Description
Dactylioceras Ammonite Fossil from the Whitby Mudstone Formation
This genuine fossil specimen is a Dactylioceras ammonite recovered from the famous Whitby Mudstone Formation near Whitby, Yorkshire, United Kingdom. These fossil-rich deposits date to the Lower Jurassic Period, approximately 183 million years ago, when a shallow marine basin covered much of what is now northern England.
Your specimen was discovered by our own team members, Alister and Alison, on 23 February 2026 along the Yorkshire coastline. Following discovery, the fossil was carefully cleaned, prepared, and treated by Alison, ensuring the natural shell detail and rib structure were revealed while maintaining the stability of the specimen.
The photographs in this listing show the exact fossil specimen you will receive, making it a unique piece for collectors and enthusiasts. The fossil is 100 percent genuine and includes a Certificate of Authenticity with a lifetime guarantee card confirming its provenance.
Full sizing can be seen in the listing photographs.
Geological Origin – Whitby Mudstone Formation
This ammonite fossil originates from the Whitby Mudstone Formation, a well-known Lower Jurassic geological unit exposed along the cliffs and foreshore around Whitby on the Yorkshire coast. These rocks were deposited during the Early Jurassic, specifically within the Toarcian Stage, when the region lay beneath a shallow sea connected to the wider Tethys Ocean.
The formation consists primarily of dark marine mudstones and shales, which accumulated as fine sediment slowly settled on the seabed. These low-energy conditions were ideal for preserving marine organisms, resulting in one of the richest ammonite fossil deposits in the United Kingdom.
Whitby has been famous for its fossils for centuries and remains one of the most productive Jurassic fossil sites in Britain. The rocks frequently yield:
- Ammonites
- Belemnites
- Marine reptile remains
- Bivalves and gastropods
- Crinoids and other echinoderms
Among these fossils, Dactylioceras ammonites are particularly abundant and are considered characteristic of the Whitby Mudstone Formation.
Dactylioceras – Early Jurassic Ammonite
The genus Dactylioceras belongs to the order Ammonitida, an extinct group of marine cephalopods closely related to modern squid, cuttlefish, and octopus.
Taxonomic classification:
- Phylum: Mollusca
- Class: Cephalopoda
- Subclass: Ammonoidea
- Order: Ammonitida
- Superfamily: Dactylioceratoidea
- Family: Dactylioceratidae
- Genus: Dactylioceras
Species within this genus are extremely important for geological dating because they occur within a well-defined stratigraphic interval known as the Tenuicostatum Biozone, part of the Toarcian Stage of the Early Jurassic.
Their widespread distribution and distinctive morphology make them excellent index fossils for correlating Jurassic rock layers across different regions.
Morphology and Shell Characteristics
Dactylioceras ammonites are easily recognised by their strong ribbed shell ornamentation, which gives the fossil a distinctive appearance.
Characteristic features of the genus include:
- A planispiral coiled shell
- Numerous fine ribs extending across the shell surface
- An evolute shell structure where inner whorls remain visible
- Ribbing that continues across the venter of the shell
- Internal chambered structure forming the buoyancy system
The shell of the ammonite was divided internally into chambers known as camerae, which were connected by a tube called the siphuncle. This structure allowed the animal to regulate its buoyancy as it moved through the water.
The ribs strengthened the shell structure while also providing the distinctive fossil pattern that makes Dactylioceras easily identifiable.
Early Jurassic Marine Ecosystem
During the Early Jurassic, the sea covering northern England supported a thriving marine ecosystem. The waters were home to a wide variety of organisms including:
- Ammonites such as Dactylioceras
- Belemnites
- Marine reptiles including ichthyosaurs and plesiosaurs
- Bivalves and gastropods
- Crinoids and other echinoderms
Ammonites were active swimmers, using jet propulsion to move through the water while hunting small marine animals such as crustaceans and planktonic organisms.
When these animals died, their shells sank to the seabed where they were buried by sediment, eventually fossilising within the mudstone layers.
Authentic Jurassic Fossil Discovered by Our Team
This specimen represents a genuine ammonite fossil discovered directly from the famous Jurassic coastline of Yorkshire. Fossils collected and prepared by experienced fossil hunters from classic British localities are highly valued by collectors.
Key features of this specimen include:
- Genuine Dactylioceras ammonite fossil
- From the Whitby Mudstone Formation
- Lower Jurassic Period
- Collected at Whitby, Yorkshire, United Kingdom
- Discovered by Alister and Alison on 23 February 2026
- Cleaned, prepared, and treated by Alison
- Photographs show the exact fossil specimen you will receive
- Supplied with a Certificate of Authenticity and lifetime guarantee
This fossil makes a superb addition to Jurassic fossil collections, ammonite displays, geology collections, and natural history exhibits, representing a beautiful example of marine life from the Jurassic seas that once covered the Yorkshire coast.
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