It is a profession, the fossil selling profession, which rarely ceases to teach and amaze in equal measure our intellect and consciousness, today that has again proven the case with one of our latest discoveries, a fossil nautilus from Madagascar. Among the various beautiful and mineral-rich chambered fossil phragmacone of the ancient cephalopoda group, we have discovered a rather strange stout individual, with lumps, bumps and looking rather forlorn with a heavy encrustation of iron pyrite. This peaked our interest and has led to questions and more questions yet without resolution, here you can make your assessment of this most unusual specimen.
A deformity around the last few living camerae of this knobbly example, the umbilicus (inner whorls), of the phragmacone (shell) are notably affected. Here the iron pyrite has infiltrated the phragmacone, and has developed around the camerae and outwardly, while still retaining the general form of the nautilus shell, in such a way, this has caused a distortion akin to elephantiasis in humans to the extinct cephalopods old home. Also creating a uniquely different event in the prehistory of Madagsacn nautili fossils. The specimen will probably interest the school of collectors of non-conformity, like deformed sharks teeth, some ammonoid and nautiloid collectors narrow their particular field of interest. This nautiloid is one that for our team is most unusual, from this location.
The palaeontologist's mind may react to such a discovery in a more lateral plane of thought than any other reasonable person! With the identification of this massive penetration post-mortem event, was damage to the phragmacone an accelerator in the forming of the iron pyrite mineral at this point? Did this mineral seep into the cellular structures of the remains of the marine mollusc and its extinct home for any other particular reason? And so on...
The author does not with any assuredly concise theory know, the answers to these questions, and perhaps there could only be the hypothesis, maybe one day there may be economical enough Magnetic resonance imaging (MRI) scan's available that may be used to discover more. To date regarding this particular specimen from the ancient past we only have our imagination and intellect to construct the story.
The penetration of the pyrite is tantalisingly in line with the growth of the molluscs last camerae of the phragmacone, and of course, this is towards the end of the cephalopods life. The earlier chambers infilled with quartz in the form of honey and treacle-coloured calcites, also dense concentrations of the seabed silts of the Triassic period (Carnian age 228- 235 million years) to Mid Jurassic (Callovian age 166 - 164 million years), these are what we expect to find in our Madagascan nautilus fossil's. This all makes this fossil that much more, a curiosity and a rarity from this location. Madagascar is not mainly known for profuse deposits of the iron ore pyrite, not so much as the heritage coastal areas of the south coast of England, or the mines of the Sierra de Alcarama, Spain, Peru and Brazil where pyrite mines produce significant quantities of iron pyrite in the form fools gold.
In the final post-image, the nautilus shell displays the saddle of the last living chamber, this exhibited with the siphuncle aperture now clogged with fossilised debris, a fascinating view, the opalescence remains in the seat of the saddle which enhances the ancient shell. From this angle the thickness of the encrusted pyrite is discernable, overlaying the outer wall of the phragmacone. While the juvenile camerae (chambers) have a dark infill of sediments and calcites, these are divided by the septa (the internal camerae walls) picked out with undulating calcified lines of lighter mineral. This darker calcite differentiated with yellow or honey calcites in the advancing larger and younger chambers.