Rare Tortilliceras approximatus Fossil Ammonite Lower Callovian Jurassic Madagascar Authentic COA

Description

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RARE Tortilliceras approximatus Fossil Ammonite Lower Callovian Jurassic Madagascar COA

Rare Tortilliceras approximatus Fossil Ammonite Lower Callovian Jurassic Madagascar Authentic COA

Rare Tortilliceras approximatus Ammonite Fossil

This listing offers a rare Tortilliceras approximatus ammonite fossil, originating from the Lower Callovian stage of the Jurassic period (approximately 166–163 million years ago). Discovered in Madagascar, this specimen is an extraordinary representation of a classic ammonite species from the Middle Jurassic. The fossil has been carefully selected for its preservation, showcasing striking morphological detail with strong ribbing and coiling that define the species. The specimen is pictured with a 1 cm scale cube for accurate sizing, and you will receive exactly the fossil shown in the photographs. As with all of our specimens, this ammonite is 100% genuine and will arrive with a Certificate of Authenticity.

Geological Context

The Lower Callovian marks a critical interval in the Jurassic period, falling within the Middle Jurassic and bridging the Bajocian and Oxfordian stages. During this time, Madagascar formed part of the southern margin of the vast Gondwanan supercontinent. Warm, shallow seas spread across the region, providing ideal conditions for marine life. Sediments deposited in these environments preserved ammonites like Tortilliceras approximatus, whose fossils are now studied worldwide for their importance in biostratigraphy.

The Callovian stage is particularly significant because of its ammonite diversity and its use in defining marine biozones across Europe, Africa, and beyond. Ammonites such as Tortilliceras are central to correlating rock sequences from Madagascar to European basins, helping palaeontologists understand Jurassic ocean circulation and faunal distribution.

Morphological Features

This Tortilliceras approximatus specimen displays diagnostic features of the genus:

• Shell form: Involute to moderately evolute, with well-exposed outer whorls.
• Ribbing: Strong, radiating ribs that extend across the flanks and curve sharply towards the venter.
• Keel: A well-developed keel, giving the ammonite improved hydrodynamic movement through the water column.
• Symmetry: Radial balance in its coiling, enhancing its visual appeal as a display specimen.
• Sutures: Complex suture lines preserved in some areas, reflecting the internal chamber structure.

These features suggest a nektonic, fast-moving lifestyle, with Tortilliceras being an active predator in Jurassic seas, feeding on smaller marine organisms.

Scientific and Collector Importance

Tortilliceras approximatus is a member of the order Ammonitida, superfamily Stephanoceratoidea, and family Stephanoceratidae. Its evolutionary importance lies in its role as a guide fossil for the Lower Callovian, being widely used in stratigraphic studies to identify and date Jurassic marine sediments.

For collectors, this fossil is more than a striking natural relic – it is a scientifically valuable specimen tied to global geological research. The strong ribbing and characteristic Callovian morphology make it an eye-catching addition to any fossil collection, while its provenance from Madagascar enhances both its rarity and appeal.

Key Details

• Species: Tortilliceras approximatus
• Age: Lower Callovian, Middle Jurassic (~166–163 million years ago)
• Location: Madagascar
• Order: Ammonitida
• Superfamily: Stephanoceratoidea
• Family: Stephanoceratidae
• Features: Strong ribbing, involute shell, distinct keel, complex sutures
• Authenticity: 100% genuine fossil with Certificate of Authenticity
• Scale reference: 1 cm cube (see photos for accurate sizing)

This rare Tortilliceras approximatus ammonite fossil from Madagascar is a perfect combination of natural history, scientific value, and aesthetic beauty. It represents a remarkable opportunity to acquire an authentic specimen from the Jurassic seas, offering both collectors and enthusiasts a tangible connection to Earth’s deep past.

Scale cube = 1 cm. Please see photographs for full sizing details.