Rare Proplanulites petrosus Fossil Ammonite, Jurassic, Callovian, Cirencester UK, Genuine Specimen with COA

Description

Offered here is a RARE Fossil Ammonite of Proplanulites petrosus from the Callovian Stage of the Jurassic Period, discovered near Cirencester, United Kingdom — a locality known for its well-preserved marine fossils within the Middle Jurassic sedimentary record.

The specimen has been carefully selected for its preservation quality and scientific value. The photograph shows the actual fossil you will receive, not a stock image.

Scale Rule Squares / Cube = 1cm — please refer to the photo for full sizing.

Key Geological and Scientific Information:

• Species: Proplanulites petrosus
• Fossil Type: Ammonite (extinct marine cephalopod)
• Geological Period: Jurassic
• Geological Stage: Callovian (~166–163 million years ago)
• Location: Cirencester, Gloucestershire, England, UK
• Formation: Possibly from the Oxford Clay or Kellaways Beds, depending on precise locality
• Order: Ammonitida
• Superfamily: Haploceratoidea (tentatively assigned)
• Family: Tulitidae (taxonomic position debated)
• Described By: Quenstedt, 1885 (original classification may vary by reference)

Morphology Features:

Proplanulites petrosus is characterised by its planulate (flat-sided) whorls, relatively compressed and involute shell, and fine radial ribbing that may become faint on the flanks. The venter (outer edge) is narrow and typically rounded. The clean, flattened shape and minimal ornamentation are distinguishing features of this genus, contributing to its streamlined, elegant profile.

This specimen reflects those features with clarity, making it a textbook example of the species and a prime reference piece.

Depositional Environment:

The fossil was preserved in a low-energy, offshore marine setting, likely within fine clays or silty marls deposited during the Jurassic marine transgression across southern England. These environments favoured the fossilisation of ammonites with minimal post-mortem disturbance.

Stratigraphic & Biozone Information:

While Proplanulites petrosus is not an index species, it is found within Middle to Upper Callovian ammonite assemblages, often in association with genera such as Macrocephalites and Reineckeia. Its presence aids in fine-tuning stratigraphic correlations within the Oxford Clay Basin and adjacent European regions.

Scientific Relevance:

The genus Proplanulites helps illustrate transitional forms in ammonite evolution during the later Middle Jurassic. P. petrosus, in particular, exemplifies a shift toward more simplified shell ornamentation. Its occurrence and morphology provide insights into paleoenvironmental adaptations during the Callovian.

Authenticity Guarantee:

All of our fossils are 100% genuine specimens, professionally selected and cleaned. Each fossil comes with a Certificate of Authenticity, detailing its species, age, and locality.

This Proplanulites petrosus ammonite from Cirencester is a rare and scientifically valuable addition to any fossil collection — ideal for collectors, educators, and Jurassic enthusiasts alike.