Description
Rare Kosmoceras (Spinikosmoceras) aculeatum Ammonite Fossil
This listing offers a rare Kosmoceras (Spinikosmoceras) aculeatum ammonite fossil, dating to the Middle Callovian stage of the Jurassic period, approximately 165 – 164 million years old. Discovered in the Ulyanovsky region of Russia, this ammonite represents one of the most striking and highly ornamented members of the Kosmoceratidae family, known for their beautifully ribbed and spined shells.
The fossil you see in the photographs is the exact specimen you will receive, shown with a 1 cm scale cube for accuracy. Each piece is carefully chosen for its quality and authenticity, and this specimen comes complete with a Certificate of Authenticity, ensuring it is a genuine piece of natural history.
Geological Setting
The Middle Callovian stage of the Jurassic was a time of extensive shallow seas covering much of Europe and Russia, creating rich marine environments ideal for the preservation of ammonites. The Ulyanovsky region is particularly famous for producing exceptionally well-preserved Kosmoceratidae, many of which display elaborate spination and ribbing patterns that make them highly sought after by both collectors and researchers.
Ammonites such as Kosmoceras (Spinikosmoceras) aculeatum are important index fossils, widely used by paleontologists to identify and correlate geological strata across different regions. Their presence in Middle Jurassic deposits helps define biozones and refine our understanding of Jurassic marine environments.
Scientific Classification
- Genus: Kosmoceras
- Subgenus: Spinikosmoceras
- Species: Kosmoceras (Spinikosmoceras) aculeatum
- Order: Ammonitida
- Superfamily: Perisphinctoidea
- Family: Kosmoceratidae
- Geological Stage: Middle Callovian, Jurassic (c. 165 – 164 million years ago)
- Locality: Ulyanovsky, Russia
Distinctive Morphological Features
The Kosmoceras aculeatum is renowned for its ornate and striking shell morphology:
- Evolute shell structure, with whorls openly coiled, exposing earlier whorls.
- Strong ribbing across the flanks, providing structural strength and a highly decorative appearance.
- Sharp spines and tubercles, especially along the ventrolateral edges, giving the shell its characteristic spiny form.
- Complex suture lines, reflecting the sophisticated chamber system that allowed buoyancy control.
These features not only served biological purposes, such as predator deterrence and hydrodynamics, but also make specimens like this visually captivating and scientifically valuable.
Paleoecological Significance
As a member of the Kosmoceratidae, Kosmoceras (Spinikosmoceras) aculeatum was an active marine predator, inhabiting the shallow epicontinental seas of the Middle Jurassic. Its chambered shell allowed it to regulate buoyancy, moving freely in the water column while preying upon smaller marine creatures such as crustaceans and mollusks.
Its wide geographic distribution and abundance during the Callovian make it an excellent biozonal indicator, helping geologists define specific intervals within the Jurassic system. Fossils like this contribute not only to paleontology but also to stratigraphy, aiding in reconstructing Earth’s geological past.
Collector’s Value
This rare Kosmoceras (Spinikosmoceras) aculeatum ammonite fossil is highly prized by collectors for its combination of scientific importance and striking appearance. The sharp ribbing and spined ornamentation highlight the evolutionary adaptations of ammonites while making the fossil a stunning display piece.
Specimens from Ulyanovsky, Russia are particularly esteemed for their quality preservation and visual appeal. Owning a fossil like this offers a tangible connection to the Jurassic seas and the fascinating creatures that thrived within them.
Key Details
- Species: Kosmoceras (Spinikosmoceras) aculeatum
- Age: Middle Callovian, Jurassic (approx. 165 – 164 million years old)
- Locality: Ulyanovsky, Russia
- Features: Strong ribbing, spines, tubercles, complex sutures
- Order: Ammonitida
- Family: Kosmoceratidae
- Authentic specimen with Certificate of Authenticity
- Exact piece photographed with 1 cm scale cube
This fossil represents a beautiful and scientifically valuable Jurassic ammonite, perfect for collectors, educators, or natural history enthusiasts seeking a rare and authentic specimen.
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