A Perisphinctes Madagascan Ammonite

5"/13cm diameter 

Weight
500g

Description

One Perisphinctes sp, Madagascan Ammonite precisely cut into two halves, the filled Calcite chambers polished to a highly glossy finish. Fine example of this genus type of Ammonite showing the internal structure of the once living Cephalopod. Now forming a pair half ammonites suitable for a unique and fine display. Some of the chambers are mineral cavities [not fully filled by mineral growth], making a aesthetically dramatic and interesting feature.

Brief Ammonite History

Ammonites, part of the Ammonitida [order], Ammonoidea [sub class], Cephalopoda [class], of marine invertebrates were fascinating and believed to be aggressive creatures, with their extremely large eyes they could easily hunt at night or at great depth where little or no light penetrates the deep oceans. The Cephalopod would grab its prey in their grappling tentacles, prey such as other crustaceans and fish, much as the persisting modern day Nautilus Pompilius [Emperor Nautilus], which swims the Pacific. Off the Great Barrier reef at a depth of between 200-400m sightings of Nautilus were made. Showing the pressures these Cephalopods can attain. The Ammonites extinction was around 74 mya, pre the great mass extinction of around 65 mya, at the end of the Cretaceous Period which ended the rule of the dinosaurs. Ammonites are very important Index Fossils, it is often possible to link the sediment layer in which they are found to specific geological time periods. The largest ammonite found to date was around 76 diameter, found in Germany. Named after the Egyptian God Pharaoh Ammon, with his rams horn ears, as the concentrically formed ammonite. Closet living relatives subclass Coleoidea [octopus, squid, and cuttlefish].

Genus

Perisphinctus Ammonite sp.

Geological age

Approximately 144 mya [Jurassic period 205- 135 mya]

Location

Tulear,Madagascar