Ammonite (5”) with exposed suture lines, Madagascar

Ammonites are fossilized cephalopod; extinct marine animals that lived in shells during the Early Cretaceous period, roughly 110 million years ago.

These Cleoniceras; coil-shelled, many-tentacled mollusks disappeared after the dinosaur-killing asteroid strike, in one of the worst mass extinctions of all time.

This ammonite is still mostly in its chambered shell; that shell has built up micro-layers of nacre (aragonite), and when light hits the stacked crystalline aragonite plates, it refracts and produces brilliant flashes of colour. The spacing and thickness of the layers dictate which colors you see. There is some purple flash and some pink flash.

In one area the shell was removed and you can see the squiggles- which are the suture lines. The lines represent the structural walls (septa) that divided the  growing creature’s shell into individual chambers.

Interesting factoid:
It is believed that the original discus used by the ancient Greeks in their Olympics was a fossilized ammonite.

From the Mahajanga region of Madagascar. Has been stabilized with resin to protect the fragile outer shell.

Measures roughly 5” x 4”.