammonite fossil of the genus Prodactylioceras originates from the famous fossil-bearing cliffs of Charmouth in Dorset, England, preserved within the Charmouth Mudstone Formation and dating to the Lower Jurassic Pliensbachian stage, approximately 190–183 million years ago. Charmouth lies within the internationally recognised Jurassic Coast UNESCO World Heritage Site, one of the most important fossil localities in the world.
The fossil shown in the photographs is the exact specimen you will receive, carefully selected for preservation, authenticity, and display quality. This fossil includes a Certificate of Authenticity lifetime guarantee generic card, confirming that the specimen is a genuine fossil. Full sizing can be seen in the accompanying photographs.
Ammonites from the Charmouth Mudstone Formation are among the most historically significant fossils from the British Jurassic and are highly prized by collectors and palaeontology enthusiasts.
Prodactylioceras – Early Jurassic Ammonite Cephalopod
Prodactylioceras is an extinct genus of ammonite belonging to the order Ammonitida, within the subclass Ammonoidea, a diverse group of marine cephalopods closely related to modern squids, octopuses, and cuttlefish. These animals possessed coiled external shells and thrived in the world’s oceans for hundreds of millions of years.
The genus Prodactylioceras is typically placed within the family Dactylioceratidae, a group known for their finely ribbed shells and distinctive coiling patterns. Ammonites in this family are particularly important for biostratigraphy because their rapid evolutionary changes make them excellent index fossils used to identify and date Jurassic rock layers.
These ammonites possessed a planispirally coiled shell divided into a series of chambers separated by complex internal walls known as septa. The living animal occupied the outermost chamber, while the inner chambers were filled with gas and fluid to regulate buoyancy.
This buoyancy system allowed ammonites to move vertically within the water column, much like modern nautiluses.
Shell Morphology and Fossil Characteristics
Ammonites of the genus Prodactylioceras are recognised by their tightly coiled shells and prominent radial ribbing that extends across each whorl. These ribs often create a striking spiral pattern that is highly visible in well-preserved specimens.
The shell structure includes the suture lines, where the internal septa met the outer shell wall. These sutures formed complex patterns that are distinctive for ammonite groups and are an important feature in identifying species and genera.
The ribbed shell likely served both structural and hydrodynamic functions, strengthening the shell while influencing how the animal moved through the water.
Fossils from the Charmouth Mudstone Formation often preserve ammonites with excellent detail, including ribbing patterns and the natural spiral structure of the shell.
Geological Formation – Charmouth Mudstone Formation
This fossil comes from the Charmouth Mudstone Formation, a Lower Jurassic geological unit exposed along the Dorset coastline between Lyme Regis and Charmouth. The formation consists primarily of dark marine mudstones and shales deposited in an offshore marine basin during the Early Jurassic.
During the Pliensbachian stage, southern Britain was submerged beneath a warm shallow sea connected to the wider Tethys Ocean. Fine clay and silt settled slowly to the seabed, burying marine organisms that died in the water column.
The resulting sediments preserved a rich fossil assemblage including ammonites, belemnites, bivalves, fish, and marine reptiles such as ichthyosaurs and plesiosaurs.
These conditions allowed ammonite shells to be rapidly buried and preserved within the sedimentary layers that now form the cliffs along the Jurassic Coast.
Early Jurassic Marine Ecosystem of Dorset
During the Early Jurassic, the seas covering what is now southern England supported a diverse marine ecosystem. Ammonites such as Prodactylioceras were among the most abundant organisms in the water column and played an important role in the marine food web.
They likely fed on plankton and small marine organisms while in turn serving as prey for larger predators such as marine reptiles and fish.
When ammonites died, their shells often sank to the seabed where they became buried in fine mud sediments. Over millions of years, these sediments lithified into rock while the shells mineralised, preserving them as fossils.
The cliffs around Charmouth continue to erode today, revealing new fossils and maintaining the region’s reputation as one of the richest Jurassic fossil localities in Europe.
Authenticity and Collector Information
This fossil is a genuine specimen from the Lower Jurassic Charmouth Mudstone Formation of Charmouth, Dorset, UK. The photographs show the exact fossil you will receive, ensuring collectors know precisely what they are purchasing.
The specimen includes a Certificate of Authenticity lifetime guarantee generic card, confirming its genuine geological origin.
Rare ammonites such as Prodactylioceras are highly sought after by collectors due to their scientific importance and distinctive shell morphology. This specimen makes an excellent addition to any fossil collection, Jurassic Coast display, ammonite cabinet, or educational natural history collection focused on the remarkable marine life of the Early Jurassic oceans.
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