RARE AEGOCRIOCERAS QUADRATUM Heteromorph Ammonite Fossil – Lower Hauterivian, Cretaceous: Speeton, UK – Alice Purnell Collection

Description

An exceptionally rare fossil heteromorph ammonite specimen of Aegocrioceras quadratum, collected from the Lower Hauterivian Stage of the Early Cretaceous, from the Speeton Clay Formation, near Flamborough, Speeton, United Kingdom. This piece is part of the esteemed Alice Purnell Collection, recognised for its curation of scientifically significant fossil specimens.

Aegocrioceras quadratum is a notable member of the Ancyloceratoidea superfamily, displaying a highly distinctive uncoiled shell structure. This heteromorphic form deviates from typical coiled ammonites, often exhibiting a sharply helical or angular structure, which provides unique insights into ammonoid morphological evolution.

Geological & Scientific Details:

• Scientific Name: Aegocrioceras quadratum
• Fossil Type: Heteromorph Ammonite
• Geological Period: Cretaceous
• Geological Stage: Lower Hauterivian (~133–130 million years ago)
• Formation: Speeton Clay Formation
• Location Found: Speeton, Flamborough, United Kingdom
• Order: Ammonitida
• Superfamily: Ancyloceratoidea
• Family: Ancyloceratidae
• Morphological Features: Tightly coiled helicoidal whorls, possible quadrate ribbing, and a characteristic irregular shell shape, typical of heteromorphs
• Depositional Environment: Marine offshore setting with fine-grained sediment accumulation, characteristic of low-energy environments ideal for the preservation of delicate ammonite forms

This fossil represents a significant evolutionary deviation in ammonite morphology, reflecting adaptive responses in Cretaceous marine ecosystems. Specimens like this are both rare and scientifically valuable, especially from British fossiliferous clay sites.

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity.

Please Note:

• Scale Rule Squares / Cube = 1cm – full sizing visible in photo
• This is the actual specimen you will receive
• From the Alice Purnell Collection – ideal for collectors, academic study, or museum-grade display

An exceptional ammonite from a renowned UK locality, perfect for collectors, researchers, and enthusiasts of Cretaceous marine life.