Ancient Gastropod Fossilized Shell of Kranaosphinctes...

Specimen of Kranaosphinctes rabei, Late Jurassic, Sakaraha — This impressive specimen represents a well-preserved fossil of Kranaosphinctes rabei, an ammonite belonging to the Perisphinctidae family. The primary mineralogical identification is recrystallized or substituted calcite, which has preserved the complex morphology of the original shell over millions of years. The crystalline formation, although not macroscopically evident as distinct crystals, is intrinsic to fossilization through permineralization and recrystallization of marine carbonate sediments. Visually, the ammonite displays a dominant coloration ranging from warm white to ivory, with elegant undertones of warm beige and honey. Patinas and crusts of ochre and brassy-brown hues are also noticeable, enriching the surface with a natural color contrast. There is no transparency, as the fossil is opaque, while the surrounding matrix is integrated into the shell itself, showing traces of the rock fossilization process. The geological provenance of this Kranaosphinctes rabei is Sakaraha, in the Atsimo-Andrefana region of southwestern Madagascar. The deposits in this area are renowned for their wealth of Late Jurassic marine fossils, particularly from the Oxfordian stage, dated approximately between 161 and 156 million years ago. This geological context indicates formation in ancient marine basins rich in organisms and sediments, where the ammonite’s shell was rapidly buried and subjected to diagenesis. The aesthetic quality of the piece is remarkable, thanks to its considerable size and well-defined morphology. The broad, deep spiral, with a distinctly visible central umbilicus, is highlighted by regular whorls and robust radial ribs that traverse the shell. These structural elements give the fossil an architectural and sculptural appearance, making it a piece of great visual impact and high ornamental value. The almost complete integrity of the shell, despite exposure of a transverse section, underscores its exceptional nature. The preservation state is excellent, with most of the shell intact and only a minimal portion of the living chamber exposed laterally, potentially revealing the internal structure. No significant damage or invasive restorations are detected, attesting to the originality and authenticity of the specimen. Given its weight and size, the piece can be displayed autonomously or on an appropriate supporting base that enhances its majesty and stability. From a collector’s perspective, a Kranaosphinctes rabei specimen of this size and with such a level of preservation is a prized acquisition. It represents not only a fascinating witness to Jurassic marine life but also a work of great natural beauty. Its rarity and its provenance from a classical ammonite fossil locality make it particularly desirable for experienced collectors and museums, placing it among reference specimens for the species.

Stima:€2,100

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