Rare Hlawiceras platyrrynum Ammonite Fossil, Upper Bajocian Stage Jurassic, Authentic Madagascar Collectors Piece with COA

Description

Authentic Jurassic Ammonite Fossil

Presented here is a genuine Hlawiceras platyrrynum Ammonite Fossil from the Upper Bajocian Stage of the Middle Jurassic, collected in Madagascar. Ammonites are an extinct order of cephalopods belonging to the subclass Ammonoidea, related to squid and octopus. Their chambered shells made them highly adapted to marine life, functioning as efficient predators and key members of the Jurassic marine ecosystem. The specimen shown is exactly what you will receive, with a 1 cm scale cube in the photos for accurate sizing.

Geological Context – Upper Bajocian, Jurassic

The Bajocian Stage, part of the Middle Jurassic (~170–168 million years ago), was a time of major diversification for ammonites. The Upper Bajocian is especially important in stratigraphy because ammonite species like Hlawiceras platyrrynum serve as index fossils, used to date and correlate Jurassic rock sequences.

During the Bajocian, Madagascar lay within the Tethys Ocean realm, characterised by shallow, warm, tropical seas. Fine marine sediments accumulated across the seafloor, entombing ammonite shells and preserving them with remarkable detail. This fossil represents not only a striking specimen for collectors but also a window into the biodiversity of Jurassic seas.

Species Profile – Hlawiceras platyrrynum

The genus Hlawiceras, and specifically the species Hlawiceras platyrrynum, belongs to the order Ammonitida, within the superfamily Stephanoceratoidea. These ammonites are notable for their ornate ribbing and distinctive coiling.

Key morphological features of Hlawiceras platyrrynum include:

• A moderately evolute shell, where inner whorls remain visible.
• Strong, closely spaced ribs that may bifurcate as they extend across the shell flanks.
• A well-rounded venter, with ribs continuing uninterrupted across it.
• A large, wide umbilicus typical of Bajocian ammonites.
• Intricate suture patterns reflecting the shell’s internal chamber divisions.

These features make Hlawiceras platyrrynum highly distinctive and valuable for paleontological classification within the Upper Bajocian.

Paleoenvironment and Scientific Importance

Ammonites such as Hlawiceras platyrrynum lived as active, nektonic predators in tropical Jurassic seas. Their streamlined, buoyant shells allowed efficient movement while they hunted small invertebrates and planktonic organisms.

From a scientific standpoint, Hlawiceras platyrrynum is a vital biostratigraphic marker for the Upper Bajocian. Its restricted stratigraphic range and broad distribution make it indispensable for correlating Bajocian deposits across Europe, Africa, and beyond. Fossils from Madagascar contribute significantly to the study of Jurassic paleoenvironments and evolutionary patterns.

100% Genuine with Certificate of Authenticity

Every specimen we supply is 100% genuine and is accompanied by a Certificate of Authenticity. This ensures that your ammonite fossil is an authentic relic of the Jurassic seas of Madagascar and not a reproduction or cast.

A Collector’s and Display Fossil

This Hlawiceras platyrrynum ammonite fossil from the Upper Bajocian of Madagascar is a superb collector’s piece. Its bold ribbing, clear shell morphology, and important geological provenance make it an exceptional addition to any fossil collection, educational setting, or natural history display.

Scale Rule Squares / Cube = 1 cm. Please see listing photos for the full sizing of this exact specimen.