Chondroceras gervillii Fossil Ammonite Bajocian Jurassic Humphriesianum Zone Romani Caen France – Alice Purnell Collection with COA

Chondroceras gervillii Fossil Ammonite – Bajocian, Jurassic, Humphriesianum Zone, Romani, Caen, France

This exquisite Chondroceras gervillii fossil ammonite is an authentic and beautifully preserved specimen from the Bajocian Stage of the Middle Jurassic, collected near Caen, Normandy, France, specifically from the Humphriesianum Zone (Romani Subzone). It originates from the esteemed Alice Purnell Collection, renowned for its scientifically significant and expertly curated fossils. The photograph shows the exact specimen you will receive, with a 1cm scale cube for accurate sizing reference. Each detail of this ammonite reveals the rich geological and biological history of the Jurassic seas that once covered northern France.

Geological Formation and Age

This fossil was formed during the Bajocian Stage of the Middle Jurassic Period, approximately 170–168 million years ago, within the Humphriesianum Zone, a biostratigraphic interval defined by the presence of specific ammonite assemblages. The Bajocian represents a time of widespread shallow marine deposition, when much of what is now northern France lay beneath a warm, tropical sea rich in life.

The sediments around Caen, Normandy, consist primarily of oolitic limestones and marls, representing deposition in a shallow epicontinental marine environment. These sediments provided excellent preservation conditions for marine invertebrates, particularly ammonites, which became encased in fine carbonate muds that later lithified into limestone.

Scientific Classification

• Kingdom: Animalia

• Phylum: Mollusca

• Class: Cephalopoda

• Order: Ammonitida

• Superfamily: Stephanoceratoidea

• Family: Graphoceratidae

• Genus: Chondroceras

• Species: Chondroceras gervillii (d’Orbigny, 1845)

• Geological Stage: Bajocian (Middle Jurassic)

• Zone: Humphriesianum Zone (Romani Subzone)

• Locality: Caen, Normandy, France

This species was first described by the eminent French naturalist Alcide d’Orbigny (1845), one of the founding figures of palaeontology, whose work on Jurassic ammonites remains foundational to modern ammonite taxonomy and zonation.

Morphology and Distinguishing Features

Chondroceras gervillii is a classic representative of the Graphoceratidae family, characterised by its elegant, involute shell with moderately compressed whorls and a narrow, rounded venter. The ribs are typically fine, sinuous, and bifurcate from near the umbilical shoulder, gently curving toward the venter where they fade smoothly, giving the shell a refined, streamlined appearance.

This specimen displays excellent preservation, with sharply defined ribbing and a clear whorl profile that beautifully illustrates the diagnostic features of the genus Chondroceras. The shell shows the distinct planispiral coiling typical of the group, forming a tightly wound spiral with minimal exposure of inner whorls.

Ammonites of this type are known for their hydrodynamic design, suggesting they were active swimmers (nektonic carnivores) inhabiting the open marine environment. The refined morphology of Chondroceras gervillii implies an adaptation to stable marine conditions with consistent oxygenation and temperature — ideal for supporting diverse ammonite populations.

Depositional Environment and Biozone

The Humphriesianum Zone, to which this specimen belongs, represents a key biozone in Bajocian stratigraphy, widely recognised across Europe. This zone is typified by ammonite faunas of the genera Stephanoceras, Graphoceras, and Chondroceras, which help define and correlate Middle Jurassic deposits between regions.

The Romani Subzone, in particular, corresponds to a relatively stable depositional phase characterised by well-oxygenated shelf environments and low sedimentation rates, allowing fine preservation of ammonite shells and other marine fossils. The limestone beds of Caen are noted for their pale coloration, fine grain, and abundance of fossil material, making them a classic locality for Bajocian ammonite research.

These fossils are often associated with other marine fauna, including bivalves, echinoids, belemnites, and brachiopods, indicating a thriving marine ecosystem. The calm, carbonate-rich depositional setting facilitated both fossilisation and aesthetic preservation, which is evident in the clarity and definition of this specimen.

Provenance – The Alice Purnell Collection

This ammonite comes from the Alice Purnell Collection, an exceptional private collection assembled with scientific precision and care. Specimens from this collection are highly regarded for their accurate locality data, expert identification, and overall quality. Each fossil has been preserved under ideal conditions and retains its natural geological context. This provenance adds both historical and academic value to the specimen, making it suitable for collectors, institutions, and enthusiasts alike.

Authenticity and Presentation

All of our fossils are 100% genuine specimens and come with a Certificate of Authenticity, verifying the fossil’s identity, age, and provenance. The photograph shows the exact specimen you will receive, carefully selected for its aesthetic appeal, preservation quality, and scientific importance. The scale cube equals 1cm, and full size details can be seen in the accompanying photo.

A Rare French Jurassic Ammonite

This Chondroceras gervillii from Caen, Normandy, represents a remarkable example of Middle Jurassic ammonite fauna from one of France’s most classic Bajocian localities. Its fine ribbing, historical provenance, and detailed preservation make it an outstanding addition to any serious fossil collection. Whether displayed for study, education, or natural beauty, this ammonite offers a genuine piece of deep geological history — a tangible connection to the life and environments of the Jurassic seas over 170 million years ago.