Amoeboceras alteratus Fossil Ammonite Upper Oxfordian Jurassic Drome France Genuine

Description

Rare Amoeboceras alteratus Ammonite Fossil from France

This listing presents a rare Amoeboceras alteratus ammonite fossil, dating from the Upper Oxfordian stage of the Late Jurassic, approximately 163–157 million years ago. Found in the Drôme region of France, this specimen represents one of the characteristic ammonites of the Oxfordian seas, a period when Europe was largely covered by shallow marine environments teeming with life. The fossil is preserved in fine detail, allowing close study of its ribbing and coiling patterns. The specimen offered here is the exact one shown in the photographs, with a 1 cm scale cube provided for size reference. All of our fossils are accompanied by a Certificate of Authenticity, ensuring its genuine origin and scientific value.

Geological Context: The Oxfordian Stage

The Oxfordian stage is the earliest subdivision of the Late Jurassic, spanning from around 163.5 to 157.3 million years ago. During this time, the area that is now southern France was part of a warm, shallow epicontinental sea with a rich ecosystem of ammonites, bivalves, echinoids, and marine reptiles. The Drôme region is particularly well-known for its well-preserved Oxfordian ammonite faunas, which play a crucial role in defining European Jurassic stratigraphy.

Ammonites such as Amoeboceras are particularly valuable as index fossils, providing important tools for biostratigraphy and helping scientists correlate rock layers across different parts of Europe.

Taxonomy and Classification

• Genus: Amoeboceras
• Species: alteratus
• Family: Cardioceratidae
• Superfamily: Stephanoceratoidea
• Order: Ammonitida
• Age: Upper Oxfordian, Jurassic (approx. 160 million years ago)
• Locality: Drôme, France

Belonging to the Cardioceratidae, this ammonite group is known for its strongly ribbed shells and stratigraphic importance within the Oxfordian and Kimmeridgian stages.

Morphological Features

This specimen of Amoeboceras alteratus displays several diagnostic features:

• Involute coiling, with inner whorls partly hidden by later growth.
• Dense, strong ribbing running across the flanks, typical of the genus.
• Pronounced rib bifurcation, where ribs split and cross the venter.
• Compressed shell form, giving the ammonite a distinctive, narrow appearance.

These features are not only of scientific importance but also give the fossil an aesthetic, textured quality that makes it attractive for collectors.

Scientific and Collecting Significance

Amoeboceras alteratus is especially valued for its role as a biozone marker in the Upper Oxfordian, making it an essential species in Jurassic stratigraphy. Specimens from the Drôme region are often studied in detail for their evolutionary significance and their use in correlating Jurassic rock sequences across Europe and beyond. For collectors, the fine ribbing and excellent preservation of this example make it a desirable and scientifically important fossil.

Key Details

• Fossil Type: Ammonite
• Species: Amoeboceras alteratus
• Geological Age: Upper Oxfordian, Jurassic (c. 160 million years ago)
• Location: Drôme, France
• Family: Cardioceratidae
• Features: Dense ribbing, compressed shell form, biostratigraphic importance
• Authenticity: Guaranteed with Certificate of Authenticity

Authenticity and Guarantee

We pride ourselves on offering only 100% genuine fossils, carefully selected for their quality and scientific importance. This Amoeboceras alteratus ammonite from the Jurassic rocks of Drôme, France, is a rare and beautifully preserved example that would make an excellent addition to any collection. With its well-defined ribbing, distinctive morphology, and scientific significance, it is both a collector’s specimen and a piece of Earth’s history preserved for over 160 million years.