Rare Neoglytoxoceras Heteromorph Ammonite Fossil Lower Maastrichtian Cretaceous Madagascar

Description

This listing is for a rare Neoglytoxoceras heteromorph ammonite fossil, dating from the Lower Maastrichtian stage of the Late Cretaceous Period, approximately 72–70 million years old. Collected in the fossil-rich marine deposits of Madagascar, this specimen represents one of the most distinctive heteromorph ammonites, renowned for their unusual, uncoiled shell structures. Its rarity, provenance, and striking morphology make it a superb fossil for collectors, researchers, and display.

All of our fossils are 100% genuine specimens and are supplied with a Certificate of Authenticity. The photographs show the exact ammonite you will receive. A 1 cm scale cube and rule squares are included for precise measurement reference—please see the images for full sizing details.

Geological Context and Age

This specimen originates from the Lower Maastrichtian stage, the final age of the Cretaceous, just before the mass extinction event that ended the reign of the ammonites and non-avian dinosaurs. At this time, Madagascar was surrounded by warm tropical seas connected to the wider Tethys Ocean. These shallow marine environments supported diverse faunas, including ammonites, belemnites, fish, and marine reptiles.

The Maastrichtian is one of the most significant intervals in the geological record, preserving the last flourishing ammonite faunas before their extinction at the Cretaceous–Paleogene boundary. Fossils from Madagascar are particularly important, as they provide some of the best-preserved examples of Late Cretaceous ammonites known worldwide.

Morphology and Distinctive Features

Neoglytoxoceras is a member of the family Diplomoceratidae, within the superfamily Turrilitoidea of the order Ammonitida. This family is characterised by its highly irregular and uncoiled shell shapes, known collectively as heteromorphs. Unlike the typical tightly coiled ammonites, Neoglytoxoceras possessed a partially uncoiled, often hook-shaped or loosely curved shell.

This specimen displays the uncoiled, irregular morphology typical of the genus, with visible ribbing along the shell. The unique form of Neoglytoxoceras likely reflects a different ecological strategy compared to planispiral ammonites, with many palaeontologists suggesting that these heteromorphs were slow-moving or even passive floaters in the water column, feeding on plankton or small nekton. Their unusual shapes represent one of the most striking evolutionary experiments among the ammonites.

Scientific Importance

The genus Neoglytoxoceras is of major interest to palaeontologists because of its place within the Maastrichtian ammonite fauna, some of the very last ammonites to exist before extinction. Its distinct morphology helps define biozones within the Maastrichtian, making it an important index fossil for stratigraphy.

Fossils like this provide insight into ammonite evolution, palaeoecology, and diversity leading up to the end-Cretaceous extinction. Specimens from Madagascar are especially valuable because of their preservation, which allows fine details of ribbing and coiling to be studied and compared with other global populations.

Collector and Display Value

This rare Neoglytoxoceras heteromorph ammonite fossil is an outstanding specimen for collectors of Cretaceous fossils. Its unusual uncoiled structure makes it visually striking and a conversation piece for any fossil collection or display. Unlike the more common planispiral ammonites, heteromorphs such as Neoglytoxoceras showcase the evolutionary diversity of ammonites at their peak.

For display purposes, its dramatic morphology highlights the extraordinary range of shell forms achieved by these extinct cephalopods. Its provenance from Madagascar, one of the world’s most famous fossil localities, further enhances its rarity and desirability.

Your Guarantee of Authenticity

• 100% genuine Neoglytoxoceras ammonite fossil from Madagascar
• Geological age: Lower Maastrichtian, Late Cretaceous (approx. 72–70 million years old)
• Supplied with a Certificate of Authenticity
• Exact specimen shown in photographs (not a stock image)
• Scale cube and rule squares = 1 cm (see photos for accurate sizing)

This Neoglytoxoceras heteromorph ammonite fossil is a rare and scientifically important specimen from Madagascar’s Maastrichtian deposits. Its unique morphology, rarity, and authentic provenance make it an exceptional addition to any fossil collection.