Rare Alocolytoceras coarctatum Fossil Ammonite Toarcian Jurassic Aveyron France Genuine

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Rare Alocolytoceras coarctatum Fossil Ammonite Toarcian Jurassic Aveyron France Genuine

Rare Alocolytoceras coarctatum Fossil Ammonite Toarcian Jurassic Aveyron France Genuine Specimen with Certificate of Authenticity

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Rare Alocolytoceras coarctatum Fossil Ammonite from France

This listing features a rare Alocolytoceras coarctatum fossil ammonite, a beautifully preserved specimen from the Toarcian Stage of the Early Jurassic Period, approximately 182–174 million years old. Unearthed in the Aveyron region of France, this ammonite represents one of the most sought-after cephalopods of the Jurassic seas. The fossil pictured is the exact specimen you will receive, photographed alongside a 1 cm scale cube for accurate sizing. Every fossil in our collection is 100% genuine and supplied with a Certificate of Authenticity, ensuring complete confidence in your purchase.

Geological Context

The Toarcian Stage is a key interval within the Early Jurassic, notable for the Toarcian Oceanic Anoxic Event (T-OAE), a global environmental shift that left a strong mark in the fossil record. The Aveyron deposits in southern France are renowned for their fine-grained sedimentary rocks, which preserved ammonites and other marine life in exquisite detail. These formations once formed part of the margins of the ancient Tethys Ocean, where abundant marine organisms thrived in warm, shallow seas.

Ammonites from this region, such as Alocolytoceras coarctatum, provide critical data for biostratigraphy, helping geologists correlate Jurassic strata across Europe and beyond. The combination of well-preserved shell morphology and stratigraphic precision makes specimens from Aveyron highly desirable to collectors and researchers alike.

Scientific Classification

• Genus: Alocolytoceras
• Species: Alocolytoceras coarctatum
• Family: Lytoceratidae
• Superfamily: Lytoceratoidea
• Order: Ammonitida
• Class: Cephalopoda
• Age: Toarcian, Early Jurassic (~182–174 million years old)
• Locality: Aveyron, France

Morphological Features

Members of the Lytoceratidae family, including Alocolytoceras coarctatum, are known for their evolute shells, meaning that each whorl is exposed rather than tightly overlapping. This gives the ammonite an open, spiraling appearance, with the whorls clearly visible. The ribbing on this species is often delicate and finely spaced, while the sutures are complex, forming intricate lobes and saddles across the shell surface.

These morphological features were adaptations that balanced buoyancy and mobility, enabling ammonites to navigate efficiently in the open seas. The shell structure indicates that Alocolytoceras was a nektonic predator, feeding actively within the water column.

Paleoecology and Importance

During the Toarcian, the warm marine environments of southern France supported a thriving ecosystem of ammonites, belemnites, bivalves, crustaceans, and marine reptiles. Alocolytoceras coarctatum occupied a vital role within this food web, both as predator and prey. Its presence in the fossil record helps paleontologists understand patterns of survival and extinction during the Toarcian Oceanic Anoxic Event, when large areas of the seafloor were deprived of oxygen, dramatically impacting marine biodiversity.

The exceptional preservation of ammonites in Aveyron allows close study of their growth lines, shell form, and suture complexity. Fossils like this not only appeal to collectors but also remain valuable for ongoing scientific research, making them an important link to Earth’s Jurassic past.

Collectability and Display

This rare Alocolytoceras coarctatum ammonite is a striking specimen, offering both scientific significance and visual appeal. Its elegant coiled form and geological provenance make it a standout addition to any fossil or natural history collection.

• Specimen: Alocolytoceras coarctatum fossil ammonite
• Geological Age: Toarcian, Early Jurassic (~182–174 million years ago)
• Location: Aveyron, France
• Scale Reference: 1 cm cube visible in photographs
• Authenticity: Supplied with Certificate of Authenticity
• Condition: The fossil shown in the photographs is the exact specimen you will receive

This specimen is not only a fossil but also a piece of natural history, carrying with it the story of the Jurassic seas and the creatures that once flourished in them nearly 180 million years ago.