Description
Rare Gulielmiceras pollux Ammonite Fossil from Russia
This listing offers a rare Gulielmiceras (Spinikosmoceras) pollux ammonite fossil from the Callovian stage of the Middle Jurassic, discovered in Ryazan, Russia. Dating back approximately 166 – 163 million years, this exceptional fossil represents one of the strikingly ornate ammonites of the Jurassic seas. Its distinctive shell morphology and well-preserved details make it an outstanding specimen for collectors, educators, and anyone passionate about natural history.
The fossil shown in the photographs is the exact specimen you will receive, with a 1 cm scale cube included for precise sizing reference. Every piece is carefully selected for quality, and all of our fossils come with a Certificate of Authenticity, guaranteeing its genuine origin and geological significance.
Geological Setting – Callovian, Middle Jurassic
The Callovian stage forms part of the Middle Jurassic and is a period marked by widespread shallow seas across much of Europe and western Russia. These seas provided ideal environments for ammonites, whose remains became buried in fine marine sediments. Over millions of years, these sediments lithified into limestone and clay, preserving the intricate shells of these ancient cephalopods.
Fossils from the Ryazan region are especially prized for their fine preservation and distinct morphology, often revealing delicate ornamentation not always seen in ammonites from other localities.
Scientific Classification
- Genus: Gulielmiceras
- Subgenus: Spinikosmoceras
- Species: Gulielmiceras pollux
- Order: Ammonitida
- Superfamily: Stephanoceratoidea
- Family: Kosmoceratidae
- Geological Stage: Callovian, Middle Jurassic (c. 166 – 163 million years ago)
- Locality: Ryazan, Russia
Distinctive Morphology and Features
The genus Gulielmiceras, particularly the subgenus Spinikosmoceras, is recognised for its striking shell ornamentation. This specimen of Gulielmiceras pollux exhibits:
- Prominent ribbing across the whorls, giving the shell a strong, sculptured appearance.
- Characteristic spines and tubercles along the ribs, which provided structural reinforcement and may have aided in hydrodynamics.
- A relatively compressed, evolute shell form, with earlier whorls clearly visible.
- Complex suture lines, a hallmark of ammonites, showing the internal chamber divisions that supported buoyancy control.
These features make Gulielmiceras one of the more distinctive and highly collectible ammonite genera, valued not only for its scientific importance but also for its dramatic natural beauty.
Paleoecological Significance
Ammonites such as Gulielmiceras pollux were nektonic predators, actively swimming in Jurassic seas and preying on smaller marine organisms including crustaceans, molluscs, and plankton. Their chambered shells provided buoyancy, enabling them to navigate through the water column with ease.
As with many ammonites, Gulielmiceras is considered an important index fossil, aiding geologists in correlating and dating marine rock layers across wide geographic areas. Their rapid evolutionary turnover and distinct morphology provide excellent markers for the Callovian stage of the Middle Jurassic.
Collector’s Value and Importance
This Gulielmiceras pollux ammonite fossil from Ryazan is not only a remarkable natural specimen but also a piece of Earth’s evolutionary history. The genus’ ornate spines and ribbing make it a visually striking addition to any fossil collection, while its precise geological dating gives it lasting scientific relevance.
Fossils of this quality are increasingly scarce, making this a highly desirable acquisition for collectors, educators, and museums alike. Its provenance, preservation, and authenticity set it apart as a specimen that embodies both aesthetic appeal and paleontological importance.
Key Details
- Species: Gulielmiceras (Spinikosmoceras) pollux
- Age: Callovian, Middle Jurassic (c. 166 – 163 million years old)
- Locality: Ryazan, Russia
- Features: Prominent ribbing, spines, tubercles, evolute coiling, complex suture lines
- Family: Kosmoceratidae
- Order: Ammonitida
- Exact specimen shown with 1 cm scale cube
- Includes Certificate of Authenticity
This is a rare opportunity to own an authentic Gulielmiceras pollux ammonite fossil from the Jurassic seas of Russia – a specimen of both beauty and scientific value.
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