RARE Kosmoceras spinosum Fossil Ammonite Iridescent Upper Callovian Jurassic Russia

Description

Rare Kosmoceras spinosum Fossil Ammonite

This listing presents a rare Kosmoceras spinosum fossil ammonite from the Upper Callovian stage of the Jurassic period, discovered in Russia. Dating to approximately 163 – 161 million years ago, this ammonite displays stunning natural iridescence across its shell, a feature that enhances both its scientific importance and its visual appeal. A true collector’s piece, this specimen is notable for its preservation, ornate shell structure, and shimmering nacre.

The specimen pictured is the exact fossil you will receive. A 1 cm scale cube is included in the photographs for precise size reference. Every fossil is carefully selected and is accompanied by a Certificate of Authenticity, guaranteeing that it is a genuine specimen.

Geological Background

The Upper Callovian stage of the Middle Jurassic was a time of thriving marine ecosystems across the shallow epicontinental seas of Eurasia. In these nutrient-rich environments, ammonites flourished alongside belemnites, bivalves, and marine reptiles. The Russian Callovian deposits are world-renowned for producing exquisitely preserved ammonites, often displaying remarkable structural detail and iridescent shell layers.

Kosmoceras spinosum is part of this unique fossil record. As an ammonite, it provides crucial evidence for biostratigraphy, serving as an index fossil for correlating rock layers across different geographic regions. Its presence helps paleontologists reconstruct ancient marine environments and understand the evolutionary developments of ammonites within the family Kosmoceratidae.

Scientific Classification

• Genus: Kosmoceras
• Species: Kosmoceras spinosum
• Order: Ammonitida
• Superfamily: Stephanoceratoidea
• Family: Kosmoceratidae
• Age: Jurassic, Upper Callovian (c. 163 – 161 million years ago)
• Locality: Russia

Morphological Features

The Kosmoceras spinosum ammonite is instantly recognisable for its elaborate and striking features:

• Spiny ornamentation along the ribbing, giving it the name spinosum.
• Evolute shell structure, with earlier whorls exposed and contributing to its ornate appearance.
• Strong ribbing and tubercles, typical of the genus Kosmoceras.
• Complex sutures, intricate folded lines marking chamber divisions.
• Iridescent nacre, reflecting light in vivid hues of green, blue, red, and gold.

These features make Kosmoceras spinosum both a valuable scientific specimen and an exceptional display fossil, treasured by collectors worldwide.

Evolutionary and Ecological Significance

Ammonites such as Kosmoceras spinosum were active predators of the Jurassic seas, preying on smaller marine organisms. Their coiled shells contained gas-filled chambers, enabling them to regulate buoyancy and move efficiently through the water. They were closely related to modern cephalopods like squid and cuttlefish, sharing similar hunting strategies and ecological niches.

The wide distribution and rapid evolutionary turnover of Kosmoceratidae make them critical to the study of Jurassic stratigraphy. Fossils like this specimen allow scientists to refine the dating of sedimentary layers and provide a clearer picture of the ancient ecosystems that once dominated the globe.

Collector’s Appeal and Display

This Kosmoceras spinosum fossil ammonite is more than a geological relic; it is a natural work of art. Its combination of scientific value, rarity, and natural iridescence makes it a sought-after piece for fossil enthusiasts, natural history collectors, and educators. When displayed, the fossil captures attention not only for its age and significance but also for its beauty, as the shell’s iridescent nacre reflects light in vivid, shimmering colours.

Whether acquired as a centrepiece specimen, for academic study, or as a unique natural history treasure, this ammonite is a remarkable link to the prehistoric oceans of the Jurassic.

Key Details

• Species: Kosmoceras spinosum
• Age: Jurassic, Upper Callovian (163 – 161 million years old)
• Locality: Russia
• Family: Kosmoceratidae
• Features: Iridescent nacre, spiny ornamentation, ribbing, complex sutures
• Certificate of Authenticity included
• Exact specimen pictured with 1 cm scale cube for size reference

This is a rare and iridescent Kosmoceras spinosum ammonite fossil, offering exceptional scientific, historical, and collector’s value.