RARE Sigaloceras calloviense Fossil Ammonite – Kellaways Sand, Lower Callovian, Jurassic – Gloucestershire UK – Alice Purnell Collection

Description

Offered here is a beautifully preserved and rare specimen of Sigaloceras calloviense, a classic Lower Callovian ammonite from the Kellaways Sand Formation, collected at Fairford, Gloucestershire, United Kingdom. This excellent fossil is part of the respected Alice Purnell Collection. The specimen in the photo is the actual one you will receive.

Geological Context:

• Species: Sigaloceras calloviense
• Geological Period: Jurassic
• Stage: Lower Callovian (~166 to 164 million years ago)
• Formation: Kellaways Sand
• Location: Fairford, Gloucestershire, UK
• Depositional Environment: Shallow marine environment with sandy silts and fine-grained clays; part of a transgressive sequence typical of the Callovian sea-level rise over the Oxfordian Basin margins

Taxonomic Classification:

• Family: Oppeliidae
• Superfamily: Haploceratoidea
• Order: Ammonitida
• Suborder: Ammonitina
• Formally Described By: Sowerby, 1817 (as part of foundational Callovian ammonite studies)

Morphological Features:

Sigaloceras calloviense is known for its compressed, involute shell with relatively flat flanks, a narrow venter, and fine, sinuous ribbing. The ornamentation is delicate, with ribs that tend to fade near the venter. The shell profile is highly streamlined, and the suture lines are modestly complex—characteristic of early members of the Oppeliidae family.

This specimen displays these hallmark features with excellent clarity, preserving both flank detail and overall shell curvature, making it a superb example of the species.

Stratigraphic and Scientific Significance:

Sigaloceras calloviense is one of the key taxa defining the Calloviense Zone, the basal ammonite biozone of the Callovian Stage in British stratigraphy. Its presence is pivotal for correlating marine sediments in both the UK and northwest Europe. As a transitional genus within the Oppeliidae, Sigaloceras also holds evolutionary significance for tracing lineages toward more tightly coiled haploceratid forms in later Jurassic intervals.

Additional Details:

• All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.
• Scale Rule Squares / Cube = 1cm. See listing photo for full size.
• This specimen comes from the scientifically curated Alice Purnell Collection, known for quality and provenance.

A rare and scientifically meaningful ammonite, perfect for collectors, educators, and enthusiasts of Britain’s Jurassic past.

Add this exceptional Sigaloceras calloviense to your collection today.