Rare Aulacostephanus autissiodorensis Fossil Ammonite – Upper Kimmeridgian, Upper Jurassic, Kimmeridge Bay Dorset UK – Genuine + COA

Description

A rare Aulacostephanus autissiodorensis Fossil Ammonite, from the Upper Kimmeridgian Stage of the Upper Jurassic, collected at Kimmeridge Bay, Dorset, United Kingdom. This ammonite is a classic representative of the genus Aulacostephanus, known for its strong ribbing and significance in Jurassic stratigraphy. The specimen shown in the photographs is the exact one you will receive, and it is supplied with a Certificate of Authenticity.

Fossil Type & Species:

• Type: Ammonite (extinct marine cephalopod)
• Species: Aulacostephanus autissiodorensis
• Order: Ammonitida
• Superfamily: Perisphinctoidea
• Family: Aulacostephanidae

Geological Context:

• Period: Jurassic
• Epoch/Stage: Upper Jurassic – Upper Kimmeridgian (approx. 155 to 152 million years ago)
• Biozone: Commonly associated with the Autissiodorensis Zone, a key ammonite biozone of the Upper Kimmeridgian
• Formation: Kimmeridge Clay Formation
• Depositional Environment: Marine shelf environment dominated by organic-rich shales and clays, renowned for excellent fossil preservation

Locality:

• Region: Kimmeridge Bay, Dorset, United Kingdom

Morphology & Features:

• Evolute shell with wide umbilicus
• Strong, coarse ribbing that bifurcates across the flanks and extends over the venter
• Robust shell morphology typical of Aulacostephanus
• Distinctive rib pattern allowing easy identification of the species

Scientific Notes:

• Aulacostephanus autissiodorensis was first described in the 19th century and is an important index species for Upper Kimmeridgian stratigraphy
• The genus Aulacostephanus is widely used in European ammonite biostratigraphy, particularly in the Jurassic successions of Britain and France

Notable Details:

• Excellent preservation with strong ribbing and well-defined shell detail
• Rare British ammonite from one of Dorset’s most famous fossil localities
• 100% genuine, natural fossil – no restoration
• Scale Reference: Each square or cube = 1cm. Please see photographs for accurate sizing

Authenticity & Guarantee: All of our fossils are 100% genuine, responsibly sourced, and professionally curated. Every purchase includes a Certificate of Authenticity. The fossil shown is the exact specimen you will receive.

This Aulacostephanus autissiodorensis ammonite is a rare and scientifically valuable fossil from the Upper Kimmeridgian of Dorset – an exceptional addition for collectors, researchers, or natural history displays.