Description
Iridescent Psiloceras Ammonite Fossil from the Blue Lias of Somerset
This genuine iridescent ammonite fossil from the genus Psiloceras originates from the Blue Lias Formation at Doniford Bay near Watchet, Somerset, United Kingdom. Preserved within Early Jurassic marine sediments dating to the Hettangian stage, approximately 201–199 million years ago, this fossil represents one of the earliest ammonites to appear following the end-Triassic mass extinction.
The specimen displays attractive natural iridescence, a shimmering effect created when the original shell layers are preserved and interact with light. This feature adds both aesthetic and scientific interest, making iridescent ammonites particularly desirable among collectors. The photographs show the exact fossil you will receive, and the specimen has been carefully selected as a quality example. Please refer to the photos for the full sizing and proportions. This fossil includes a Certificate of Authenticity lifetime guarantee generic card confirming its authenticity.
About Psiloceras – One of the Earliest Jurassic Ammonites
Psiloceras is a well-known genus of ammonite belonging to the order Ammonitida and the family Psiloceratidae within the superfamily Psiloceratoidea. These marine cephalopods were among the first ammonites to diversify after the end-Triassic extinction event and are widely used by palaeontologists as index fossils for identifying the base of the Jurassic period.
Species of Psiloceras are particularly associated with the earliest Jurassic biozones, including the well-known Psiloceras planorbis Zone that marks the beginning of the Hettangian stage. Their widespread distribution and rapid evolutionary changes make them extremely valuable for correlating Early Jurassic rock layers across Europe and other regions.
Ammonites such as Psiloceras were active marine animals related to modern squid and octopus, though unlike their living relatives they possessed an external coiled shell divided into chambers.
Shell Morphology and Iridescent Preservation
The shell of Psiloceras is typically smooth and relatively simple compared with later Jurassic ammonites. The whorls are moderately compressed and gently rounded, giving the shell an elegant, streamlined appearance. Unlike many later ammonite species, Psiloceras generally lacks heavy ribbing, displaying instead a smoother surface with subtle growth lines.
Internally, the shell is divided into a series of chambers separated by septa. The living animal occupied the outermost chamber while the inner chambers contained gas and liquid regulated by a tube known as the siphuncle, allowing the ammonite to control buoyancy.
The iridescence visible in some specimens occurs when thin layers of the original aragonite shell are preserved. Light reflecting through these microscopic layers produces shimmering colours, often displaying blues, greens, and gold tones depending on the angle of illumination.
Geological Setting – Blue Lias Formation
The Blue Lias Formation is a famous sequence of alternating limestone and shale layers deposited during the earliest Jurassic period. These sediments formed in a shallow marine basin that covered large parts of southern Britain shortly after the end-Triassic extinction.
At Doniford Bay near Watchet in Somerset, coastal erosion continually exposes these fossil-rich strata. The fine-grained sediments of the Blue Lias preserved a wide variety of marine organisms including ammonites, bivalves, fish, and marine reptiles.
The alternating limestone and shale layers reflect periodic environmental changes in the ancient sea, possibly linked to climatic cycles and fluctuations in oxygen levels on the seabed.
Early Jurassic Marine Ecosystem
During the Hettangian stage, the region that is now Somerset lay beneath a warm shallow sea connected to the wider Tethyan Ocean. These waters supported a diverse marine ecosystem recovering from the major extinction event at the end of the Triassic.
Ammonites such as Psiloceras rapidly diversified and became one of the dominant marine invertebrates. They likely fed on planktonic organisms, small crustaceans, and other marine prey while themselves serving as food for larger predators including fish and marine reptiles.
The fossil record of the Blue Lias provides important evidence for understanding how marine ecosystems recovered and evolved during the earliest stages of the Jurassic.
Authenticity and Collectability
• Genuine iridescent ammonite fossil identified as Psiloceras
• Blue Lias Formation, Early Jurassic
• Hettangian stage, approximately 201–199 million years old
• Collected from Doniford Bay, Watchet, Somerset, United Kingdom
• The fossil shown in the photographs is the exact specimen you will receive
• Includes a Certificate of Authenticity lifetime guarantee generic card
Iridescent ammonites from the Blue Lias are highly sought after due to their visual beauty and geological significance. This Psiloceras specimen from the Jurassic coastline of Somerset represents a stunning and scientifically important fossil, making it an exceptional addition to any fossil collection, geological display, or natural history study.
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