Cardioceras alphacordatum Fossil Ammonite Oxford Clay Lower Oxfordian Jurassic Dorset UK

Description

Genuine Cardioceras alphacordatum Ammonite Fossil

This listing offers a superb Cardioceras alphacordatum ammonite fossil, discovered in the Oxford Clay Formation at Weymouth, Dorset, United Kingdom. Dating from the Lower Oxfordian Stage of the Jurassic Period, approximately 163–161 million years ago, this specimen is a scientifically valuable fossil as well as a visually striking collector’s piece. The fossil shown in the photographs is the exact one you will receive, and it comes with a Certificate of Authenticity, guaranteeing that it is a 100% genuine specimen.

Geological Context

The Oxford Clay Formation is one of Britain’s most famous Jurassic fossil-bearing deposits, renowned for its abundance of exceptionally preserved marine life. Deposited during the Lower Oxfordian, this formation records a shallow epicontinental sea that covered much of southern England. Ammonites, belemnites, bivalves, marine reptiles, and other organisms thrived in this marine environment. Fine-grained sediments preserved the shells and skeletal remains in remarkable detail, allowing specimens such as this ammonite to survive for millions of years.

Weymouth, Dorset, lies within the Jurassic Coast UNESCO World Heritage Site, celebrated worldwide for its accessible geological record and diverse fossil finds. The Oxford Clay exposed in this region provides important evidence for the reconstruction of Jurassic marine ecosystems and remains a reference point for palaeontologists.

Scientific Classification

• Species: Cardioceras alphacordatum
• Genus: Cardioceras
• Family: Cardioceratidae
• Superfamily: Stephanoceratoidea
• Order: Ammonitida
• Class: Cephalopoda
• Age: Lower Oxfordian, Jurassic (~163–161 million years ago)
• Formation: Oxford Clay
• Locality: Weymouth, Dorset, United Kingdom

Morphological Features

Cardioceras alphacordatum is characterised by its strongly ribbed, evolute shell with ribs that bifurcate across the flanks and curve gracefully toward the venter. These prominent ribs provide both visual appeal and important taxonomic features for identifying the species. The whorl section is relatively compressed, and the ornamentation creates a highly sculptural shell surface.

The name alphacordatum reflects its position within the lineage of Cardioceras, closely related to Cardioceras cordatum. Its features make it a significant species for understanding evolutionary changes within the Cardioceratidae during the Oxfordian.

Stratigraphic and Palaeontological Significance

This ammonite plays a key role as an index fossil for the Lower Oxfordian, helping to define important ammonite biozones within the Jurassic. Index fossils such as Cardioceras alphacordatum are crucial for correlating rock layers across different regions, allowing geologists to reconstruct a precise timeline of Earth’s history.

The Oxford Clay ammonites are particularly important because of their abundance and diversity, providing detailed evidence of faunal succession within the Jurassic seas of Western Europe. Cardioceras alphacordatum is a distinctive and scientifically valuable representative of this evolutionary sequence.

Depositional Environment

The Oxford Clay was laid down in a shallow, warm marine setting. The fine, silty muds created low-energy depositional conditions that allowed for excellent preservation of shells and marine vertebrate remains. Ammonites such as Cardioceras alphacordatum thrived in this environment, their shells eventually settling into the mud and becoming fossilised. These conditions contributed to the formation of one of the world’s most significant Jurassic fossil repositories.

Collector and Display Value

This Cardioceras alphacordatum ammonite fossil represents a superb piece of Jurassic history from one of Britain’s most iconic fossil localities. Its combination of scientific importance, distinctive ribbed ornamentation, and well-preserved features make it an ideal acquisition for collectors, educators, and enthusiasts of natural history.

• Type: Fossil Ammonite – Cardioceras alphacordatum
• Age: Lower Oxfordian, Jurassic (~163–161 million years ago)
• Formation: Oxford Clay
• Location: Weymouth, Dorset, United Kingdom
• Scale: Rule squares/cube = 1 cm (see photographs for accurate sizing)
• Authenticity: 100% genuine specimen with Certificate of Authenticity
• Specimen: The actual fossil shown in the photographs is the one you will receive

This rare ammonite from the Oxford Clay of Weymouth, Dorset provides a direct link to the Jurassic seas of southern England, making it a remarkable and highly desirable specimen for any serious collection.