Macrocephalites macrocephalus Fossil Ammonite Koenigi Zone Gowerianus Subzone Kellaways Formation Callovian Jurassic Wiltshire UK

Description

Genuine Macrocephalites macrocephalus Fossil Ammonite from Wiltshire

This listing is for an authentic Macrocephalites macrocephalus fossil ammonite from the Jurassic deposits of Maud Heath’s Causeway, Wiltshire, UK. Found within the Koenigi Zone, Gowerianus Subzone of the Kellaways Formation, this specimen dates to the Callovian stage of the Middle Jurassic, approximately 165–163 million years ago. The exact ammonite pictured is the one you will receive, with a 1 cm scale cube shown for accurate sizing.

The specimen was collected on 04 May 2024 by our own team members, Alister and Alison, and has been carefully cleaned, prepped, and treated by Alison to preserve its features while ensuring long-term stability. As with all our fossils, it is supplied with a Certificate of Authenticity, confirming that it is a 100% genuine specimen with secure provenance.

Geological Context and Age

The Kellaways Formation, where this ammonite was discovered, is a Middle Jurassic marine deposit that stretches across parts of southern England. It is well known for its fine-grained sandy and silty sediments, which represent deposition in a shallow shelf sea environment.

This specimen originates specifically from the Koenigi Zone, Gowerianus Subzone, which is an important stratigraphic interval within the Callovian stage. Ammonites such as Macrocephalites macrocephalus serve as biostratigraphic markers for these deposits, helping geologists to identify and correlate layers across Europe.

Species Information – Macrocephalites macrocephalus

Macrocephalites macrocephalus is a large, robust ammonite species within the order Ammonitida, superfamily Perisphinctoidea, and family Macrocephalitidae. As its name suggests, the genus is known for its relatively broad and inflated whorls, with strong ribbing that runs across the shell.

The ribs of M. macrocephalus are typically coarse and radiate outward across the whorl, sometimes bifurcating (splitting) towards the outer shell edge. This ornamentation provides a distinctive appearance that differentiates it from other genera within the same family. Its shell morphology suggests it was a nektonic predator, adapted for active swimming in the warm, shallow seas of the Jurassic.

Fossil Features and Preservation

This specimen represents a partial but well-preserved ammonite, displaying characteristic ribbing and the thickened whorl structure typical of the species. Despite natural compression and geological wear, the fossil retains the essential features used to identify Macrocephalites macrocephalus.

The ammonite is preserved in its natural limestone matrix, offering both scientific context and display appeal. The preparation process has enhanced the visibility of key morphological traits while maintaining authenticity. This makes it both an attractive display fossil and a specimen of palaeontological value.

Scientific and Collector Importance

Macrocephalites macrocephalus is a key index fossil for the Callovian stage of the Jurassic, making it particularly important in the study of biostratigraphy. Its presence helps geologists define the Koenigi Zone and the Gowerianus Subzone, which are internationally recognised ammonite biozones.

For collectors, this fossil offers an opportunity to own a scientifically significant specimen from a classic British Jurassic locality. Its strong provenance, combined with its clear stratigraphic context, enhances its value for both private collectors and academic study.

A Unique Fossil from the Middle Jurassic

This Macrocephalites macrocephalus fossil ammonite is a rare and authentic specimen from Wiltshire’s Jurassic deposits. With its carefully prepared detail, historical significance, and accompanying Certificate of Authenticity, it is both a beautiful display fossil and a scientifically valuable piece of Britain’s deep-time heritage.

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.