Titanites giganteus Giant Portland Stone Ammonite Jurassic Dorset UK

Titanites giganteus – Giant Portland Stone Ammonite from the Jurassic Coast, Dorset, UK

This impressive Titanites giganteus ammonite is a genuine giant of the Jurassic seas, preserved within the iconic Portland Stone of the Isle of Portland, Dorset, UK. Dating to the Tithonian Stage of the Late Jurassic, this fossil represents one of the largest ammonite genera found in Britain. Its broad whorls, bold ribbing, and monumental form make Titanites among the most spectacular fossils from the Jurassic Coast UNESCO World Heritage Site.

You will receive the exact fossil shown in the photographs. Full sizing is visible in the images for precise scale. Every ammonite is individually selected for quality, preservation, and display appeal.

All of our fossils are 100% genuine specimens and include a Certificate of Authenticity.

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Geological Background – Tithonian, Late Jurassic

This ammonite originates from the Tithonian (approximately 152–145 million years ago), the final stage of the Jurassic Period. At this time, the region that is now southern England formed part of a warm, shallow tropical sea. Thick layers of carbonate sediment accumulated on the seabed, ultimately forming the Portland Stone, a world-famous oolitic limestone used in major historic buildings across Britain—including St Paul’s Cathedral.

The depositional environment of the Portland Stone was characterised by:

• Warm, shallow marine conditions

• High carbonate productivity

• Oolitic shoals and lagoons

• Periodic storm influences that redistributed sediments

The Jurassic Coast exposures of Portland Stone are internationally known not only for their architectural value but also for producing exceptional large ammonites such as Titanites giganteus.

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Fossil Type & Species – Titanites giganteus

Titanites giganteus belongs to the order Ammonitida, superfamily Perisphinctoidea, and is one of the most iconic ammonites of the Upper Jurassic of Britain. It is renowned for its enormous size—some specimens exceeding 1 metre in diameter—and serves as a classic index fossil of the Tithonian stage.

Key morphological features of Titanites giganteus include:

• Very large, thick whorls with massive shell expansion

• Bold, widely spaced ribs sweeping across the outer whorls

• Strongly involute coiling, giving the ammonite a robust circular profile

• Broad umbilicus, typical of Tithonian ammonites

• Strong, sculptured ornamentation visible even in partially preserved specimens

These features help palaeontologists identify Titanites and distinguish it from other Jurassic ammonite genera.

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Depositional Environment & Palaeoecology

The Portland Stone environment supported a rich marine ecosystem. Titanites was a nektonic ammonite, likely an active swimmer that preyed upon smaller marine organisms. Its large size suggests it was a top-tier ammonoid species within its ecosystem.

Fossils preserved within the Portland Stone often show evidence of:

• High-energy shoal conditions

• Rapid burial due to storm or sediment influx

• Exceptional preservation due to carbonate-rich sediments

Titanites ammonites frequently appear as large moulds or partially preserved shells within the limestone, demonstrating the durability and environmental dominance of this giant cephalopod.

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Scientific, Historical & Collecting Importance

Titanites giganteus is highly significant because:

• It is one of the largest ammonites in Britain

• It serves as a key Tithonian index fossil

• It provides insight into Late Jurassic ammonite evolution

• It occurs within the historically important Portland Stone Formation

Collectors value Titanites both for its size and for its deep connection to British geological heritage.

This specimen is ideal for:

• Advanced fossil collections

• Interior display and geological décor

• Educational and museum-style presentations

• Jurassic Coast enthusiasts and British fossil collectors

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Authenticity & Presentation

• 100% genuine Titanites giganteus ammonite fossil
• Certificate of Authenticity included
• Exact specimen photographed is the one you will receive
• Full sizing visible in photos for accurate scale
• Carefully selected for preservation, scientific value, and aesthetic display

This Titanites giganteus ammonite is a rare and extraordinary piece of Britain’s Jurassic past—an outstanding centrepiece for any serious fossil collection.