Rare 7.5″ Fossil Ammonite Macrocephalites macrocephalus | Jurassic Callovian Wiltshire UK | Genuine + COA

Description

This listing offers a rare and large 7.5-inch fossil ammonite, Macrocephalites macrocephalus, from the Lower Callovian Stage of the Jurassic Period, collected at Kentland Quarry, Wiltshire, United Kingdom. The specimen is photographed clearly — you will receive the exact fossil shown. Each cube or square in the scale image = 1cm — see photos for full sizing.

This is a striking collector-grade ammonite with strong visual appeal and biostratigraphic significance, making it perfect for fossil enthusiasts, scholars, or display collectors alike.

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

Geological & Scientific Information:

• Fossil Type: Ammonite
• Species: Macrocephalites macrocephalus
• Order: Ammonitida
• Superfamily: Stephanoceratoidea
• Family: Macrocephalitidae
• Geological Stage: Lower Callovian (approx. 166.1 – 164.7 million years ago)
• Biozone: Possibly within the Macrocephalites macrocephalus Zone — used as a key marker horizon in Callovian sequences
• Formation: From the lower beds of the Oxford Clay or equivalent mudstone units
• Period: Jurassic
• Locality: Kentland Quarry, Wiltshire, England, UK
• Depositional Environment: Shallow marine basin with low energy, anoxic bottom conditions favouring preservation — fine-grained clays and muds dominate

Morphology & Notable Features:

• Large, involute and discoidal shell structure
• Broad, gently curving flanks with strong radial ribbing extending across the venter
• Ribbing is coarse but orderly, with occasional secondary ribs; no keels
• Venter is broad and rounded — ideal for showcasing characteristic features of the Macrocephalites genus
• Excellent definition of whorls and sutures
• Fine preservation shows natural shell architecture and ornamental patterning

Scientific Significance:

Macrocephalites macrocephalus is a prominent index fossil for the early Callovian. First described in the 19th century, this species is a vital tool for dating and correlating strata across Europe and parts of Asia. The genus name Macrocephalites refers to the “large head” — a reference to the broad, rounded nature of its whorls.

Its occurrence helps define the Macrocephalites macrocephalus Zone, a globally recognised ammonite biozone used in Jurassic chronostratigraphy. Specimens of this calibre and size are rarely found so well-preserved outside of museum or academic settings.

Ideal For:

• Dedicated ammonite collectors
• Museum-grade fossil displays
• Educational and university reference collections
• Gifts for palaeontology enthusiasts or geology lovers

What You Will Receive:

• The exact 7.5″ specimen of Macrocephalites macrocephalus shown in the listing photos
• Certificate of Authenticity
• Protective and secure packaging for safe worldwide delivery