LARGE BEAUTIFUL AMMONITE

LARGE BEAUTIFUL AMMONITE

SIZE: 166 x 135 x 16mm

WEIGHT: 410g

ORIGIN: Madagascar

Polished.

Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda, phylum Mollusca.
Because ammonites and their close relatives are extinct, little is known about their way of life. Their soft body parts are very rarely preserved in any detail. Nonetheless, much has been worked out by examining ammonoid shells and by using models of these shells in water tanks.
Many ammonoids probably lived in the open water of ancient seas, rather than at the sea bottom. This is suggested by the fact that their fossils are often found in rocks that were laid down under conditions where no bottom-dwelling life is found. Many of them (such as Oxynoticeras) are thought to have been good swimmers with flattened, discus-shaped, streamlined shells, although some ammonoids were less effective swimmers and were likely to have been slow-swimming bottom-dwellers. Ammonites and their kin probably preyed on fishes, crustaceans and other small creatures; while they themselves were preyed upon by such marine reptiles as mosasaurs. Fossilized ammonoids have been found showing teeth marks from such attacks.
The ammonoids survived several major extinction events, with often only a few species surviving. Each time,however, this handful would diversify into a multitude of forms. Ammonite fossils became less abundant during the latter part of the Mesozoic, with none surviving into the Cenozoic era. The last surviving lines disappeared along with the dinosaurs 65 million years ago in the Cretaceous-Tertiary extinction event. That no ammonites survived the extinction event at the end of the Cretaceous, while some nautiloid cousins survived, might be due to differences in ontogeny. If their extinction was due to an meteor strike, plankton around the globe could have been severely diminished, thereby dooming ammonite reproduction during its planktonic stage.

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