RARE Bostrychoceras elongatum Fossil Heteromorph Ammonite | Upper Coniacian Cretaceous | Tsiribina Madagascar | Authentic Specimen

Description

Presenting a RARE and scientifically significant fossil specimen of Bostrychoceras elongatum, a heteromorph ammonite from the Upper Coniacian Stage of the Late Cretaceous, discovered in the Tsiribina Basin, Madagascar. This specimen showcases the unique and exotic morphology that defines the Nostoceratidae family, with beautiful preservation of its spiral, loosely coiled shell.

Fossil Overview:

• Species: Bostrychoceras elongatum
• Fossil Type: Heteromorph Ammonite
• Geological Age: Cretaceous – Upper Coniacian (~87 to 86 million years ago)
• Location: Tsiribina Basin, Madagascar
• Formation: Marine sedimentary units of the Morondava Basin Group
• Photo Specimen: You will receive the exact item shown
• Scale Cube: 1cm – see photo for full sizing
• Authenticity: 100% Genuine Fossil with Certificate of Authenticity

Scientific Classification:

• Kingdom: Animalia
• Phylum: Mollusca
• Class: Cephalopoda
• Order: Ammonitida
• Superfamily: Turrilitoidea
• Family: Nostoceratidae
• Genus: Bostrychoceras
• Species: Bostrychoceras elongatum
• First Described by: Spath, 1926

Geological and Environmental Context:

The specimen originates from Coniacian-aged marine limestone and shale units within the Tsiribina sub-basin of western Madagascar. During the Late Cretaceous, this region was submerged under warm, shallow epicontinental seas, rich with ammonites, bivalves, gastropods, and marine reptiles.

This fossil formed in low-energy marine settings, where fine sediment allowed excellent preservation of delicate shell ornamentation. The Coniacian stage marks an important interval in ammonite diversification following the extinction at the Turonian-Coniacian boundary.

Morphological Features:

• Uncoiled, helical to irregularly curved shell, unlike standard planispiral ammonites
• Commonly shows ribs, nodes, or spines along the whorls
• Shell structure may appear irregularly curved or spiraled, an adaptation theorized to affect buoyancy and swimming style
• The elongatum species is particularly known for its long and narrow shell coils, giving it its species name

Notable Traits & Collector Appeal:

• Rare and striking heteromorph ammonite, distinct from common spiral ammonites
• Sought after by collectors for its ornate and unusual shell geometry
• Strong educational and display value – a key piece illustrating ammonite evolutionary experimentation
• Professionally cleaned and prepared, retaining fine structural details

Summary:

• Name: Bostrychoceras elongatum
• Age: Upper Coniacian, Late Cretaceous (~87 Mya)
• Location: Tsiribina, Madagascar
• Type: Heteromorph Ammonite
• Preservation: Beautiful shell coiling and detail
• Authenticity: Certificate included
• Scale Reference: 1cm cube shown in image
• What You Get: The exact fossil shown in the photo

Note:

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

Your specimen has been discovered, cleaned, prepped, and treated by our trusted field team, ensuring full traceability and quality.