Polished Nautilus Ammonite From Madagascar
Middle Jurassic to the Oligocene Period – C. 176-34 Million Years Ago
Order to which the fossil belongs: Nautilida
Name of which the family belongs: Nautilidae
Informal name of the fossil: Nautilus
The coiling of the shell is very involute with the outline of the shell nearly globular and a broadly rounded venter. The individual chambers are also fewer.
Ammonites are a form of ammonoid which are distinguished by their complex suture lines. They evolved very rapidly to produce numerous species and genera, but it was during the Late Cretaceous period that the ammonites and other marine groups, like belemnites, and terrestrial groups, like dinosaurs became extinct.
The name ammonite, was inspired by the spiral shape of their fossilized shells, resembling tightly coiled rams’ horns. Many ammonoids probably lived in the open water rather than at the sea bottom, this is due to the fact that their fossils are often found in rocks that were laid down under conditions where no bottom-dwelling life is found. They are typically evolute with the inner whorls exposed, but some are commonly stout and more involute and strongly ribbed with pronounced tubercles.
A nice example of a polished Nautilus.
Size: 55mm x 79mm approx