Rare Pseudogrammoceras fallaciosum Ammonite Fossil from Aalenian Jurassic Stroud Gloucestershire UK

Description

Geological Context

This genuine Pseudogrammoceras fallaciosum ammonite fossil dates back to the Aalenian Stage of the Middle Jurassic, approximately 174–170 million years ago. It was unearthed near Stroud, Gloucestershire, United Kingdom, a region renowned for its rich Jurassic marine deposits. During the Aalenian, much of Britain was covered by warm, shallow seas, allowing ammonites and other cephalopods to flourish in thriving ecosystems.

The fossil comes from strata that formed in these marine environments, most likely deposited under calm conditions that preserved fine details of the ammonite shell. Such deposits are part of the wider Inferior Oolite Group, a classic Middle Jurassic sequence across the Cotswolds.

Taxonomic Classification

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Order: Ammonitida
• Superfamily: Hildoceratoidea
• Family: Hildoceratidae
• Genus: Pseudogrammoceras
• Species: Pseudogrammoceras fallaciosum

As a member of the family Hildoceratidae, Pseudogrammoceras represents an important ammonite lineage, valuable for its role in biostratigraphy. These ammonites are widely used as index fossils, enabling geologists to accurately date and correlate rock formations from the Jurassic.

Morphological Features

The fossil displays the distinctive traits of Pseudogrammoceras fallaciosum:

• Planispiral shell with a compressed, discoidal form.
• Fine ribbing running across the flanks, giving the fossil a beautifully detailed appearance.
• A clearly defined venter (outer rim), often with a faint keel or sharp edge.
• Complex suture lines visible on the shell surface, marking the junctions of internal chambers.

These features reflect the ammonite’s adaptations for efficient movement and buoyancy control within the open marine environment. The intricate ribbing and fine ornamentation also make this specimen particularly attractive as a display fossil.

Depositional Environment

The Aalenian seas around present-day Gloucestershire were part of a shallow shelf environment in the Jurassic. Rich in marine life, these seas supported corals, brachiopods, echinoids, and ammonites. Sedimentation was dominated by oolitic limestones and calcareous muds, which are well known for producing exceptionally preserved fossils. The conditions of burial preserved delicate shell structures and provide insight into ancient marine ecosystems.

Scientific and Collector Value

• Scientific Importance: Pseudogrammoceras fallaciosum is a significant index fossil of the Aalenian, helping to define stratigraphic boundaries.
• Educational Use: This specimen demonstrates ammonite morphology, palaeobiology, and Jurassic depositional environments.
• Collector’s Appeal: With its fine ribbing, elegant form, and historical provenance from Stroud, this fossil is an excellent addition to both private and museum collections.

Authenticity and Presentation

• 100% genuine fossil specimen, supplied with a Certificate of Authenticity.
• The photographs show the exact fossil you will receive—no substitutes or stock images.
• A 1 cm scale cube is included in the photos for accurate sizing.

This Pseudogrammoceras fallaciosum ammonite fossil from the Aalenian Stage of Stroud, Gloucestershire, is a scientifically significant and visually striking specimen. It represents an authentic fragment of Britain’s Jurassic past and makes a unique addition for fossil collectors, educators, and enthusiasts alike.